Downloaded from www.ajronline.org by 50.48.152.100 on 11/11/15 from IP address 50.48.152.100. Copyright ARRS. For personal use only; all rights reserved
1095
Stuart
G. Silverman1
David Steven Glare M. C. Douglass
A. Bloom E. Seltzer Ternpany F. Adams
Needle-Tip CT-Guided
Localization Abdominal
Comparison
of Conventional
OBJECTIVE.
This study
was performed
During Biopsy: and Spiral
to determine
whether
CT
the time required
for
needle-tip localization during biopsy of the abdomen would be reduced if continuousvolume data acquisition, also known as spiral CT, were used for guidance instead of conventional CT.
SUBJECTS
underwent
AND METHODS.
needle-tip
Forty patients had biopsies of an abdominal mass; half with conventional CT and half with spiral CT. The
localizations
times required to localize the needle for 104 needle passes and reconstruction times were included, and the radiologist’s
difficulties
were deliberately
excluded.
tional and spiral CT were compared
The mean needle
were calculated; scanning technique and procedural
localization
for the upper abdominal
times with conven-
regions by using the two-tailed unpaired Student’s t-test. RESULTS. The mean time (±SE) for spiral CT was 35 ± 2 sec compared with 105 ± 18 sec for conventional CT (p < .001). When analyzed by region, times with spiral CT were shorter in both the upper abdomen (means, 37 sec for spiral CT vs 150 sec for conventional CT, p < .001) and pelvis (means, 25 sec for spiral CT vs 74 sec for conventional CT, p = 038); the magnitude of the improvement was greater in the upper abdomen. CONCLUSION. The time required to find the needle tip during guided biopsy of an abdominal mass is reduced with spiral CT compared with conventional CT. This improvement is partly a result of the ability to eliminate respiratory misregistration with spiral CT, which is not possible with conventional multisectional CT; hence the greater advantage in upper abdominal biopsy. AJR
159:1095-1097,
The
usefulness
of CT-guided
‘All authors: Department of Radiology, Brigham and Women’s Hospital, 75 Francis St., Boston, MA 021 1 5. Address reprint requests to S. G. Silverman. 0361 -803X/92/1 0 American
595-1095
Roentgen
Ray Society
and
biopsy
has
been
which occurs
careful
prevents
because
instructions,
level. This results
Presented at the annual meeting of the American Roentgen Ray Society, Orlando, FL, May 1992.
aspiration
misregistration,
the needle after revision
percutaneous
[1 -8]. The principal advantage of CT guidance has been the ability locate the needle tip precisely, an important step in the successful lesions [8-1 1]. Conventional multisectional CT, which consists of obtained during separate breath-holds, can be limited by respiratory
despite
6, 1992; accepted
1992
widely reported to position and sampling of all individual scans registration
Received March May 29, 1992.
November
and pelvic
in “skip”
consistent
of respiratory
some
do not end each
breath-hold, resulting
through
during
precise
requiring rotating
the scanner
reconstructed
are truly contiguous,
that
breath
mis-
cycles,
and
at the same
multisectional CT sequence. of the needle tip can
visualization
multiple detector
such
Respiratory
respiratory
organ or lesion, and consequently
a conventional
misregistration,
and subsequently
images
patients
areas in the imaged
be a time-consuming procedure Spiral CT uses a continuously of the CT table
scanning.
vary between
tip may not be imaged
Because
contiguous
tidal volumes
scans. system data
at selected
free of gaps
and continuous
are acquired
section
or overlapping
during
feeding a single
intervals. sections
The
caused
by respiratory misnegistration [1 2]. We hypothesized that use of spiral CT would reduce the time required to localize the needle tip compared with that needed for
1096
SILVERMAN
conventional
CT
during
CT-guided
biopsy
of
CT (p
abdominal
masses.
and Methods
Downloaded from www.ajronline.org by 50.48.152.100 on 11/11/15 from IP address 50.48.152.100. Copyright ARRS. For personal use only; all rights reserved
conventional
CT-guided
CT was used to localize
biopsy of abdominal
masses,
the needle tip in half the patients
and spiral CT was used in the other half. All biopsies were performed by using the Siemens Somatom Plus CT scanner (Siemens Medical Systems, Iselin, NJ). Our usual routine method (with conventional
was to obtain individual scans, await the result, and then decide
if additional
scans were required.
CT consisted
The localization
of individual
scans
protocol
for con-
(1 0 x 1 0 mm sequence,
2-sec exposure,
120 kVp, 21 0 mA) beginning at the suspected location of the needle tip within the patient; scans were repeated until the needle tip was visualized. The localization protocol for spiral CT consisted of a 10-mm-thick volumetric data acquisition (1 20 kVp, 165 mA) obtained with a table feed rate of 10 mm/sec and beginning 1 cm above the estimated location of the needle tip within the patient. During a 5-sec exposure a total volume of 5 cm was scanned during a single breath-hold. Images were then reconstructed by using a 10mm slice thickness
and 1 0-mm
intervals;
the first and last slices were
yielding a 3-cm volume ofimaged tissue. The interventional radiology team (including a staff radiologist and a resident or fellow) aligned the scan sections for both groups by using the localizer light and was instructed to repeat the scan or scan sequences until the needle tip, as indicated by the low-attenuation beam-hardening artifact, was detected [8]. The time required to localize the needle, defined as the interval between when the technologist begins the scan and the radiologist discarded,
views the needle tip, was calculated for 104 needle placements in the 40 patients. The time for each conventional
CT sequence
a 3-sec start-up delay, 2 sec for the first scan, the time
included
between
the
first localization image and the image showing the needle tip (which includes scanning times for the remainder of the images and reconstruction times for all but the final image showing the needle tip), and the reconstruction time for the last image (8 sec). The time for each spiral sequence included a 3-sec start-up delay, a 5-sec scan time, and a time determined by the number of images necessary to visualize the needle tip multiplied by 1 1 sec (the reconstruction time, per image, of the software for this spiral CT scanner). The time determination deliberately excludes operator technique and lesion size and location, which generally determine the number of needle passes. It also excludes variables such as the skill of the technologist and the medical
condition “upper
abdomen,”
including
the
liver,
two
spleen,
the two-tailed
The
needle
use
of spinal
localizations
CT
in biopsies
pelvic organs and of netropenitoneal lymph nodes (mean time for spiral CT, 25 sec; mean time for conventional CT, 74 sec). The improvement accorded by using spiral CT was greaten in the upper
abdomen
group
than
in the netnopenitoneum/pelvis
group. When spiral CT was used, upper abdominal
needle-tip
localizations took an average of only 1 2 sec longer than those in the pelvis, but there was still a statistically significant difference between the two regions (p = .001). With conven-
tional CT, the time required for localization of the needle tip was longer for masses in the upper abdomen than for pelvic masses on netnopenitoneal lymph nodes. Discussion Compared
with
sonography
of CT-guided
abdominal
and procedure
length.
on fluonoscopy,
biopsy
include
disadvantages
its cost,
The accessibility
availability,
of the lesion
and the
radiologist’s skill are important determinants of overall procedure times. In addition, biopsy with conventional CT requines intermittent imaging between needle manipulations, a disadvantage not associated with real-time sonography on fluoroscopy. The results of our study suggest that continuous-volume data acquisition, although it does not eliminate the need to image the needle after placement, reduces the time needed
to perform
this step compared
with conventional
average amount of time saved by using spinal CT was approximately 70 sec for each needle placement. There are several reasons for this improvement. CT.
The
In conventional abdomen, where
CT-guided respiratory
cant, the times required than those for biopsies lymph nodes. Elimination
TABLE 1: Needle Abdominal Biopsy
biopsies of organs in the upper misnegistration may be signifi-
for needle localization were longer of pelvic organs or retroperitoneal of respiratory misnegistration pnob-
Localization
Times
During
CT-Guided
unpaired
Student’s
No. of Sec ± SE (No. of Needle Placements)
groups: those adrenal
Mean
gland,
kidney, and pancreas, and those in the “pelvis,” including pelvic masses as well as retroperitoneal lymph nodes. These assignments, although admittedly arbitrary, are based on the hypothesis that respiratory misregistration is greater during biopsies of the upper abdominal organs than during biopsies of pelvic organs and retroperitoneal lymph nodes, where little or no respiratory misregistration should occur. Mean needle localization times with conventional and spiral CT were compared for each organ and abdominal region by using
shortened the time of upper abdom(mean time for spinal CT, 37 sec; mean time for CT, 1 50 sec) and biopsies of masses in the
for
of the patient.
Data were analyzed by dividing the biopsies into in the
.001).
1095
Stuart
G. Silverman1
David Steven Glare M. C. Douglass
A. Bloom E. Seltzer Ternpany F. Adams
Needle-Tip CT-Guided
Localization Abdominal
Comparison
of Conventional
OBJECTIVE.
This study
was performed
During Biopsy: and Spiral
to determine
whether
CT
the time required
for
needle-tip localization during biopsy of the abdomen would be reduced if continuousvolume data acquisition, also known as spiral CT, were used for guidance instead of conventional CT.
SUBJECTS
underwent
AND METHODS.
needle-tip
Forty patients had biopsies of an abdominal mass; half with conventional CT and half with spiral CT. The
localizations
times required to localize the needle for 104 needle passes and reconstruction times were included, and the radiologist’s
difficulties
were deliberately
excluded.
tional and spiral CT were compared
The mean needle
were calculated; scanning technique and procedural
localization
for the upper abdominal
times with conven-
regions by using the two-tailed unpaired Student’s t-test. RESULTS. The mean time (±SE) for spiral CT was 35 ± 2 sec compared with 105 ± 18 sec for conventional CT (p < .001). When analyzed by region, times with spiral CT were shorter in both the upper abdomen (means, 37 sec for spiral CT vs 150 sec for conventional CT, p < .001) and pelvis (means, 25 sec for spiral CT vs 74 sec for conventional CT, p = 038); the magnitude of the improvement was greater in the upper abdomen. CONCLUSION. The time required to find the needle tip during guided biopsy of an abdominal mass is reduced with spiral CT compared with conventional CT. This improvement is partly a result of the ability to eliminate respiratory misregistration with spiral CT, which is not possible with conventional multisectional CT; hence the greater advantage in upper abdominal biopsy. AJR
159:1095-1097,
The
usefulness
of CT-guided
‘All authors: Department of Radiology, Brigham and Women’s Hospital, 75 Francis St., Boston, MA 021 1 5. Address reprint requests to S. G. Silverman. 0361 -803X/92/1 0 American
595-1095
Roentgen
Ray Society
and
biopsy
has
been
which occurs
careful
prevents
because
instructions,
level. This results
Presented at the annual meeting of the American Roentgen Ray Society, Orlando, FL, May 1992.
aspiration
misregistration,
the needle after revision
percutaneous
[1 -8]. The principal advantage of CT guidance has been the ability locate the needle tip precisely, an important step in the successful lesions [8-1 1]. Conventional multisectional CT, which consists of obtained during separate breath-holds, can be limited by respiratory
despite
6, 1992; accepted
1992
widely reported to position and sampling of all individual scans registration
Received March May 29, 1992.
November
and pelvic
in “skip”
consistent
of respiratory
some
do not end each
breath-hold, resulting
through
during
precise
requiring rotating
the scanner
reconstructed
are truly contiguous,
that
breath
mis-
cycles,
and
at the same
multisectional CT sequence. of the needle tip can
visualization
multiple detector
such
Respiratory
respiratory
organ or lesion, and consequently
a conventional
misregistration,
and subsequently
images
patients
areas in the imaged
be a time-consuming procedure Spiral CT uses a continuously of the CT table
scanning.
vary between
tip may not be imaged
Because
contiguous
tidal volumes
scans. system data
at selected
free of gaps
and continuous
are acquired
section
or overlapping
during
feeding a single
intervals. sections
The
caused
by respiratory misnegistration [1 2]. We hypothesized that use of spiral CT would reduce the time required to localize the needle tip compared with that needed for
1096
SILVERMAN
conventional
CT
during
CT-guided
biopsy
of
CT (p
abdominal
masses.
and Methods
Downloaded from www.ajronline.org by 50.48.152.100 on 11/11/15 from IP address 50.48.152.100. Copyright ARRS. For personal use only; all rights reserved
conventional
CT-guided
CT was used to localize
biopsy of abdominal
masses,
the needle tip in half the patients
and spiral CT was used in the other half. All biopsies were performed by using the Siemens Somatom Plus CT scanner (Siemens Medical Systems, Iselin, NJ). Our usual routine method (with conventional
was to obtain individual scans, await the result, and then decide
if additional
scans were required.
CT consisted
The localization
of individual
scans
protocol
for con-
(1 0 x 1 0 mm sequence,
2-sec exposure,
120 kVp, 21 0 mA) beginning at the suspected location of the needle tip within the patient; scans were repeated until the needle tip was visualized. The localization protocol for spiral CT consisted of a 10-mm-thick volumetric data acquisition (1 20 kVp, 165 mA) obtained with a table feed rate of 10 mm/sec and beginning 1 cm above the estimated location of the needle tip within the patient. During a 5-sec exposure a total volume of 5 cm was scanned during a single breath-hold. Images were then reconstructed by using a 10mm slice thickness
and 1 0-mm
intervals;
the first and last slices were
yielding a 3-cm volume ofimaged tissue. The interventional radiology team (including a staff radiologist and a resident or fellow) aligned the scan sections for both groups by using the localizer light and was instructed to repeat the scan or scan sequences until the needle tip, as indicated by the low-attenuation beam-hardening artifact, was detected [8]. The time required to localize the needle, defined as the interval between when the technologist begins the scan and the radiologist discarded,
views the needle tip, was calculated for 104 needle placements in the 40 patients. The time for each conventional
CT sequence
a 3-sec start-up delay, 2 sec for the first scan, the time
included
between
the
first localization image and the image showing the needle tip (which includes scanning times for the remainder of the images and reconstruction times for all but the final image showing the needle tip), and the reconstruction time for the last image (8 sec). The time for each spiral sequence included a 3-sec start-up delay, a 5-sec scan time, and a time determined by the number of images necessary to visualize the needle tip multiplied by 1 1 sec (the reconstruction time, per image, of the software for this spiral CT scanner). The time determination deliberately excludes operator technique and lesion size and location, which generally determine the number of needle passes. It also excludes variables such as the skill of the technologist and the medical
condition “upper
abdomen,”
including
the
liver,
two
spleen,
the two-tailed
The
needle
use
of spinal
localizations
CT
in biopsies
pelvic organs and of netropenitoneal lymph nodes (mean time for spiral CT, 25 sec; mean time for conventional CT, 74 sec). The improvement accorded by using spiral CT was greaten in the upper
abdomen
group
than
in the netnopenitoneum/pelvis
group. When spiral CT was used, upper abdominal
needle-tip
localizations took an average of only 1 2 sec longer than those in the pelvis, but there was still a statistically significant difference between the two regions (p = .001). With conven-
tional CT, the time required for localization of the needle tip was longer for masses in the upper abdomen than for pelvic masses on netnopenitoneal lymph nodes. Discussion Compared
with
sonography
of CT-guided
abdominal
and procedure
length.
on fluonoscopy,
biopsy
include
disadvantages
its cost,
The accessibility
availability,
of the lesion
and the
radiologist’s skill are important determinants of overall procedure times. In addition, biopsy with conventional CT requines intermittent imaging between needle manipulations, a disadvantage not associated with real-time sonography on fluoroscopy. The results of our study suggest that continuous-volume data acquisition, although it does not eliminate the need to image the needle after placement, reduces the time needed
to perform
this step compared
with conventional
average amount of time saved by using spinal CT was approximately 70 sec for each needle placement. There are several reasons for this improvement. CT.
The
In conventional abdomen, where
CT-guided respiratory
cant, the times required than those for biopsies lymph nodes. Elimination
TABLE 1: Needle Abdominal Biopsy
biopsies of organs in the upper misnegistration may be signifi-
for needle localization were longer of pelvic organs or retroperitoneal of respiratory misnegistration pnob-
Localization
Times
During
CT-Guided
unpaired
Student’s
No. of Sec ± SE (No. of Needle Placements)
groups: those adrenal
Mean
gland,
kidney, and pancreas, and those in the “pelvis,” including pelvic masses as well as retroperitoneal lymph nodes. These assignments, although admittedly arbitrary, are based on the hypothesis that respiratory misregistration is greater during biopsies of the upper abdominal organs than during biopsies of pelvic organs and retroperitoneal lymph nodes, where little or no respiratory misregistration should occur. Mean needle localization times with conventional and spiral CT were compared for each organ and abdominal region by using
shortened the time of upper abdom(mean time for spinal CT, 37 sec; mean time for CT, 1 50 sec) and biopsies of masses in the
for
of the patient.
Data were analyzed by dividing the biopsies into in the
.001).
