CT and MR Findings of Parotid Masses: Benign versus Malignant

PURPOSE: To determine the differential findings of benign and malignant parotid masses, as seen on CT and MRimaging. MATERIALS AND METHODS: The CT(24 cases of benign and 10 cases of malignant masses) and MR imaging(18cases of benign and 9 cases of malignant masses) findings of parotid gland masses confirmed by surgery orhistopathology were analyzed by two radiologists ; they focused on size, cystic change, the presence ofcalcification within the mass, density or signal intensity and margin, degree of contrast enhancement andhomogeneity, location and bilaterality, associated findings-including infiltration into surrounding structures andlymphadenopathy. RESULTS: In one of the 34 cases seen on CT, precontrast images were not available. In 15 of 23benign cases(65.2%), the density of the mass, as seen on pre-contrast enhanced CT scan, was lower than that ofmuscle. In ten malignant cases, density lower than that of muscle was noted in only two cases (20%). OnT2-weighted images, low signal intensity to fat was noted in five of nine cases(55.5%) of malignant lesion, but inno cases involving benign parotid masses. On CT scanning, an indistinct margin of the masses was observed in fiveof 24 benign cases(20.8%) and three of ten malignant cases(30%), but on MR imaging, this was seen in three of 18benign cases(16.7%) and 6 of 9 malignant cases(66.7%). On pre-contrast enhanced CT scan, 15 of 23 benign casesshowed homogenous density, but 12 of these 15 (80%) changed to inhomogenous on post-contrast enhanced CT scan.Among the 12, pleomorphic adenoma accounted for ten cases(83.3%). On CT scanning, infiltration into surroundingstructures including subcutaneous fat tissue was observed in three of 24 benign cases(12.5%) and four of tenmalignant cases(40.0%) ; and on MR imaging, in one of 18 benign cases(5.5%) and six of nine malignantcases(66.7%). CONCLUSION: If a mass of lower attenuation than that of muscle is seen on pre-contrast enhanced CTscan, or density patterns change from homogenous on pre-contrast CT to inhomogenous on post-contrast CT scan, themass may be benign. However, for the differential diagnosis of benign and malignant parotid masses, the margin ofthe mass is not helpful. Masses which on T2-weighted MR images show an indistinct margin, lower signal intensityto fat and infiltration into surrounding structure are more likely to be malignant. CT and MR findings relating tomass size, cystic change within mass, and lymphadenopathy are not, however, helpful for the differential diagnosisof benign and malignant parotid masses.

Contrast Enhanced Two-Phase Spiral CT of Urinary Bladder

PURPOSE: To determine optimal scan time for the early phase of two-phase spiral CT and to evaluate its usefulness in the detection and assessment of extension of urinary bladder lesions. MATERIALS AND METHODS: In four normal adults, we performed dynamic scanning and obtained time-density curves for internal and external iliac arteries and veins, and the wall of the urinary bladder. Sixty patients with 68 lesions of the urinary bladder or prostate underwent precontrast and two-phase spiral CT scanning. After injection of 100ml of noninonic contrast material, images for the early and delayed phases were obtained at 60 seconds and 5 minutes, respectively. We measured CT H.U. of the wall, the lesion, and lumen of urinary bladder as seen on axial scanning, in each image in which the lesion was best shown. For the detection of bladder lesions and assessment of their extension, precontrast, early-, and delayed phase images were compared. RESULTS: Dynamic study of normal adults showed maximum enhancement of bladder wall between 60 and 100 seconds. The difference of CT H.U. between bladder wall and the lesion was greatest in the early phase. The best detection rate (98.5%) was seen during this phase, and for the detection of bladder lesion, this same phase was superior or equal (66/68,97.1%) to the delayed phase. The precontrast image was also superior or equal (31/68,45.6%) to that of the delayed phase. For the assessment of extension of bladder lesion, the early phase was superior (36/68,52.9%) to the delayed phase, and precontrast image was superior (1/68, 1.5%) to that of the delayed phase. For determining the stage of bladder cancer, the early phase was most accurate if the stages was below B2 or D, while for stage C, the delayed phase was most accurate. CONCLUSION: In two-phase spiral CT scanning, we consider the optimal time for the early phase to be between 60 and 100 seconds after injection of contrast material. For the detection and assessment of extension of urinary bladder lesion, the early phase was superior to the late phase, and for evaluation of the ureter, the delayed phase was useful. The precontrast image was inferior to that of the delayed phase. We suggest that for the detection and assessment of extension of urinary bladder lesion without scanning of the precontrast image, two-phase spiral CT is reliable.

PTBD Spiral CT Cholangiography: Utility in Patients with Extrahepatic Biliary Obstruction

PURPOSE: The purpose of this study is to assess the utility of PTBD spiral CT cholangiography, after infusion of contrast media through a PTBD tube, for evaluation of a biliary lesion after emergency PTBD due to severe jaundice. MATERIALS AND METHODS: Forty patients with emergency PTBD due to extrahepatic biliary obstruction were transferred to our clinic and prospectively studied. The causes of obstruction were 17 extrahepatic cholangiocarcinomas (including three Klatskin's tumors), seven pancreatic head carcinomas, six calculous diseases of the common bile duct, six periampullary lesions, two ampulla of Vater carcinomas, one gall bladder carcinoma with invasion of the common hepatic duct, and one cholangitis. Diagnosis was on the basis of pathologic, radiologic, and clinical findings. Pre-contrast CT scanning was performed. After the infusion of contrast media (iothalamate : normal saline=1:10) through a PTBD tube, spiral CT scans were obtained. After IV infusion of contrast media (Ultravist, 100cc), early- and delayed-phase spiral CT scans were obtained at 45 and 210 seconds, respectively, with an interscan interval of 5mm. 3-D CT cholangiograms were then reconstituted. Spiral CT without infusion of contrast media through a PTBD tube and PTBD spiral CT cholangiography were performed in 14 cases. The level of extrahepatic biliary obstruction was categorized as either upper, middle, or lower third. In 21 surgically confirmed cases, we evaluated the accuracy with which the level and cause of obstruction was determined; levels and causes during surgery and by as seen on PTBD cholaniography were compared. RESULTS: The levels of obstruction diagnosed on PTBD spiral CT cholangiography and on 3-D CT cholangiography corresponded in all cases to the levels during surgery and on PTBD cholangiography [upper third (n=7), middle third (n=12), lower third (n=21)], and the level diagnosed on spiral CT without infusion of contrast media through a PTBD tube corresponded to the level during surgery in ten of 14 cases. The cause of obstruction diagnosed on PTBD spiral CT cholangiography corresponded to pathologic findings in 19 of 21 cases. In 15 cases, 3-D CT cholangiography was diagnostically helpful. CONCLUSION: PTBD spiral CT cholangiography is a useful diagnostic method for determining the level and cause of biliary obstruction.

Thoracic Intramedullary Schwannoma: 2 Cases Report

Two cases of thoracic intramedullary schwannoma confirmed by surgery and pathology are reported. These tumors were hypointense on T1WI, and hyperintense on T2WI with good enhancement on MRI. One case showed typical intramendullary tumor, associated with peritumoral cord swelling and syrinx, and another showed both intramedullary and extramedullary location. Schwannomas of the spinal cord, although very rare, Should be included in the differential diagnosis of intramedullary tumor.

Radiologic Findings of Hemophilic Arthropathy of the Knee: Focusing on MR Imaging & Plain Radiography

PURPOSE: To evaluate the characteristic MR findings of hemophilic arthropathy of the knee. MATERIALS & METHOD: Seven knees in six patients with hemophilia (five hemophilia A and one hemophilia B) were retrospectively studied with MR images and plain radiographs. Patients were aged between 2 and 20 years (mean, 11) and all had a clinical history of repeated hemarthrosis. MR images of the knee were analyzed with respect to intra- andextra-articular hemorrhage, the state of synovial tissue, articular cartilage, bone, menisci, and ligaments. RESULTS: Synovial hypertrophy and articular cartilage destruction were revealed in all seven knees ; pannus wasfound in four, and was seen as low signal intensity on T1-weighted image and high signal intensity on T2-weighted images. All five instances of synovial hypertrophy and pannus were enhanced. Joint effusion, presented in five ofseven knees, demonstrated slightly low signal intensity on T1-weighted image and high signal intensity on T2-weighted images, and was associated with peripheral low signal intensity of hemosiderin. Subchondral and marginal erosion was seen in six cases, patellar deformity in three, meniscal damage in four and cruciate ligament damage in one case. CONCLUSION: MR is superior to plain radiography in demonstrating chronic repeated hemarthrosis (manifested as thick intra-articular effusion), hemosiderin, synovial hypertrophy, erosion ordestruction of articular cartilage and bone, and meniscal or cruciate ligament injury of hemophilic arthropathy ofthe knee. MR is therefore thought to be a useful imaging study for accurate evaluation of hemophilic arthropathyof the knee.