Spiral CT scanning technique in the detection of aspiration of LEGO foreign bodies

BACKGROUND

Radiolucent foreign bodies (FBs) such as plastic objects and toys remain difficult to identify on conventional radiographs of the neck and chest. Children may present with a variety of respiratory complaints, which may or may not be due to a FB.

OBJECTIVE

To determine whether radiolucent FBs such as plastic LEGOs and peanuts can be seen in the tracheobronchial tree or esophagus using low-dose spiral CT, and, if visible, to determine the optimal CT imaging technique.

MATERIALS AND METHODS

Multiple spiral sequences were performed while varying the CT parameters and the presence and location of FBs in either the trachea or the esophagus first on a neck phantom and then a cadaver. Sequences were rated by three radiologists blinded to the presence of a FB using a single scoring system.

RESULTS

The LEGO was well visualized in the trachea by all three readers (both lung and soft-tissue windowing: combined sensitivity 89 %, combined specificity 89 %) and to a lesser extent in the esophagus (combined sensitivity 31 %, combined specificity 100 %). The peanut was not well visualized (combined sensitivity < 35 %). The optimal technique for visualizing the LEGO was 120 kV, 90 mA, 3-mm collimation, 0.75 s/revolution, and 2.0 pitch. This allowed for coverage of the cadaver tracheobronchial tree (approximately 11 cm) in about 18 s. Although statistical power was low for detecting significant differences, all three readers noted higher average confidence ratings with lung windowing among 18 LEGO-in-trachea scans.

CONCLUSION

Rapid, low-dose spiral CT may be used to visualize LEGO FBs in the airway or esophagus. Peanuts were not well visualized.

Accuracy and utility of 3-dimensional computed tomography in evaluating donors for adult living related liver transplants

Three-dimensional (3D) computed tomography (CT) is an imaging technique that renders anatomic detail in 3D images from helical computed tomographic scans. The purpose of this study is to assess 3D CT in the preoperative evaluation of adult living related liver transplant donors. Nine patients underwent right-lobe liver resection for adult living related liver transplants between October 1999 and September 2000. All donors underwent triphasic helical CT of the liver with 3D computed tomographic reconstruction and conventional angiography. The 3D images were correlated with angiography and intraoperative findings. The origin of vessels, relative length of segments, and position of branches were considered for accuracy. The 3D computed tomographic images were compared with angiograms to determine whether angiography could be replaced by 3D CT. 3D CT identified all variations of the hepatic vein confluences and portal vein trifurcations and all hepatic arterial variants. At surgery, the 3D computed tomographic images of hepatic and portal veins were judged to be accurate and helpful in 8 of 9 cases, and images of the hepatic artery, accurate and helpful in 5 of 9 cases. The 3D computed tomographic images of hepatic and portal veins were better than or equivalent to angiograms in nearly all cases. The 3D computed tomographic images of the hepatic artery were better than or equivalent to angiography in 5 of 9 cases. By providing an accurate 3D map of the liver and its vasculature, 3D computed tomographic reconstructions of the hepatic vasculature are a useful adjunct for surgical planning in adult living related liver donors. 3D CT clearly delineates portal and hepatic veins as well as or better than the angiogram and can identify the hepatic artery and its branches well enough to consider replacing angiography, thus reducing cost, inconvenience, and risk to the donor.

Power injection of contrast media using central venous catheters: feasibility, safety, and efficacy

OBJECTIVE

This study evaluates the feasibility, safety, and efficacy of power-injecting IV contrast media through central venous catheters for CT examinations.

SUBJECTS AND METHODS

Two hundred ninety-five CT examinations were performed during an 18-month period in 225 patients with indwelling central venous catheters. Patients were randomized to power injection either through peripheral IV catheter or through central venous catheter. Feasibility was defined as the percentage of patients with contrast material injected successfully through the randomized access route. Safety was evaluated by comparing patients with complications. Efficacy was evaluated by comparing contrast enhancement of the thoracic aorta, pulmonary artery, abdominal aorta, and liver.

RESULTS

Two hundred nine patients had randomization data recorded. One hundred three (94%) of 109 patients were successfully injected through their indwelling catheter compared with 42 (42%) of 100 through a peripherally placed IV catheter (p < 0.001). After reassignment for unsuccessful access, 174 patients underwent central venous catheter injection, and 51, peripheral IV catheter injection. No statistically significant difference was noted in the complications between the central venous catheter and peripheral IV catheter groups. Enhancement was greater in the thoracic aorta, pulmonary artery, and liver for the peripheral IV catheter group (p < 0.03).

CONCLUSION

Power injection of contrast media through central venous catheters for CT examinations is feasible and safe when set hospital guidelines and injection protocols are followed. This technique provides an acceptable alternative in patients without adequate peripheral IV access when bolus contrast enhancement is desired.

Feasibility of instructing radiology technologists in the performance of gastrointestinal fluoroscopy

OBJECTIVE

We sought to determine if dedicated gastrointestinal technologists could be trained to properly perform esophagography and double-contrast barium enema examinations.

SUBJECTS AND METHODS

Ninety-four patients undergoing double-contrast barium enema examinations and 123 patients undergoing esophagographic examinations were included in the study. The study was conducted over a 4-month period, with examinations performed by eight gastrointestinal technologists, 10 radiology residents, and four staff radiologists. Four random lists were generated for each set of examinations. Each staff gastrointestinal radiologist, who was unaware of who had performed the examination, independently scored the representative radiographs.

RESULTS

For the double-contrast barium enema examinations, no statistically significant differences were found between the technologists and residents for amount of barium used, degree of distention, cecal opacification, and quality of spot radiographs. The technologist-performed examinations had a statistically significant lower mean fluoroscopy time (3.2 min, compared with 4.0 min for staff radiologists and 5.7 min for residents). For the esophagrams, no statistically significant differences between technologists and residents were found for single-contrast esophagrams; radiographs of the gastric cardia; assessment of motility, reflux, and transit of a solid bolus; and fluoroscopy time. Double-contrast esophagrams obtained by technologists received a better mean score than did those of the residents.

CONCLUSION

Radiology technologists can be trained to perform high-quality esophagography and double-contrast barium enema examinations without an unacceptably high radiation dose.

Imaging guided biopsies of renal masses

Percutaneous fine-needle aspiration biopsy can be used for the diagnosis of many abdominal masses. It is safe and accurate, and is often all that is necessary to determine treatment. Fine-needle aspiration biopsy is both accurate and cost-effective, comparing favorably with open surgical biopsy. The use of percutaneous biopsy for the diagnosis of renal masses is now more commonplace as urologists and radiologists become familiar with its indications, contraindications, accuracy and complications.

Preoperative use of 3D volume rendering to demonstrate renal tumors and renal anatomy

With increased use of computed tomography (CT) and abdominal ultrasonography, the indications for nephron-sparing surgery are also increasing. Triphasic helical CT and three-dimensional (3D) volume rendering can be combined into a single noninvasive test to delineate renal tumors and normal and complex renal anatomy prior to nephron-sparing surgery. This combination technique has proved accurate and very useful for both preoperative and intraoperative planning by demonstrating renal position, tumor location and depth of tumor extension into the kidney, relationship of the tumor to the collecting system, and renal vascular anatomy. Knowledge of the position of the kidney relative to the lower rib cage, iliac crest, and spine helps in planning the initial surgical incision. By depicting tumor location and depth of extension, helical CT with 3D volume rendering helps ensure complete tumor excision and conservation of adjacent normal renal parenchyma. Depiction of the relationship of the tumor to the collecting system helps anticipate further tumor extension and minimize postoperative complications. Identification of normal renal vasculature and anatomic variants can help minimize ischemic injury and intraoperative bleeding. Radiologists should be familiar with current indications for nephron-sparing surgery and understand what information is required prior to surgery.

Prospective, blinded comparison of laparoscopic ultrasonography vs. contrast-enhanced computerized tomography for liver assessment in patients undergoing colorectal carcinoma surgery

PURPOSE

To prospectively and blindly compare intraoperative laparoscopic ultrasonography to preoperative contrast-enhanced computerized tomography in detecting liver lesions in colorectal cancer patients. Additionally, we compared conventional (open) intraoperative ultrasonography with bimanual liver palpation to contrast-enhanced computerized tomography in a subset of patients.

METHODS

From December 1995 to March 1998, 77 consecutive patients underwent curative (n = 63) or palliative (n = 14) resections for colorectal cancer. All patients undergoing curative resections were randomized to either laparoscopic (n = 34) or conventional (n = 29) surgery after informed consent. All patients underwent contrast-enhanced computerized tomography, diagnostic laparoscopy, and laparoscopic ultrasonography before resection. In those patients who had conventional procedures, intraoperative ultrasonography with bimanual liver palpation was also done. All laparoscopic ultrasonography and intraoperative ultrasonography evaluations were performed by one of two radiologists who were blinded to the CT results. All hepatic segments were scanned using a standardized method. The yield of each modality was calculated using the number of lesions identified by each imaging modality divided by the total number of lesions identified.

RESULTS

In 43 of the 77 patients, both the laparoscopic ultrasonography and CT scan were negative for any liver lesions. In 34 patients, a total of 130 lesions were detected by laparoscopic ultrasonography, CT, or both. When compared with laparoscopic ultrasonography, intraoperative ultrasonography with bimanual liver palpation identified one additional metastatic lesion and no additional benign lesions. laparoscopic ultrasonography identified two patients with mets who had negative preoperative contrast-enhanced computerized tomography.

CONCLUSIONS

Laparoscopic ultrasonography of the liver at the time of primary resection of colorectal cancer yields more lesions than preoperative contrast-enhanced computerized tomography and should be considered for routine use during laparoscopic oncologic colorectal surgery.

Triphasic helical CT of the kidneys: contribution of vascular phase scanning in patients before urologic surgery

OBJECTIVE

The purpose of this study was to evaluate the potential benefits of performing vascular phase scanning of the kidneys in addition to unenhanced and parenchymal phase contrast-enhanced CT in patients being examined for urologic surgery.

MATERIALS AND METHODS

Parenchymal and vascular phase images from triphasic renal helical CT of 50 patients were sequentially evaluated in a randomized, retrospective fashion by two independent observers. The number of renal arteries and veins and the presence of vein or collecting system anomalies were recorded for each scan phase along with a subjective 10-point-scale score of the visibility of the vasculature and collecting system. Correlation of these findings was made with surgical or angiographic findings in 67 of the 87 kidneys and was made by consensus review in the remaining 20 kidneys.

RESULTS

Accessory renal arteries were seen significantly more often (p < .05, chi-square test) on the vascular phase scans. The subjective scores for the visibility of the renal arteries and renal veins were significantly higher on the vascular phase scans (p < .0001, Wilcoxon's rank sum test). The subjective scores for the visibility of the filling of the collecting system and renal pelvis were significantly higher for the parenchymal phase scans, despite the use of a small contrast bolus before each scan (p < .0001, Wilcoxon's rank sum test). CONCLUSION; Triphasic renal CT better reveals the artery and vein anatomy of the kidney than does parenchymal phase imaging only. Triphasic helical CT is indicated in patients undergoing planning for urologic surgery when vascular anatomy is clinically important.

3-dimensional volume rendered computerized tomography for preoperative evaluation and intraoperative treatment of patients undergoing nephron sparing surgery

Background:

Live donor nephrectomy has gained popularity on account of the laparoscopic technique, to overcome a small donor pool. Laparoscopic donor nephrectomy requires a precise study of the vascular and morphological renal anatomy, as laparoscopy is technically challenging due to the limited field of vision. In-depth knowledge of the renal anatomy before a laparoscopic procedure is essential for a successful transplant. The left kidney is preferred over the right even in cases of multiple vessels because of the long renal vein, which requires precise preoperative vascular mapping. Helical computerized tomography (CT) angiography, with its axial, coronal, and 3D reconstruction, gives a better understanding of renal anatomy. There are instances where the helical CT findings are misleading and less informative in a small number of cases. This study highlights a case study of the helical CT findings compared with the intraoperative findings of 200 live donors, who underwent laparoscopic donor nephrectomy, and the renal anatomy has been understood at the same time.

Aims:

1. To compare the helical CT findings on the operated side with the intraoperative findings. 2. To analyze the CT findings

Materials and Methods:

Two hundred cases of laparoscopic transperitoneal donor nephrectomy were included in this study.

Statistical Method Used:

Chi square test was the statistical test used to compare the findings between CT and the intraoperative data.

Results:

The axial, coronal, and 3D images of the CT findings were on par with the intraoperative findings in most of the cases. Incidental findings help in the better planning of surgery. Multiple vessels on the left side are preferred over the right sided normal anatomy; with not much technical difficulty with the aid of a helical CT. Male donors had more incidences of multiple vessels, gonadal vein, Retroaortic Renal Vein (RARV), lumbar vein, and duplication of ureter, compared to females. Furthermore, these variations are more in the left side donors. Ninety-two percent of the cases in this study are left-sided donors. The helical CT finding shows that renal vein variations are more on the right side.

Conclusions:

Helical CT is important in delineating the arterial, venous, and ureteral anatomy and can show the important incidental findings. Left renal donors and males have more variations in their renal anatomy. Technically challenging laparoscopic nephrectomy on the multiple-vessel-side donor is possible with the aid of helical CT. The importance of the CT in evaluating donor renal anatomy for a technically challenging laparoscopic donor nephrectomy is commendable.

3-dimensional volume rendered computerized tomography for preoperative evaluation and intraoperative treatment of patients undergoing nephron sparing surgery

PURPOSE

Computerized tomography (CT) is the diagnostic and staging modality of choice for renal neoplasms. Existing imaging modalities are limited by a 2-dimensional (D) format. Recent advances in computer technology now allow the production of high quality 3-D images from helical CT. Nephron sparing surgery requires a detailed understanding of renal anatomy. Preoperative evaluation must delineate the relationship of the tumor to adjacent normal structures and demonstrate the vascular supply to the tumor for the surgeon to conserve as much normal parenchyma as possible. We propose that helical CT combined with 3-D volume rendering provides all of the information required for preoperative evaluation and intraoperative management of nephron sparing surgery cases. We prospectively evaluated the role of 3-D volume rendering CT in 60 patients undergoing nephron sparing surgery for renal cell carcinoma at the Cleveland Clinic Foundation.

MATERIALS AND METHODS

Triphasic spiral CT was performed preoperatively in 60 consecutive patients undergoing nephron sparing surgery for renal neoplasms. A 3 to 5-minute videotape was prepared using volume rendering software which demonstrated the position of the kidney, location and depth of extension of the tumor(s), renal artery(ies) and vein(s), and relationship of the tumor to the collecting system. These videotapes were viewed by a radiologist and urologist in the operating room at surgery, and immediately correlated with surgical findings. Corresponding renal arteriograms of 19 patients were retrospectively compared to 3-D volume rendering CT and operative findings.

RESULTS

A total of 97 renal masses were identified in 60 cases evaluated with 3-D volume rendering CT before nephron sparing surgery. There were no complications related to the 3-D protocol and 3-D rendering was successful in all patients. The number and location of lesions identified by 3-D volume rendering CT were accurate in all cases, while enhancement and diagnostic characteristics were consistent with pathological findings in 95 of 97 tumors (98%). Of 77 renal arteries identified at surgery 74 were detected by 3-D volume rendering CT (96%). Helical CT missed 3 small accessory arteries, including 1 in a cross fused ectopic kidney. All major venous branches and anomalies were identified, including 3 circumaortic left renal veins. Of 69 renal veins identified at surgery 64 were detected by 3-D volume rendering CT (93%). All 5 renal veins missed by CT were small, short, duplicated right branches of the main renal vein. Renal fusion and malrotation anomalies were correctly identified in all 4 patients.

CONCLUSIONS

The 3-D volume rendering CT accurately depicts the renal parenchymal and vascular anatomy in a format familiar to most surgeons. The data integrate essential information from angiography, venography, excretory urography and conventional 2-D CT into a single imaging modality, and can obviate the need for more invasive imaging. Additionally, the use of videotape in an intraoperative setting provides concise, accurate and immediate 3-D information to the surgeon, and it has become the preferred means of data display for these procedures at our center.

Comparison of two barium suspensions for dedicated small-bowel series

OBJECTIVE

The in vivo radiographic features of two commercially available formulations of barium used as contrast media in dedicated small-bowel series were compared.

SUBJECTS AND METHODS

Fifty-six consecutive outpatients referred for a dedicated small-bowel series were randomly administered either E-Z-Paque or Entrobar. Representative survey radiographs from each examination were randomized and reviewed by six gastrointestinal radiologists from three institutions. Each observer assigned a numeric score (1 = poor, 2 = fair, 3 = good, and 4 = excellent) that rated the quality of the radiograph with respect to these characteristics: definition of fold pattern, translucency, distention, and integrity of the barium column. Statistical analysis was performed for each characteristic using Wilcoxon's two-sample rank sum test.

RESULTS

All six observers found a statistically significant difference between the two barium formulations for mean scores for definition of fold pattern and translucency. Mean scores for fold pattern were 3.3, 3.0, 3.2, 3.6, 3.3, and 3.4 for Entrobar and 2.1, 2.3, 2.4, 3.2, 2.6, and 2.7 for E-Z-Paque. Mean scores for translucency were 2.5, 2.7, 2.8, 3.1, 2.7, and 3.3 for Entrobar and 1.6, 1.7, 2.1, 2.3, 1.9, and 2.7 for E-Z-Paque. No statistically significant difference was found for mean score for distention or integrity of the barium column.

CONCLUSION

On radiographs, Entrobar was found to have superior characteristics for visualization of fold pattern and translucency but offered no advantages for distention or integrity of the barium column. Improved translucency and definition of fold pattern may translate into improved sensitivity and confidence in diagnosing small-bowel abnormality.

Endoleak after aortic stent graft repair: diagnosis by color duplex ultrasound scan versus computed tomography scan

PURPOSE

The purpose of this study was to compare the accuracy of a color duplex ultrasound scan (CDU) to a computerized axial tomography scan (CT) in the diagnosis of endoleaks after stent graft repair of abdominal aortic aneurysms.

METHODS

The Endovascular Aneurysm Clinical Trial Core Laboratory records were reviewed from 117 concurrent CDU and CT studies that were performed in 79 patients who were implanted with the Endovascular Technologies stent graft device between December 1995 and January 1997. All of the studies were interpreted by the Core Laboratory as having the presence or the absence of an endoleak or as being indeterminate because of technical factors. Of the 117 videotaped CDU studies available for reexamination, 100 were reassessed for technical adequacy on the basis of the following criteria: a satisfactory imaging of the aneurysm sac and of the stent graft with gray scale, and both color and spectral Doppler scan evaluation for endoleak outside the endograft and within the aneurysm sac.

RESULTS

Of the 117 studies, 103 CDUs (88%) and 114 CTs (97%) were recorded as having the presence or the absence of an endoleak and 14 CDUs (12%) and 3 CTs (3%) were indeterminate. For the studies that were recorded to have the presence or the absence of an endoleak, the sensitivity, the specificity, the positive and the negative predictive values, and the accuracy of CDUs as compared with CTs were 97%, 74%, 66%, 98%, and 82%, respectively. Of the 100 CDU videotaped studies available for review, the following results were seen: (1) 93 CDUs had satisfactory B-mode images, (2) 76 had satisfactory color Doppler scan images to evaluate for endoleaks, (3) 55 had color Doppler scan assessment of the entire abdominal aortic aneurysm sac for endoleak, and (4) 27 had spectral Doppler scan waveform confirmation of suspected endoleaks. Only 19 CDU studies (19%) with all 4 criteria for complete assessment of endoleak were performed.

CONCLUSION

Although most of the CDU studies were technically suboptimal, the CDUs reliably identified endoleaks with an excellent sensitivity and a negative predictive value as compared with CT scans.

Helical CT and CT angiography for the identification of crossing vessels at the ureteropelvic junction

In comparison with pyeloplasty, endourologic procedures for the treatment of ureteropelvic junction obstruction offer good success rates with less morbidity and a shorter hospitalization; however, studies have found lower success rates and increased complications in patients with crossing vessels. Conventional diagnostic angiography and intravenous urography have both been used to identify crossing vessels at the UPJ; but, a reliable, less invasive, less costly, and simpler preoperative procedure to identify crossing vessels is needed. Helical CT with CT angiography is a promising noninvasive technique for the identification of crossing vessels at the ureteropelvic junction, which can be used for surgical planning of endourologic treatment of UPJ obstruction.

Comparison of examination times between CT scanners: are the newer scanners faster?

OBJECTIVE

The purpose of this study was to determine if a newer technology helical CT scanner can reduce CT examination times.

MATERIALS AND METHODS

Data from 1049 CT examinations were recorded prospectively during a 5-week period. "Room time" was defined as the time each patient spent in the CT room (time patient exited minus time patient entered) and "scanner time" was defined as the time a scanner was dedicated to a specific patient (longer of either time that image processing was complete minus time patient entered room, or total time that patient spent in the scanner room). Data to calculate the room and scanner times were recorded along with the scanner type, examination protocol, and five other covariates. Both times were calculated for the 10 most common examination protocols (n = 769 patients) and compared between the older and newer model CT scanner using analysis of covariance models. The most common protocols were abdomen and pelvis (n = 211); head (n = 146); chest (n = 99); simple sinus (n = 99); and chest, abdomen, and pelvis (n = 68).

RESULTS

The mean room and scanner times, adjusted for covariates, were both significantly shorter for the newer scanner (p = .0001). The results for room time were statistically significant for six of the 10 examination protocols (84% of examinations). Likewise, the results for scanner time were statistically significant for four examination protocols (68% of examinations). Examination times were longer for inpatients (p = .0001) and when problems occurred during the examination (p = .0001). Sex and age did not significantly affect examination times (p > .08).

CONCLUSION

The newer helical CT scanner we studied significantly reduced the time for many types of examinations.

Spiral noncontrast CT versus combined plain radiography and renal US after extracorporeal shock wave lithotripsy: cost-identification analysis

PURPOSE

To investigate the costs of spiral computed tomography (CT) versus those of combined plain radiography and renal ultrasound (US) in screening for postprocedural complications after extracorporeal shock wave lithotripsy (ESWL).

MATERIALS AND METHODS

Twenty-five adult patients who had undergone ESWL were prospectively examined with spiral CT, renal US, and plain abdominal radiography. Each examination was timed, and direct technical costs were calculated by using a procedural-based cost-accounting system. The combined cost of US and plain radiography was compared with the cost of spiral CT.

RESULTS

The average time for spiral CT was 15.3 minutes compared with 37.2 minutes for combined US and plain radiography. The direct technical cost of spiral CT was $36.86 compared with $57.60 for combined US and plain radiography. Average examination times were varied to assess the effect on overall costs. Within reasonable time ranges, combined US and plain radiography cannot be cost equivalent to spiral CT.

CONCLUSION

Spiral CT is faster and is associated with less direct technical cost than combined US and plain radiography when used to examine patients after ESWL, given the dependence of this model on time of examination. Further studies are needed to assess the relative accuracy of these alternative approaches.

Pelvic computed tomography of breast carcinoma patients. Should it routinely be added to abdominal computed tomography?

BACKGROUND

This study was conducted to determine if pelvic computed tomography (CT) should routinely be appended to abdominal CT in the workup of patients with breast carcinoma.

METHODS

The abdominal-pelvic CTs of 139 breast carcinoma patients (195 exams) were reviewed. Scans were grouped by indication and whether pelvic pathology was known before CT. Pelvic CT results were correlated with their effect on patient management.

RESULTS

Among the 119 patients without pre-CT evidence of pelvic disease, a nonosseous pelvic metastasis was identified in only 1; this patient also had liver metastases and management was not changed. No unsuspected pelvic CT finding altered therapy for breast carcinoma. However, three patients underwent surgery for asymptomatic masses discovered on pelvic CT; all were benign.

CONCLUSIONS

Pelvic CT is unlikely to affect the management of patients with breast carcinoma by detecting occult metastatic disease.

Power injection of intravenous contrast material through central venous catheters for CT: in vitro evaluation

PURPOSE

To determine the feasibility of use of a power injector to deliver contrast material through central venous catheters for computed tomographic (CT) examinations.

MATERIALS AND METHODS

Ioversol 240 and iothalamate meglumine 43% were separately injected through three 9.6-F Hickman catheters and three 10.0-F Leonard catheters with a power injector in an in vitro study. Flow rates of 1.0, 1.5, 2.0, and 2.5 mL/sec were tested. Peak pressures were mechanically recorded from two sites. A 95% prediction interval was calculated for each peak pressure, and the upper limits at the prediction interval were evaluated to determine if it was less than the recommended limit of 25 psi (175 kPa).

RESULTS

Contrast medium, flow rate, and catheter type each statistically significantly affected the measured peak pressures (P = .0001). For each flow rate tested, the upper limits of the prediction interval for the peak pressure at the connection between the coiled tubing and the catheter were below the manufacturer's specified peak pressure.

CONCLUSION

In vitro analysis demonstrates that power injection of intravenous contrast medium through central venous catheters does not exceed the pressure limits of these catheters at the flow rates tested. In vivo testing to evaluate the safety and efficacy of power injection through central venous catheters is necessary.

The current role of percutaneous biopsy in the evaluation of renal masses

Percutaneous biopsy of intraabdominal masses is a safe and accurate means of obtaining a tissue diagnosis without surgical exploration. It is often sufficient to determine treatment plans and in many instances, obviates the need for surgery. Percutaneous biopsy of renal masses has traditionally had a limited role in the United States. However, with a recent increase in the detection of small renal masses because of the widespread use of abdominal computed tomography (CT), there is an increasing role for percutaneous biopsy in the management of renal masses. Percutaneous biopsy of renal masses is indicated to differentiate between a primary renal cell carcinoma and metastatic disease in patients with a known extrarenal primary. Percutaneous biopsy is also indicated to establish a diagnosis of renal lymphoma and abscess. Complications of percutaneous biopsy include bleeding, pneumothorax, and tumor seeding along the needle tract; fortunately, these complications are uncommon. We will review the indications, techniques, complications, sensitivity, and accuracy of CT and ultrasound-guided biopsy of renal masses. Urologists and radiologists should both be familiar with the indications and contraindications of percutaneous biopsy to insure the appropriate management of renal masses.

Determination of spiral CT slice sensitivity profiles using a point response phantom

OBJECTIVE

This study was done to compare the slice sensitivity profiles (SSP) for combinations of collimation, pitch, and table speed for spiral CT using a point response phantom. The goal was to determine the optimal combination of parameters to reduce partial volume averaging without compromising z-axis coverage.

MATERIALS AND METHODS

A copper ball bearing measuring 0.4 mm was embedded in a closed-cell air-foam background to create a point response input phantom. The phantom was scanned at pitches from 0.1 to 2.0 for collimations of 5, 8, and 10 mm. The full width half maximums (FWHMs) and full width tenth maximums (FWTMs) were estimated from SSP curves generated by plotting the maximum pixel value in HU for each reconstructed image against table position. FWHMs and FWTMs were compared separately for constant collimation and increasing table speed and for constant table speed and decreasing collimation using either a two-tailed z-test or chi-square test.

RESULTS

Differences between FWHMs and between FWTMs for comparisons made between different collimations at constant table speeds of 8 and 10 mm/s were significantly different (p < or = 0.0001). Differences between FWHMs and between FWTMs showed a linear trend, increasing with increasing pitch for constant collimation (p < or = 0.0013).

CONCLUSION

Scanning at narrower collimation but higher pitch provides a narrower SSP when scanning at equivalent table speeds without compromising z-axis coverage.

Evaluation of renal masses detected by excretory urography: cost-effectiveness of sonography versus CT

OBJECTIVE

The purpose of this study was to compare the cost-effectiveness of sonography and CT for the evaluation of renal masses discovered at excretory urography.

MATERIALS AND METHODS

The records of 225 patients with a renal mass shown by urography who then had either sonography or CT within 3 months were reviewed retrospectively. The number, location, and size of lesions; initial and subsequent imaging tests; and final diagnoses were determined. Using the current Medicare reimbursements for sonography and CT, we calculated the economic implications of using sonography or CT as the initial examination. Any effect of the location or size of the lesion on the most cost-effective examination was also determined.

RESULTS

Twenty-one percent of patients had both initial sonography and follow-up CT because of indeterminate findings or detection of a solid mass that required further staging. When CT was done first, CT findings were equivocal in 12%, necessitating follow-up sonography. At the prevailing charges, CT would have to be needed in 70% of patients initially imaged with sonography to justify the use of CT as the initial examination. The location and size of the lesion did not affect the need for CT at a rate (greater than 70%) that would economically justify use of CT as the first imaging test. Eighty-six percent of patients with a mass detected by urography had either a simple cyst or no evidence of a mass on sonography or CT.

CONCLUSION

Sonography is the most cost-effective imaging method for the workup of a renal mass detected at urography. The number of sonographic examinations in which findings are indeterminate or positive (for a solid mass) is not sufficiently high to warrant replacement of sonography by CT, regardless of the size and location of the lesion. CT should be reserved for a limited number of specific indications.

Use of contrast material for spiral CT of the abdomen: comparison of hepatic enhancement and vascular attenuation for three different contrast media at two different delay times

OBJECTIVE

The purpose of this study was to determine the relative effects of delay time, contrast agent concentration, and contrast agent volume on hepatic enhancement and on aortic and portal vein attenuation for contrast-enhanced spiral CT of the abdomen. The effect of delay time was evaluated by comparing two different delay times for each of three IV contrast media. Three different media were tested to identify whether the effects were different with different iodine concentrations and doses or with different volumes of contrast medium.

SUBJECTS AND METHODS

A total of 169 patients who underwent contrast-enhanced CT of the abdomen with spiral CT imaging were evaluated for enhancement of the liver parenchyma and for postenhancement attenuation of the aorta and portal vein. Total iodine doses of 30 g as 100 ml of iohexol 300 or 125 ml of ioversol 240 and of 40 g as 125 ml of ioversol 320 were evaluated at delay times of 45 and 60 sec and with a low-flow monophasic injection at a rate of 2 ml/sec.

RESULTS

For each contrast medium tested, a 60-sec delay provided greater hepatic enhancement than did a 45-sec delay (43 vs 32 H for iohexol 300, 37 vs 28 H for ioversol 240, and 50 vs 39 H for ioversol 320; all comparisons, p < or = .0001). The aortic attenuation achieved in the abdomen after contrast medium administration was significantly greater with a 45-sec delay than with a 60-sec delay for iohexol 300 (p = .0290) but not for the other contrast media. The portal vein attenuation achieved after contrast medium administration was significantly greater with a 60-sec delay than with a 45-sec delay for all three contrast media (p = .0051).

CONCLUSION

When IV contrast material was injected with a low-flow-rate monophasic bolus, a delay time of 60 sec, longer than that typically used for dynamic incremental scanning, provided greater hepatic enhancement in spiral CT. This result was significant for the three contrast media tested. Aortic attenuation was significantly greater at shorter delay times when a smaller volume of contrast material was injected. Portal vein attenuation was greater at longer delay times, suggesting that the optimal delay time may be longer than 60 sec. Further work to determine the optimal scanning window for hepatic enhancement in spiral CT by use of time-density curves is indicated.

Cystic artery pseudoaneurysm as a complication of laparoscopic cholecystectomy

A 39-year-old man presented with a subhepatic fluid collection 3 weeks after undergoing a laparoscopic cholecystectomy. This was mistakenly thought to represent an abscess, and a drainage catheter was placed at an outside institution. Upon transfer, the collection was diagnosed as a pseudoaneurysm by spiral computed tomography (CT) and angiography. This is the first report of a pseudoaneurysm complicating laparoscopic cholecystectomy.

Spiral CT of the abdomen: artifacts and potential pitfalls

Spiral CT has been advocated as a major advancement in CT technology. Spiral CT scanning is rapid, the volume of IV contrast material can potentially be decreased, and high-quality coronal, sagittal, and three-dimensional reconstruction is possible. However, when compared with dynamic CT, because of the shorter acquisition time of spiral CT, vascular and organ enhancement on spiral CT scans is more dependent on factors that affect the delivery of contrast material into the bloodstream and on the time that scanning begins after the start of injection of contrast material. Additionally, organs other than the liver are scanned earlier than they typically are during a dynamic study, particularly the kidneys and spleen. In our experience to date, these aspects of spiral scanning have led to several difficulties in the interpretation of spiral CT scans. This essay illustrates potential pitfalls in the interpretation of spiral CT scans associated with scanning too soon after injection of contrast material.

High-attenuation lymphadenopathy in AIDS patients: significance of findings at CT

A retrospective evaluation was performed of the location and attenuation characteristics of abdominal and pelvic lymphadenopathy, identified at dynamic sequential bolus computed tomography (CT) in 69 patients with acquired immunodeficiency syndrome (AIDS). Lymph node appearance at CT was characterized as hyperattenuating, isoattenuating, or hypoattenuating relative to the iliopsoas muscle. The significance of finding hyperattenuating adenopathy in the patient population was evaluated. Thirty-three patients had hyperattenuating adenopathy, including 26 with the epidemic form of Kaposi sarcoma (KS). Of 38 patients with epidemic KS, 26 had hyperattenuating, 11 had isoattenuating, and one had hypoattenuating lymphadenopathy. The positive predictive value of hyperattenuating adenopathy for epidemic KS was 79%. These findings were statistically significant at the 95% confidence interval (P < .005). Hyperattenuating lymphadenopathy, identified on dynamic sequential bolus CT scans in AIDS patients, was seen with disseminated KS in approximately 80% of cases.