Improved detection of small cavernous hemangiomas of the liver with high-resolution three-headed SPECT

The purpose of this study was to review our experience with 99mTc-red blood cell scintigraphy for diagnosis of cavernous hemangiomas of the liver using a new three-headed, high-resolution dedicated SPECT system. Of 19 patients referred with a total of 38 lesions seen on CT, US, or MRI, 14 patients had 24 lesions that were hemangioma-positive with SPECT (all true-positives). Six of these 14 patients also had 9 hemangioma-negative lesions; all were less than or equal to 1.3 cm in size and false-negative. The remaining five patients had hemangioma-negative lesions only (1 false-negative, 4 true-negatives). Two hemangiomas were seen by SPECT that were not detected by CT, US, or MR. The sensitivity for hemangiomas greater than or equal to 1.4 cm. was 100% (20/20). The sensitivity was 33% for lesions 0.9-1.3 cm, and 20% for lesions less than or equal to 0.8 cm. The smallest hemangioma detected was 0.5 cm. These results show a definite improvement in sensitivity with high-resolution triple-headed SPECT over previously reported results using single-headed SPECT. High-resolution SPECT has improved our ability to detect small cavernous hemangiomas of the liver.

Gallstone lithotripsy: results when number of stones is excluded as a criterion for treatment

The Siemens Lithostar Plus protocol (Siemens Medical Systems, Iselin, NJ) allows investigators to perform gallstone lithotripsy on patients regardless of the number of stones they have, provided the stones occupy less than 50% of the gallbladder lumen. The purpose of this study was to determine the interrelationships between stone burden, fragmentation response, and stone-free rates when treatment is not limited to three stones or fewer. Of 200 patients initially examined, 80 (40%) underwent lithotripsy. The mean number of treatments per patient was 2.1, and the mean number of shock waves per patient was 7386. In 60 patients in whom 6-month follow-up was available, the overall stone-free rate, based on actual results, was 32% (19/60). The stone-free rates for solitary stones, two or three stones, and four or more stones were 50%, 12%, and 26%, respectively. Regardless of number of stones, patients who ultimately became stone free had significantly smaller mean fragment size (0.25 cm) 2 weeks after lithotripsy than did those who did not become stone free (0.51 cm). Retrospective volume analysis showed that seven (47%) of 15 patients with multiple stones occupying less than 2000 mm3 were stone free; none became stone free when this volume was exceeded. Lithotripsy remains a practical option for patients with solitary stones. Comparable stone-free rates to those achieved for solitary stones can be obtained in patients with multiple stones, regardless of their number, provided treatment is aggressive and the stone aggregate is less than 2000 mm3.

MR imaging of the portal venous system: value of gradient-echo imaging as an adjunct to spin-echo imaging

We evaluated the use of gradient-echo (GRE) as an adjunct to spin-echo (SE) MR imaging of the portal venous system. GRE imaging was performed in 31 subjects, 15 normal volunteers and 16 patients with documented portal venous disease (15 cases) or suspected disease (one case). Eight of 16 patients had venous thrombosis, five had focal thrombus, and three had complete occlusion. Six patients had extrinsic venous compression by tumor. Of the two other patients, one had an arteriovenous fistula and the other a falsely positive angiogram, suggesting portal vein occlusion. In normal subjects, GRE scans had excellent visualization of the portal venous system with high intravascular signal compared with surrounding tissues. Nine (60%) of 15 normal subjects and three patients had an artifact consisting of a curvilinear area of decreased signal that could mimic clot. In three of five patients with focal thrombus, clot was identified on GRE but not on SE images. In all three patients with occlusion, SE and GRE images demonstrated similar findings. In five of the six patients with extrinsic venous compression by tumor, SE and GRE studies showed similar findings. Of the two patients, an arteriovenous fistula was seen on GRE MR in one, and in the other, patency of the left portal vein was seen on SE and GRE images after angiography had suggested portal vein occlusion. Collateral vessels were seen in nine of 16 patients. In five of nine cases, GRE MR demonstrated more extensive collaterals than did SE MR. In summary, GRE MR provides a useful adjunct to standard SE MR imaging. Benefits include high contrast between vascular structures and surrounding tissues, reduced motion artifact, and rapid scanning within a breath-hold.

Detection of tissue injury after extracorporeal shockwave lithotripsy of gallstones

We evaluated seven patients undergoing gallstone lithotripsy for evidence of hepatic or renal trauma after each of 10 lithotripsy treatments. Postlithotripsy magnetic resonance imaging (MRI) and sonography showed no evidence of hepatic or renal injury as compared with baseline studies. Four treatments resulted in sonographic evidence of gaseous hepatic microbubbles (analogous to "the bends") due to cavitation effects of the shockwaves. Three of these four treatments produced serum glutamicoxaloacetic transaminase and -pyruvic transaminase elevation. One patient had microscopic hematuria. Minimal tissue damage results from gallstone lithotripsy. MRI and ultrasound, performed after lithotripsy, appear to be less sensitive than transaminasemia in detecting this low-grade injury.

PACS clinical experience at Georgetown University

Georgetown University Hospital has been operating an image management and communications system (IMACS or PACS) for three-and-a-half years. This work was initially funded under the Army Medical Research and Development Command Digital Imaging Network Systems (DINS) project. The system was taken from a research system supporting only radiology tasks to one extended to clinical use, and has been used in clinical work for two-and-a-half years. This paper will summarize our PACS clinical experience and will describe the operational features implemented and those still necessary.

Gallbladder varices: imaging findings in patients with portal hypertension

A retrospective review of the medical and imaging records of 50 patients with portal hypertension examined in the authors' department during a 2-year period identified six patients with gallbladder wall varices. Imaging studies performed in these patients included computed tomography (CT) (four patients), duplex and color Doppler flow (five patients), and magnetic resonance (MR) (four patients). Five of six patients with gallbladder varices had portal vein thrombosis. Anechoic areas within the gallbladder wall detected with ultrasonography could be distinguished from intramural edema by using duplex or color Doppler flow imaging in all five patients in whom it was used. Contrast material enhancement of these varices was detected with CT in three patients, two of whom also had adjacent mesenteric collaterals. Gradient-echo MR imaging (fast imaging in steady precession/fast low-angle shot) showed flow-related enhancement within the gallbladder wall in two patients. The presence of gallbladder wall varices may imply the presence of portal vein thrombosis. Since these varices can be a source of major blood loss, surgeons must be made aware of them when operating on patients with portal hypertension.

Gallstone fragmentation during biliary lithotripsy: effect of stone composition and structure

In vitro lithotripsy with the Siemens Lithostar was conducted on 36 radiolucent or minimally calcified gallstones housed in an anthropomorphic phantom. The ease and pattern of fragmentation were correlated with global composition for the entire stone, regional or microcomposition (determined by Fourier-transform infrared spectroscopy), and microstructure (determined by scanning electron microscopy). Stones made up of more than 62% cholesterol required 50% more shock waves to pulverize all fragments to 0.3 cm or less than did stones of less than 62% cholesterol (p less than .01). An inverse relationship was found between the number of shock waves needed for fragmentation and the cholesterol content (r = .77). Although a broad range of fragmentation responses occurred, little variation was seen in the ease of fragmentation within stone families. The majority of stones fractured along radially oriented cholesterol plates, but one third of stones treated showed initial chipping or flaking at the periphery before radial fracture. This type of peripheral erosion most often occurred in stones with peripheral pigment rims. These stones required more shock waves and lagged in pulverization compared with more homogeneous cholesterol stones. The efficiency of fragmentation during biliary lithotripsy correlates with the stones' global cholesterol content. A stone's architecture, as reflected by its regional composition and microstructure, partially predicts the mechanism of fragmentation. These in vitro data may be useful in further refining criteria for selecting patients and understanding the fragmentation process.

Gallbladder imaging. The state of the art

Cholelithiasis and its sequelae are readily identified by the myriad imaging techniques available. Understanding the technical issues and correlation of specific findings with the clinical symptoms is essential for accurate diagnosis.

Gallstone lithotripsy: relevant physical principles and technical issues

A basic understanding of shock wave generation is essential for the radiologist who performs gallstone lithotripsy. Shock waves differ from ordinary acoustic waves in that they have a rapid rise time, a positive pressure component that gives rise to compressive forces approaching 1,000 atm, and a low-amplitude sustained negative pressure (rarefactive) component. Shock waves are created by means of three different types of shock wave generators: spark-gap, electromagnetic, and piezoelectric. The authors describe and compare these three types of shock wave generators with regard to equipment selection. Regardless of how shock waves are generated, they share common interactions with tissue. These interactions are reviewed along with the proposed mechanisms of stone fragmentation.

Evaluation of STIR imaging as a complement to spin-echo MR and CT of the porta hepatis/hepatoduodenal ligament

Short TI inversion-recovery (STIR) imaging provides specific advantages over standard spin-echo (SE) MR sequences by producing additive effects of T1 and T2 brightening of pathology and suppression of the signal from surrounding fat. We retrospectively evaluated 12 patients with abnormalities, primarily neoplastic, of the porta hepatis/hepatoduodenal ligament (PH/HdL) with CT and MR imaging, including SE and STIR imaging. Masses on CT were of slightly decreased density compared to liver and seen in contrast to surrounding fat in the PH/HdL region. On MR, T1-weighted images provided comparable anatomic detail to CT, with masses clearly distinguished from surrounding fat due to the low signal intensity of masses as compared to fat. T2-weighted images clearly depicted intrahepatic lesions because of their high signal intensity relative to liver. Increased signal in extrahepatic lesions made them less distinctly seen from surrounding fat. STIR images best demonstrated tumor relative to fat. In six cases, CT was equivalent in demonstrating pathology to the best MR sequence. At least one MR sequence demonstrated pathology better than CT in 6 of 12 cases. In five of these six cases, the STIR sequence was better than CT. Thus, MR, particularly STIR imaging, provides a useful technique in imaging of PH/HdL pathology.

Cavitation effects during lithotripsy. Part I. Results of in vitro experiments

Cavitation effects and microbubble formation are due to the rarefactive (negative pressure) component of shock waves. The in vitro application of shock waves generated by a commercial lithotriptor to an anthropomorphic phantom showed that stone fragmentation occurred more completely in fluid media that support cavitation than in a solid agar-graphite gel. Various fluids (saline, iodinated contrast material, bile) supported different degrees of cavitation. Bile exhibited cavitation at low energy and gave rise to intense microbubble formation at 19 kV. Cavitation increased dramatically with an increase in the rate of generation from 1.0 to 1.8 shock waves per second. The authors conclude that during biliary lithotripsy the environment of a stone will influence the extent of cavitation and fragmentation.

Cavitation effects during lithotripsy. Part II. Clinical observations

Cavitation effects during biliary lithotripsy can produce sonographically visible microbubbles. The relationship between microbubble formation and clinical outcome of gallstone lithotripsy performed with a commercial lithotriptor was studied in 50 treatments in 29 patients. Microbubble formation in bile was a useful predictor of successful stone fragmentation in 31 of 34 treatments. Microbubble formation in the liver correlated with transient hepatocellular damage (as indicated by a twofold rise in serum transaminase levels) immediately after seven of 10 treatments. Advancing the focal volume of the lithotroptor deeper into the patient (placing the stone at the proximal point of the focal zone) may be a useful strategy for reducing hepatic cavitation effects, which appear to be responsible for temporary hepatocellular damage.

Relationship between stone motion, targeting, and fragmentation during experimental biliary lithotripsy

In vitro experiments in an anthropomorphic phantom were performed to clarify the relationship between stone motion, targeting, and fragmentation. Stone motion was minimized by pinning the stone against the dependent wall of a mock gallbladder cavity during shock wave treatment. Fragmentation was most effective (probably due to increased cavitation effects) when the shock wave traversed fluid at the point of its impact with a stone. The results suggest that treatment with the patient in the supine or oblique position may produce a better outcome than treatment in the prone position. Buoyant stones exhibited the greatest motion, which was often to-and-fro in nature. Although restricting the size of the mock gallbladder cavity reduced stone motion, maintaining a 1-cm fluid path was beneficial for achieving optimal pulverization.

Visibility of gallstone fragments at US and fluoroscopy: implications for monitoring gallstone lithotripsy

To assess the value of ultrasound (US), fluoroscopy, and spot radiography in the detection, counting, and measurement of gallstone fragments during lithotripsy, in vitro visibility studies were conducted on fragments from 20 stones. Fluoroscopic visibility was evaluated during and after lithotripsy on 185 fragments placed in an anthropomorphic phantom. Three US experiments were performed on the fragments to study the visibility of fragments as a function of size, the accuracy of the count with large numbers of fragments, and the ability of observers to detect and count fragments larger than both 4 mm and 5 mm. With fluoroscopy, fragment detection rates ranged from 20% (fragments larger than 2.5 mm) to 80% (fragments larger than 4.5 mm). With US, all fragments larger than 1.5 mm were detected, and US was significantly better than fluoroscopy and spot radiography for detection of fragments 2.5 mm or smaller. US was also more accurate than fluoroscopy (11% vs 59% error) in the assessment of the number of fragments. When fragments larger than 4 mm or 5 mm were being counted with US, 92% of the fragments were visualized. The results suggest that US is more accurate for monitoring gallstone lithotripsy than fluoroscopy or spot radiography.

Infected abdominal tumors: percutaneous catheter drainage

Sixteen patients underwent percutaneous catheter drainage of infected primary (n = 9) or metastatic (n = 7) abdominal tumors. Twelve of the patients improved clinically, as evidenced by defervescence and decrease or normalization of leukocytosis. Four patients did not respond to catheter drainage and required surgery. Three of the twelve who improved underwent operations for attempts at surgical cure or debulking of tumor volume despite an initial "good" response to percutaneous drainage. Of the nine patients who did not undergo surgery after percutaneous drainage, four underwent catheter removal after 5 weeks of drainage and had no recurrence of infection, two remained alive with the catheter in place up to 8 months and 1 year after drainage, and two died with the catheter in place. One patient had the catheter removed inadvertently after 3 weeks of drainage and had recurrences that required replacement of the catheter until his death. The major differences between drainage of necrotic tumors and drainage of standard abscesses were the need for surgery in the majority of the cases and the fact that patients needed the catheters for continued palliation until their death.

Rhabdomyolysis: need for high index of suspicion

Rhabdomyolysis, both traumatic and nontraumatic, may be defined as a triad of skeletal muscle injury, pigmented urine, and acute renal failure. Nontraumatic rhabdomyolysis may be more of a subtle diagnosis and requires a high index of suspicion. Pertinent findings in the history as well as clinical evidence of muscle injury with a marked elevation of creatinine kinase will suggest the diagnosis. A disproportionate elevation of serum creatinine to blood urea nitrogen may also occur. Treatment consists of adequate hydration to help prevent oliguric or anuric renal failure without additional calcium or bicarbonate supplementation in most cases. Radiologic studies involving intravenous contrast media as well as urologic instrumentation should be avoided in the acute setting. With early diagnosis and prompt treatment the prognosis for recovery is excellent.

Environmental designs for reading from imaging work stations: ergonomic and architectural features

Despite the rapid progress made in the electronic design of imaging work stations for medicine, much less effort has gone into the design of environments in which such systems will be used. Based on studies of radiologist film reading sessions, considerable time will be spent working at such viewing systems. If the rooms in which the work stations are placed are not conducive to comfortable work, it will certainly not favor electronic viewing over film reading. In examining existing reading environments, it is also apparent that they are not optimal, even for film. Since some of the problems for film and electronic viewing overlap, such as heat generation (by the alternators, viewboxes, or work station electronics) and glare from light sources, it should be possible to develop solutions that are applicable to both environments, or to rooms that will feature both viewing systems. This paper will discuss some of the approaches to designing environments in which viewing of images is supported by the room architecture and engineering, rather than being degraded by it. To illustrate these points a design, based on the constraint of a real room size and available architectural materials, will be developed.

Dynamic CT vs 0.5 T MR imaging in the detection of surgically proven hepatic metastases

Seventeen patients with 52 surgically proven hepatic metastases were studied preoperatively with dynamic CT and 0.5 T magnetic resonance (MR). Dynamic CT detected 38 metastases (73%), and the combination of short echo time (T1-weighted) and T2-weighted pulse sequences detected 46 lesions (88%). Magnetic resonance was also superior at assessing potential resectability. This study suggests that MR excels in detecting and anatomically localizing individual hepatic metastases.

A marked guide wire facilitates esophageal dilatation

Esophageal dilatation by endoscopists is a commonly performed procedure. The introduction of tapered polyvinyl dilators by Savary has made the procedure even more popular. In the United States, esophageal dilatation with guide wires has been traditionally performed with fluoroscopy. By using a marked guide wire and by adhering to specific safety guidelines, the passage of the guide wire can be precise, even without fluoroscopy, and radiographic definition is not always required. This study describes the new guide wire and the technique.

Primary carcinoma of the gallbladder: a pictorial essay

This paper is an overview of the imaging characteristics of primary carcinoma of the gallbladder, based on the premise that more general knowledge of the imaging patterns of the primary tumor and its modes of spread might increase the likelihood of accurate preoperative diagnosis of this lesion. Primary tumor patterns discussed and illustrated are: (I) an intraluminal mass, (II) focal or diffuse thickening of the gallbladder wall, and (III) replacement of the gallbladder by a mass. Illustrated patterns of tumor spread include direct extension and lymphatic and hematogenous metastases.

CT evaluation of suspected hepatic metastases: comparison of techniques for i.v. contrast enhancement

Although IV injection of contrast material is widely used for detection and follow-up of hepatic metastases on CT, the optimal method of contrast enhancement has not yet been defined. A prospective study was performed in 50 consecutive patients with suspected hepatic metastases. Lesion size and detectability were compared on unenhanced CT scans, scans obtained during a bolus injection of contrast material (early bolus phase), and scans obtained during a rapid infusion after the loading bolus. A total of 60 hepatic lesions were evaluated in 26 patients, 19 with histologic confirmation of metastases and seven with strong supportive evidence. The bolus phase allowed detection of 15% more lesions than did examination during the rapid-infusion phase. Lesion size varied, depending on the timing and method of contrast administration; the largest measurements were obtained during bolus injection of contrast material. In addition, bolus administration of contrast material subjectively resulted in the best lesion detection. Because the three techniques of IV contrast enhancement may produce different size measurements, sequential examinations must be tailored appropriately. Scanning during the bolus phase is technically possible with current CT equipment and is recommended as the primary CT screening examination for hepatic metastases.

Pancreatic pseudotumor in pancreas divisum: CT characteristics

We report a case in which a focally spared area of pancreatic tissue in a gland otherwise replaced by fat created a "pseudomass" mimicking neoplasm on sonography and CT. The "pseudomass" appearance was related to the anomalous ductal anatomy in pancreas divisum. The spared area of pancreas creating a "pseudomass" was drained by the dorsal duct and the remainder of the pancreas that had undergone relative fatty replacement was drained by the ventral duct.