Thomas L. Lawson

Radiology of the pancreas.

The techniques and applications of pancreatic imaging and interventional pancreatic radiology continued to expand in 1991. The most notable progress was the use of MR imaging for evaluation of the pancreas, particularly the investigation of contrast agents to produce enhancement of the pancreatic parenchyma. These agents offer considerable promise for the future of pancreatic MR imaging. The use of CT for detection and evaluation of complications of pancreatitis continued to grow and new investigations appeared that attempted to define the role of surgery vis-a-vis percutaneous and endoscopic interventional techniques. Finally, further understanding of cystic pancreatic neoplasms developed as the result of new investigations.

The sacroiliac joints: anatomic, plain roentgenographic, and computed tomographic analysis.

Due to its unique bicompartmental anatomy and spatial configuration, the sacroiliac joint can be more accurately defined by computed tomography (CT) than conventional radiography. Using a tilted gantry and paraaxial scanning technique, the synovial portion of the joint is oriented vertically on the CT image, while the ligamentous portion is oriented oblique-horizontally. The tilted CT gantry technique allows full ventral-dorsal imaging of the synovial portion of the sacroiliac joint. We have found the accuracy of CT to be superior to conventional radiography in the detection of early erosive sacroiliitis and joint space narrowing. In all patients with discrepancy between the two radiologic techniques, the changes were either only demonstrated or better demonstrated by CT than conventional radiography.

Efficacy of Quantitative Hepatobiliary Scintigraphy and Fatty-Meal Sonography for Evaluating Patients With Suspected Partial Common Duct Obstruction

In this study we evaluated by blinded design the diagnostic efficacy of two noninvasive techniques, quantitative hepatobiliary scintigraphy (QHS) and fatty-meal sonography (FMS), for evaluating patients with suspected partial common duct obstruction. Quantitative hepatobiliary scintigraphy was performed on 56 cholecystectomized individuals (22 asymptomatic controls, 28 patients with suspected partial common duct obstruction, and 6 nonjaundiced cirrhotics) and FMS was done in 51 cases. For QHS, time-activity curves were generated for regions of interest over the liver, hepatic hilum, and common duct. For FMS, we measured common duct diameter before and 45 min after a fatty meal (Lipomul, 1.5 ml/kg). Each of the 28 patients with suspected partial common duct obstruction and 6 cirrhotic patients underwent endoscopic retrograde cholangiography, often accompanied by sphincter of Oddi manometry. Findings from these examinations were taken as the gold standard to determine the presence or absence of conditions that could account for intermittent symptomatic partial common duct obstruction. The most sensitive indicators for a positive test were a 45-min isotope clearance of less than 63% for QHS and a common duct increase of greater than or equal to 2 mm after the fatty meal for FMS. Of 28 patients with suspected partial common duct obstruction, 15 were judged to be true-positive and 13 true-negative. The 6 cirrhotic patients were without common duct obstruction. The study findings showed that each test had a 67% sensitivity that improved to 80% when the findings from both test results were combined. The specificity of QHS was 85% and that of FMS was 100%. All 6 cirrhotic patients had negative findings on FMS and 4 were false-positive on QHS. The true-positives included 8 patients with a small common duct stone and 6 with obstructive sphincter of Oddi dysfunction (4 stenosis, 2 dyskinesia). We conclude that noninvasive QHS and FMS afford good sensitivity and specificity for evaluating cholecystectomized patients with suspected partial common duct obstruction.

Computed tomography, ultrasonography, and endoscopic retrograde cholangiopancreatography in the diagnosis of pancreatic disease: A comparative study

A prospective study was performed comparing the sensitivity of computed tomography, ultrasonography, and endoscopic retrograde cholangiopancreatography (ERCP) in the diagnosis of pancreatic disease. Forty patients with suspected pancreatic carcinoma, acute recurrent or chronic pancreatitis, and/ or jaundice were studied. CT was the most sensitive study in evaluation of pancreatitis. ERCP was most accurate in evaluation of pancreatic malignancy. Ultrasonography was the least sensitive method in detecting pancreatic disease and dilatation of the extrahepatic biliary ducts.

Evaluation of renal transplants with pulsed Doppler duplex sonography.

Sixty‐seven patients who had had renal transplants were examined 184 times by pulsed Doppler duplex sonography, and a pulsed Doppler index (PDI) was developed to provide an indicator of renal blood‐flow patterns. Arterial Doppler signals were obtained from transplant vessels during all technically satisfactory examinations of viable allografts; interpretations of transplant status based on the PDI and clinical function studies agreed with radionuclide renogram diagnoses in more than 90 per cent of cases when both sonograms and renograms were available. Pulsed Doppler analysis may differentiate between arterial occlusion and severe rejection and may decrease the need for radionuclide studies in some patients.

Complications of Pancreatitis

Three types of inflammatory masses may form as sequelae of severe pancreatitis: fluid collections (pseudocysts), phlegmons, and abscesses. Each of these masses has a unique clinical presentation, radiologic manifestation, natural history, and preferred modality of treatment. Thus, it is necessary to distinguish between them.

Sensitivity of Pancreatic Ultrasonography in the Detection of Pancreatic Disease

Pancreatic ultrasonography was correct 87% of the time separating patients with a normal pancreas from those with an abnormality. Of those patients felt to have a normal pancreas by ultrasonography, only 81% wre ultimately found normal. In this group, errors occurred primarily in patients with chronic pancreatitis. An abnormal pancreatic ultrasonogram is significant and usually indicates disease; ultrasonography correctly identified 94% of those patients ultimately found to have an abnormal pancreas.

Periportal halo: a CT sign of liver disease.

Periportal halos are defined as circumferential zones of decreased attenuation identified around the peripheral or subsegmental portal venous branches on contrast-enhanced computed tomography (CT). These halos probably represent fluid or dilated lymphatics in the loose areolar zone around the portal triad structures. While this CT finding is nonspecific, it is abnormal and should prompt close scrutiny of the liver in search of an underlying etiology. Periportal halos which may be due to blood are commonly seen in patients with liver trauma. Periportal edema may cause this sign in patients with congestive heart failure and secondary liver congesion, hepatitis, or enlarged lymph nodes and tumors in the porta hepatis which obstruct lymphatic drainage. This CT sign has also been observed in liver transplants (probably secondary to disruption and engorgement of lymphatic channels) and in recipients of bone marrow transplants who might develop liver edema from microvenous occlusive disease. While the precise pathophysiologic basis of periportal tracking has not been proven, it represents a potentially important CT sign of occult liver disease.

Color Doppler sonography in the evaluation of the adult acute scrotum.

Color Doppler sonography (CDS) was used to evaluate 35 adult males with acute scrotal discomfort. Correlative nuclear scintigraphy was performed in 15 patients. Surgical correlation was available in 10 patients with clinical follow‐up in the remaining 25. The complete absence of intratesticular color flow was used as our criterion for testicular ischemia. This was found to be 100% sensitive and 100% specific in 8 patients with surgically confirmed testicular ischemia. Spontaneous detorsion was noted in one patient with hyperemia demonstrated by color imaging. Increased color flow was found in 20 patients with the clinical impression of scrotal inflammation. Nuclear scintigraphy and color Doppler imaging had 100% agreement in 15 patients. Color Doppler sonography is a useful and highly accurate diagnostic method in the evaluation of patients with the acute scrotal syndrome. Color flow imaging is comparable to nuclear scintigraphy in the diagnosis of testicular ischemia.

Hepatic Metastases: CT Versus MR Imaging at 1.5T

A prospective multi-institutional study was performed to compare the sensitivity of computed tomography (CT) and high-field magnetic resonance (MR) imaging (1.5T) in the detection of hepatic metastases, T1-weighted and T2-weighted spin-echo (SE) MR images were compared with noncontrast, dynamic, and delayed CT. Sixty-nine oncology patients were studied. Non-contrast CT showed an overall sensitivity of 57%, dynamic CT 71%, delayed CT 72%, T1-weighted SE MR 47%, and T2-weighted SE MR 78%. Although there was no statistically significant (p}<0.05) difference among dynamic CT, delayed CT, and T2-weighted SE MR, these three methods were significantly more sensitive (p< 0.005) than non-contrast CT or T1-weighted SE MR. T2-weighted SE MR was significantly more sensitive (p< 0.006) than CT or T1-weighted SE MR in the detection of small (<1 cm) lesions. CT was more sensitive in the detection of extrahepatic disease. These data confirm the superiority of T2-weighted SE over T1-weighted SE pulse sequences at 1.5T.