The position of the cerebellar tonsils relative to the foramen magnum was measured with sagittal magnetic resonance (MR) images in 221 patients aged 5 months to 89 years who were considered not to have disorders that would affect tonsillar position. All patients were grouped according to age. All measurements of the tonsils were obtained directly from the video console. Statistically significant (P less than .05) differences in tonsillar position were found between the 1st and 9th decades (P less than .001) and the 3rd and 9th decades (P less than .003) of life. An obvious trend existed: tonsillar ascent with increasing age. Therefore, the authors believe that a single reference standard that indicates the normal distance of the cerebellar tonsils from the foramen magnum is inappropriate unless age is considered. They suggest that the following distances below the foramen magnum (more than 2 standard deviations out of the normal range) be used as criteria for ectopia of the cerebellar tonsils: 1st decade of life, 6 mm; 2nd and 3rd decades, 5 mm; 4th to 8th decades, 4 mm; and 9th decade, 3 mm.

The authors describe the technical results in 127 patients who underwent diagnostic gallbladder puncture and percutaneous cholecystostomy. The procedures were performed for a variety of indications including treatment of acute calculous or acalculous cholecystitis, drainage of obstructive jaundice or gallbladder perforation, percutaneous removal or dissolution of gallstones, diagnostic cholecystocholangiography, and gallbladder biopsy. Successful completion of the intended procedure was achieved in 125 of 127 patients (98.4%). Major complications occurred in 11 patients (8.7%); these included bile peritonitis, bleeding, vagal reactions, hypotension, catheter dislodgement, and acute respiratory distress. Minor complications were noted in five patients (3.9%). The 30-day mortality rate was 3.1% (four patients); the deaths were due to the underlying diseases. The data help support percutaneous cholecystostomy as a primary interventional radiologic procedure that has an extremely high likelihood of technical success. Recommendations to minimize or avoid complications are presented.

Ultrasound (US)-guided transvaginal needle or catheter drainage was performed in 14 women for a variety of pelvic abscesses and fluid collections; tubo-ovarian abscesses and postoperative collections were most common. Diagnosis was achieved in all 14 patients (100%), including one patient with suspected ovarian carcinoma who underwent only diagnostic needle aspiration and no therapeutic drainage. Abscesses or fluid collections were evacuated in 13 of 13 patients (100%) with either needle (n = 7) or catheter (n = 6) drainage (with appropriate antibiotics). Twelve of the 14 patients (86%) were spared an operation; surgery was undertaken in two patients for a persistent tubo-ovarian phlegmon. No major complications were associated with drainage. Catheters were removed an average of 6.7 days after insertion. The success, safety, and advantages of US-guided transvaginal drainage in our early experience suggest its use as an alternative to standard percutaneous catheter procedures to diagnose and drain certain pelvic abscesses and fluid collections.

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The authors describe the value of computed tomographic (CT) guidance for percutaneous gastrostomy (PG) or gastroenterostomy (PGE) in 22 patients with anatomic or pathologic difficulties precluding fluoroscopic guidance. Indications for PG or PGE were decompression for gastrointestinal obstruction (n = 15) or for feeding (n = 7). Thirteen patients previously underwent an unsuccessful attempt at or had been rejected as unsuitable for percutaneous endoscopic gastrostomy. CT guidance was selected because of inability to pass a nasogastric tube due to esophageal obstruction (n = 4), inability to tolerate gastric distention (n = 1), abnormal morphology in or around the stomach (n = 16), or simultaneous performance of a PG in one patient who was undergoing emergency CT-guided abscess drainage. Catheters were placed successfully in all 22 patients. No major complications occurred. CT is valuable for PG or PGE when anatomic or pathologic problems make fluoroscopic or endoscopic puncture unsafe or impossible.

The most accurate prognostic indicator in patients with musculoskeletal sarcomas is the percentage of tumor necrosis after intraarterial chemotherapy. Magnetic resonance (MR) imaging was evaluated to determine its ability to indicate the percentage of necrosis in musculoskeletal neoplasms after treatment. Fourteen patients with musculoskeletal neoplasms underwent treatment protocols including intraarterial chemotherapy (n = 14), radiation therapy (n = 6), and systemic chemotherapy (n = 14). All patients underwent MR imaging before and after treatment, and all underwent either limb salvage surgery (n = 8) or amputation (n = 6) within 1 week of the last MR examination. Standard unehanced spin-echo T1-, spin-density-, and T2-weighted MR sequences were used. The MR images were compared with the pathologic specimens. On T2-weighted images, the signal intensities of viable tumor, tumor necrosis, edema, hemorrhage, and necrosis overlapped. With the unenhanced spin-echo technique, MR imaging cannot be used to predict the percentage of tumor necrosis in musculoskeletal neoplasms after intraarterial chemotherapy.

Unilateral hyperlucent hemithorax is a common pediatric chest radiographic finding that may also be seen at computed tomography. It may result from congenital or acquired conditions involving the pulmonary parenchyma, airway, pulmonary vasculature, pleural space, and chest wall, as well as from technical factors such as patient rotation. Unilateral hyperlucent hemithorax has a broad differential diagnosis that includes unilateral emphysematous or bullous disease, pneumatocele, foreign body aspiration, Swyer-James syndrome, congenital lobar emphysema, endobronchial mass, unilateral pulmonary agenesis, proximal interruption of the pulmonary artery, scimitar syndrome, diaphragmatic hernia, and Poland syndrome. Although certain causes of unilateral hyperlucent hemithorax are clinically significant and potentially life threatening, others are of minimal or no clinical significance. When evaluating a patient with this finding, it is important to establish whether the apparent unilateral hyperlucent hemithorax is truly too lucent (hypoattenuating) or if the contralateral hemithorax is too opaque (hyperattenuating). It is imperative that radiologists be aware of the various causes of unilateral hyperlucent hemithorax so that they may diagnose the underlying condition and appropriately guide patient management.

Insertion of metal stents in the ureter is technically straightforward and was well tolerated by patients. However, the efficacy is variable, and a greater beneficial effect than is achieved with plastic stents is not established.