Robert W. Holden

MR imaging of central pontine myelinolysis

Central pontine myelinolysis is a demyelinating disorder with characteristic magnetic resonance features. Findings on T1-weighted scans include a symmetric region of low signal involving the basilar pons with sparing of the descending corticospinal tracts as well as the peripheral pontine tissues. The T2-weighted images show an area of high signal corresponding to the abnormal region identified on T1-weighted scans. Associated extrapontine demyelinating lesions are also demonstrated.

Duplex carotid sonography: correlation with digital subtraction angiography and conventional angiography.

Duplex sonography is a relatively new technique for noninvasive evaluation of the extracranial carotid arteries. In a prospective, double‐blind study of 453 vessels (229 patients) over a one‐year period, an excellent correlation was found with intravenous digital subtraction angiography (DSA) in 66.3 per cent of vessels, good correlation in an additional 28.4 per cent of vessels, and poor correlation in only 5.3 per cent. Duplex was compared with conventional biplane angiography in 86 vessels (45 patients); there was excellent correlation in 71 per cent, good correlation in 20 per cent, and poor agreement in 9 per cent of vessels. Duplex sonography is a highly accurate method of evaluating the cervical carotid system and it has a complementary role with DSA.

Real-time ultrasonographic demonstration of vascular invasion by hepatocellular carcinoma.

The ultrasonographic appearance of hepatocellular carcinoma is quite variable. 3 These tumors may range from hypoechogenic to densely echogenic, and patterns may be mixed. The sonographic pattern can be impossible to differentiate from those of other liver neoplasms or metastases. However, hepatocellular carcinoma has been reported to be associated with thrombosis or tumor invasion of the portal venous system in 30 to 68 per cent of cases.~ 9 This is much higher than the incidence of thrombosis or vascular invasion associated with metastatic tumors (5 per cent), or thrombosis in cirrhosis (5 per cent). As many as 13 per cent of cases of hepatocellular carcinoma may invade the hepatic veins,9 and the tumor may also invade the biliary tree.10 Demonstration of vascular or biliary invasion by ultrasonography can therefore greatly improve the specificity of the examination for the diagnosis of hepatocellular carcinoma. There have been a few reports of demonstrution of vascular invasion by B-mode ultrasonography.5•11 •12 However, modem real-time equipment greatly facilitates careful examination of the vascular and biliary systems of the liver, making detection of vascular involvement much eusier.

Influence of cardiac function on the quality of intravenous digital subtraction arteriograms

In a retrospective comparison between 22 pairs of matched intravenous digital subtraction angiogram (DSA) images, five angiographers made independent determinations as to which one of each pair was superior in image quality (110 image comparisons). Matched pairs were identical for anatomic region filmed, catheter position during injection, amount of contrast material injected, injection rate, and iodine concentration of the contrast material. Each pair consisted of images from one patient with a normal (less than 1 S.D. above the mean) sodium dehydrocholate circulation time and images from one patient with a prolonged (greater than 1 S.D. above the mean) circulation time. In 85 of the 110 instances (77.3%) an image judged superior in quality to its matched counterpart derived from a DSA exam in a patient with normal circulation time; images from the exam with prolonged circulation time were judged equal in quality to the ones with the normal circulation time in 14 comparisons (12.3%); in 11 comparisons (10%) the images from the DSA with the prolonged circulation time were judged superior to the ones from the DSA with the normal circulation time. These results show that with statistically significant frequency (P less than 0.001) observers judge intravenous DSA images deriving from patients with normal circulation times superior in quality to those deriving from patients with prolonged circulation times.

Experimental lung nodule model: CT numbers, nodule size, and actual calcium content.

An experimental pulmonary nodule model was developed to study the effect of nodule size, nodule environment, and calcium content on the attenuation values in two computed tomography (CT) scanners. The experimental results show that (a) calcium is the moiety most responsible for the CT number, (b) small nodules may have falsely low CT numbers, (c) CT numbers vary from scanner to scanner when scanning the same nodule, and (d) higher CT numbers are obtained when experimental nodules are scanned in air rather than water.

Sonographic diagnosis of adult hypertrophic pyloric stenosis.

Hypertrophic pyloric stenosis is a widely recog· nized entity in infants, and the diagnosis can easily be made by sonography. l J The disease also occurs in adults, but is often overlooked. In adult pa· tients, the diagnosis is usually made on barium upper gastrointestinal examination or at surgery. We know of no previous report of the sonographic diagnosis of hypertrophic pyloric stenosis in adults.

Portal hypertension due to jejunal vascular malformation

We report a case of hepatic portal venous hypertension secondary to a small-bowel vascular malformation in a 24-year-old man with anemia. Preoperative diagnostic evaluation included gastrointestinal barium studies and endoscopy (showing esophageal varices), hepatic panangiography, peroral small-bowel biopsy, percutaneous transhepatic portal venography, and manometry. Preoperative injection of methylene blue dye into the jejunal arteries supplying the malformation resulted in easy localization of the lesion at surgery. Direct manometry at the time of segmental jejunal resection yielded a portal pressure of 35 mmHg, with subsequent reduction to 21 mmHg.

The triangle sign: a CT sign of intraperitoneal fluid.

Ninety-four abdominal CT examinations of 91 patients with intraperitoneal fluid were reviewed, and in 25 scans (27%) triangular fluid collections were found within the leaves of the mesentery or adjacent to bowel. In a control group of 30 patients without CT evidence of intraperitoneal fluid, no triangular densities were identified. Triangular fluid collections were visualized in a higher percentage of patients when the quantity of intraperitoneal fluid was moderate to large, IV contrast was given, good bowel opacification was obtained, the amount of mesenteric fat was moderate to large, and the abdominal CT examination included cuts through the pelvis. A triangular fluid collection was reproduced in a cadaver by intraperitoneal infusion of saline. Percutaneous needle aspiration confirmed that the saline collection was responsible for the CT findings. The CT appearance of this new triangle sign is demonstrated.

Detection of Acute Gastrointestinal Bleeding by Intra-arterial Tc-99m Sulfur Colloid Scintigraphy in a Canine Model Preliminary Study

The diagnostic sensitivities of arteriography, intravenous (IV) Tc-99m sulfur colloid scintigraphy, and intra-arterial (IA) Tc-99m sulfur colloid scintigraphy were evaluated in a canine model of gastrointestinal bleeding. Fifteen dogs were studied at bleeding rates ranging from .4 to 1.0 ml/minute. All three studies were obtained in six of the 15 dogs. Intravenous scintigraphy was superior to angiography in two cases, inferior in three, and equal in one. No significant difference could be shown between these two tests at these bleeding rates. Intra-arterial scintigraphy was superior to angiography in four cases and equal in two (P = .06). It was superior to IV scintigraphy in five cases and inferior in one (P = .10). In this small preliminary study, IA scintigraphy appears to be superior to the other two modalities and may prove useful in the detection of acute bleeding at the time of negative arteriography, and in serial studies in patients receiving Pitressin.

Indeterminate lung imaging. Can the number be reduced

During a 2½-year period, 1131 patients with suspected pulmonary embolism had ventilation-perfusion lung scans; 150 of these patients also underwent pulmonary angiography. In a retrospective study, these 150 patients were re-evaluated using the reference criteria of Biello and Alderson, with 62% read as indeterminate. Twenty patients who had chronic obstructive pulmonary disease with retention of Xe-133 in greater than 50% of the lung fields without corresponding radiographic abnormality were included. Ventilation/perfusion matches and mismatches could be correctly determined in 15 of these patients. These 15 of 20 studies could be correctly reclassified as low-probability, while the other five remained indeterminate. With increasing intervals between ventilation/perfusion lung imaging and the onset of symptoms, the percentage of patients with proven pulmonary emboli correctly diagnosed as high probability continuously decreased, and the percentage of studies read as indeterminate constantly increased. Serial chest radiographs suggested that the development of infiltrates in the region of the embolus convert high-probability ventilation/perfusion scans to indeterminate.