AJR 2000; 174:319-321
© American Roentgen Ray Society
Near Real-Time CT Fluoroscopy Using Computer Automated Scan Technology in Nonvascular Interventional Procedures
Randy D. Ernst1,2,
Hyun S. Kim1,3,
Akira Kawashima1,
Mike R. Middlebrook1 and
Carl M. Sandler1
1
Department of Radiology, The University of Texas Medical School at Houston,
5656 Kelley St., Houston, TX 77026
2
Present address: Department of Radiology, Emory University, 1364 Clifton Rd.
N.E., Atlanta, GA 30322
3
Present address: Department of Radiology, Johns Hopkins Hospital, 600 N. Wolfe
St., Baltimore, MD 21287-2182
Received April 1, 1999;
accepted after revision July 28, 1999.
Address correspondence to R. D. Ernst.
Introduction
Fluoroscopic and sonographic realtime guidance facilitates the performance
of various interventional procedures, but such guidance is impossible for many
internal targets. CT guidance provides the best spatial resolution, but
CT-guided biopsy and drainage procedures are slow and cumbersome. A technique
combining the precise realtime guidance of sonography or fluoroscopy with the
spatial resolution and accuracy of CT guidance would result in faster and more
accurate procedures and increased patient comfort. We achieved this objective
by modifying parameters of the computer automated scan technology (CAST)
Smartprep function available on HiSpeed Advantage CT scanners (General
Electric Medical Systems, Milwaukee, WI). This report describes near real-time
CT fluoroscopy-guided biopsy and abscess drainage procedures using low-energy
CAST.
Subjects and Methods
We performed 18 biopsies and three abscess drainage procedures using the
Smartprep function on a Hi-Speed Advantage CT scanner. Patients were
positioned in the gantry to allow needle manipulation during scanning. After a
conventional axial scan was obtained for localization, the patient's skin was
marked. The biopsy needle was located under the gantry laser light and a CAST
series was performed at the marked location. CT scans were obtained at one
prescribed tomographic plane every 15-30 sec. We viewed the monitor and
advanced or repositioned the needle during interscan delays. After placing the
coaxial guiding needle, fineneedle aspiration and core biopsies were
performed. Abscess aspiration was performed using an 18-gauge spinal needle.
Radiation exposure was minimized by observing the technologist's monitor
before advancing the needle, wearing lead aprons, and setting the amperage and
voltage to 40 mA and 80 kVp, respectively.
Results
On 19 of 21 attempts, the target was punctured on the first CAST series.
Precise needle positioning was performed in 15-300 sec (average, 85.9 sec).
This finding is comparable with an average of 74 sec for puncture as reported
by Katada et al. [1]. The
average interscan delay was 21.9 sec, and the average number of 1-sec scans
for needle placement was 3.7. Because of intolerance, two patients required a
second CAST series to complete the biopsy. The mode number of scans per CAST
series was four (minimum, two; maximum, 11). For all biopsies, aspirate and
tissue samples were obtained for cytohistologic diagnosis. We successfully
placed drainage tubes for three drainage procedures. No immediate
complications occurred, and no increase in radiation exposure was recorded for
the radiologist.
Discussion
Using CT-guided procedures for conventional techniques is time-consuming.
Often, multiple scans are required to ensure precise needle advancement and
location. A second biopsy is often necessary causing further radiation
exposure to the patient. Nonetheless, CT guidance provides superior spatial
resolution in comparison with fluoroscopic or sonographic real-time guidance.
Operator expertise is a major factor in both sonography and fluoroscopy, and
many internal targets that must be avoided are not detected using these
techniques. Real-time CT-guidance provides significant advantages for
radiologists and patients.
Various techniques are used to achieve near real-time CT guidance
[1,
2,
3,
4]. Near real-time CT
fluoroscopy systems are available from manufacturers as stand-alone
instruments. One is a CT fluoroscopy unit (Xpress SX Aspire CI-CT; Toshiba
Medical Systems, Tokyo, Japan) for monitoring interventional procedures
[1,
2]. This dedicated scanner uses
slip ring, 896-channel solid-state detector array technology with high-speed
computers to provide real-time visualization of biopsy, aspiration, and
drainage procedures [1].
However, this machine may be cost-prohibitive at institutions other than major
tertiary care centers.
In 1998, one manufacturer introduced addon hardware for its helical scanner
(Smartview; General Electric Medical Systems) (frames per sec, six; matrix,
256 x 256; amperage, 10 mA). The scanner enables continuous fluoroscopy
for 90 sec, flat panel screen ceiling-mounted display, and hand-held
control.
We used the CAST function to perform near-real-time CT-guided procedures at
no additional cost. The CAST function (Smartprep) available on HiSpeed
Advantage CT scanners is a contrast bolus tracking system designed to optimize
contrast material administration by compensating for patient variability
[5,
6]. The function uses a series
of rapidly reconstructed low-radiation-dose monitoring scans. Target
structures (liver, aorta, and portal vein) are displayed graphically and
numerically as the scanner tracks bolus contrast material as it passes through
each structure. When a predetermined level of enhancement is achieved, manual
transition to routine scan series is performed. Studies by Silverman et al.
[5,
6] revealed that more effective
and greater hepatic enhancement with less individual variability can be
achieved using the CAST function. The CAST function costs less to use than
routine studies because it uses less than or equal amounts of contrast
material.
After we modified the parameters of the CAST function to reduce radiation,
the images using this technique were noisy because of decreased photons.
However, the image quality was adequate to facilitate biopsy and drainage
procedures (Fig. 1). The CAST
function can also be used when the gantry is tilted, a useful position to
avoid the intervening bowel or lung.
View larger version (54K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1. —54-year-old woman with pancreatic mass. Sequential soft-tissue
window helical CT scan was obtained with Smartprep (General Electric Medical
Systems, Milwaukee, WI) during pancreatic biopsy. Note graininess of images
because of low-energy technique (40 mA, 80 kVp). Guiding needle (18-gauge) was
placed posterior to inferior vena cava in pancreatic head mass. Needle
placement took 30 sec.
|
|
One limitation of the CAST function is that the interscan delay cannot be
changed during a series. However, it takes less than 30 sec to start the next
series with a different interscan delay. The estimated interscan delay depends
on the technologist's monitor location, operator experience, anatomic target
location, and patient cooperation. It is important to keep the tip of the
needle in the tomographic plane at all times during the procedure because one
tomographic plane image is obtained continuously. Furthermore, it is
imperative to observe the artifact from the tip of the needle (needle tip
sign) on all images (Fig. 2A,
2B). A needle holder such as
the one described by Katada et al.
[1], Kato et al.
[7], and Templeton et al.
[3] helps manipulate the needle
in the gantry and minimizes radiation exposure to the radiologist. However,
the use of such a device causes the loss of tactile sensation, a sensation
that most operators find helpful for needle placement. The operators in our
study had no difficulty performing procedures without this type of device.
View larger version (140K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2A. —67-year-old man with lung nodule. Sequential lung-window helical CT
scan obtained with Smartprep (General Electric Medical Systems, Milwaukee, WI)
during lung biopsy shows advancement of needle in lung nodule.
|
|
We performed near real-time CT fluoroscopy-guided procedures by modifying
the contrast bolus tracking system available on HiSpeed Advantage scanners.
This low-energy technique improved accuracy and increased patient comfort. In
our series, the technique was useful for pulmonary, gastrointestinal, and
musculoskeletal applications. Near realtime CT-guided procedures using the
CAST function (Smartprep) provide significant advantages without additional
cost.
References
-
Katada K, Kato R, Anno H, et al. Guidance with real-time CT
fluoroscopy: early clinical experience. Radiology
1996;200:851-856[Abstract/Free Full Text]
-
White CS, Templeton PA, Hasday JD. CT-assisted transbronchial
needle aspiration: usefulness of CT fluoroscopy. AJR
1997;169:393-394[Free Full Text]
-
Templeton PA, White CS, Protopapas Z, Latief KH, Fournier RS,
Tillett RT. Real-time continuous imaging: CT guidance for lung biopsy (abstr). Radiology
1996;201(P):270
-
Damascelli B, Porcelli G, Spreafico C, et al. CT-fluoroscopy
link-up (CTF): potential for special procedures. Eur J Radiol
1990;11:81-86[Medline]
-
Silverman PM, Roberts S, Tefft MC, et al. Helical CT of the liver:
clinical application of an automated computer technique, Smartprep, for
obtaining images with optimal contrast enhancement. AJR
1995;165:73-78[Abstract/Free Full Text]
-
Silverman PM, Roberts SC, Ducic I, et al. Assessment of a
technology that permits individualized scan delays on helical hepatic CT: a
technique to improve efficiency in use of contrast material. AJR
1996;167:79-84[Abstract/Free Full Text]
-
Kato R, Katada K, Anno H, Suzuki S, Ida Y, Koga S. Radiation
dosimetry at CT fluoroscopy: physician's hand dose and development of needle
holders. Radiology
1996;201:576-578[Abstract/Free Full Text]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
|
|
 
C. A. Binkert, F. R. Verdun, M. Zanetti, C. W. Pfirrmann, and J. Hodler
CT Arthrography of the Glenohumeral Joint: CT Fluoroscopy Versus Conventional CT and Fluoroscopy--Comparison of Image-Guidance Techniques
Radiology,
October 1, 2003;
229(1):
153 - 158.
[Abstract]
[Full Text]
[PDF]
|
|
|
Top
Introduction
Subjects and Methods
