Standardisation of liver MDCT by tracking liver parenchyma enhancement to trigger imaging.

OBJECTIVE: To assess parenchymal bolus-triggering in terms of liver enhancement, lesion-to-liver conspicuity and inter-image variability across serial follow-up MDCTs. METHODS: We reviewed MDCTs of 50 patients with hepatic metastases who had a baseline CT and two follow-up examinations. In 25 consecutive patients CT data acquisition was initiated by liver parenchyma triggering at a 50-HU enhancement threshold. In a matched control group, imaging was performed with an empirical delay of 65 s. CT attenuation values were assessed in vessels, liver parenchyma and metastasis. Target lesions were classified according to five enhancement patterns. RESULTS: Compared with the control group, liver enhancement was significantly higher with parenchyma triggering (59.8 ± 7.6 HU vs. 48.8 ± 11.2 HU, P = 0.0002). The same was true for conspicuity (liver parenchyma - lesion attenuation) of hypo-enhancing lesions (72.2 ± 15.9 HU vs. 52.7 ± 19.4 HU, P = 0.0006). Liver triggering was associated with reduced variability for liver enhancement among different patients (P = 0.035) and across serial follow-up examinations in individual patients (P < 0.0001). The number of patients presenting with uniform lesion enhancement pattern across serial examinations was significantly higher in the triggered group (20 vs. 11; P = 0.018). CONCLUSION: Liver parenchyma triggering provides superior lesion conspicuity and improves standardisation of image quality across follow-up examinations with greater uniformity of enhancement patterns. KEY POINTS: Liver parenchyma tracking improves liver enhancement and lesion-to-liver conspicuity in abdominal CT. In serial CT studies this technique reduces variability of conspicuity and enhancement patterns. Higher liver-to-lesion conspicuity is a prerequisite for reliable detection of liver lesions. Stabilisation of enhancement permits more accurate follow-up of oncology patients.

Complications associated with thoracentesis. A prospective, randomized study comparing three different methods.

To determine what role the technique plays in complications associated with thoracentesis performed by physicians in training, we undertook a prospective study of thoracentesis in the medical service at our institution in which the sampling method was randomized among needle, needle with catheter, and needle with direct sonographic guidance. Fifty-two spontaneously breathing, cooperative patients with free-flowing effusions obliterating more than half of the hemidiaphragm on an upright, posteroanterior chest roentgenogram were randomized. When we analyzed those complications that were potentially life-threatening (eg, pneumothorax) and/or placed patients at increased risk for further morbidity (eg, pneumothorax, dry tap, inadequate tap), the sonography-guided method was associated with significantly fewer serious complications (0 of 19) than the needle-catheter (9 of 18) or needle-only methods (5 of 15). The sonography-guided method was associated with fewer pneumothoraces (0 of 19) than the needle-catheter (7 of 18) or needle-only methods (3 of 15). The difference between needle-catheter and needle-only methods was not significant. From our results, we conclude that the method by which thoracentesis was performed significantly influenced the spectrum and frequency of complications, and the sonography-guided method was the safest.

Computed tomography of life-threatening complications of abdominal aortic aneurysm. The disrupted aortic wall.

A localized disruption of the conspicuity of the wall of the aorta was noted on intravenous contrast-enhanced computed tomography (CT) scans of ten patients with ruptured abdominal aortic aneurysm (n = 6) or aortoenteric fistula (n = 4). Subsequently, we reviewed 84 scans of patients with uncomplicated aneurysm (n = 70) or aneurysm graft repair (n = 14) to determine if a disrupted wall has diagnostic implications. In this control group, the wall of the aneurysm was conspicuous throughout in 95% of 64 patients who received iodinated contrast material intravenously and in 55% of 20 patients who did not. In the proper clinical setting, CT scans performed with intravenous administration of iodinated contrast material can provide direct evidence of disruption of the wall of an abdominal aortic aneurysm. In selected cases, this may be important for the diagnosis of rupture. Disrupted conspicuity of the wall, in combination with effacement of the fat plane between an aneurysm and the juxtaposed intestine, increases the accuracy of CT for the diagnosis of aortoenteric fistula.

Imaging of the bowel wall. Computed tomography and fat density oral-contrast agent in an animal model.

In this study, we reassessed the problems encountered in computed tomographic (CT) examinations performed with conventional bowel preparations, and developed a fat density oral contrast in dogs. Conventional high-density agents, water, fat (negative) density, and air were administered using a nasogastric tube to eight dogs (25 separate CT scans). Optimal and consistent identification of the gastrointestinal (GI) tract and mural visualization were achieved with 400 ml of 12.5% to 50% corn oil emulsions administered in four hourly divided doses. Mild diarrhea was observed with the 50% concentration only, but no untoward effect was noted clinically with 25% and 12.5% emulsions. Mixing the negative (fat) density oral contrast with the GI contents produced conditions optimal for high-CT contrast resolution of the GI wall. Standard intravenous administration of iodinated contrast agent enhanced mural visualization and, in conjunction with dynamic scanning, time density curves. This suggests that vascular perfusion could be portrayed. This animal model may be used for the experimental evaluation of a number of GI abnormalities, including ischemic, neoplastic, and inflammatory conditions.

Saline microbubbles monitoring sonography-assisted abscess drainage.

The objective of this study was to assess the use of saline microbubbles as a sonographic contrast medium in monitoring abscess drainage. Seven abscesses were localized and drained with sonographic guidance. Four were in the brain and three were small abscesses in the liver, the subhepatic region, and the pancreas. After aspiration of the purulent material, irrigation with saline produced a highly echogenic sonographic pattern that was free of artifacts and distinctly different from the abscess contents and capsule, and the surrounding parenchyma. In one case, previously unsuspected loculation was detected, requiring repositioning of the needle for complete drainage. All abscesses were resolved and no untoward effects, such as sepsis, were encountered. In one additional patient, microbubble sonographic evaluation was used to monitor the progress of an abscess in which a percutaneous catheter was placed. Saline microbubbles may be used as a sonographic contrast medium to monitor sonography-assisted abscess drainage.

The effect of time and cholecystectomy on experimental biliary tree dilatation. A multi-imaging evaluation.

The changes of the biliary tree following distal bile duct obstruction and its release were confirmed by biliary scintigraphy and monitored by serial ultrasonography, computed tomography, and values of serum bilirubin and alkaline phosphatase in 14 mongrel dogs. The degree and rate of biliary dilatation were independent of cholecystectomy. The most rapid rate of extrahepatic dilatation occurred within the first 48 hours, while dilated intrahepatic ducts were first recognized three to six days after obstruction. Following release of the obstruction, the degree and rate of resolution of the biliary dilatation were independent of the duration of ligation (one vs. two weeks) and cholecystectomy. The dilatation resolved slowly. Dilated intrahepatic ducts were recognized for as long as eight to 13 days, while extrahepatic biliary dilatation was still present for 13 weeks, at which time the experiment was terminated. It is postulated that the extrahepatic biliary dilatation will approach a plateau approximately one month after total biliary obstruction. It appears that if the obstruction lasts more than one week, it results in irreversible damage to the elasticity of the extrahepatic ducts. Thus, after release of the obstruction, serial biliary imaging is indicated until a new baseline of the biliary tree diameter has been established.

Live donor adult liver transplantation using right lobe grafts: donor evaluation and surgical outcome.

HYPOTHESIS: Live donor adult liver transplantation (LDALT) is a safe and efficacious treatment for patients with end-stage liver disease. DESIGN: Case-control study. SETTING: Hepatobiliary surgery and liver transplantation unit. PATIENTS: From December 10, 1998, through April 10, 2000, a single team performed 15 LDALT procedures with 2 simultaneous living donor kidney transplants. During this period, 66 potential donors were screened and evaluated. INTERVENTIONS: Potential donors were evaluated with 3-dimensional helical computed tomographic scan, including volume renderings for hepatic lobar volume, vascular anatomy, virtual resection planes, and morphologic features. Suitable donors undergo complete medical and psychiatric evaluation and preoperative arteriography. MAIN OUTCOME MEASURES: Donor demographics, evaluation data, operative data, hospital length of stay, and morbidity. RESULTS: A total of 38 men (58%) and 28 women (42%) were evaluated with 15 donors participating in LDALT. Two additional donors provided kidney grafts for simultaneous transplantation at the time of LDALT. Thirty-two donors (48%) were rejected for either donor or recipient reasons, and 10 patients (15%) elected not to participate after initial screening. Three-dimensional volume renderings by helical computed tomographic scan predicted right lobe liver volume within 92% of actual graft volume. Donor morbidity, including all complications, was 67% with no mortality. Residual liver regenerated to approximately 70% of initial volume within 1 week and 80% within 1 month after surgery. CONCLUSIONS: Donor evaluation is an important component of LDALT. Significant donor morbidity is encountered even with careful selection. To minimize donor morbidity, groups considering initiating living donor programs should have expertise in hepatic resection and vena cava preservation using the "piggyback" technique during liver transplantation.

Evaluation of necrotizing pancreatitis in the opossum by dynamic contrast-enhanced computed tomography: correlation between radiographic and morphologic changes.

BACKGROUND: The ability to quantitate the extent of acinar cell necrosis with contrast-enhanced computed tomography (CT) during acute pancreatitis is uncertain. STUDY DESIGN: Acute hemorrhagic necrotizing pancreatitis was induced in opossums by obstructing their biliopancreatic duct for up to seven days or by retrograde injection of a bile-trypsin taurocholate mixture into the opossum pancreatic duct. At selected times, groups of three animals each were examined by dynamic contrast-enhanced CT, and the abnormalities on the images were quantitated. Immediately following CT, the animals were sacrificed and the extent of necrosis was quantitated by morphometric analysis of tissue samples at the light microscope level. RESULTS: The CT severity score as well as the degree of nonenhancement on dynamic contrast-enhanced CT were both closely correlated with the extent of acinar cell necrosis (r = 0.91 and r = 0.97, respectively). CONCLUSIONS: The degree of pancreatic nonenhancement on dynamic contrast-enhanced CT can be used to quantitate the extent of pancreatic necrosis during acute necrotizing pancreatitis.

Abdominal trauma. Emphasis on computed tomography.

CT scans have been the champion in the diagnosis and management of abdominal injuries, and their use has decreased the number of negative exploratory laparotomies. Traditional areas for the use of CT scans include the assessment of injuries to the spleen and the liver and to signs of organ rupture into the peritoneal cavity. New technologic advances and increased experience have expanded the value of this modality to less than hemodynamically stable patients as well as to less common and more difficult to diagnose injuries of the pancreas, bowel, and the mesentery.

Technical principles in CT evaluation of the gut.

Computed tomography (CT) of the abdomen is a sophisticated, multifaceted, and expensive test that requires meticulous attention to technique and extensive pretest planning. Evaluation of the gut is an integral part of every abdominal CT, and a successful examination requires knowledge of the characteristics of oral and intravenous contrast materials, the available technology, and the ways these factors interact and influence the quality of the images. Careful tailoring of the examination and flexibility to combine the various techniques ensures a successful CT examination not only of the gastrointestinal tract but of the entire abdomen as well.

Is CT angiography sufficient for prediction of resectability of periampullary neoplasms?

The optimal preoperative evaluation of periampullary neoplasms remains controversial. The aim of this study was to analyze the accuracy of helical computed tomography (CT) and CT angiography with three-dimensional reconstruction in predicting resectability. Between March 1996 and May 1999, a total of 100 patients with periampullary neoplasms were prospectively staged by helical CT and CT angiography with three-dimensional reconstruction. Vascular involvement was graded from 0 to 4, with grade 0 representing no vascular involvement and grade 4 total encasement of either the superior mesenteric vein or artery. Patients with grade 4 lesions were considered unresectable. Sixty-eight patients underwent surgical exploration with intent to perform a pancreaticoduodenectomy. Forty-four lesions were grade 0, five were grade l, eight were grade 2, and 11 were grade 3. Resectability for grades 0 to 3 was 96%, 100%, 50%, and 9%, respectively, for an overall resectability rate of 76%. Resectability in patients with vascular encroachment (grade 2) is usually determined by the extent of local disease rather than the presence of extrapancreatic disease. Resection is rarely possible in patients with evidence of vascular encasement (grade 3). Additional imaging modalities such as diagnostic laparoscopy are superfluous in patients with no evidence of local vascular involvement on CT angiography (grades 0 and 1) because of the high resectability rate and infrequency of unsuspected distant metastatic deposits.

Extent of myocardial collateralization: determination with three-dimensional elastic-subtraction spiral CT.

RATIONALE AND OBJECTIVES: This study was undertaken to develop a standard that can be used to assess new high-resolution collateral zone imaging methods. MATERIALS AND METHODS: The authors performed ex vivo helical CT in seven pig hearts after microsphere studies of blood flow and coronary angiography. They compared the zones of collateralization depicted at CT and at microsphere studies. RESULTS: The extent of the collateral zone at CT, computed by using elastic subtraction, correlated well with the coronary blood flow distribution determined with microsphere analysis (r = .95). The root-mean-square error was 6.5%, which indicates good agreement. CONCLUSION: Accurate assessment of collateralization extent has become an important goal because of the discovery of agents that stimulate the growth of coronary collateral vessels. The precision of elastic-subtraction CT and its validation with respect to the blood flow distribution at microsphere analysis indicate that elastic-subtraction CT can serve as a standard for the measurement of collateralization extent.

Imaging of questionable and unusual pelvic masses.

Ultrasonography is usually the initial diagnostic examination performed for evaluating gynaecological conditions and pelvic masses. The authors' experience with 11 "problem cases" and a review of the literature of such enigmas has led to the following recommendations in the following order: a plain radiograph or repeat ultrasound study; ultrasound study with the water enema technique; gastrointestinal examination if the answer is still not apparent, followed by computed tomography or a real-time ultrasound study during a clinical pelvic examination.

Radiographic determination of total lung capacity in patients with pneumonectomy.

To determine whether total lung capacity (TLC) can be measured from plain chest radiographs in patients with pneumonectomy, we examined 20 such patients (17 male, 3 female) who had pneumonectomy for lung carcinoma. In 16 patients the right lung was preserved, and in 4 the left. The TLC was measured with the helium dilution method and by planimetry of the anterior and lateral projections of the lung on chest radiographs, summing the anterior and lateral projected areas of the lung to a single value, S. The correlation between S and TLC by helium gas dilution was r = 0.95. Linear fit of TLC to S explained 99.5% of the variance in TLC, with the equation. The side resected did not influence the predictive value (p < 0.001). The interquartile range of the residual error was +/-130 ml, and standard error was 64 ml. Therefore in patients with pneumonectomy, TLC of the preserved lung may be estimated within +/-130 ml by planimetry of the anterior and lateral chest radiographs.

Contrast-Enhanced CT colonography.

Computed tomography (CT) colonography provides both a multiplanar and endoluminal perspective of the air-filled, distended, cleansed colon, offering an alternative to traditional approaches to colorectal cancer screening. However, there are still limitations associated with CT colonography that need to be resolved, including inadequate bowel distention and poorly prepared colons that make it difficult to distinguish between stool and mucosal lesions including submerged polyps as well as flat or sessile polyps which can often be overlooked. In an effort to help distinguish the bowel wall and mural abnormalities from luminal contents, we have found the use of intravenous contrast material significantly improves both bowel wall conspicuity and reader confidence for examining the colon. In addition, we have found that the use of intravenous contrast material improves the diagnostic accuracy for the detection of medium and probably large polyps.

Virtual colonography: techniques and current clinical applications.

The advent of volumetric helical computed tomography (CT), coupled with the almost universal use of oral and intravenous contrast agents, has resulted in CT becoming the diagnostic and therapeutic cornerstone for alimentary tract disease. Recent technical advances, further enhanced by innovative software developments, now permit multiplanar and endoluminal projections of the entire abdomen, and have resulted in the development of novel diagnostic applications in the abdomen.

Improved pelvicalyceal visualization with multidetector computed tomography urography; comparison with helical computed tomography.

Our aim was to compare the quality of pelvicalyceal visualization on computed tomography (CT) urography using a small intravenous contrast material dose, hydration, and high-resolution multidetector CT (MDCT) with that of conventional helical CT. The test (MDCT) group (49 consecutive patients, 98 kidneys) was scanned 5 min following an intravenous bolus of 30 ml of iodinated contrast material. The control (helical CT) group (50 consecutive patients, 95 kidneys) was scanned 5 min following injection of 120-150 ml of intravenous contrast material. Enhancement and quality of calyceal detail were measured using a five-scale grading system (1 for no detail, 5 for cupped calyces). Calyceal attenuation was substantial in both groups (more than 220 Hounsfield units, HU) but less in the test group compared with the control group (mean 475 and 920 HU, respectively), p<0.0001. In the test group, the calyceal attenuation was less than 500 HU in the majority of cases (65/98 kidneys), while the opposite was true for the control group, where calyceal attenuation was more than 750 HU in 50/95 kidneys (p<0.001). The quality of calyceal detail was 3.4/5 in the test group compared with 1.8/5 in the control group (p<0.0001). The combination of hydration, low-contrast dose, and the high image resolution achieved with MDCT significantly improves calyceal visualization in CT urography.

Peritoneal mesothelioma.

The definitive diagnosis of peritoneal mesothelioma and its differentiation from metastatic peritoneal carcinomatosis may be difficult because of the clinical, macroscopic, and microscopic variability of the tumor. To this purpose, a combination of criteria, including the clinical picture, the gross pathologic findings, the exclusion of other primary neoplasms, and the microscopic findings, must be taken into consideration. Conventionally, these criteria may be established only after surgical exploration and extensive sampling. Our experience with patients with peritoneal mesothelioma and metastatic peritoneal carcinomatosis, as well as a review of the recent imaging literature, shows excellent correlation between computed tomography or ultrasound and the operative or autopsy findings. These imaging modalities showed soft-tissue masses or nodules; thickened omentum ("omental cake"), peritoneum, mesentery, and bowel wall; pleural plaques; and usually disproportionally small, if any, ascites. The latter two observations may be useful in differentiating mesothelioma from carcinomatosis macroscopically. Furthermore, fine-needle aspiration biopsy, after performing wide sampling of the tumors in different locations under ultrasonic or computed tomographic guidance, produced diagnostic cytologic specimens. Thus, the need for exploratory surgery may be alleviated, and the diagnosis of peritoneal mesothelioma may be made prospectively and relatively noninvasively with the use of computed tomography or ultrasound and fine-needle aspiration biopsy. Since epidemiologic studies predict increasing incidence of this neoplasm, especially among asbestos workers, it is suggested that these techniques be seriously considered as screening methods for high-risk populations.

Computed tomography of the superior vena cava.

The superior vena cava (SVC) can be visualized and reliably evaluated by computed tomography (CT). Opacification of this vessel with iodinated contrast material and multiplanar reformations can provide information concerning the patency of the lumen and the relationship of the SVC with adjacent mediastinal and lung structures, both normal and abnormal. SVC obstruction leading to SVC syndrome is the most common condition affecting this vessel. It can be caused by both extrinsic compression and intraluminal thrombosis. Numerous collateral pathways have been described by conventional radiographic and anatomic studies with the azygos vein being the most important collateral vessel. From this aspect, five distinct grades of SVC obstruction can be identified. Grade 0: SVC narrowing without clinical evidence of SVC syndrome. Grade I: Moderate SVC narrowing without collaterals. Grade II: Severe SVC narrowing with the azygos vein serving as partial collateral. Grade III: SVC obstruction above the azygos arch. Grade IV: SVC obstruction at or below the level of the azygos arch. Patients with Grades I to IV have clinical evidence of SVC syndrome, and the CT grading roughly corresponds to the severity of clinical findings. CT accurately depicts both the site of SVC obstruction and important collateral pathways and clearly distinguishes between SVC thrombosis and external compression. In this regard, it provides unique information not available from other modalities such as conventional or radioisotope venography. Furthermore, in a number of patients with suspected SVC obstruction, this vessel may be patented, leading to clinical reassessment. The only disadvantage of CT as compared with radionuclide flow studies is the potential hazard from i.v. administration of iodinated contrast material. Less common abnormalities of the SVC include congenital or developmental conditions, such as persistent left SVC, aneurysms, dilation of the vessel due to heart failure, and variations (usually tortuosity) of the thoracic inlet vessels. We conclude that CT should be used as the procedure of choice for the diagnosis of SVC abnormalities, especially in patients with suspected SVC syndrome.