RSNA

‘¿90

70th Scientific Assembly and Annual Meeting Notes Part

2

Table of Content. 902

913

Neuroradiology

Hervey D. Segall, MD, Chairman David L. Daniels, MD Charles R. Fitz, MD John R. Hesseling, MD Robert W. Jahnke, MD Stephen A. Kieffer, MD Norman E. Leeds, MD Kenneth R. Maravilla, MD Robert M. Quencer, MD Arthur E. Rosenbaum, MD Eric J. Russell, MD Gordon K. Sze, MD Michael S. Tenner, MD William T. C. Yuh, MD Robert D. Zimmerman, MD 907

Magnetic

L. Ehman, MD

R. Nick

Bryan,

910

Technical

914

Musculoskeletal

Radiology

William A. Murphy, Chairman

Jr. MD,

William

PhD,

F. Conway,

MD

Arthur A. DeSmet, MD Phoebe A. Kaplan, MD John B. Kneeland, MD

916 Thoracic Radiology Reginald Greene, MD, Chairman Dixie J. Anderson, MD Warren B. Gefter, MD Robert C. Levitt, MD Theresa McLoud, MD Jorg Oestmann, MD Comnelia Schaefer, MD Paul W. Spimn, MD Paul Stark, MDO 918

Cardiovascular/Interventional

Radiology

Exhibits

David W. Hunter, MD, Chairman Flavio Castaneda, MD Andrew H. Cragg, MD Michael D. Darcy, MD Xiaoping Hu, MD Deborah G. Longley, MD Louis G. Martin, MD Temence Matalon, MD Fred Steinberg, MD Arthur Stillman, MD Patricia Thorpe, MD Robert L. Vogelzang, MD E. Kent Yucel, MD

Joel E. Gray, PhD, Chairman Richard L. Morin, PhD Gamy T. Barnes, PhD

911

and

Ronald L. Arenson, MD, Chairman Samuel J. Dwyem III, MD H. K. Huang, DSc Harold L. Kundel, MD Sridhar B. Seshadni, MSEE

MD, PhD

John V. Crues, MD Hedvig Hnicak, MD Herbert Y. Kressel, MD Robert E. Lenkinski, PhD Donald G. Mitchell, MD Michael E. Moseley, PhD Stephen 1. Riederer, PhD Jeffrey R. Ross, MD

Applications

Digital Imaging

Resonance

Richard

Computer

Abdominal-Gastrointestinal Radiology Dennis M. Balfe, MD, Chairman Judith Chezmanm, MD Robert E. Koehler, MD Joel E. Lichtenstein, MD Rendon Nelson, MD 920

Official

Registration

Figures

cited a single

Neuroradiology

David L. Daniels, MD, Medical College of Wisconsin, Milwaukee Washington,

DC

John R. Hesselink, MD, University of California at San Diego,

San Diego

Robert W. Jahnke, MD, Lovelace Medical Center, Albu querque

Stephen A Kieffer, MD, State University of New York Health

Science Center,

Syracuse

Norman E. Leeds, MD, Beth Israel Medical Center, New York

Kenneth R. Maravilla, MD, University of Washington School of Medicine,

Seattle

Robert M. Quencer, MD, University of Miami School of Medicine, Miami Arthur E. Rosenbaum, MD, State University York Health Science Center, Syracuse

of New

Eric J. Russell, MD, Northwestern University Hospitals, Chicago

Gordon K. Sze, MD, Yale University School of Medicine, New Haven,

Connecticut

Michael S. Tenner, MD, New York Medical College, Valhalla

William T. C. Yuh, MD, University of Iowa Hospitals, Iowa City

Robert D. Zimmerman, Center, New York

MD, Cornell

University

Medical

that “¿. . . this

c@RSNA,

hold promise

was introduced.

This year, four

on applications

of MR angiogma

concentrated

phy in neumomadiology. A special focus session, chaired by Kieffer and Bradley and with presentations also by Edelman,

Hasso, and Turski,

1991

has been made to improve

DURING RSNA ‘¿90, the spotlight turned to magnetic resonance (MR) angiography, the subject command ing the greatest interest in neunonadiology. Mean while, new information and innovative ideas sprang forth from many other areas in the 26 scientific ses sions, 18 refresher courses, and 71 scientific exhibits devoted to topics of neuroradiologic interest. In addi tion, a special focus session on MR angiography of the

successful.

Cerebrovascular Disease The theme of this year's meeting, “¿UncommonVi sion,― would

generated is being

however.

certainly

apply

to the beautiful

images

at the premier sites where MR angiography developed;

such quality

is not widespread,

It is also quite evident the technique

has

before it rivals conventional

cerebral angiography

method

imaging

of providing

the quality

quality

information.

Yet, it is amazing how quickly MR angiogmaphy is evolving. In these notes only 2 short years ago, we 902 •¿ Radiology

as a

of MR angiog

the method. This year, phase-contrast MR angiogma phy emerged as a particularly exciting and flexible ap

proach, despite the fact that it is time-consuming. In this section, we review the content of a number of this year's MR angiogmaphy presentations but in dude as well other techniques being utilized in the evaluation of cemebmovascular disease. Extracranial carotid and vertebral occlusive disease.— Edelman and co-workers (1 ) performed a prospective

blinded comparison of time-of-flight MR angiography and conventional angiognaphy in depicting patholog ic conditions involving the extnacnanial carotid arter ies. They found that “¿brightblood― gradient-echo MR angiography exaggerated the severity of carotid le sions in 13 of 33 instances, mostly in severe patholog ic cases. On the other hand, “¿black blood― projection

angiognams in their hands enabled more precise de lineation of stenoses and ulcerations; initially these were fabricated

from thin-section

spin-echo

sequences (performed with flow pnesatunation) in volving a minimum-intensity projection algorithm. The authors recently switched to a faster “¿black blood―technique employing a gradient-echo se quence with a modified preexcitation pulse. The me images

have been encouraging,

(2) developed

although

post

with “¿bright a method

to im

prove the quality and resolution of carotid bifurcation MR angiography images. They obtained a three-di mensional (3D) time-of-flight sequence and then per formed two-dimensional (2D) multiplanar meconstruc tions from the 3D data set. Maximum-intensity

projection

was performed

multiplanam

next on a limited number of

reconstruction

sections.

Half Fourier

transform was also used to obtain better images. This multiplanam reconstruction-maximum intensity pro jection method required less postpnocessing time than that for the full 3D rotating format and provided sharper images. Superimposed vessels and high-sig nal fat could also be eliminated, since only a few sec tions were displayed.

Blatter et al (5) described their experience to date with multiple overlapping thin-slab 3D acquisition (MOTSA)

many inherent problems that need to be circumvent ed. With the obvious and highly important exception of risk, MR angiogmaphy clearly has a long way to go

a state

maphy studies. There has been much greaten interest in determining the clinical application and value of

Smith and colleagues

brain was particularly

provided

of-the-art synopsis. During the past year, a great effort

processing is more difficult compared blood―studies.

1991; 178:902-906

non

tool.―

spatial presaturation

suiting Radiology

may indeed

At RSNA ‘¿89 there were numerous presentations dealing with time-of-flight techniques and the use of

images

Index terms: Angiography, comparative studies, 10.1214, 10.124. Brain, MR studies, 10.1214 •¿ Brain neoplasms, diagnosis, 10.3 •¿ Cere bral blood vessels, MR studies, 17.1214 •¿ Radiological Society of North America, 76th scientific assembly and annual meeting. Spine, MR studies, 30.1214

at RSNA ‘¿88 deal as a useful

sessions

Charles R. Fitz, MD, Children's Hospital National

presentation

technique

invasive screening

Hervey D. Segall, MD, University of Southern California School of Medicine, Los Angeles

Medical Center,

clinical

ing with the subject and commented

in studying

neck

combines the advantages

arteries.

This

of 2D (multiple

technique

individual

sections) and 3D (volume) acquisitions for time-of flight MR angiogmaphy. Good detail of vessels was

produced artifacts

despite disturbing traversing

the images

linear “¿venetian-blind― at the slab interfaces.

The authors were able to minimize

these artifacts by

adjusting

the flip angle,

the z-fmaction,

increasing

and

March 1991

RSNA ‘¿90 Meeting combining

the overlapping

section

feasible.

at the brightest

pixel. Imaging time was approximately

has been unreliable

in identi

fying small carotid ulcerations. However, seven of 10 ulcerations seen with conventional angiognaphy were demonstrated with MOTSA. Thus fan, no high-grade stenoses have been interpreted with MOTSA as total occlusions. In such cases, the use of the 15-mm-thick 3D slabs has improved appreciation at MR imaging of the “¿stringsign― confirmed with conventional angi ognaphy.

In a study of cervicocephalic

arterial dissections,

Rowley et al (932) found that the lesions were poorly seen on gradient-echo images in five instances but

could be readily identified on spin-echo Ti weighted images. One angiographically proved dissection was missed

with

performed

MR imaging

sufficiently

because

imaging

with the usual 3D time-of-flight

MR angiogmams, these images showed decreased

13-16 mm

utes. Eighty-six carotid vessels studied with cut-film conventional angiognaphy were correlated with

MOTSA. The technique

Compared

Notes

was not

low in the neck.

Cerebral infarction. —¿Several authors reported MR imaging findings in early cerebral infarction. Investi gatoms at the University of Iowa (exhibits 249, 250)

ing much less degraded

noted that brain swelling may be appreciated on Ti weighted images as early as 2 hours before signal

sig

nal-to-noise ratio, but there was good contrast conspi cuity of the vessels in the region. Blatter and colleagues (5) have applied the MOTSA technique to the study of the cerebral vasculature. Their series included 14 aneurysms found with con ventional angiogmaphy that correlated in size (within 1 mm) with the findings at time-of-flight MR angiog raphy. However, MR angiography certainly cannot be relied on to detect all small aneurysms, particularly in patients who are less than fully cooperative (exhibit 230). The reliability of MR angiogmaphy in detecting vasospasm has not been adequately assessed, and many other details await evaluation in the clinical set ting (5). Aneurysms with slow flow will likely be missed with time-of-flight MR angiography, but Turski et al showed that low-velocity-encoded phase contrast MR angiognaphy has great promise in such cases (1166). Phase-contrast techniques also seem to be preferable for aneurysms larger than 1.5 cm (1165). Phase-contrast studies also have the advantage of be

by the presence of surgical

ty-one patients were studied with gadopentetate di meglummne within the first 24 hours. Enhancement of

clips than time-of-flight studies do (1165). Sevick and coworkers (1027) reported on preliminary experience with time-of-flight MR angiography in the evaluation of intracranial aneurysms treated by means of endo vascular balloon occlusion. Angiographic correlation was obtained; however, the usefulness of 3D time-of flight MR angiography as an independent technique

individual

was diminished

changes are seen on T2-weighted early finding was lack of arterial

images. Another flow void on the in

volved side in patients with large infanctions. Twen vessels supplying

observed (exhibit Elster and Moody

the infarcted area were

249). This finding was also noted (928) in 77% of patients studied

from days 1 to 3. Dumal enhancement infarct further

by

adjacent to the

was seen at 2-6 days (928). Elsten and Moody observed pamenchymal enhancement with ga

dopentetate

dimeglumine

ing the second

in all patients studied dur

week.

Interest in the use of MR angiography ation of intracranial

arterial

occlusions

in the evalu has been limit

ed to date. Tumski, however, showed some excellent examples in which ventebrobasilam disease was docu mented

with phase-contrast

studies

employing

multi

pie velocity encodings (special focus session). Smaller branch occlusions can also be shown and collateral flow patterns can be depicted with phase-contrast di nectional flow images. This year there was an increased

interest

evaluation

in cemebrovasculam

occlusive

of blood flow dynamics disease

and infarction.

in the

Bolus injections

of

gadopentetate dimeglumine followed by fast, sequen tial gradient-echo or echo-planar imaging, or both, were employed in studies done by a number of inves tigatons

(193, 195, 1169). However,

these methods

the application

of

in the clinical setting has not been

great as yet. Aneurysms.—Many workers continue giography as a screening and follow-up

to test MR an technique for

evaluating intracranial aneurysms. Pertinent techni cal refinements are being developed rapidly (5, 1025, 1165, 1175; special focus session; exhibit 121). For ex ample, Chew and Tsunuda (1025) have obtained high resolution images in the region of the circle of Willis in volunteers by means of an experimental high-gra dient-strength local coil incorporated into the head

coil of a i.5-T imagem. A full 512 X 512 points were ac quimed and in-plane resolution of 0.5 X 0.5 mm was Volume 178 •¿ Number 3

by some of the limitations

of the

method. For example, slow flow may pose a problem in such assessments. Also, subacute thrombus on the maximum-intensity projection images can be a source of confusion, but Ti-weighted images will make the distinction. Vascular malformations.—The detailed study of ante niovenous malformations (AVMs) continues to pose a difficult challenge for MR techniques. Blatter and as sociates (5) observed that high-quality time-of-flight MR angiography

did not adequately

eight of 1 1 intracranial

characterize

AVMs although

all 1 1 could be

detected. Both Tumski et al (1 166; special focus session) and Huston et al (1165) showed the advantages of phase-contrast MR angiognaphy in studying these le sions. Variable velocity encoding enables arterial and venous components of AVMs to be selectively dis played. Huston's group noted that, although 3D time of-flight MR angiography showed the feeding arteries and nidus of medium- and high-flow AVMs, the tech nique was deficient in demonstrating the nidus of slow-flow AVMs. On the other hand, slow-velocity encoded 3D phase contrast nicely facilitated visualiza tion of the nidus and draining veins of AVMs. Unfor tunately, phase-contrast MR angiography is time consuming at present (exhibit 121); one exhibited technique requires 33 minutes (exhibit 230).

Bowen and collaborators

(8) studied cerebrovasculam

malformations

with time-of-flight

and attempted

to determine

such studies.

MR angiography

optimal parameters

The use of gadolinium

for

was not advocat

ed for evaluation of uncomplicated AVMs. However, the authors found that gadolinium in conjunction with arterial presatumation enabled better imaging of venous components to depicting venous

and, thus, was particularly suited angiomas. Thinner sections also

proved to be of value. Hemorrhagic

AVMs were bet Radiology . 903

ter visualized

with subtraction

techniques.

Venous

presaturation contributed to imaging of carotid-cay emnous fistula. Tunski (special focus session) pointed out the virtues of phase-contrast MR angiogmaphy in imaging arteniovenous fistulas.

The quest for accurate noninvasive

imaging in fol

low-up of treated vascular lesions continues. Peters and colleagues (326; exhibit 266) correlated follow-up

conventional

angiogmaphy studies with MR imaging

in evaluation

of AVMs after linear

surgery. Multiplanar

accelerator

gradient-echo

Neoplasms.—The

imaging was per

angiognaphy was also noted

on the gradient-echo studies. On the other hand, in 42 instances in which conventional angiognaphy studies depicted residual transnidus flow, persistent flow was found on parallel gradient-echo studies. Venous thrombosis.—Boyko and colleagues (934)

evaluated quences

the use of flow-sensitive in evaluating

for dural

MR pulse se

sinus patency

or oc

clusion. Flow-sensitive MR pulse sequences included 2D phase-contrast MR angiognaphy, 2D time-of-flight MR angiogmaphy with 3D projection reconstruction, and a promising phase-sensitive sequence named ye locity imaging and gradient-recall echo (VIGRE). VIGRE is performed in a cross-sectional manner. Sec tions perpendicular to the plane of flow will provide

the best directional

imaging information.

Flow into or

away from the imaging plane will have either a low intensity on high-intensity signal on the subtraction

images, while stationary tissue will appear gray. Lack of flow was particularly easy to appreciate with the phase images, although flow abnormalities were noted with the other sequences in this series when spin-echo MR imaging showed dumal sinus clot. When there is difficulty with standard MR techniques in determining whether a high-intensity signal signi fies thrombus

or slow flow, phase

be useful. Unfortunately, relation

imaging

obtaining

has been difficult.

appears

to

angiogmaphic cor

The various

flow-sensitive

MR pulse sequences showed flow in every instance in control patients in whom venous sinus patency was demonstrated

at conventional

flow void at spin-echo Interventional

angiognaphy

or by a

MR imaging.

(38) performed supenselective catheterization of an am tenial pedicle feeding cerebral AVMs. A second cathe ten with an inflatable microballoon was placed proxi mally. It was used to produce a total flow arrest while acrylate was injected. This allows greater confidence

that liquid embolic agent will not occlude the drain ing veins with possible catastrophic results. Because technique

would

have added

risk, it

will probably not be used routinely; however, it de serves continued evaluation. Dowd and coworkers (35) performed embolization with particulate materials in i5 AVMs supplied by the anterior chomoidal artery. This embolization can be useful, but it is dangerous because it is difficult to catheterize the anterior chomoidal artery and because the vessel

supplies

the internal

capsule.

In vitro work by Laurent et al (39) revealed that chemical incompatibilities between latex balloons and polyhydroxyethylmethyl-methacrylate

can result

surface cracks and fissures, eventual tion, and undesirable 904 . Radiology

clinical

results.

balloon defla

in

placed

within

the

use of gadolinium-enhanced

MR

imaging in the evaluation of intracranial neoplasms continues to be actively studied. Hintz and Forbes (ex hibit 268) compared

this relatively

new method

metro

spectively with computed tomography (CT) employ ing iodinated contrast material. They sought to clarify and test certain existing assumptions. Gadopentetate dimeglumine was proved to be the superior contrast agent. In iO% of cases, lesions that were enhanced at MR imaging were not enhanced at CT. In 30% of cases, a greater amount of enhanced tissue was appre ciated at MR imaging, whereas a greater amount of abnormal contrast enhanced tissue was never detected at CT; CT-related artifacts were an added hindrance. The authors confirmed that the diagnostic criteria for contrast-enhanced CT are generally valid for contrast enhanced MR imaging. Yuh et al (432) imaged patients with intracranial tu mors by using

conventional

concentrations

as well as

one-half, double, and triple doses of Gd-HP-DO3A (Pmohance; Squibb, Princeton, NJ). They compared

le

sion enhancement

in

in the same subject

with studies

which a standard 0.1 mmol/kg concentration of gado pentetate dimeglumine was administered. Despite the limited number of cases, their work strongly suggest ed a relationship between dosage and lesion detect ability

and delineation.

A double-dose

shown to be capable of depicting Russell

et al (exhibit

study

was

many more lesions.

217) proposed

a reshuffling

of

imaging sequences when screening for cerebral me tastases. They and others have noted that metastases become more intensely enhanced and conspicuous with time after infusion of gadolinium. They start the MR examination with noncontrast Ti-weighted imag ing. Then gadolinium is injected. A time delay is built in by next performing

neuroradiology. —¿Chin and colleagues

this complicated

Once the coil had been optimally

aneurysm, it could be detached by activation of the la sen. Although the device seems complicated, it has been workable in an experimental setting. Other Brain and Skull Conditions

radio

formed with presatunation pulses and with and with out flow compensation. Completed thrombosis found

by means of conventional

Gememia et al (1174; exhibit 228) introduced the novel concept of affixing a detachable coil (for place ment within an aneurysm) at the tip of a laser probe.

long TR, double-echo

imaging.

Only then are postcontrast Ti-weighted images ob tamed. Several papers dealt with newer methods of using gadopentetate dimeglumine in the evaluation of pitu itary adenomas (556) and other sellar region tumors (555, 557). Davis et al (556) found that a half dose pro

vided as much information as a standard dose as well as reduced costs in studying suspected pituitary ade nomas. Tissue contrast discrimination was thus im proved, and overly intense contrast opacification was avoided. Delayed images offered no significant ad vantage. Costs were reduced with half-dose studies. Konogi et al (555) and Takahashi and associates (557) performed dynamic MR imaging to heighten the distinction between sellam region lesions and normal contrast-enhanced structures. A standard gadolinium bolus was followed by 6—8serial spin-echo images ob tamed every 30 seconds. The authors found the tech nique useful in distinguishing tumor tissue from adja cent cavernous sinus. The technique also improved detection of cranial nerves. In addition, it displayed a normal pad of gradually enhanced connective tissue March 1991

RSNA ‘¿90 Meeting between the gland and the medial wall of the sinus that has not been appreciated on conventional stud ies. It is interesting that the posterior pituitary gland is enhanced before the anterior lobe on dynamic stud ies; this is apparently related to the more direct sup ply to the posterior gland from the inferior hypophy seal artery. Le Bihan et al (i93) observed that contrast agents in conjunction with neal-time echo-planar imaging con relate well with intravoxel incoherent motion echo planar imaging studies of brain tumor perfusion and have applications in separating cystic and solid areas and in tumor grading. Although studies involving contrast material have been more successful, intra voxel incoherent motion echo-planar imaging pro vides diffusion data; repeated measurements can also be made because contrast material is not used. Gray et al (659) presented 10 cases of primary cere bral neoplasm that mimicked infarct (they were wedge-shaped, cortically based, and in a vascular dis tmibution). All but one was enhanced with gadolini um. The authors observed that findings favoring a neoplasm include a preserved rim of cortex overlying the tumor, heterogeneous signal intensity, less edema than would be expected with an infarct, and a sharp medial margin between the tumor and white matter. Differentiation may become clearer on follow-up MR images. In such instances, a subtle mass effect that persists or grows is an important feature suggesting neoplasm, which should be sought. In attempting to assess brain tumor metabolism, several authors tried to compare results from H-i spectroscopy studies with information from fluorine 18 fluorodeoxyglucose (FDG) positron emission to mogmaphy. Although Heindel et al (660) and Frank and coinvestigatoms (661) were able to identify lactate signals (they detected elevated levels of the metabo lite more frequently in hypemmetabolic lesions), it be came apparent that correlation with FDG positron emission tomography studies is difficult. It was not easy to include exactly the same area on both studies on to confirm whether one has done so. Furthermore, when clinical MR imagems were used for H-i spectros copy, the volumes that were used for collecting meta bolic information were too large to compare with FDG positron emission tomography. Volume averaging of metabolite signal in heterogeneous tumors can affect results and make correlations difficult. Frank et al (661)

concluded

that they

tinguish hypemmetabolic with MR spectroscopy.

could

not yet reliably

on hypometabolic

dis

tumors

Trauma.—Betz and Wiener (663) pointed out that aim seen within the glenoid fossa of the tempomomandib ulam joint (on routine head CT studies) may be a useful sign indicating the presence of temporal bone fmac tunes that are otherwise inconspicuous. This finding (noted in 20% of 1 14 patients) was the only sign in three patients. Mirvis and colleagues (665) made the point that a midline hemorrhage within the midbrain may be secondary to stretching and rupture of pemfo mating basilar artery branches resulting from sudden downward displacement of the brain stem (after fron tal impact). This can be mistakenly interpreted as blood within the interpeduncular fossa. These obsem vations were made by correlating experimental canine studies with actual patient CTs. Such cases had a bet ten clinical outcome than one might expect.

Volume 178 •¿ Number 3

Notes

Lexa et al (666) demonstrated increased hypointen sity, presumably iron deposition, in deep gray matter nuclei in patients with severe closed head trauma (compared with age-matched control subjects). This finding correlates with other ipsihatemal pamenchymal lesions and appears to imply a poor clinical outcome. Mark et al (559, exhibit 259) pointed out that the supe nor contrast resolution of MR imaging may permit demonstration of the subtleties of the following sellam region traumatic injuries: chiasmatic transection, teams of the floor of the third ventricle, third nerve avul sion, and pituitary stalk disruption.

Congenital and destructive brain lesions in children.— Fitz (686) pointed out that vemmian aphasia and hypo plasia are more recognizable with MR imaging. Such anomalies can be due to many causes; they are not necessarily related to Dandy-Walker complex on Jou bert syndrome. Seven cases (associated with neither Dandy-Walker non Joubert), three of them associated with encephaloceles, were described. In such cases, genetic counseling was in order. Dietmich et al (685) found that MR imaging enabled demonstration of cer ebmal white matter hypoplasia in four children. Dif fusely sparse white matter and dilated ventricles were seen. No abnormal myelin deposition, gliosis, on oth em evidence suggesting destructive change, were not ed. Excellent correlation between MR imaging and autopsy was obtained in one case. Theme was a history of maternal cocaine abuse in two cases. Using MR im aging, Baker (1170) demonstrated a distinct appear ance of the hippocampal formation and the temporal horns, similar to the fetal configuration, in patients with agenesis of the corpus callosum and agymia. Belfan and colleagues (2ii) found cystic changes of periventmicular leukomalacia observable on the first day of life in 11 neonates. Since such cysts do not ap pear until 6 days after insult at the earliest, this find ing provides further evidence that destructive brain processes can predate delivery. This has considerable medicolegal significance. Nelson et al (782) reported on MR findings in pa tients receiving treatment for galactosemia. Higher than-normal signal on T2-weighted images in peniph eral white matter is thought to be related to synthesis of an altered myehmn that is less hydrophobic than normal. However, routine MR studies have no practi cal value in following up patients with galactosemia. Connelly et al (784), Austin et al (785), and Gnodd and associates (210) studied, by means of proton MR spectnoscopy, children with metabolic and destructive brain disorders. It is interesting that N-acetyl-aspam tate is significantly increased in Canavan disease (210, 785), whereas a substantial decrease in N-acetyl-aspam tate was detected in other neurodegenemative diseases of childhood (as would be expected with extensive neumonal and axonal loss).

Other considerations.—Kanal et al (434) reviewed 4,260

bolus

intravenous

injections

of 0.1 mmoh

of ga

dopentetate dimeglumine pen kilogram and pointed out, despite the exquisite safety of the agent, that se veme and even life-threatening reactions have been as sociated with its use. One case of a true anaphylactic reaction to the drug was added to the few incidents that have already been recorded. The data suggest that bolus injections are not associated with an in creased incidence of significant adverse reactions.

A study by Augenstein

and Sze (439) showed that Radiology . 905

contrast enhancement

was not seen as well on 3D

Fourier transform radiofrequency-spoiled gradient echo images when compared with 2D spin-echo stud ies. Zimmerman and Gusnand (200) reviewed the ad vantages of continuous-rotation CT in obtaining rapid examinations in children. Spinal scanning is obtained

because the table moves during rotational Good studies are obtained, and radiation dation are held to a minimum. Dynamic

imaging. dose and se scanning af

ten a bolus injection of contrast material can be useful in demonstrating

absence

of vessel enhancement

in

brain death studies. A data set can also be obtained for the creation of 3D craniofacial reconstruction images. Schoennem et al (329) showed in patient studies that T2*@weighted imaging was associated with a success mate of 97% in detecting 141 CT-proved pathologic cer ebral calcifications. They showed in phantom studies that signal reduction and size of calcifications appear greatest when they contain iron components. Menon et al (871) observed that abnormal findings can be noted at proton spectroscopy in areas of the

brain that appear normal at MR imaging in patients with the acquired immunodeficiency syndrome (AIDS). The findings are most likely related to low levels of N-acetyl-aspartate resulting from neumonal loss as a consequence of AIDS encephalopathy. Moonen and coworkers (199) demonstrated in vol

unteers and with phantoms that effective, short-echo time, 3D proton spectmoscopic imaging with water suppression is technically and clinically feasible with a standard

clinical

instrument.

Several papers illustrated ways in which a neuroma diologist can help neumosurgeons in planning and performing their surgery. Boyko and colleagues (1030) obtained

MR angiograms

of the cortical

veins

fants aged less than 2 years, contrast enhancement of the bone marrow is marked; normal marrow contrast enhancement continues in all patients aged less than 7 years (186). However, gadolinium is by no means me qummedroutinely in evaluating the child's spine. Trauma.—Categonical notions that the acute post traumatic central cord syndrome results from central hematomyelia were proved incorrect by Quencen and

associates (190), who performed

a thorough

clinical,

MR imaging, and pathologic study in 10 patients. In no instance were blood products found, either at MR

imaging or in pathologic tensity

abnormalities

weighted

specimens.

High-signal-in

were seen only on T2- and T2*@

images; the findings

in the lateral white col

umns correlated with edema and varying degrees of myelmn breakdown and axonal loss. Davis et al (i89) demonstrated the ability of MR im aging to show anterior longitudinal ligamentous dis

ruptions, disk injuries, and subtle fractures of the an tenon vertebral end plate in patients with cervical hyperextension injuries. Disk disease.—Delauche-Cavalier et al (879) reported on CT studies in patients with herniated nucleus pul posus treated conservatively. In a subset of 21 patients who did not undergo surgery, resolution of symptoms

was excellent in five patients and good in 16. Despite clinical relief, seven disks (33%) were unchanged; in 50% of cases there was a significant decrease in size and the hemniation disappeared in some instances.

Obvious decrease in size is more frequent

in large

hemniations than in small ones. Atlas et al (881) performed high-resolution 3D Fou mien transform gradient-echo studies (using contigu ous axial 1.5-mm sections) in a series of patients, eval uating for herniated disk or neuroforaminal stenosis in the cervical spine. In a thorough evaluation they

and superimposed sections thus derived on conven tional spin-echo images. Having both surface venous

found no clinical benefit from reformatting

landmarks and intmaoperative ultrasound is helpful at surgery. Tan et al (787) demonstrated an interactive steneotaxic imaging device that displays cross-section al brain images or 3D views of gyral anatomy and can be used to ensure more accurate placement of craniot

hand, Ross et al (880) recommend a 3D MP RAGE se quence with meconstructions for the evaluation of cer

ies; the axial studies

alone sufficed.

such stud

On the other

vical spine degenerative disease. Their standard pro tocol also includes the use of gadolinium. However,

the extent to which gadolinium

contributes

to the

omy incisions and electroencephalographic elec trodes. Neumosurgeons are currently displaying con sidemable interest in such methods, since it is obviously of great importance for them to have accu

study was not addressed

mate spatial

Rosenbaum et al (883) performed MR diskography on cadavers with diluted gadolinium, and then sectioned

localization

available

at surgery.

Although

in detail.

diskography

has seldom been used by

North American neunomadiologists, the technique is ideal for demonstrating tears in the annulus fibrosus.

Spine

the lumbar

Spine development. —¿Anelegant cryomicrotome-MR study of the developing spine was performed by Yu and colleagues (568). Using clinical material, Sze (186)

images thus obtained provided insights regarding pathologic changes in degenerative disk disease that

observed

on non-contrast-enhanced

short TR MR im

ages that the ovoid vertebral bodies are the structures of lowest intensity in the infant's spine. In this age group, the hypenmntense cartilage is as thick as the vertebral body. Within it (if it can be seen) is the slightly hypomntense nucleus pulposus. After an in fant is 4 months old, the vertebral bodies and cartilage are isointense. The nucleus pulposus is hypomntense to both (i86). By 8-10 months, the relative signal in tensities have reversed; the vertebral body is hypenin

spine

with a cryomicnotome.

The excellent

were helpful in the interpretation of standard MR im ages. They were much more informative than compa

rable CT diskography

studies.

tense relative to the cartilage (i86). Sze (186) also noted that, after injection tetate dimeglumine, contrast enhancement tilage is striking in infants aged less than

906 •¿ Radiology

of gadopen of the can 1 year. In in

March 1991

RSNA ‘¿90 Meeting phantom

Magnetic Resonance Richard L. Ehman, MD, Mayo Clinic, Rochester, Minnesota R. Nick Bryan, MD, PhD, The Johns Hopkins Hospital, Baltimore

John V. Crues, MD, SB. Cottage Hospital, Santa Barbara, California

Hedvig Hricak, MD, University of California Medical Herbert Y. Kressel, MD, Hospital of the University of Pennsylvania,

PhD, Hospital

of the University

of

Pennsylvania, Philadelphia Donald G. Mitchell, MD, Thomas Jefferson Hospital, Philadelphia

Michael E. Moseley, PhD, University of California Medical School, San Francisco

and

have made a leap toward clinical utility.

Two general

categories

of techniques

these studies: those involving ents and those involving

are used in

strong external gradi

tracer materials.

Both of

these approaches benefit from new high-speed imag ing capabilities provided by echo-planar and snapshot perfusion

dephasing

continues

methods

for

(193, 741), but the

tracer methods had greater prominence at this meet ing. Rapid imaging of the effect of a first-pass contrast agent bolus was shown to provide qualitative and per haps semiquantitative information about regional cer ebral perfusion in animal models of early ischemia (i94, ii69), as well as in humans (i93, i95). These

Jeffrey R. Ross, MD, Cleveland Clinic, Cleveland

studies employed gradient-echo or echo-planar se quences for high-speed imaging and gadopentetate dimeglumine, Dy-DTPA, or iron oxide particles as T2*@shontening contrast agents. Photostimulation was also shown to cause observable changes in dynamic

Index terms:

MR tracer studies

Stephen J. Riederer, PhD, Mayo Clinic, Rochester, Minnesota

Angiography, comparative studies . Angiography,

technology •¿ Magnetic resonance (MR), contrast enhancement. Magnetic resonance (MR), diffusion study . Magnetic resonance

(MR), perfusion study •¿ Magnetic resonance (MR), spectroscopy. Magnetic resonance (MR), technology •¿ Radiological Society of North America, 76th scientific assembly and annual meeting

Radiology 1991; 178:907-910 @

perfusion

measuring

Philadelphia

E. Lenkinski,

effective in captum

ing signal from severe stenoses (MR categorical course). Perfusion and diffusion.—MR studies of diffusion

gradient-echo methods. Research in the gradient

School, San Francisco

Robert

studies were particularly

Notes

RSNA, 1991

the possibility

with MR imaging, level. While radiology

Neurologic

ing techniques

Volume 178 •¿ Number 3

SC202), suggesting

for MR imaging similar tomography. The goal of of tissue perfusion

awaits the development of methods for obtaining a me liable linear measure of dynamic tracer concentration

reflecting

Imaging

course

to those of positron emission true quantitative measurement

MAGNETIC resonance (MR) imaging was the primary subject or was specifically referenced in more than 600 of the i,46i scientific presentations at RSNA ‘¿90. The modality continues to demonstrate depth and versatility in that the pace of development, introduc tion, and clinical evaluation of new applications show no sign of abating.

MR angiography.—Investigation of MR angiography continues to be active, with at least 29 papers in the neurologic area alone. Many technical approaches have been proposed, and theme is as yet no clear con sensus on the best method for each neunologic appli cation. In the evaluation of the carotid bifurcation region, the combination of time-of-flight MR angiog naphy and duplex ultrasound shows excellent comrela tion with conventional angiography (6, 7) suggesting that this may represent the most effective noninva sive screening examination and a potential route away from conventional angiogmaphy. Encouraging results were also reported for intracra nial vascular imaging applications. A multiple over lapping thin-slab acquisition technique demonstrated, in a prospective study, 100% detection of intracranial aneurysms and arteriovenous malformations (AVMs) (but only partial characterization of the AVMs) (5). A time-of-flight technique was found useful in identifi cation of carotid-cavernous fistulas (8). Methods of phase-contrast MR angiography have advantages in the evaluation of intracranial aneurysms and arterio venous malformations (i i65). Specialized madio-fre quency head coil and local gradient coil assemblies permit shorter echo times, which in preliminary

(refresher

of capabilities

especially modalities

at the arterial

input

have produced

images

cerebral blood volume or perfusion

many years, no other

noninvasive

technique

used to assess regional water proton diffusion. sion-weighted

images

better than conventional

depict

early cerebral

T2-weighted

for can be

Diffu

ischemia

images (i98,

930). The phenomenon of proton diffusional anisotro py in white matter of the central nervous system con tinues to be explored (196, 197). Most diffusion imag

involve echo-planar

methods;

however, diffusion imaging resistant to motion arti fact may also be performed with snapshot gradient echo techniques (964). Progress in clinical neurologic MR imaging.—Mone than

i65 abstracts dealt with neurologic MR imaging in some manner, and the understanding of the indica tions, mole, and interpretation of studies continues expand in parallel with the technical development

to of

the field. Spinal imaging serves as an example of the trends

in the entire

field of neurologic

the following summary. The theory of central hematomyelia, plains

the appearance

MR imaging

in

which ex

of acute posttmaumatic

central

cord syndrome, appears incorrect in that myelmn loss and tissue edema are found without hemorrhage, sim ilam to the findings in brain shear injuries (i90). In trauma to the brachial plexus, proof of medullary cen vical radicular

avulsion

raphy, with computed

necessitates

tomographic

cervical

myelog

(CT) myelogma

phy and MR imaging useful to define traumatic meningoceles (191). In extension injuries of the cervi

cal spine, MR imaging can depict anterior

longitudi

nal ligament injuries, occult vertebral body fractures, cord injury, and posttraumatic hemniations (189).

Screening

the entire spine with enhanced

Ti Radiology •¿ 907

weighted

images is recommended

in patients with

neurofibromatosis type 2 because of the striking pro pensity for intradunal tumors to form (324). Three-di mensional Fourier transform (3DFT) imaging appears to be a technique of choice for evaluation of cervical extradural degenerative disease in that a single con

trast-enhanced

Ti -weighted

acquisition

can provide

sensitivity for extradural disease that is equivalent to a standard set of multiple two-dimensional sequences (880). Reformatting of 3DFT image data was found not to be advantageous in evaluation of cervical degenera tive disease, compared with direct use of the unpro

cessed set of transaxial

images (881). The use of multi

ple, simultaneously active radio-frequency coils allows the entire spine to be imaged in one acquisi

tion, with improved image quality and markedly de creased total examination time (1220). A quickly ac quined slow-flow-sensitive MR sequence can be used to distinguish 95%-100% of spinal canal blocks from lesser degrees of stenosis (885). A camdiac-gated phase contrast method is useful in a wide variety of patho

logic conditions affecting cord motion (886). The utility of gadolinium-enhanced imaging of

tients with avascular necrosis reflect the distribution of vasculanized granulation tissue (100, 1314). MR examinations of the shoulders of healthy per sons often demonstrate areas of increased signal in tensity that could simulate the presence of a team in

the superaspinatus

tendon region of the rotator cuff,

especially on Ti-weighted, proton-density, and gradi ent-echo images (89, i245). Strongly T2-weighted im

ages may be more specific for detecting

rotator cuff

tears. The role of gadolinium-enhanced MR anthrog maphy of the shoulder joint has been explored, and its utility is probably limited to identification of inferior surface partial tears of the rotator cuff (90, 1246).

Shoulder imaging with a field of view of 24 cm and i92 views does not provide adequate resolution for me liable evaluation of the glenoid labrum (92). MR im aging is useful for detecting medial dislocation of the bicipital

tendon

(95).

Internal derangement of the tempomomandibular joint is apparent in 25% of asymptomatic persons stud ied with MR imaging (235). Specialized, high-nesolu tion imaging techniques improve depiction of the me nisci without

increasing

imaging

time (234). The joint

postdiskectomy patients in the immediate postopera tive period of questionable, since apparent protmu sions are often seen at the surgical site even in asymp

morphology observed in postoperative examinations does not correlate with symptoms of patients (239). Kinematic imaging of the tempomomandibulam joint

tomatic patients and most of these space-occupying features are resolved in MR images obtained 6—9

may be helpful in the evaluation of splint therapy (240). High-resolution 2DFT and 3DFT techniques for im

months

later (882). A lively

cons of diskognaphy

debate

was stimulated

on the pros and

by paper 883, in

which MR diskogmaphy was used to define more accu rately than CT diskography the intervertebral disk an

chitecture

of the complex 1243).

structure

Measurements

in a cadaveric model.

Body Imaging Musculoskeletal imaging—Multiple studies continue to document the effectiveness of MR imaging in eval uation of the knee. MR imaging is equal to competent arthroscopy in evaluation of the menisci (836, 837).

Patient came costs could be substantially reduced by wide use of MR imaging in preoperative screening of arthroscopy candidates (1248). Recognition that some meniscal tears may be asymptomatic and clinically in significant is increasing. Cine on dynamic MR imag ing and other new techniques may provide a way to assess the functional significance of meniscal teams,

improve detection

aging and analysis appear to be useful for evaluation

of loose meniscal fragments,

and

assess disorders of the patellofemonal apparatus (1065, 1067). Certain characteristic lesions such as cantilagi nous avulsions, madiographically occult fractures, and

of the wrist (1075, 1076,

of T2* in trabecular

bone correlate

well with mineral density, as determined by means of QCT (247, 248). High-field-strength MR microscopy of bone specimens could provide an alternative to op

tical microscopy

for laboratory

assessment

of tnabecu

lam microstructure (609). MR imaging appears to provide unique information in assessing rheumatoid arthritis in the hand (580), hip (581), and knee (582, 819). A study also suggests

that the modality is more sensitive than radiography or CT in depicting the severity and extent of osteoan thnitis of the knee (583). In the assessment of musculoskeletal tumors, con tmast enhancement with gadopentetate dimeglummne does not permit more accurate assessment of tumor

boundaries than is achieved with conventional non enhanced spin-echo techniques (703, 715, 814). Con trast enhancement with gadolinium help in differentiation of recurrent

does appear to musculoskeletal

collateral ligament injuries are frequently associated with acute tears of the anterior cruciate ligament

sarcoma tissue from posttreatment

(1071, 1250). MR imaging is useful for evaluating an tenor cruciate ligament grafts (1070, 1251). Posttrau

does recognition temns of contrast

matic edema of bone marrow, a frequent

features (81 1) correlate in pant with the response of sarcomas to chemotherapy.

finding in

knee MR imaging, usually requires no specific thena py beyond that directed at any associated injuries

(919). Asymptomatic

prevalent

avasculam necrosis

(6%) in a population

in a prospective

MR imaging

is surprisingly

at risk, as determined study

(98). Dynamic,

contrast-enhanced fast MR imaging can demonstrate changes in perfusion of femoral head bone marrow in animal studies (97). This suggests that similar tech niques may be helpful for early detection of avasculam necrosis in humans. The patterns of contrast enhance ment with gadolinium in spin-echo imaging of pa 908 •¿ Radiology

Abdominal

changes (813), as

of tissue textural patterns (704). Pat enhancement (812) and other image

and pelvic imaging.—A striking

feature

of

the abdominal MR imaging presentations was the large number of abstracts of discussions of the use of contrast

enhancement,

imaging techniques.

especially

with dynamic

MR

Fast imaging of the abdomen

can

be achieved with echo-planar techniques (ili7), but many alternatives exist. These include gradient-echo (17, 23, 133) and magnetization-prepared gradient

echo (1186—1188)techniques

and fast spin-echo

ods (21, 591). For the liver, however,

Ti-weighted

gradient-echo

technique

meth

a multisection

outperformed March 1991

RSNA ‘¿90 Meeting both magnetization-prepared gradient-echo and breath-hold spin-echo techniques (i i88, 1439). Among

Ti-weighted

multisection

echo techniques

techniques because

fat-suppressed

gradient-echo

of ischemic

techniques,

and breath-averaged

outperformed

breath-hold

spin

spin-echo

(1439) for imaging the pancreas, probably

of higher

signal-to-noise

heart disease.

comes hypemintense

to dynamic, gadolinium-enhanced gradient-echo im ages (22). A novel approach involving MR arterial portogmaphy and gadopentetate dimeglumine was shown to be effective in improving liven-lesion con

myocandium

be

on delayed images after adminis

tration of gadopentetate dimeglumine on Gd-DOTA, presumably because of interstitial accumulation (76, 801-803). The infancts continue to become enhanced for approximately 6 weeks, after which there is no sig

nificant difference

ratio.

Dynamic imaging with gadolinium was found to be helpful for the evaluation of focal liver lesions in a number of studies (17, 21, 23, 769). One study showed that nonenhanced T2-weighted images were superior

Infarcted

Notes

and healthy

between enhancement

myocardium

of infarcted

(802). Superpamamagnetic

particles cause decreased signal in infarcted myocardi um (803). Blood pool agents such as polylysine gado pentetate dimeglumine enhance healthy myocardium but not infancts (80). Wall thinning and decreased mo tion also help identify dium (76). Dobutamine

ischemic or infarcted myocam or isopmotemenol may be used

trast (19). Two studies (18, 20) that were comparisons

to stress undempenfused myocardium, inducing wall motion abnormalities that may be detected by means

of MR imaging complementary

of MR imaging (79, 1155). Preliminary work shows promise in qualitative assessment of myocardial per

and CT arterial portognaphy showed roles for the two. Reports were pre

sented on the use of MR angiognaphy tive flow measurements

and quantita

in the evaluation

of the por

fusion with “¿first-pass― contrast enhancement studies involving gadopentetate dimeglumine on iron oxide

tal system (766—768)and renal arteries (1387). Fat

tracers

suppression sequences were found useful for MR im aging of the pancreas (1438, 1439), and a dynamic con

(77, 78, i36, 1153).

trast-enhanced

dalities for evaluating night ventricular Myocandial motion in three dimensions

technique

showed promise for evalua

tion of pancreas transplant function (403). A number of abstracts presented evidence of the usefulness of gadopentetate dimeglumine in detect

ing and characterizing aging

sequences

the prostate is facilitated and endorectal

by combinations

of

of external

coils and the use of fat suppression

quences (i39i—i393). An expandable

se

intravesicle

MR imaging

or echo-planar

may be more effective

sequences than other

mo

function (73). can now be

quantitatively studied by means of saturation tag methods (75) or phase-contrast techniques (467, 469,

renal masses with various im

(590, 591, 593, i388). MR imaging

and gradient-echo

coil

510). Other applications—Increased

attention

was paid to

the possible application of MR imaging to the evalua tion of lung parenchyma. Obstructive atelectasis has

thral trauma (936) and in evaluation of neoplastic dis ease affecting the female urethra (935). The utility of MR imaging in evaluating cervical carcinoma and

an appearance different from that of nonobstructive atelectasis in T2-weighted spin-echo images (318). MR imaging shows promise for assessing certain aspects of chronic infiltrative lung disease (1365). A prospec tive study demonstrated that observers were able to detect pulmonary pamenchymal metastases slightly

ovarian and endometnial plored (107, 940, 941).

better at MR imaging than at CT and considerably bet ten at MR imaging than at chest radiography (5i). Cur

was also demonstrated

for imaging

the bladder

(938). MR imaging is useful in the assessment

Cardiovascular

masses continues

imaging.—Vasculam

cluding MR angiogmaphy,

wall

of ure

to be ex

MR imaging,

allows detection

in

of lower

extremity arterial disease (687), clinical follow-up of patients who have undergone arterial bypass (347) or recanalization (348), and measurement of velocity in calf arteries (346), although such detection is already

possible with Doppler ultrasound. Color Doppler ul trasound was found more effective than MR imaging for evaluating lower extremity arteries, although MR imaging was more useful for the iliac arteries (344). For detection of venous thrombus, spin-echo and gra dient-echo techniques are complementary, with great en accuracy and confidence resulting when both are used (692). In patients with suspected acute dissection of the thoracic aorta, longitudinal wall thickening

may be an early sign of aortic dissection,

even if no

flow is depicted (689). This may represent intramural hematoma occurring before establishment of flow in the false lumen. Quantitative flow imaging techniques can be used to measure pulmonary arterial flow (3i4) and estimate coronary sinus flow (466). Central pulmonary artery

thromboemboli can be cleanly identified with a novel technique involving spatial modulation of magnetiza tion (315). A system

capable

of meal-time,

interactive

phase-contrast color flow imaging shows promise for rapid vascular mapping and quantitation (1105). There continues to be great interest in MR imaging Volume 178 •¿ Number 3

rent research

projects

involve

ical basis for the appearance MR images

exploration

of the phys

of lung parenchyma

in

(317, 504, 1363, 1364).

Technical Developments Spectroscopy.—Mome

than 40 papers

on various

as

pects of MR spectroscopy were presented in both din ical and technical sessions. A continued trend is the incorporation of spectroscopic techniques into MR imaging sequences. For example, six of the eight pa pers presented in a physics session dealing with imag ing contrast involved chemical shift selective imaging

(275-280). Technical

description

advances

in MR spectroscopy

include

a

of a doubly tuned bird-cage coil design

(i43i), double irradiation decoupling methods (374, 375, 760, 1431), wide line methods for studies of bone and bone cement (752, 753), automatic eddy-current correction (1429), and simultaneous multinuclear ac

quisition (376). Glycogen in muscle can be studied by means of C-13 MR spectroscopy (474). C-i3 can also be employed to investigate tumor metabolism (375). The cellular

density

of suspensions

can be determined

with Na-23 methods (963). The free magnesium con centration in the brain can be determined from an analysis of the resonance frequency of the /3-adeno sine tniphosphate peak in P-3i spectra (756). Theme is continued

interest

in employing

spatially

Radiology •¿ 909

localized

proton

velopment

spectroscopy

to investigate

es such as multiple

sclerosis

(378) and infection

the human immunodeficiency lations

brain

de

(209, 210, 784, 785), certain disease process

between

proton

(660, 661). Spin-echo

virus (871), and corre

spectroscopy

emission tomography

with

and positron

in patients with brain tumors schemes

for localized

proton

spectroscopy have superior characteristics compared with STEAM methods (1430). There is a continuation of the trend of acquiring data by means of chemical shift imaging methods and displaying the results as metabolite maps (199, 377). Clinical P-31 abstracts included abstracts addressing muscular disorders (473, 476), vascular diseases (478, 758), testicular

disease

(249), head and neck tumors

(1023), liver disease (754, 1190, 1191, 1432, 1433), and cardiac metabolism (755). Methods of chemical shift imaging for P-3i have progressed (757, 1431). MR contrast media.—Several

agents are on the horizon. oxide particles, of liver, spleen,

(740) because it appears to separate local gradient ef fects due to B0variations from intravoxel dephasing T2' effects.

new classes of contrast

Supenpanamagnetic

iron

Technical

Exhibits

Joel E. Gray, PhD, Mayo Clinic, Rochester, Minnesota Richard L. Morin, PhD, Mayo Clinic, Jacksonville, Florida Gary T. Barnes, PhD, University

of Alabama at

Birmingham, Birmingham Index terms: Images. display •¿ Images, processing •¿ Images, stor age and retrieval •¿ Radiological Society of North America, 76th sci entific assembly and annual meeting Radiology C RSNA,

1991; 178:910-911 1991

which shorten the T2 relaxation time and marrow, continue to appear effec

tive (1442), although toxicity remains an issue. Lipid coated particles accumulate at the periphery of ab scesses (1444). Smaller magnetic particles remain in the bloodstream longer, appear to have lower toxicity, and also label lymph nodes (i29-13i). These ultra

THE technical

exhibits

at RSNA ‘¿90, as over the past

several years, can best be described opposed

to revolutionary.

technologies of companies,

as evolutionary

A trend

toward

as

mergers

of

from several vendors, as well as mergers was apparent.

binogalactan, which targets them to hepatocyte necep tons, allowing anatomic as well as functional hepatocellular imaging (132, il2i, 1443). Mn-DPDP is

The major change noted this year was the addition of infoRAD in McCormick Place North, along with the scientific exhibits. infoRAD consisted of a demonstma tion area where meeting attendees could gain hands

also selectively

on experience

small “¿nanoparticles―can also be complexed

taken

up by hepatocytes,

to ama

as well as by

with computer-based

video disks. Twenty-two

demonstrate

their picture archiving

tion systems al programs,

(PACS), telenadiology, LANS, education and other electronic and computer-based

on Mn-DPDP-enhanced Ti-weighted more than twice that of conventional

liver and lesion

images were Ti- and T2-

weighted images (i44i). Several classes of intestinal contrast agents are be ing developed. While it is possible to increase the in tensity of bowel lumen, most efforts involve decreas

ing the intensity with barium (exhibits 951, 962), supempamamagnetic particles (1 i34, i435, i436; exhibit 949), perfluoroctylbmomide

(400, 40i), or clay suspen

sions (1434). Complex polymers appear to increase Ti and T2 relaxation enhancement of many of these agents, allowing reduced concentration (402). Technical developments

in imaging—Magnetization

transfer contrast MR imaging (also known as spin locking) can drastically alter tissue contrast depen dent on water proton—macmomoleculan interaction (960-96i).

This appears

to work at low and high

fields. Iterative methods can be used to reduce respiration induced artifact in 2DFT MR imaging with a transla tion-dilation model and monitor echoes (505). A “¿square spiral―ordering of phase-encoding views can be used to markedly reduce motion artifacts on im prove contrast in 3DFT imaging (506). Schemes for

segmented

and reordered

phase encoding

can also be

on-line literature

includ

1.5 T, contrast-to-noise

ratios between

ing video programs,

systems

the pancreas, increasing the signal intensity of both of these organs on Ti-weighted images (i437, 1441). At

vendors

searches, and

were also able to

and communica

systems. infoRAD was located in a spacious and quiet area, and remained

open until

noon on Friday,

allow

ing a last minute look at these newer technologies. Sony demonstrated, among many medically related products, high-definition television (HDTV) which is already available in Japan. (It will be at least 3—5years before HDTV will be available in the United States, due to a delay by the Federal Communications Com mission on a decision regarding the appropriate U.S. standard.) There always seemed to be a crowd watch ing the HDTV, with its high-quality stereo sound, showing symphony concerts, ballet, and piano con cents on a screen with a width approximately twice its height. The color quality and image detail were out standing—much more like watching a movie than present cable television programming. This technol ogy may find its way into diagnostic imaging, at least the image-recording

technology.

Unfortunately,

the

display format may not be well suited for today's medical imaging systems. However, pie images on a single video display from the wide-screen HDTV format.

displays of multi could benefit

In the past it has been almost impossible

to develop

the quality and speed of MR angiogmaphic techniques

a phantom that mimics any part of the human body. RMI showed a breast phantom that was produced

(ii6O, 1176) and cardiac dine MR techniques (471). A method involving ultrashort echo time and pro

from an actual mammogram. The patient mammo gram is digitized, and the digital data are used to

used with

rapid

gradient-echo

techniques

to improve

jection reconstruction can be used to image proton densities, T2*, T2', and B0 shifts in vivo and is of spe cial interest in assessing the lung (504) and joints 910 •¿ Radiology

operate

a computer-controlled

milling

machine.

A

phantom is then produced that has transmission char actenistics similar to those of the original breast. A March 1991

RSNA ‘¿ 90 Meeting mammognaphic image of this phantom, compared with the original mammogmam, cleanly demonstrated the potential for this technique. At least two x-ray film manufacturers introduced reduced cycle time photographic processing, allowing for more rapid access to radiographic images. This may be beneficial in trauma and special procedures areas, where quick access to a few images on more rap id processing of many films is advantageous. Also, Eastman Kodak introduced a new screen-film system for chest radiography. This system is based on an asymmetric screen-film system consisting of a very thin front screen and a thick near screen pained with a film with a high-contrast emulsion on the front and a

low-contrast suits

in more

emulsion density

on the rear of the film. This me and

contrast

in areas

of typically

low density—that is, mediastinum and retmocandiac and metmodiaphragmatic areas—with normal contrast and density in the lungs while increasing sharpness in the higher density regions. In the area of computed tomography (CT) new tech nologies centered on fast CT, economical CT, and workstation technologies. Several vendors demon strated systems that are capable of acquiring CT data in less than 1 second. In conjunction with these de vices, several vendors demonstrated as either prod ucts or works in progress the capability to perform spinal or helical scanning. With this technique CT transmission

data are acquired

tient couch is moved through This scan technique

continuously

as the pa

the gantry opening.

has substantial

implications

(particularly

in the chest

and abdomen).

Several vendors demonstrated an increase in product offerings ranging from economical models (capable of competing with madiogmaphic-fluomoscopic systems for space and finances) to sophisticated fast CT systems with diagnostic workstations. Many vendors demon strated enhancements of product offerings for post processing of image data for both three-dimensional as well as multifommatting meconstructions. In the area of PACS, workstation technology and network communications were highly featured among vendors. A large variety of workstation capa bihities were demonstrated ranging from the economi cal microcomputer-based systems to sophisticated, dedicated parallel-processing systems. Particularly for multimodality

settings,

a large number

exhibited packages.

MR spectroscopy Of interest

is the

hardware excellent

and

image

quality that is obtained with midfield systems—in many instances i.0-T image quality was competitive or superior to that with 1.5 T. The better midfield sys tems offer a cost-effective alternative to 1.5-T systems. Also important were the improved compact magnets that were exhibited—most notably the designs of Ox ford Instruments and Hitachi. Employing either ac tive on passive magnetic shielding, these designs were much more compact, in some instances do not utilize liquid nitrogen as a buffer cryogen, and limited the 5G field to within a few feet of the magnet. From a site planning point of view, they offer numerous advan tages and few, if any, disadvantages. The availability of actively shielded 1.5-T magnets is now fact rather than fiction—several installations were referenced. GE Medical

Systems

demonstrated

a variation

of an

old MR technique known as RARE. Eight to 16 phase encoding views are acquired in each repetition time as multiple echoes. This permits acquisition of high quality T2-weighted spin-echo images in a fraction of the time previously required; for example, 2562 multi section acquisition can be obtained in 32 seconds in stead of 8.5 minutes.

Abdominal-Gastrointestinal Radiology

in

the areas of volume imaging, three-dimensional imag ing, and the efficiency and economics of conventional CT imaging

equipment software

Notes

of offerings

Dennis M. Balfe, MD, Washington University, St Louis Judith Chezmar, MD, Emory University, Atlanta Robert E. Koehier, MD, University of Alabama in Birmingham, Birmingham Joel E. Lichtenstein, MD, University of Cincinnati, Cincinnati Rendon Nelson, MD, Emory University, Atlanta Index terms:

Gallbladder, interventional procedure, 762.1299.

Gastrointestinal tract, CT, 70.1211 •¿ Gastrointestinal tract, MR stud ies, 70.1214 •¿ Lithotripsy, 762.1299 •¿ Radiological Society of North America, 76th scientific assembhy and annual meeting

Radiology 1991; 178:911-913 C RSNA,

1991

THE first RSNA

meeting

of the new

decade

saw

the

was demonstrated for three-dimensional and cornela tive processing and display. Display technologies and formats continue to demonstrate somewhat wide van ation, with several different approaches among yen dons. Within an individual vendor line theme seemed to be an increased emphasis on communication among several modalities with a common display con sole. In general, these display consoles were most effi ciently utilized only with the vendor's equipment. An improvement in magnetic resonance (MR) im aging technology was evident, particularly with me gand to fast image quality. Also evident was that all

role of gastrointestinal radiology increase, with 203 papers presented at 20 scientific sessions, 65 designat ed exhibits, and a special focus session. As in past years, the trends established at the annual meeting me flected two major forces driving radiology: finding a niche for new technology and improvising solutions to new clinical problems. One of the major challenges today cleanly is to pro vide help for the hepatic surgeon: There were no few emthan 38 presentations in this category dealing with preoperative localization of hepatic neoplasms (18—20,

medium-

1443), imaging of posttmansplantation complications (24, 167, 168, 204, 42i, 422, i 189), and alternative ma diologic therapies (17, 155, 156, 205, 310, 416-418, 999,

and high-field-strength

MR imaging

equip

ment vendors exhibited MR angiogmaphy pulse se quences and software packages. Particularly impres sive was the clever contrast-transfer angiogmaphy technique developed by Instrumentanium for their low-field-strength system. Also, all vendors of 1.5-T Volume 178 •¿ Number 3

202,311,312,847,849—851, 854,ii93—ii96, 1440—

1000,1033).

Major liver resection for metastatic cancer is in creasing in popularity since improvement in patient Radiology •¿ 911

survival has been demonstrated; however, it is map pnopniate when tumor deposits are present in extrahe patic locations or within multiple liven segments. 5ev

and susceptibility to fragmentation based on radiolog ic features have met with only modest success. As a generalization, the best stone-free rates were obtained

enal papers compared the results of invasive and noninvasive preoperative imaging strategies; in all studies, routine dynamic computed tomography (CT), delayed CT, magnetic resonance (MR) imaging, on im munoscintigmaphy were inadequately sensitive to the presence of small intrahepatic tumor deposits. Al

with treatment

though

CT angiognaphy

or angioportognaphy

were

clearly superior intrahepatic techniques, both suffer from inadequate sensitivity to extrahepatic disease. One infrequently

addressed

problem

received

con

sidemable attention

at RSNA ‘¿90: the need to commu

nicate the complex al imaging studies

data contained on two-dimension in a way understandable to the

hepatic surgeon. patic images

Three-dimensional

(obtained

rendering

of he

with both MR imaging

and

CT) allows the surgeon to use observable morphologic landmarks to ascertain the position of the tumor and the major hepatic vessels. After liver transplantation, the major complications are rejection and vascular compromise. Reports from several series have confirmed that Doppler ultra sound (US) is a reliable means to diagnose vascular complications; angiography may be reserved for con firmation in doubtful cases. Other methods, such as

MR angiography

on subsecond

CT, were also shown

to be useful but are clearly less easily available than Doppler US. One paper (422) addressed the phenome

non of collateral steal, which may reduce hepatic blood flow in the absence of demonstrable vascular compromise. The diagnosis of rejection remains enig matic; two reports laid to rest the notion that a pen portal collar was at all specific for rejection. However, one interesting paper (204) showed that scintigmaphy can be used to reliably distinguish between rejection and cholestasis;

this bears further

Finally, radiology who are not surgical

testing.

provides some help for patients candidates.

Several

studies

me

ported hopeful results in patients with primary or metastatic hepatic malignancies treated in various ways: intraarterial Lipiodol (155, i56), intraoperative cryosurgery (i57, 416), percutaneous ethanol injection (4i7,

4i8),

YAG

laser

tion with degradable

hypenthemmia

starch

spheres (1033). Attempted

(i000)

(999),

or emboliza

or Y-90 micro

ablation with percutaneous

of single lucent stones less than 2 cm

in size with adjuvant

oral bile acid therapy.

It is inter

esting that theme is evidence that bile acids may de press gallbladder contractility (765), which suggests that lithotnipsy alone may be useful in patients with sufficient initial contractility (1305). The reproducibil ity of gallbladder contractility measurements remains

in question,

however.

It is clear that lithotnipsy offers moderate success in selected patients; the issue that was not addressed at

this meeting is the impact of lapamoscopic cholecystec tomy, which, at many institutions (or own included), has virtually

gallbladder

supplanted

all other

forms of therapy

of gallstones

in patients

for

stone disease.

For the management

who

are not operative candidates and for the treatment of intrahepatic biliary strictures, both benign and malig nant, theme were continuing advances in technique. Experience with the metallic self-expanding Wallstent (Medinvent,

Lausanne,

Switzerland)

has been largely

favorable. Of interest, two papers noted the deletemi ous effect of applying radiation therapy in patients with biliary drainage catheters: In one study (996), one-third

of patients

who underwent

cholangiocarcmnoma in vitro study

had infectious

of catheter

material

drainage

for

complications;

an

(306) determined

that both polyvinyl chloride and polyurethane cathe tens underwent severe degradation when exposed to radiation. One of the newest imaging methods, is finding a niche in the gastrointestinal

MR imaging, system, chief

ly in imaging the liver. Although hepatic enhance ment has been noted after the intravenous adminis tration

of gadopentetate

dimeglummne,

the imaging

technique used is critical in determining whether there will be an improvement in lesion-to-liver con trast. Fast imaging techniques such as rapid acquisi tion spin-echo

(21), gradient-echo

(17, 769), and Turbo

fast low-angle shot (i 186) have demonstrated im proved lesion conspicuity but have not consistently shown

superiority

over noncontrast

T2-weighted

se

quences at high magnetic field strengths. Gadopente tate dimeglummne is also useful for characterizing le sions (i7, 23, 769), especially cavernous hemangiomas

ethanol injection was less helpful in patients with metastatic disease than for those with small (