Multidetector computed tomography of acute vascular injury in blunt abdominal/pelvic trauma: imaging predictors of treatment

PURPOSE

The purpose of this study was to analyze the multidetector computed tomography (MDCT) morphologic characteristics of non-aortic acute vascular injuries (AVI) in patients with blunt abdominopelvic trauma that predict treatment.

METHODS

CT scans of 65 trauma patients with non-aortic AVI were reviewed. AVI morphology was categorized as linear or round. The organ of involvement, location of hemorrhage, initial size of hematoma, and hemodynamic status were recorded. Expansion rates of the hematoma were calculated in 40 patients who had delayed imaging. Multivariate regression was used to analyze the morphologic features of AVI and treatment.

RESULTS

Patients with linear AVI were four times more likely to require aggressive treatment (surgery or embolization) than those with a round morphology, independent of the hemodynamic status. There was no main effect of the organ involved, location of hemorrhage, initial bleed size, or expansion rate on the probability of aggressive treatment.

CONCLUSION

The location, initial size, and expansion rate of AVI are not significant predictors of aggressive treatment with surgery or embolization. Linear morphology of AVI, however, is more likely to require aggressive treatment than round AVI, independent of the hemodynamic status. Linear AVI likely reflects a spurting jet of active extravasation, whereas round AVI likely represents a pseudoaneurysm or slow bleed.

Multidetector-row helical CT and advanced postprocessing techniques for the evaluation of pancreatic neoplasms

An important feature of multidetector-row helical computed tomography (CT) is the increased speed of scanning that permits routine use of very thin collimation and acquisition of near isometric imaging data of the abdomen within the time span of a single breath-hold. The parallel escalation in the capabilities of workstations makes feasible the practical use of advanced postprocessing techniques to create high quality volumetric imaging. This article highlights the unique contributions of multidetector-row CT and advanced postprocessing techniques to the evaluation of the pancreas and peripancreatic vascular structures and their value in the diagnosis and staging of pancreatic neoplasms.

Impact of multidetector CT hepatic arteriography on the planning of chemoembolization treatment of hepatocellular carcinoma

OBJECTIVES

We examined the impact of the increased sensitivity for hypervascular masses of multidetector CT hepatic arteriography on treatment decisions involving selective chemoembolization of hepatocellular carcinomas.

SUBJECTS AND METHODS

Thirty patients were referred for chemoembolization of unresectable hepatocellular carcinoma. Initial selective chemoembolization plans were formulated on the basis of diagnostic biphasic CT or MR imaging. Ultrafast CT hepatic arteriography was performed using a multidetector CT scanner and selective contrast material injection into the hepatic artery. The entire liver was scanned in a single breath-hold of approximately 20 sec with a slice thickness of 1 mm. Lesions and their arterial supplies were identified, and these data were immediately used to formulate a final plan for chemoembolization.

RESULTS

Hypervascular masses were detected in 29 patients. In 16 (53%) of the patients, preprocedural CT or MR imaging underestimated the number of lesions. In nine (30%) of these 16 patients, the additional lesions were detected only on CT hepatic arteriography, not on conventional angiography. CT hepatic arteriography findings had a major impact on planning the way in which chemoembolization treatment was performed. In three of the nine patients, the previously undetected lesions were treated with additional superselective chemoembolization. In the other six patients, chemoembolization was performed less selectively than originally planned.

CONCLUSION

Primarily because of the high sensitivity of multidetector CT hepatic arteriography in revealing small and multifocal hepatomas, findings of this modality frequently alter treatment plans involving selective administration of chemoembolic material.

A statistical 3-D pattern processing method for computer-aided detection of polyps in CT colonography

Adenomatous polyps in the colon are believed to be the precursor to colorectal carcinoma, the second leading cause of cancer deaths in United States. In this paper, we propose a new method for computer-aided detection of polyps in computed tomography (CT) colonography (virtual colonoscopy), a technique in which polyps are imaged along the wall of the air-inflated, cleansed colon with X-ray CT. Initial work with computer aided detection has shown high sensitivity, but at a cost of too many false positives. We present a statistical approach that uses support vector machines to distinguish the differentiating characteristics of polyps and healthy tissue, and uses this information for the classification of the new cases. One of the main contributions of the paper is the new three-dimensional pattern processing approach, called random orthogonal shape sections method, which combines the information from many random images to generate reliable signatures of shape. The input to the proposed system is a collection of volume data from candidate polyps obtained by a high-sensitivity, low-specificity system that we developed previously. The results of our ten-fold cross-validation experiments show that, on the average, the system increases the specificity from 0.19 (0.35) to 0.69 (0.74) at a sensitivity level of 1.0 (0.95).

Tissue harmonic imaging techniques: physical principles and clinical applications

Tissue harmonic imaging (THI) is a new gray-scale sonographic technique that improves image clarity. Harmonics form within the insonated tissue as a consequence of nonlinear sound propagation. Imaging with endogenously formed harmonics means that the distorting layer of the body wall is traversed only once by the harmonic beam--during echo reception. Both image contrast and lateral resolution are improved in harmonic mode compared with conventional (fundamental mode) sonography. This article summarizes the physics and various implementations of harmonic imaging mode, and reviews the clinical applications that have emerged to date.

Parathyroid crisis in a 20 year old--an unusual cause of hypercalcaemic crisis

Since the advent of automated serum analysis, patients with primary hyperparathyroidism (PHPT) are often asymptomatic at presentation or have mild symptoms attributable to the disease. Parathyroid crisis is a rare and potentially fatal complication of PHPT in which patients develop severe hypercalcaemia with signs and symptoms of multiple organ dysfunction. A case of parathyroid crisis in a 20 year old man who presented with brown tumours and renal stones is described.

Preoperative duplex ultrasonography evaluation for deep venous thrombosis in revision hip arthroplasty patients

In a prospective consecutive series, 53 revision hip arthroplasties were performed in 51 patients. Pre- and postoperative Duplex ultrasonography examinations were reviewed by an independent, experienced radiologist. Three of 51 patients (53 procedures) had evidence of chronic deep venous thrombosis (DVT) or other venous abnormality preoperatively, yielding an incidence of 5.6%. One (1.9%) patient developed an acute DVT postoperatively despite pharmacological and mechanical preventative measures. These results indicate the use of preoperative ultrasonography as a screening tool prior to revision hip arthroplasty is not warranted based on the low incidence of acute or chronic DVT detected preoperatively. Long-term anticoagulation, when necessary, can be based on the findings of a postoperative scan.

Imaging the patient with right upper quadrant pain

A variety of high-resolution imaging techniques are currently available for the evaluation of patients with RUQ pain. In these patients, an imaging approach that is based on identifying the presence of certain clinical signs and symptoms can aid in choosing the appropriate imaging modality and establishing the diagnosis. For patients presenting with a positive Murphy sign, sonography and biliary scintigraphy are the most useful initial imaging techniques. In patients with fever and a negative Murphy sign, a combination of sonography and contrast-enhanced CT can establish the diagnosis in most cases. And finally, in patients without fever or a positive Murphy sign, CT and MR are appropriate first-line imaging techniques.

Intraoperative ultrasonography for localization of recurrent thyroid cancer

Advances in measurement of thyroglobulin (Tg) and in imaging techniques including high resolution ultrasound, magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography (PET) scan have increased our ability to detect thyroid cancer recurrences at an earlier stage. (1,2) After thyroidectomy, patients are often treated with radioiodine, but the recurrent cancers may not image with radioiodine. In these instances, the only definitive treatment is surgical resection. Reoperative neck surgery can be challenging, especially when trying to find a small cancer nodule within the central neck that contains dense fibrotic scar tissue. Herein we describe the use of intraoperative ultrasonography to identify the location of recurrent thyroid cancer. This technique can aid in tumor localization and may help to avoid complications such as recurrent nerve injury.

Tissue harmonic imaging techniques: physical principles and clinical applications

Tissue harmonic imaging (THI) is a new gray-scale sonographic technique that improves image clarity. Harmonics form within the insonated tissue as a consequence of nonlinear sound propagation. Imaging with endogenously formed harmonics means that the distorting layer of the body wall is traversed only once by the harmonic beam--during echo reception. Both image contrast and lateral resolution are improved in harmonic mode compared with conventional (fundamental mode) sonography. This article summarizes the physics and various implementations of harmonic imaging mode, and reviews the clinical applications that have emerged to date.

Ultrasonographically guided thyroid biopsy: a review with emphasis on technique

We describe our technique for ultrasonographically guided fine-needle aspiration biopsy of the thyroid that achieves a high rate of diagnostic specimens. Indications for ultrasonographically guided fine-needle aspiration biopsy included a difficult-to-palpate thyroid nodule and previously unsuccessful palpation-guided fine-needle aspiration. Ultrasonographically guided fine-needle aspiration biopsy was performed on 316 thyroid nodules in 306 patients. Adequate cytologic specimens were obtained in 97.2% of the nodules in which biopsy was performed, with a 2.8% rate of inadequate cellularity. Two helpful aspects of this technique that were thought to improve the overall diagnostic yield were the use of color and power Doppler "vascular mapping" of the nodule just before biopsy and on-site cytologic control.

Thickened submucosal layer: a sonographic sign of acute gastrointestinal abnormality representing submucosal edema or hemorrhage. 2000 ARRS Executive Council Award II. American Roentgen Ray Society

OBJECTIVE

We correlated the sonographic appearance of bowel wall thickening with the acuity of the underlying disease process.

SUBJECTS AND METHODS

Sonograms of thickened bowel walls were reviewed in 37 patients with proven gastrointestinal abnormalities. Sonographic findings were correlated with clinical presentation, endoscopy, histology, laboratory data, barium studies, and CT.

RESULTS

Twenty-eight patients presented acutely, and nine patients had chronic or subacute disease processes. Two of the 28 patients had concurrent acute and chronic processes. In 27 of 28 patients with acute processes, the abnormal bowel segments were characterized by an echogenic submucosal layer thicker than 2.5 mm. In contrast, nine patients with chronic or subacute processes had relatively uniform hypoechoic thickening of the bowel wall with loss of visualization of a discrete echogenic submucosal layer. CT was available for comparison in 30 of 37 patients. Of the 28 patients with acute abnormalities, the thickened echogenic submucosal layer on sonography corresponded to either low-attenuation submucosal edema (n = 25) or acute submucosal hemorrhage (n = 3).

CONCLUSION

The finding of a thickened submucosal layer suggests an acute disease process of the bowel and corresponds to either submucosal edema or hemorrhage.

Automated polyp detector for CT colonography: feasibility study

An abdominal computed tomographic scan was modified by inserting 10 simulated colonic polyps with use of methods that closely mimic the attenuation, noise, and polyp-colon wall interface of naturally occurring polyps. A shape-based polyp detector successfully located six of the 10 polyps. When settings that enhanced the edge profile of polyps were chosen, eight of 10 polyps were detected. There were no false-positive detections. Shape analysis is technically feasible and is a promising approach to automated polyp detection.

Focal liver lesions: pattern-based classification scheme for enhancement at arterial phase CT

PURPOSE

To present our early experience with a classification scheme for categorizing focal liver lesions on the basis of the enhancement patterns that they exhibit in the arterial phase of computed tomography (CT) and to determine whether particular enhancement patterns suggest particular diagnoses.

MATERIALS AND METHODS

The authors reviewed arterial phase CT images in 100 consecutive patients with focal liver lesions, excluding simple cysts. The enhancement pattern of the dominant or representative lesion in each patient was classified into one of five categories-homogeneous, abnormal internal vessels or variegated, peripheral puddles, complete ring, or incomplete ring-by three radiologists blinded to the proved diagnosis. Lesions without enhancement were recorded separately. Agreement was reached by consensus in all cases. Standards of reference included findings at histologic examination, correlative imaging, or clinical and imaging follow-up.

RESULTS

Ninety-two percent of the 100 lesions demonstrated arterial phase enhancement. Patterns associated with positive predictive values of 82% or greater and specificity of 80% or greater included abnormal internal vessels or variegated (hepatocellular carcinoma), peripheral puddles (hemangioma), and complete ring (metastasis).

CONCLUSION

The appearance of hepatic lesions in the arterial phase of enhancement has potential use in the determination of specific diagnoses. The classification scheme used in this study may be a useful tool for the interpretation of arterial phase CT studies.

Aortic aneurysmal disease: assessment of stent-graft treatment-CT versus conventional angiography

PURPOSE

To compare computed tomographic (CT) angiography and conventional angiography for determining the success of endoluminal stent-graft treatment of aortic aneurysms.

MATERIALS AND METHODS

Forty patients underwent conventional angiography and CT angiography following treatment of aortoiliac aneurysms with endoluminal stent-grafts. Six additional sets of conventional angiographic-CT angiographic examinations were performed in five patients after placement of additional stent-grafts or coil embolization to treat perigraft leakage. Three faculty CT radiologists who were blinded to patient clinical data and outcome independently interpreted the CT angiograms, and three faculty angiographers, who were not involved in the stent-graft deployment, interpreted the conventional angiograms. Images were assessed for the presence of postdeployment complications. A reference standard was developed by experienced radiologists using all available images and clinical data. Sensitivities, specificities, and kappa values were calculated.

RESULTS

Perigraft leakage was the most commonly identified complication. Twenty perigraft leaks were detected in the results of 46 examinations. Sensitivities and specificities for detecting perigraft leakage were 63% and 77% for conventional angiography and 92% and 90% for CT angiography, respectively. The kappa value was 0. 41 for conventional angiography and 0.81 for CT angiography.

CONCLUSION

CT angiography is the preferred method for establishing the presence of perigraft leakage following treatment of aortoiliac aneurysms with stent-grafts.

Visualization modes for CT colonography using cylindrical and planar map projections

PURPOSE

The purpose of this study was to demonstrate the limitations to the effectiveness of CT colonography, colloquially called virtual colonoscopy (VC), for detecting polyps in the colon and to describe a new technique, map projection CT colonography using Mercator projection and stereographic projection, that overcomes these limitations.

METHOD

In one experiment, data sets from nine patients undergoing CT colonography were analyzed to determine the percentage of the mucosal surface visible in various visualization modes as a function of field of view (FOV). In another experiment, 40 digitally synthesized polyps of various sizes (10, 7, 5, and 3.5 mm) were randomly inserted into four copies of one patient data set. Both Mercator and stereographic projections were used to visualize the surface of the colon of each data set. The sensitivity and positive predictive value (PPV) were calculated and compared with the results of an earlier study of visualization modes using the same CT colonography data.

RESULTS

The percentage of mucosal surface visualized by VC increases with greater FOV but only approaches that of map projection VC (98.8%) at a distorting, very high FOV. For both readers and polyp sizes of > or =7 mm, sensitivity for Mercator projection (87.5%) and stereographic projection (82.5%) was significantly greater (p < 0.05) than for viewing axial slices (62.5%), and Mercator projection was significantly more sensitive than VC (67.5%). Mercator and stereographic projection had PPVs of 75.4 and 78.9%, respectively.

CONCLUSION

The sensitivity of conventional CT colonography is limited by the percentage of the mucosal surface seen. Map projection CT colonography overcomes this problem and provides a more sensitive method with a high PPV for detecting polyps than other methods currently being investigated.

Suspected acute appendicitis: nonenhanced helical CT in 300 consecutive patients

PURPOSE

To determine the accuracy of helical computed tomography (CT) without the oral, intravenous, or rectal administration of contrast material in confirming suspected acute appendicitis.

MATERIALS AND METHODS

Three hundred consecutive patients referred from the departments of surgery and emergency medicine were examined for suspected acute appendicitis by using thin-section nonenhanced helical CT. All transverse CT scans were obtained in a single breath hold from the upper abdomen (T12 vertebra) to the pubic symphysis with 5-mm collimation and a pitch of 1.6. All scans were obtained without oral, intravenous, or rectal contrast material. Criteria for diagnosis of acute appendicitis included an enlarged appendix (> 6 mm) and periappendiceal inflammation. CT diagnoses were recorded prospectively. Final diagnoses were established with the results of surgical or clinical follow-up or both.

RESULTS

There were 110 true-positive diagnoses, 181 true-negative diagnoses (63 of which were an alternative diagnosis correctly established prospectively), five false-negative diagnoses, and four false-positive diagnoses, which yielded a sensitivity of 96%, a specificity of 99%, and an accuracy of 97%.

CONCLUSION

Nonenhanced helical CT is a highly accurate technique for diagnosing or excluding acute appendicitis. Developing experience with the technique and understanding the subtleties of interpretation can further improve diagnostic accuracy.

Computed tomographic angiography: historical perspective and new state-of-the-art using multi detector-row helical computed tomography

Since its clinical introduction in 1991, volumetric computed tomography scanning using spiral or helical scanners has resulted in a revolution for diagnostic imaging. In addition to new applications for computed tomography, such as computed tomographic angiography and the assessment of patients with renal colic, many routine applications such as the detection of lung and liver lesions have substantially improved. Helical computed tomographic technology has improved over the past eight years with faster gantry rotation, more powerful X-ray tubes, and improved interpolation algorithms, but the greatest advance has been the recent introduction of multi detector-row computed tomography scanners. These scanners provide similar scan quality at a speed gain of 3-6 times greater than single detector-row computed tomography scanners. This has a profound impact on the performance of computed tomography angiography, resulting in greater anatomic coverage, lower iodinated contrast doses, and higher spatial resolution scans than single detector-row systems.

Treatment and stabilization of complex wounds involving the pelvic bone, groin, and femur with the inferiorly based rectus abdominis musculocutaneous flap and the use of power color Doppler imaging in preoperative evaluation

The authors present case reports demonstrating the trilevel utility of the inferiorly based rectus abdominis musculocutaneous flap in the closure of complex wounds involving the pelvis, groin, and femur that had failed previously or were not amenable to traditional closure techniques. The use of the rectus abdominis flap was especially advantageous for achieving infection eradication and large dead space closure. Additionally they present the emerging technique of power color Doppler imaging as a valuable tool in preoperative flap planning. This technique is particularly useful in evaluating the candidacy for rectus abdominis musculocutaneous flap placement of patients with a prior history of abdominal surgeries, trauma, infection, irradiation, or other conditions that might compromise the patency of the deep inferior epigastric vessels.

Disseminated peritoneal plasmacytoma following cardiac transplantation

Posttransplant lymphoproliferative disorders (PTLD) are an important comorbidity in immunosuppressed transplant patients. We describe a unique case of PTLD, a disseminated peritoneal plasmacytoma in a 56-year-old cardiac transplant patient presenting with ascites. The associated computed tomographic findings include omental thickening, mesenteric stranding, and ascites.

Parathyroid localization with high-resolution ultrasound and technetium Tc 99m sestamibi

HYPOTHESIS

High-resolution ultrasound and technetium Tc 99m sestamibi scanning can be used for preoperative localization of abnormal parathyroid glands in patients with hyperparathyroidism.

DESIGN

Ultrasound and sestamibi scanning were performed in patients undergoing neck exploration for hyperparathyroidism. If the 2 scans agreed in identifying a single adenoma, and surgery confirmed the location of a single adenoma and an ipsilateral normal gland, a unilateral exploration was performed.

SETTING

University tertiary care center.

PATIENTS

Sixty-one consecutive patients undergoing surgery for hyperparathyroidism from September 1, 1994, through September 30, 1997.

INTERVENTIONS

High-resolution ultrasound was performed in 59 patients and sestamibi scanning in 58 patients; all patients underwent neck exploration by a single surgeon.

MAIN OUTCOME MEASURES

The results of preoperative ultrasound and sestamibi scanning were compared with operative and histological findings.

RESULTS

All patients were cured of hypercalcemia. Specificity of ultrasound and sestamibi scanning was 98% and 99%, respectively; however, their sensitivity was only 57% and 54%, respectively. Both imaging modalities had lower sensitivities in the setting of multigland disease. If both imaging studies were considered as a single test, sensitivity for imaging in patients with primary hyperparathyroidism reached 78%. Our localization protocol allowed a unilateral approach in 43% of patients (23 of 53).

CONCLUSIONS

These results confirm the value of preoperative localization in patients with hyperparathyroidism. A unilateral approach can be used with a high degree of success in cases when ultrasound and sestamibi scanning agree in the identification of a single adenoma confirmed by surgical exploration with the identification of a normal ipsilateral gland.

Display modes for CT colonography. Part II. Blinded comparison of axial CT and virtual endoscopic and panoramic endoscopic volume-rendered studies

PURPOSE

To determine the sensitivity of radiologist observers for detecting colonic polyps by using three different data review (display) modes for computed tomographic (CT) colonography, or "virtual colonoscopy."

MATERIALS AND METHODS

CT colonographic data in a patient with a normal colon were used as base data for insertion of digitally synthesized polyps. Forty such polyps (3.5, 5, 7, and 10 mm in diameter) were randomly inserted in four copies of the base data. Axial CT studies, volume-rendered virtual endoscopic movies, and studies from a three-dimensional mode termed "panoramic endoscopy" were reviewed blindly and independently by two radiologists.

RESULTS

Detection improved with increasing polyp size. Trends in sensitivity were dependent on whether all inserted lesions or only visible lesions were considered, because modes differed in how completely the colonic surface was depicted. For both reviewers and all polyps 7 mm or larger, panoramic endoscopy resulted in significantly greater sensitivity (90%) than did virtual endoscopy (68%, P = .014). For visible lesions only, the sensitivities were 85%, 81%, and 60% for one reader and 65%, 62%, and 28% for the other for virtual endoscopy, panoramic endoscopy, and axial CT, respectively. Three-dimensional displays were more sensitive than two-dimensional displays (P < .05).

CONCLUSION

The sensitivity of panoramic endoscopy is higher than that of virtual endoscopy, because the former displays more of the colonic surface. Higher sensitivities for three-dimensional displays may justify the additional computation and review time.

Display modes for CT colonography. Part I. Synthesis and insertion of polyps into patient CT data

PURPOSE

To develop and validate a method for the insertion of digitally synthesized polyps into computed tomographic (CT) images of the human colon for use as ground truth for evaluation of virtual colonoscopy.

MATERIALS AND METHODS

Spiral CT simulator software was used to generate 10 synthetic polyps in various configurations. Additional software was developed to insert these polyps into volume CT scans. Ten polyps in eight patients were selected for comparison. Three radiologists evaluated whether two-dimensional (2D) CT images and three-dimensional (3D) volume-rendered CT images showed synthetic or real polyps.

RESULTS

Edge-response profiles and noise of simulated polyps matched those of native polyps. Frequency distributions of reviewers' responses were not significantly different for synthetic versus real polyps in either 3D or 2D images. Responses were clustered around the response of "unsure" if lesions were real or synthetic. Receiver operating characteristic curves had areas of 0.54 (95% CI = 0.39, 0.68) for 3D and 0.39 (95% CI = 0.25, 0.53) for 2D images, which were not significantly different from random guessing (P = .70 and .28 for 3D and 2D images, respectively).

CONCLUSION

Synthetic polyps were indistinguishable from real polyps. This method can be used to generate ground truth experimental data for comparison of CT colonographic display and detection methods.

Malignant fibrous histiocytoma presenting as cystic pancreatic mass

Although malignant fibrous histiocytoma (MFH) is a common sarcoma of late adulthood, it has rarely been reported to involve the pancreas. We describe the clinical and imaging features of a 27-year-old patient presenting with a predominantly cystic MFH. The cystic appearance of the lesion corresponded histologically to necrosis and hemorrhage within the mass.

Virtual endoscopy using perspective volume-rendered three-dimensional sonographic data: technique and clinical applications

OBJECTIVE

We present a technique for obtaining three-dimensional external and virtual endoscopy views of organs using perspective volume-rendered gray-scale and Doppler sonographic data, and we explore potential clinical applications in the carotid artery, the female pelvis, and the bladder.

CONCLUSION

Using the proposed methods, radiologists will find it possible to create virtual endoscopy and external perspective views using sonographic data. The technique works well for revealing the interior of fluid-filled structures and cavities. However, expected improvements in computer performance and integration with existing sonographic equipment will be necessary for the technique to become practical in the clinical environment.

Power Doppler imaging of acute renal transplant rejection

PURPOSE

We evaluated the usefulness of power Doppler imaging (PDI) in diagnosing acute renal-transplant rejection.

METHODS

Twenty-eight patients underwent 33 renal-transplant biopsies for suspected acute rejection. Patterns of renal parenchymal vascularity revealed by PDI in patients with abnormal biopsy results were compared with patterns in a group who had normal biopsy results. PDI examinations were reviewed retrospectively by 2 independent radiologists who had no knowledge of the biopsy results. A PDI diagnosis of acute rejection required marked vascular pruning in both the cortex and medulla. PDI results then were compared with transplant-biopsy results.

RESULTS

The sensitivity and specificity of PDI for diagnosing acute renal-transplant rejection were 40% and 100%, respectively. None of the patients with negative biopsy results had PDI abnormalities. The negative predictive value of PDI was 33%, and the positive predictive value was 100%.

CONCLUSIONS

In our study, an abnormal sonogram was highly predictive of acute transplant rejection. However, a normal sonogram did not exclude the possibility of rejection.

The acute abdomen: current CT imaging techniques

Currently, CT plays a pivotal role in the evaluation of the patient with an acute abdomen. Several competing techniques have been described and investigated. Each appears to possess advantages and disadvantages which will be examined. Each imaging center needs to modify these protocols to satisfy local scanner availability, patient demographics, radiologic expertise, and economic considerations.

Hepatic abscess following transhepatic drainage of subphrenic abscess

A case of an hepatic abscess that developed after percutaneous transhepatic drainage of a subphrenic abscess is presented. The location of the abscess immediately along the tract of the drainage catheter and the similar organisms recovered from bacteriologic culture suggest that the abscess was related to direct contamination along the tract of the drainage catheter. The potential for abscess formation within the liver should be considered in the choice of access route for percutaneous drainage of retroabdominal abscesses. It may be preferable to avoid transhepatic drainage in patients in whom it is anticipated that the catheter drainage will require considerable length of time.

CT angiography of the abdominal and thoracic aorta

Evaluation of the abdominal and thoracic aorta is one of the most common indications for CT angiography (CTA). CTA largely has replaced conventional angiography in the assessment of aortic aneurysms and dissections because it provides all the relevant anatomic information at reduced cost, morbidity, and radiation exposure. This article will focus on the technique, interpretation, and pitfalls in the CTA evaluation of the abdominal and thoracic aorta.

CT angiography of the visceral vasculature

CT angiography (CTA) is a minimally invasive technique that has proven to be clinically useful in evaluating the vasculature of the abdominal viscera. In many instances, the diagnostic information obtained from abdominal CTA is sufficient to avoid the expense and morbidity of conventional angiography. This article reviews the indications, technique, and pitfalls of abdominal CTA with specific emphasis on disorders of the hepatic, splenic, and superior mesenteric arteries and the portal venous system.

Use of color and power Doppler sonography to identify feeding arteries associated with parathyroid adenomas

OBJECTIVE

The objective of our study was to determine the value of using color and power Doppler sonography to reveal extrathyroidal feeding arteries in the detection of abnormal parathyroid glands.

SUBJECTS AND METHODS

Forty-four patients with primary hyperparathyroidism were imaged prospectively with high-resolution gray-scale, color flow, and power Doppler sonography. The presence of extrathyroidal arteries supplying the adenomas was noted. All patients underwent subsequent neck exploration. The locations of the abnormal glands were recorded.

RESULTS

At surgery, 51 abnormal parathyroid glands were removed in the 44 patients. Sonography correctly revealed an adenoma in 40 of the 44 patients. Likewise, sonography revealed 42 of the 51 adenomas. Nine false-negative and two false-positive interpretations of the sonograms were made. Thus, overall sensitivity was 83%, specificity was 98%, and accuracy was 94%. Three of the false-negative interpretations were ectopic glands within the superior mediastinum. Excluding these three glands from analysis, the sensitivity for detection of adenomas within the neck was 88%, specificity was 98%, and accuracy was 95%. An extrathyroidal artery leading to a parathyroid adenoma was seen in 35 of the 42 adenomas revealed by sonography. The presence of an extrathyroidal artery leading to an adenoma was found to aid in the detection of an otherwise inconspicuous parathyroid gland in five patients, which improved sensitivity from 73% to 83%.

CONCLUSION

Prominent vessels supplying parathyroid adenomas are frequently revealed by color flow and power Doppler sonography. These vessels can serve as "road maps" to abnormal parathyroid glands.

Detection of colonic polyps in a phantom model: implications for virtual colonoscopy data acquisition

PURPOSE

Virtual colonoscopy is a new method of colon examination in which computer-aided 3D visualization of spiral CT simulates fiberoptic colonoscopy. We used a colon phantom containing various-sized spheres to determine the influence of CT acquisition parameters on lesion detectability and sizing.

METHOD

Spherical plastic beads with diameters of 2.5, 4, 6, 8 and 10 mm were randomly attached to the inner wall of segments of plastic tubing. Groups of three sealed tubes were scanned at 3/1, 3/2, 5/1 collimation (mm)/pitch settings in orientations perpendicular and parallel to the scanner gantry. For each acquisition, image sets were reconstructed at intervals from 0.5 to 5.0 mm. Two blinded reviewers assessed transverse cross-sections of the phantoms for bead detection, using source CT images for images for acquisitions obtained with the tubes oriented perpendicular to the gantry and using orthogonal reformatted images for scans oriented parallel to the gantry.

RESULTS

Detection of beads of > or = 4 mm was 100% for both tube orientations and for all collimator/pitch settings and reconstruction intervals. For the 2.5 mm beads, detection decreased to 78-94% for 5 mm collimation/pitch 2 scans when the phantom sections were oriented parallel to the gantry (p = 0.01). Apparent elongation of beads in the slice direction occurred as the collimation and pitch increased. The majority of the elongation (approximately 75%) was attributable to changing the collimator from 3 to 5 mm, with the remainder of the elongation due to doubling the pitch from 1 to 2.

CONCLUSION

CT scanning at 5 mm collimation and up to pitch 2 is adequate for detection of high contrast lesions as small as 4 mm in this model. However, lesion size and geometry are less accurately depicted than at narrower collimation and lower pitch settings.

Automated flight path planning for virtual endoscopy

In this paper, a novel technique for rapid and automatic computation of flight paths for guiding virtual endoscopic exploration of three-dimensional medical images is described. While manually planning flight paths is a tedious and time consuming task, our algorithm is automated and fast. Our method for positioning the virtual camera is based on the medial axis transform but is much more computationally efficient. By iteratively correcting a path toward the medial axis, the necessity of evaluating simple point criteria during morphological thinning is eliminated. The virtual camera is also oriented in a stable viewing direction, avoiding sudden twists and turns. We tested our algorithm on volumetric data sets of eight colons, one aorta and one bronchial tree. The algorithm computed the flight paths in several minutes per volume on an inexpensive workstation with minimal computation time added for multiple paths through branching structures (10%-13% per extra path). The results of our algorithm are smooth, centralized paths that aid in the task of navigation in virtual endoscopic exploration of three-dimensional medical images.

Ultrasound-guided fine-needle aspiration biopsy of thyroid masses

The purpose of this study was to determine the impact of ultrasound-guided fine-needle aspiration biopsy (USFNA) in the cytological diagnosis of nodular thyroid disease. It remains unclear exactly what role USFNA should play in the cytological diagnosis of nodular thyroid disease. All patients who underwent fine-needle aspiration (FNA) for nodular thyroid disease at Stanford University Medical Center from 1991 to 1996 were included in the study. Histopathologic diagnoses were compared to cytological diagnoses for those patients who underwent surgery. FNA was performed on a total of 497 thyroid nodules. Palpation-guided FNA (pFNA) was performed on 370 nodules, and USFNA was done on 127. The USFNAs were performed for the following reasons: 95 (75%) for nonpalpable or difficult-to-palpate nodules; 14 (11%) for previously failed FNA; and 18 (14%) for incidentally detected nodules. FNA had an unsuccessful biopsy rate of 16% and a sensitivity and specificity of 89% and 69%, respectively. USFNA had an unsuccessful biopsy rate of 7% and a sensitivity and specificity of 100% and 100%, respectively. The cancer yield at surgery for pFNA was 40%, and the cancer yield at surgery for USFNA was 59%. The complementary use of USFNA with pFNA improves the diagnostic approach to nodular thyroid disease. The use of USFNA has increased the cancer yield at surgery and the sensitivity of thyroid biopsy at our institution.

Dual-phase helical CT of locally invasive pancreatic adenocarcinoma

Dual-phase helical CT permits imaging of the pancreas and the peripancreatic structures in the arterial dominant and portal venous phases of enhancement, providing information crucial in the assessment of the local extent of pancreatic adenocarcinoma. This essay reviews the dual-phase helical CT findings of local extension that preclude potentially curative surgery, including vascular involvement, ligamentous or mesenteric invasion, extension of the tumor to involve the stomach or duodenum, and invasion of adjacent solid organs.

Power Doppler imaging in preoperative planning and postoperative monitoring of muscle flaps

PURPOSE

We assessed the utility of power Doppler imaging (PDI) in preoperative planning and postoperative evaluation of microvascular tissue transfers.

METHODS

Twenty-five PDI studies were performed on 23 patients using a 5-10-MHz linear-array transducer. Thirteen patients were assessed preoperatively for patency of the desired donor vessel; 8 of them had surgical scars overlying the desired vascular territory. Twelve patients (including 2 from the first group) were evaluated postoperatively for patency of the vascular anastomoses and adequacy of the blood supply to the transferred tissue.

RESULTS

Twelve of the 13 patients assessed preoperatively had successful flap transfers. Four of the 8 patients with scars over the desired vascular territories had absent or aberrant arteries, necessitating a change in the operative plan. None of these patients had operative complications. Eight of the 12 patients scanned postoperatively had patent anastomoses. In 2 of these patients, impending surgery was averted when the adequacy of the tissue blood supply was established with PDI. In 4 patients, PDI showed arterial or venous compromise, which was confirmed at surgery.

CONCLUSIONS

PDI is a useful technique in microsurgical tissue transfer for assessing the patency of desired donor vessels preoperatively and for postoperative evaluation of blood supply.

Preliminary experience with power Doppler imaging of solid breast masses

OBJECTIVE

The purpose of our study was to assess the potential of power Doppler imaging (PDI) to differentiate benign from malignant solid breast masses.

MATERIALS AND METHODS

Sixty-nine biopsy-proven solid breast masses were evaluated with PDI using 7- to 10-MHz transducers optimized for low-volume flow sensitivity. The extent of flow on PDI was estimated as a percentage of the lesion area on multiple longitudinal and transverse static sonographic images. Flow was categorized as avascular; less than 10%; 10-25%; 25.1-50%; and greater than 50%.

RESULTS

Of the 69 lesions evaluated, 33 were malignant and 36 were benign. Of the avascular lesions, nine were malignant and eight were benign. Significant overlap was seen in the vascularity of the other 52 lesions: both malignant and benign lesions revealed a similar range of vascular patterns.

CONCLUSION

Preliminary experience with PDI suggests that both malignant and benign lesions can be avascular and that the presence of color within a solid breast mass is a nonspecific finding. Assessing the extent of vascularity with PDI appears to be of limited value in the diagnostic evaluation of solid breast masses.

Acalculous cholecystitis in patients undergoing bone marrow transplantation

OBJECTIVE

To evaluate factors associated with acalculous cholecystitis in patients undergoing bone marrow transplantation and the role of repeat ultrasound examinations.

DESIGN

Retrospective study.

SETTING

University hospital, United States.

SUBJECTS

381 Patients who underwent bone marrow transplantation between 1987 and 1992.

INTERVENTIONS

Abdominal ultrasound examination (n = 134), repeat ultrasound in those considered to have acalculous cholecystitis (n = 8), and acute cholecystectomy (n = 5).

RESULTS

14 Patients (4%) with acalculous cholecystitis were identified. The 8 who had had liver tissue examined also had veno-occlusive disease of the liver. It was possible to follow progressing or resolving acalculous cholecystitis by repeat ultrasound examinations. 4 Of the 5 patients treated surgically survived, compared with 3 of the 9 not operated on.

CONCLUSIONS

Acalculous cholecystitis was associated with veno-occlusive disease of the liver. Repeat ultrasound examinations were valuable in showing progressing or resolving acalculous cholecystitis and may guide treatment. Cholecystectomy seems to be a safe procedure for acalculous cholecystitis in patients undergoing bone marrow transplantation.

Do arterial phase helical CT images improve detection or characterization of colorectal liver metastases?

Our goal was to determine if arterial phase images from dual phase helical CT improve either the detection or the characterization of hepatic metastases in patients with colorectal carcinoma. Sixty-two patients with known colorectal cancer underwent 65 dual phase helical CT examinations to evaluate for possible liver metastases. Three blinded reviewers independently evaluated the portal venous phase images alone to determine if hepatic metastases were present or absent. Arterial phase images were then analyzed to determine if they identified additional lesions or aided in characterizing small hepatic lesions. Scores of the two methods for diagnosing metastases were compared with the "gold standard" established by a consensus panel of three other radiologists who reviewed all images together with clinical, pathologic, and other imaging data. The addition of arterial phase imaging did not detect any new metastases. However, in 6 of the 64 technically adequate examinations, hepatic arterial phase images increased lesion conspicuity and significantly increased diagnostic confidence when compared with portal vein phase scans alone. In patients with colorectal cancer, the addition of arterial phase imaging does not increase sensitivity, but improves the specificity in diagnosing liver metastases in a small number of cases. Dual phase helical CT does not appear to be indicated in the evaluation of liver metastases from colorectal cancer.