Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 06/19/15 from IP address 128.122.253.212. Copyright ARRS. For personal use only; all rights reserved
875
Meeting
. .
.
..
News
:.
Society
of Thoracic
Postgraduate Elizabeth
Radiology
Course,
May
and
Whalen1
techniques
in cardiopulmonary
radiology
(MR
Imaging
and CT of the Thorax, Cardiovascular Imaging, Chest Roentgenology-The Art, Chest Neoplasms, Immune Deficiency Infections, Pediatric Thoracic Radiology, and Diffuse Lung Disease) and two scientific sessions featured 33 presentations of original scientific investigations in thoracic imaging and intervention. Two annual highlights of the meeting were the Scanlon Memorial Research Symposium (a 2-hr discussion of digital radiography of the thorax) and the Benjamin Felson Annual Lecture, this year featuring Robert J. Ginsberg (Memorial Sloan-Kettering Institute, New York) speaking about the limitations of surgical resection for lung carcinoma. Speakers from seven different countries participated, and their levels of experience ranged from residents to experienced expert radiologists. Because of AJR space limitations, we cannot include coyerage of all the activities provided at this 5-day meeting. However, we have summarized the following: 1 0 of the presentations of original scientific research, six of the up-to-date
1
Meeting
1991
The ninth annual meeting and postgraduate course of the Society of Thoracic Radiology was held May i 3-i 7, i 99i , at the Four Seasons Hotel-Yorkville, Toronto, Ontario, Canada. The meeting consisted of five sections: a postgraduate course, scientific sessions, a research symposium, workshops, unknown cases of the day, and the annual Benjamin Felson Lecture. The postgraduate course included seven plenary sessions that provided detailed reviews of state-ofthe-art
Ninth Annual
Contributing
editor,
American
Journal
of Roentgenology,
Editor’s note.-”Meeting News” articles report the substantive, and accurate reviews of topics of current The articles will not undergo the peer review usually the series is to apprise AJR readers of topics of current AJR i57:875-88i,
October
i99i
0361 -803X/9i/i
reviews given in the postgraduate Felson Lecture.
Presentations
of Original
Scientific
plenary
sessions,
and the
Research
Most of the 33 short scientific presentations concerned thoracic CT or chest radiography. Our page limitations do not allow summaries of the others, which were on thoracic sonography, biopsy techniques, and urokinase treatment of empyema.
Conventional
CT of the
Thorax
J. R. Standen, R. J. Knudsen, K. Rehm, W. T. Kaltenborn, and D. E. Knudson (University of Arizona, Tucson) prospectively studied the assessment of emphysema with CT in 64 patients. Emphysema is abnormal, permanent enlargement of air spaces
distal
to the terminal
bronchioles,
with
destruc-
tion of the walls of the bronchioles but without fibrosis. Both smokers and nonsmokers were among the 64 subjects, pulmonary function test results were correlated with CT findings, and some patients were followed up for as long as 20 years. CT scans were obtained of 8-mm sections during both inspiration and expiration; CT measurements were used to arrive at a “pixel-index”: the percentage of all pixels with a CT density between -900 and -1 024 H. Several of the patients with normal lungs had a high inspiratory pixel index; the
Ste. 103, 2223 Avenida de Ia Playa, La Jolla, CA 92037.
highlights of important national radiology meetings. The intent is to provide Journal readers with succinct, interest, written in a readable fashion and published promptly after the meeting. required of AJR publications, nor will they offer a critique of the information provided. The sole purpose of concern in an interesting and timely fashion.
574-0875
© American
Roentgen
Ray Society
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 06/19/15 from IP address 128.122.253.212. Copyright ARRS. For personal use only; all rights reserved
876
MEETING
researchers labeled these cases as “disappearing emphysema” when the inspiratory densities were -900 to -1 024 H but the expiratory densities were normal. All of the patients with disappearing emphysema were asymptomatic and had normal diffusing capacity and spirometry, leading the researchers to think that this phenomenon might be related to an early stage of emphysema or a higher risk of emphysema; future studies will focus on careful follow-up of these patients and on determination of the limits of normal lung density and the effects of aging and asthma. If disappearing emphysema does prove to be an early form of the disease, these CT measurements will be an objective way to measure it, will enable quantification of the disease early in its cycle, may add to information about the natural history of emphysema, and may help indicate interventions (e.g., smoking cessation) that could prevent or delay the development of the disease. The CT assessment of broncholithiasis was the subject of a study by D. J. Conces, R. D. Tarver, and V. A. Vix (Indiana University).
An uncommon
disease,
broncholithiasis
often
pre-
sents a diagnostic challenge; it is characterized by peribronchial or endobronchial calcified lymph nodes. CT findings were reviewed in 15 patients with broncholithiasis (all patients lived in a region of endemic histoplasmosis). Ten of these patients had endobronchial lymph nodes, and five had peribronchial lymph nodes. Cough was the most common sign (1 3 patients). Other signs and symptoms included hemoptysis (six), chest pain (three), and sputum-producing cough (three). Chest radiographs
showed
calcified
lymph
nodes
in
1 1 patients,
atelectasis in nine, infiltrates in two, and peripheral calcified granulomatosis in four. Of the 1 4 bronchoscopies performed, only five showed broncholiths, seven showed bronchial distortion, and three showed bronchial blood; the bronchus was obscured in two cases. CT scans showed calcified lymph nodes in all i 5 patients. Changes due to bronchial obstruction were seen on the CT scans (atelectasis in 10, bronchiectasis in four, infiltrates in four, and air trapping in one). No softtissue masses were seen in any of the patients. In the 10 patients with endobronchial calcified lymph nodes, CT results indicated the location of six correctly, and in the five patients with peribronchial calcified lymph nodes, CT located four correctly (the errors in location were due to the effects of volume averaging). These researchers conclude that bronchoscopy is definitely necessary for the diagnosis of broncholithiasis and that the combination of bronchoscopic and CT results should be sufficient to suggest the diagnosis of broncholithiasis.
High-Resolution Pulmonary
CT fibrosis
in dyspneic
smokers
as evaluated
by
high-resolution CT(HRCT)was the focus of a study presented by Jeffrey A. Galvin for J. A. Galvin, P. J. Chang, D. S. Schwartz, M. Mori, R. A. Helmers, W. Stanford, and G. W. Hunninghake, of the University of Iowa, Iowa City. In 10 smokers with pulmonary fibrosis who were referred for evaluation of new or worsening dyspnea, chest radiography, pulmonary function tests, and HRCT were performed. Spirometry and lung volumes were often normal despite severe dyspnea; chest radiographs provided a reasonable assess-
NEWS
AJR:157,
October
1991
ment of fibrosis but underestimated the severity of emphysema (and agreement of interpretation of radiographic severity of emphysema was poor: kappa scores ranged from .i 4 to .38). Although HRCT resulted in reliable quantification of emphysema that showed a good correlation with pulmonary function measurements of airway obstruction, HRCT results did not quantify fibrosis as effectively. These researchers therefore tried to assess fibrosis severity by using an automated measurement of fractal dimension; this calculation process is simple to use and automate, results in a single quantitative measure, and has the features and advantages of statistical, structural, and spectral methods. The fractal dimension of a normal lung proved to be i .3, whereas the fractal dimension of a fibrotic lung was 1 .7; also, the fractal dimension directly correlated with lung volume, and, as the fractal dimension increased, flow rates increased. Considering the results of this preliminary study, the researchers concluded that smokers with both dyspnea and radiographic evidence of fibrosis may have pulmonary function results that do not reflect the severity of damage. However, HRCT reliably measures emphysema severity and, by use of fractal dimensions, can provide a useful representation of fibrosis. Jung-Gi Im discussed HRCT findings of fresh and healing lesions in pulmonary tuberculosis that were collected by J.-G. Im, J. H. Lee, V. S. Shim, J. M. Ahn, and M. C. Han, of Seoul National University, Seoul, Korea. The objective of the study was to use HRCT (1 5-mm collimation, 20-cm field of view) to describe pretreated lesions and then sequential changes with chemotherapy in 3i patients with newly diagnosed tuberculosis. The HRCT findings in patients before treatment were small (2-4 mm), centrilobular branching in 26 patients; larger (5-6 mm) fuzzy nodules in 2i ; lobular consolidations in 20; cavities in 1 8; thickened interlobular septa in i 4; and large branching lesions in five. Posttreatment followup was obtained in 2i of these patients; HRCT showed that (i ) the small centrilobular lesions disappeared and left lobular emphysema with a central dot and minimal distortion of the bronchovascular bundle, (2) lobular consolidations resolved from the periphery with more bronchovascular distortion and emphysema, (3) thickening of interlobular septa disappeared without residue, and (4) treatment caused some effects in cavities, including thinning of walls with minimum distortion and fibrotic bands with marked distortion. In these patients, HRCT showed disease at the lobular level and provided helpful information about ongoing healing activity. A patient who has conventional HRCT is exposed to 120140 mGy. To investigate whether a lower dose impairs image quality, C. V. Zwirewich, J. R. Mayo, and N. L. MUller, of Vancouver, Canada, compared 1 .5-mm-collimation, 2-sec images obtained in high-dose HRCT studies (200 mA [400 mAs]) with those obtained in low-dose HRCT studies (20 mA [40 mAs]). Without knowledge of HRCT technique, three observers evaluated the scans of 3i patients for demonstration of pulmonary anatomy (vessels, bronchi, secondary nodules), pathology (interstitial disease, air-space disease, and bronchiectasis), and the presence of linear stratification artifacts. The McNemar statistical test for significance was used to assess whether the quality of high-dose HRCT images was significantly better than that of the low-dose HRCT images.
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 06/19/15 from IP address 128.122.253.212. Copyright ARRS. For personal use only; all rights reserved
AJR:157,
October
1991
MEETING
In a large percentage of patients, the two techniques resulted in the same quality of visualization of vessels, segmental and lobar bronchi, secondary pulmonary nodules, reticulation, honeycomb cysts, and thickened interlobular septa. In three cases, high-dose images revealed ground-glass opacities or emphysema not seen on low-dose images, but the evidence for these was subtle even at 400 mAs. Although artifacts were more prominent on images acquired with the low-dose technique, the two techniques yielded images with equal visual quality in 97% of cases. Overall, low-dose HRCT seems to have potential usefulness, especially in young patients and for follow-up studies. However, high-dose HRCT remains preferable for initial examinations because of the few cases in which mild emphysema and ground-glass opacity were seen only with the high-dose technique and because artifacts were more prominent on low-dose HRCT.
Ultrafast
CT
J. J_ Geraghty, W. Stanford, J. R. Galvin, and K. S. Landas, of the University of Iowa Hospitals and Clinics, Iowa City, performed a canine study to determine the usefulness of ultrafast CT in the diagnosis of peripheral pulmonary embolisms. In seven deeply anesthetized mongrel dogs, three 7by 1 5-mm gelatin-sponge emboli were introduced into the right femoral vein; after administration of 60 ml of contrast media, 3-mm axial ultrafast CT scans were obtained. All dogs were sacrificed after scanning, and the locations of the emboli were recorded by a pathologist: 19 emboli were in the third and fourth division pulmonary arteries, and two emboli were in more proximal pulmonary arteries. In the reviews of the ultrafast CT scans by three chest radiologists, all 21 emboli were identified unequivocally; moreover, the locations determined by the radiologists correlated exactly with pathologic findings. The researchers concluded that ultrafast CT can demonstrate reliably the presence and location of gelatinsponge emboli; their plans for further research in this area include studies of in vivo blood clots, different sizes of emboli, and the possible role of three-dimensional imaging. J. Bormann, W. Stanford, R. Stenberg, M. Winniford, J. R. Galvin, K. S. Bernbaum, and C. Talman, of the University of Iowa Hospitals and Clinics, Iowa City, investigated using ultrafast CT to evaluate coronary artery calcification and correlated those findings with coronary artery stenosis as shown by quantitative angiography. Areas with >70% stenosis were considered to have significant stenosis. In each of 50 patients, 20 axial, contiguous, 3-mm, unenhanced, ultrafast CT scans of the proximal 2 cm of each coronary artery were obtained and interpreted by three radiologists. The area of calcification was determined by software inherent to the system and the density grade was based on Hounsfield units. A calcium score was calculated as follows: calcium score = area of calcification x density grade. For 37 sites (1 7 with stenosis), calcium scores failed to predict a significant stenosis at the calcification site (for patients older than 60 years, however, the correlation between calcium score and presence of lesion approached significance). Calcium was found in 92 vessels, 33 of which had stenosis, but the calcium-score sums in any individual vessel were not predictive of stenosis
NEWS
877
in that vessel. However, for the sums of the scores within the left main coronary artery, a significant (p < .Oi 4) difference was found between calcium scores of vessels with stenosis and calcium scores of vessels without stenosis. Because of the great variation in calcium scores, the sums of all calcium scores for a patient did not correlate with significant stenosis in that patient (40 patients with calcium, 23 with stenosis). These researchers concluded that calcium scores obtained from ultrafast CT were not helpful in predicting stenosis, except in the left main coronary artery.
Chest
Radiography
To evaluate clinically the use of computed radiography in imaging lung cancer, E. Itouji, K. Yamasaki, E. Sakai, M. Kusumoto, S. Adachi, and M. Kono, of Kobe University, Kobe, Japan, compared conventional radiographs with plain computed radiographs, image-processed (tomographic) computed radiographs, and energy-subtraction computed radiographs in five patients with lung cancer (three with peripheral lung cancer and two with hilar lung cancer). Twenty-three radiologists
from
1 5 university
hospitals
rated
the
computed
radiographs on the following scale: 1 = inferior to conventional radiography, 2 = slightly inferior to conventional radiography, 3 = equal to conventional radiography, 4 = slightly superior to conventional radiography, and 5 = superior to conventional radiography. The following results were found for the evaluation of lung anatomy: scores for energy-subtraction computed radiography were better than those for conventional radiography in the bronchus and paratracheal strips and equal for other anatomic structures studied; scores for computed radiography tomography were better than those for conventional tomography; and scores of high-pass processed computer radiography were better than those for conventional radiography.
In peripheral
lung
cancer,
images
obtained
with
energy-subtraction technique had the best scores; in hilar lung cancer, images obtained with computed radiographic tomography were judged as showing anatomy and pathology better than images generated by the other three techniques. M. L. Rosado-de-Christenson (Armed Forces Institute of Pathology, Washington, DC) presented a 40-year retrospective study done by M. L. Rosado-de-Christenson, R. D. Pugatch, M. Koss, and J. Galobardes, of patients with thymolipoma, which is a rare thymic neoplasm of unknown etiology. From i 950 to i 990, 25 pathologically proved cases of thymolipoma were referred for radiologic studies; radiographs were obtained in all 25, CT scans were obtained in nine, and MR images were obtained in two. In only one of these 25 cases was thymolipoma considered in the prospective differential diagnosis. Radiographic locations of the thymolipomas were the anterior inferior mediastinum in 20 and the anterior superior mediastinum in five; i 4 were unilateral and 1 1 were bilateral. In 1 0 patients, the thymolipoma conformed to the cardiac silhouette and looked like cardiomegaly; in eight patients, the neoplasm extended along the diaphragm, mimicking diaphragmatic elevation on lateral views. Other radiographic findings included hyperlucency in 1 2 cases, large sizes (occupying more than one-third of a hemithorax) in 10 cases, lack of diaphragmatic silhouetting in five cases; and
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878
MEETING
mobility or positional change in shape in six cases. Fat density was seen in the mass in eight of the nine CT studies (in six, the pattern was an even mixture of fat and soft-tissue density; in two, the pattern was predominantly fat density). The contiguity of the thymolipoma with the thymus was also seen on CT. Contiguity with the thymus and the mixture of fat and soft tissue characterized these neoplasms on the two MR studies also; coronal MR images of the diaphragm were useful. Dr. Rosado-de-Christenson suggested that thymolipoma should be part of the differential diagnosis when patients who are asymptomatic or minimally symptomatic have a paracardiac mass that simulates cardiomegaly or drapes along the hemidiaphragm with lack of diaphragmatic silhouetting; the diagnosis is supported by MR or CT evidence of fat in the mass. Although surgery cannot be avoided, a specific diagnosis with important anatomic information can be suggested preoperatively. A study comparing the subjective judgments of expert radiologists with analysis by Bayesian theory was done by J. W. Gurney, J. A. McKay, and D. Lyddon of the University of Nebraska Medical Center, Omaha. Radiographs from 66 patients with lung lesions (44 malignant and 22 benign) were evaluated by the radiologists and by using Bayesian analysis to determine the likelihood of malignancy. To obtain the Bayesian likelihood ratios, the researchers reviewed the literature and derived 1 5 characteristics associated with malignancy (four of the top five malignant signs were radiographic) and 21 characteristics associated with benignity (five of the top six were radiographic signs). In this group of patients, the patients with malignant tumors tended to be older and to have smoked more than those with benign tumors; furthermore, the size of the malignant tumors was not significantly different from the size of the benign tumors. The experts rated the likelihood of malignancy on a scale of 0 to i 00, and receiver-operating-characteristic (ROC) analysis was used to assess the ability of each observer to differentiate benign from malignant masses. For both expert and Bayesian likelihood scores, success in recognizing malignant lesions was not affected by knowledge of clinical history. Without the aid of clinical history, the area under the ROC curve for radiologists was 66-67 and for Bayesian analysis it was 80-81; when information on the patients’ clinical histories was provided, the areas under the ROC curves were 68-7i for radiologists and 8i for Bayesian analysis. Use of Bayes’ theorem
and
likelihood
ratios
was
significantly
better
than
expert subjective opinion in judging the malignancy of a lung lesion. Dr. McKay and her colleagues conclude that the use of Bayesian analysis can improve the accuracy of a radiologist’s subjective recognition of the benign or malignant nature of lung tumors.
Plenary
Session
on MR Imaging
and CT of the Thorax
MR Imaging
NEWS
AJR:157,
October
and pulse sequences in thoracic MR. MR imaging can be complementary to CT and can help with problematic diagnoses; MR imaging is a noninvasive method in which no ionizing radiation is used, and it provides increased soft-tissue contrast and multiplanar capacity. Modification of standard pulse sequences are needed to overcome two limitations of thoracic MR imaging: slow acquisition compared with physiologic
motion
and
low
signal-to-noise
ratio
of
lung
paren-
chyma. Dr. Mayo briefly described the pulse-sequence parameters (TR/TE), imaging plane, and sequence modifiers (cardiac gating, respiratory compensation, flow compensation, and presaturation) to overcome artifacts. He discussed the application of each of these parameters to imaging the chest wall, mediastinum, vascular structures, and lung parenchyma. For chest wall and mediastinum imaging, suggested parameters include Ti -weighted imaging (TR = i R-R interval, TE = 20 msec, and two to four excitations) and proton-density/T2weighted imaging (TA 2-3 R-R intervals, TE = 20/80 msec, and two excitations); respiratory compensation and presaturation should always be used, but flow compensation should be used with caution because it decreases vascular contrast. Ti-weighted images (TR = i R-R, TE = 20 msec, two to four excitations, and respiratory compensation) without flow compensation should be used for vascular MR imaging to provide maximum flow contrast (with dark blood). Ultrafast spin-echo or gradient-echo sequences are effective for further evaluation of intravascular masses. Finally, MR imaging of the lung parenchyma is still at the research stage. A major problem is that the air/soft-tissue interfaces in inflated lung induce magnetic field inhomogeneity that causes rapid signal loss and results in the failure of conventional MR sequences to show lung parenchyma. Researchers have suggested using very short echo delays, with either gradient-echo or spin-echo sequences to limit the amount of signal loss, or using Carr=
Purcell-Mibloom-GilI
(CPMG)
sequences,
which
partially
com-
pensate for the loss of phase coherence. However, even with conventional MR imaging, abnormal lung with thickened lobular septa and pleural effusions can be seen. In addition, infiltrated lung parenchyma (e.g., alveolitis) can be seen. MR imaging of the lung parenchyma was discussed further by Colleen J. Bergin (Stanford University, Stanford, CA). Dr. Bergin noted the following five obstacles that must be overcome or minimized for successful imaging: low proton density of the lung, a relatively short 12, susceptibility effects, motion artifacts, and diffusion/perfusion effects. Possible solutions to these challenges include the following: for a short T2 relaxation time, susceptibility effects, and signal loss from diffusion/perfusion, the echo time must be short relative to 12 (TE
875
Meeting
. .
.
..
News
:.
Society
of Thoracic
Postgraduate Elizabeth
Radiology
Course,
May
and
Whalen1
techniques
in cardiopulmonary
radiology
(MR
Imaging
and CT of the Thorax, Cardiovascular Imaging, Chest Roentgenology-The Art, Chest Neoplasms, Immune Deficiency Infections, Pediatric Thoracic Radiology, and Diffuse Lung Disease) and two scientific sessions featured 33 presentations of original scientific investigations in thoracic imaging and intervention. Two annual highlights of the meeting were the Scanlon Memorial Research Symposium (a 2-hr discussion of digital radiography of the thorax) and the Benjamin Felson Annual Lecture, this year featuring Robert J. Ginsberg (Memorial Sloan-Kettering Institute, New York) speaking about the limitations of surgical resection for lung carcinoma. Speakers from seven different countries participated, and their levels of experience ranged from residents to experienced expert radiologists. Because of AJR space limitations, we cannot include coyerage of all the activities provided at this 5-day meeting. However, we have summarized the following: 1 0 of the presentations of original scientific research, six of the up-to-date
1
Meeting
1991
The ninth annual meeting and postgraduate course of the Society of Thoracic Radiology was held May i 3-i 7, i 99i , at the Four Seasons Hotel-Yorkville, Toronto, Ontario, Canada. The meeting consisted of five sections: a postgraduate course, scientific sessions, a research symposium, workshops, unknown cases of the day, and the annual Benjamin Felson Lecture. The postgraduate course included seven plenary sessions that provided detailed reviews of state-ofthe-art
Ninth Annual
Contributing
editor,
American
Journal
of Roentgenology,
Editor’s note.-”Meeting News” articles report the substantive, and accurate reviews of topics of current The articles will not undergo the peer review usually the series is to apprise AJR readers of topics of current AJR i57:875-88i,
October
i99i
0361 -803X/9i/i
reviews given in the postgraduate Felson Lecture.
Presentations
of Original
Scientific
plenary
sessions,
and the
Research
Most of the 33 short scientific presentations concerned thoracic CT or chest radiography. Our page limitations do not allow summaries of the others, which were on thoracic sonography, biopsy techniques, and urokinase treatment of empyema.
Conventional
CT of the
Thorax
J. R. Standen, R. J. Knudsen, K. Rehm, W. T. Kaltenborn, and D. E. Knudson (University of Arizona, Tucson) prospectively studied the assessment of emphysema with CT in 64 patients. Emphysema is abnormal, permanent enlargement of air spaces
distal
to the terminal
bronchioles,
with
destruc-
tion of the walls of the bronchioles but without fibrosis. Both smokers and nonsmokers were among the 64 subjects, pulmonary function test results were correlated with CT findings, and some patients were followed up for as long as 20 years. CT scans were obtained of 8-mm sections during both inspiration and expiration; CT measurements were used to arrive at a “pixel-index”: the percentage of all pixels with a CT density between -900 and -1 024 H. Several of the patients with normal lungs had a high inspiratory pixel index; the
Ste. 103, 2223 Avenida de Ia Playa, La Jolla, CA 92037.
highlights of important national radiology meetings. The intent is to provide Journal readers with succinct, interest, written in a readable fashion and published promptly after the meeting. required of AJR publications, nor will they offer a critique of the information provided. The sole purpose of concern in an interesting and timely fashion.
574-0875
© American
Roentgen
Ray Society
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 06/19/15 from IP address 128.122.253.212. Copyright ARRS. For personal use only; all rights reserved
876
MEETING
researchers labeled these cases as “disappearing emphysema” when the inspiratory densities were -900 to -1 024 H but the expiratory densities were normal. All of the patients with disappearing emphysema were asymptomatic and had normal diffusing capacity and spirometry, leading the researchers to think that this phenomenon might be related to an early stage of emphysema or a higher risk of emphysema; future studies will focus on careful follow-up of these patients and on determination of the limits of normal lung density and the effects of aging and asthma. If disappearing emphysema does prove to be an early form of the disease, these CT measurements will be an objective way to measure it, will enable quantification of the disease early in its cycle, may add to information about the natural history of emphysema, and may help indicate interventions (e.g., smoking cessation) that could prevent or delay the development of the disease. The CT assessment of broncholithiasis was the subject of a study by D. J. Conces, R. D. Tarver, and V. A. Vix (Indiana University).
An uncommon
disease,
broncholithiasis
often
pre-
sents a diagnostic challenge; it is characterized by peribronchial or endobronchial calcified lymph nodes. CT findings were reviewed in 15 patients with broncholithiasis (all patients lived in a region of endemic histoplasmosis). Ten of these patients had endobronchial lymph nodes, and five had peribronchial lymph nodes. Cough was the most common sign (1 3 patients). Other signs and symptoms included hemoptysis (six), chest pain (three), and sputum-producing cough (three). Chest radiographs
showed
calcified
lymph
nodes
in
1 1 patients,
atelectasis in nine, infiltrates in two, and peripheral calcified granulomatosis in four. Of the 1 4 bronchoscopies performed, only five showed broncholiths, seven showed bronchial distortion, and three showed bronchial blood; the bronchus was obscured in two cases. CT scans showed calcified lymph nodes in all i 5 patients. Changes due to bronchial obstruction were seen on the CT scans (atelectasis in 10, bronchiectasis in four, infiltrates in four, and air trapping in one). No softtissue masses were seen in any of the patients. In the 10 patients with endobronchial calcified lymph nodes, CT results indicated the location of six correctly, and in the five patients with peribronchial calcified lymph nodes, CT located four correctly (the errors in location were due to the effects of volume averaging). These researchers conclude that bronchoscopy is definitely necessary for the diagnosis of broncholithiasis and that the combination of bronchoscopic and CT results should be sufficient to suggest the diagnosis of broncholithiasis.
High-Resolution Pulmonary
CT fibrosis
in dyspneic
smokers
as evaluated
by
high-resolution CT(HRCT)was the focus of a study presented by Jeffrey A. Galvin for J. A. Galvin, P. J. Chang, D. S. Schwartz, M. Mori, R. A. Helmers, W. Stanford, and G. W. Hunninghake, of the University of Iowa, Iowa City. In 10 smokers with pulmonary fibrosis who were referred for evaluation of new or worsening dyspnea, chest radiography, pulmonary function tests, and HRCT were performed. Spirometry and lung volumes were often normal despite severe dyspnea; chest radiographs provided a reasonable assess-
NEWS
AJR:157,
October
1991
ment of fibrosis but underestimated the severity of emphysema (and agreement of interpretation of radiographic severity of emphysema was poor: kappa scores ranged from .i 4 to .38). Although HRCT resulted in reliable quantification of emphysema that showed a good correlation with pulmonary function measurements of airway obstruction, HRCT results did not quantify fibrosis as effectively. These researchers therefore tried to assess fibrosis severity by using an automated measurement of fractal dimension; this calculation process is simple to use and automate, results in a single quantitative measure, and has the features and advantages of statistical, structural, and spectral methods. The fractal dimension of a normal lung proved to be i .3, whereas the fractal dimension of a fibrotic lung was 1 .7; also, the fractal dimension directly correlated with lung volume, and, as the fractal dimension increased, flow rates increased. Considering the results of this preliminary study, the researchers concluded that smokers with both dyspnea and radiographic evidence of fibrosis may have pulmonary function results that do not reflect the severity of damage. However, HRCT reliably measures emphysema severity and, by use of fractal dimensions, can provide a useful representation of fibrosis. Jung-Gi Im discussed HRCT findings of fresh and healing lesions in pulmonary tuberculosis that were collected by J.-G. Im, J. H. Lee, V. S. Shim, J. M. Ahn, and M. C. Han, of Seoul National University, Seoul, Korea. The objective of the study was to use HRCT (1 5-mm collimation, 20-cm field of view) to describe pretreated lesions and then sequential changes with chemotherapy in 3i patients with newly diagnosed tuberculosis. The HRCT findings in patients before treatment were small (2-4 mm), centrilobular branching in 26 patients; larger (5-6 mm) fuzzy nodules in 2i ; lobular consolidations in 20; cavities in 1 8; thickened interlobular septa in i 4; and large branching lesions in five. Posttreatment followup was obtained in 2i of these patients; HRCT showed that (i ) the small centrilobular lesions disappeared and left lobular emphysema with a central dot and minimal distortion of the bronchovascular bundle, (2) lobular consolidations resolved from the periphery with more bronchovascular distortion and emphysema, (3) thickening of interlobular septa disappeared without residue, and (4) treatment caused some effects in cavities, including thinning of walls with minimum distortion and fibrotic bands with marked distortion. In these patients, HRCT showed disease at the lobular level and provided helpful information about ongoing healing activity. A patient who has conventional HRCT is exposed to 120140 mGy. To investigate whether a lower dose impairs image quality, C. V. Zwirewich, J. R. Mayo, and N. L. MUller, of Vancouver, Canada, compared 1 .5-mm-collimation, 2-sec images obtained in high-dose HRCT studies (200 mA [400 mAs]) with those obtained in low-dose HRCT studies (20 mA [40 mAs]). Without knowledge of HRCT technique, three observers evaluated the scans of 3i patients for demonstration of pulmonary anatomy (vessels, bronchi, secondary nodules), pathology (interstitial disease, air-space disease, and bronchiectasis), and the presence of linear stratification artifacts. The McNemar statistical test for significance was used to assess whether the quality of high-dose HRCT images was significantly better than that of the low-dose HRCT images.
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 06/19/15 from IP address 128.122.253.212. Copyright ARRS. For personal use only; all rights reserved
AJR:157,
October
1991
MEETING
In a large percentage of patients, the two techniques resulted in the same quality of visualization of vessels, segmental and lobar bronchi, secondary pulmonary nodules, reticulation, honeycomb cysts, and thickened interlobular septa. In three cases, high-dose images revealed ground-glass opacities or emphysema not seen on low-dose images, but the evidence for these was subtle even at 400 mAs. Although artifacts were more prominent on images acquired with the low-dose technique, the two techniques yielded images with equal visual quality in 97% of cases. Overall, low-dose HRCT seems to have potential usefulness, especially in young patients and for follow-up studies. However, high-dose HRCT remains preferable for initial examinations because of the few cases in which mild emphysema and ground-glass opacity were seen only with the high-dose technique and because artifacts were more prominent on low-dose HRCT.
Ultrafast
CT
J. J_ Geraghty, W. Stanford, J. R. Galvin, and K. S. Landas, of the University of Iowa Hospitals and Clinics, Iowa City, performed a canine study to determine the usefulness of ultrafast CT in the diagnosis of peripheral pulmonary embolisms. In seven deeply anesthetized mongrel dogs, three 7by 1 5-mm gelatin-sponge emboli were introduced into the right femoral vein; after administration of 60 ml of contrast media, 3-mm axial ultrafast CT scans were obtained. All dogs were sacrificed after scanning, and the locations of the emboli were recorded by a pathologist: 19 emboli were in the third and fourth division pulmonary arteries, and two emboli were in more proximal pulmonary arteries. In the reviews of the ultrafast CT scans by three chest radiologists, all 21 emboli were identified unequivocally; moreover, the locations determined by the radiologists correlated exactly with pathologic findings. The researchers concluded that ultrafast CT can demonstrate reliably the presence and location of gelatinsponge emboli; their plans for further research in this area include studies of in vivo blood clots, different sizes of emboli, and the possible role of three-dimensional imaging. J. Bormann, W. Stanford, R. Stenberg, M. Winniford, J. R. Galvin, K. S. Bernbaum, and C. Talman, of the University of Iowa Hospitals and Clinics, Iowa City, investigated using ultrafast CT to evaluate coronary artery calcification and correlated those findings with coronary artery stenosis as shown by quantitative angiography. Areas with >70% stenosis were considered to have significant stenosis. In each of 50 patients, 20 axial, contiguous, 3-mm, unenhanced, ultrafast CT scans of the proximal 2 cm of each coronary artery were obtained and interpreted by three radiologists. The area of calcification was determined by software inherent to the system and the density grade was based on Hounsfield units. A calcium score was calculated as follows: calcium score = area of calcification x density grade. For 37 sites (1 7 with stenosis), calcium scores failed to predict a significant stenosis at the calcification site (for patients older than 60 years, however, the correlation between calcium score and presence of lesion approached significance). Calcium was found in 92 vessels, 33 of which had stenosis, but the calcium-score sums in any individual vessel were not predictive of stenosis
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877
in that vessel. However, for the sums of the scores within the left main coronary artery, a significant (p < .Oi 4) difference was found between calcium scores of vessels with stenosis and calcium scores of vessels without stenosis. Because of the great variation in calcium scores, the sums of all calcium scores for a patient did not correlate with significant stenosis in that patient (40 patients with calcium, 23 with stenosis). These researchers concluded that calcium scores obtained from ultrafast CT were not helpful in predicting stenosis, except in the left main coronary artery.
Chest
Radiography
To evaluate clinically the use of computed radiography in imaging lung cancer, E. Itouji, K. Yamasaki, E. Sakai, M. Kusumoto, S. Adachi, and M. Kono, of Kobe University, Kobe, Japan, compared conventional radiographs with plain computed radiographs, image-processed (tomographic) computed radiographs, and energy-subtraction computed radiographs in five patients with lung cancer (three with peripheral lung cancer and two with hilar lung cancer). Twenty-three radiologists
from
1 5 university
hospitals
rated
the
computed
radiographs on the following scale: 1 = inferior to conventional radiography, 2 = slightly inferior to conventional radiography, 3 = equal to conventional radiography, 4 = slightly superior to conventional radiography, and 5 = superior to conventional radiography. The following results were found for the evaluation of lung anatomy: scores for energy-subtraction computed radiography were better than those for conventional radiography in the bronchus and paratracheal strips and equal for other anatomic structures studied; scores for computed radiography tomography were better than those for conventional tomography; and scores of high-pass processed computer radiography were better than those for conventional radiography.
In peripheral
lung
cancer,
images
obtained
with
energy-subtraction technique had the best scores; in hilar lung cancer, images obtained with computed radiographic tomography were judged as showing anatomy and pathology better than images generated by the other three techniques. M. L. Rosado-de-Christenson (Armed Forces Institute of Pathology, Washington, DC) presented a 40-year retrospective study done by M. L. Rosado-de-Christenson, R. D. Pugatch, M. Koss, and J. Galobardes, of patients with thymolipoma, which is a rare thymic neoplasm of unknown etiology. From i 950 to i 990, 25 pathologically proved cases of thymolipoma were referred for radiologic studies; radiographs were obtained in all 25, CT scans were obtained in nine, and MR images were obtained in two. In only one of these 25 cases was thymolipoma considered in the prospective differential diagnosis. Radiographic locations of the thymolipomas were the anterior inferior mediastinum in 20 and the anterior superior mediastinum in five; i 4 were unilateral and 1 1 were bilateral. In 1 0 patients, the thymolipoma conformed to the cardiac silhouette and looked like cardiomegaly; in eight patients, the neoplasm extended along the diaphragm, mimicking diaphragmatic elevation on lateral views. Other radiographic findings included hyperlucency in 1 2 cases, large sizes (occupying more than one-third of a hemithorax) in 10 cases, lack of diaphragmatic silhouetting in five cases; and
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MEETING
mobility or positional change in shape in six cases. Fat density was seen in the mass in eight of the nine CT studies (in six, the pattern was an even mixture of fat and soft-tissue density; in two, the pattern was predominantly fat density). The contiguity of the thymolipoma with the thymus was also seen on CT. Contiguity with the thymus and the mixture of fat and soft tissue characterized these neoplasms on the two MR studies also; coronal MR images of the diaphragm were useful. Dr. Rosado-de-Christenson suggested that thymolipoma should be part of the differential diagnosis when patients who are asymptomatic or minimally symptomatic have a paracardiac mass that simulates cardiomegaly or drapes along the hemidiaphragm with lack of diaphragmatic silhouetting; the diagnosis is supported by MR or CT evidence of fat in the mass. Although surgery cannot be avoided, a specific diagnosis with important anatomic information can be suggested preoperatively. A study comparing the subjective judgments of expert radiologists with analysis by Bayesian theory was done by J. W. Gurney, J. A. McKay, and D. Lyddon of the University of Nebraska Medical Center, Omaha. Radiographs from 66 patients with lung lesions (44 malignant and 22 benign) were evaluated by the radiologists and by using Bayesian analysis to determine the likelihood of malignancy. To obtain the Bayesian likelihood ratios, the researchers reviewed the literature and derived 1 5 characteristics associated with malignancy (four of the top five malignant signs were radiographic) and 21 characteristics associated with benignity (five of the top six were radiographic signs). In this group of patients, the patients with malignant tumors tended to be older and to have smoked more than those with benign tumors; furthermore, the size of the malignant tumors was not significantly different from the size of the benign tumors. The experts rated the likelihood of malignancy on a scale of 0 to i 00, and receiver-operating-characteristic (ROC) analysis was used to assess the ability of each observer to differentiate benign from malignant masses. For both expert and Bayesian likelihood scores, success in recognizing malignant lesions was not affected by knowledge of clinical history. Without the aid of clinical history, the area under the ROC curve for radiologists was 66-67 and for Bayesian analysis it was 80-81; when information on the patients’ clinical histories was provided, the areas under the ROC curves were 68-7i for radiologists and 8i for Bayesian analysis. Use of Bayes’ theorem
and
likelihood
ratios
was
significantly
better
than
expert subjective opinion in judging the malignancy of a lung lesion. Dr. McKay and her colleagues conclude that the use of Bayesian analysis can improve the accuracy of a radiologist’s subjective recognition of the benign or malignant nature of lung tumors.
Plenary
Session
on MR Imaging
and CT of the Thorax
MR Imaging
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AJR:157,
October
and pulse sequences in thoracic MR. MR imaging can be complementary to CT and can help with problematic diagnoses; MR imaging is a noninvasive method in which no ionizing radiation is used, and it provides increased soft-tissue contrast and multiplanar capacity. Modification of standard pulse sequences are needed to overcome two limitations of thoracic MR imaging: slow acquisition compared with physiologic
motion
and
low
signal-to-noise
ratio
of
lung
paren-
chyma. Dr. Mayo briefly described the pulse-sequence parameters (TR/TE), imaging plane, and sequence modifiers (cardiac gating, respiratory compensation, flow compensation, and presaturation) to overcome artifacts. He discussed the application of each of these parameters to imaging the chest wall, mediastinum, vascular structures, and lung parenchyma. For chest wall and mediastinum imaging, suggested parameters include Ti -weighted imaging (TR = i R-R interval, TE = 20 msec, and two to four excitations) and proton-density/T2weighted imaging (TA 2-3 R-R intervals, TE = 20/80 msec, and two excitations); respiratory compensation and presaturation should always be used, but flow compensation should be used with caution because it decreases vascular contrast. Ti-weighted images (TR = i R-R, TE = 20 msec, two to four excitations, and respiratory compensation) without flow compensation should be used for vascular MR imaging to provide maximum flow contrast (with dark blood). Ultrafast spin-echo or gradient-echo sequences are effective for further evaluation of intravascular masses. Finally, MR imaging of the lung parenchyma is still at the research stage. A major problem is that the air/soft-tissue interfaces in inflated lung induce magnetic field inhomogeneity that causes rapid signal loss and results in the failure of conventional MR sequences to show lung parenchyma. Researchers have suggested using very short echo delays, with either gradient-echo or spin-echo sequences to limit the amount of signal loss, or using Carr=
Purcell-Mibloom-GilI
(CPMG)
sequences,
which
partially
com-
pensate for the loss of phase coherence. However, even with conventional MR imaging, abnormal lung with thickened lobular septa and pleural effusions can be seen. In addition, infiltrated lung parenchyma (e.g., alveolitis) can be seen. MR imaging of the lung parenchyma was discussed further by Colleen J. Bergin (Stanford University, Stanford, CA). Dr. Bergin noted the following five obstacles that must be overcome or minimized for successful imaging: low proton density of the lung, a relatively short 12, susceptibility effects, motion artifacts, and diffusion/perfusion effects. Possible solutions to these challenges include the following: for a short T2 relaxation time, susceptibility effects, and signal loss from diffusion/perfusion, the echo time must be short relative to 12 (TE
