Magnetic resonance imaging in internal carotid artery agenesis with computed tomography and angiographic correlation--case reports.

The authors present two cases of agenesis of the internal carotid artery (ICA) discovered incidentally on magnetic resonance imaging and confirmed on computed tomography, magnetic resonance angiography, and conventional angiography. They also propose a clinical algorithm for the workup of patients with suspected absence of the ICA.

Renal lymphoma mimicking clear cell sarcoma in a pediatric patient.

Lymphoma involving the kidneys typically presents as bilateral renal enlargement with multiple nodules [1-6]. Solitary masses, diffuse parenchymal infiltration, or engulfment of the entire kidney by diffuse disease may occur but are more rare. We report the case of a child with non-Hodgkin s lymphoma presenting as a focal unilateral renal mass with bony metastases.

Easily missed injuries around the knee.

Most fractures around the knee are easily detected on high-quality radiographs. However, some fractures and musculotendinous and ligamentous injuries have subtle findings and may be difficult to detect even with optimal images; these injuries include tibial plateau fractures, Segond fractures, stress fractures, fibular head fractures and dislocations, injuries to the patella and extensor mechanism, and Salter type fractures. Clinically suspected tibial plateau fractures unseen on standard views may be seen on tangential or tunnel projections. Segond fractures usually have a characteristic appearance on anteroposterior radiographs but occasionally are seen only on tunnel views. Stress fractures of the proximal tibia may be accompanied by a vague band of increased sclerosis or endosteal callus on either side of the epiphyseal scar. Correct diagnosis of fibular head dislocations requires clinical suspicion, since these injuries often are not recognized on initial radiographs. Careful evaluation of the congruity of the tibiofibular joint on the lateral projection is the key to diagnosis. Vertical patellar fractures are often nondisplaced and are best evaluated with sunrise or Merchant views; avulsion fractures from the proximal or distal poles, with lateral views; and osteochondral fractures, with sunrise or internal oblique views. Salter I injuries can be visualized on oblique and anteroposterior views obtained with stress applied to the knee. Some occult Salter I fractures are diagnosed on follow-up radiographs, which show periosteal reaction. Imaging modalities other than radiography are rarely needed to diagnose fractures but are useful for evaluating the extent of displacement or confirming soft-tissue injuries.

Effects of proteolytic and thermal action on the activity of lactate dehydrogenase isozymes LD-1 and LD-5.

L-Lactate dehydrogenase (LD) catalyzes the interconversion of pyruvate and lactate. Using a spectrophotometric assay to determine LD activity, incubation of rabbit, porcine, and bovine LD-1 and LD-5 isozymes with the protease subtilisin (Carlsberg) gave first-order degradation kinetics. Degradation half-lives were significantly lower for the LD-5 isozymes from the three species when incubated with subtilisin at temperatures from 4 degrees C to 25 degrees C. The energy involved in the degradation process, however, was not different. The activation energy for the conversion of pyruvate to lactate by LD-1 at pH 7.4 was significantly higher than that for LD-5 for all three species examined (P less than 0.005). Thermocalorimetry showed that the LD-1 isozymes have both a higher mean temperature of denaturation and a higher heat uptake during the denaturation process than corresponding LD-5 forms. The results suggest that the LD-5 isozymes in the species studied are more metabolically efficient, whereas the LD-1 forms have greater structural stability.

MR cholangiography: technical advances and clinical applications.

Magnetic resonance (MR) cholangiography is a fast, accurate, noninvasive alternative to endoscopic retrograde cholangiography (ERC) in the evaluation of biliary tract disease. Technical improvements in imaging sequences (eg, half-Fourier rapid acquisition with relaxation enhancement) and use of phased-array coils allow high-quality imaging comparable to that available with ERC. In choledocholithiasis, common bile duct stones as small as 2 mm can be detected with MR cholangiography and appear as low-signal-intensity foci within the high-signal-intensity bile. MR cholangiography may help establish the diagnosis of malignant obstruction and is useful in the evaluation of patients in whom ERC was unsuccessful or incomplete. The role of MR cholangiography in the evaluation of intrahepatic duct disease continues to evolve. MR cholangiography plays a crucial role in evaluating postsurgical biliary tract alterations and can be used to demonstrate a variety of congenital anomalies of the biliary tract (eg, aberrant ducts, choledochal cysts, pancreas divisum). In addition, intentional or incidental imaging of the gallbladder with MR cholangiography can be used to identify calculi or help determine the presence and extent of neoplastic disease.

Thoracopancreatic fistula: clinical and imaging findings.

PURPOSE: The goal of this work was to describe the clinical and imaging features of thoracopancreatic fistula, a rare complication of pancreatitis. METHOD: Nine cases of thoracopancreatic fistula proved by thoracentesis, endoscopic retrograde cholangiopancreatography (ERCP), or surgery were retrospectively and independently reviewed by two abdominal radiologists. All available imaging examinations [chest radiographs = 9, CT = 9, MR and MR cholangiopancreatography (MRCP) = 2, and ERCP = 6] were analyzed, and findings were recorded on a standardized datasheet. Available medical records (n = 7) were reviewed to determine the clinical presentation of the patients and thoracentesis results. RESULTS: Seven of the nine patients presented with pulmonary symptoms such as dyspnea or cough. Of the seven patients with pleural fluid analysis, all demonstrated elevated amylase levels (mean 13,007 U/L). Imaging examinations revealed pancreaticopleural fistulas in six patients, a mediastinal pseudocyst in one patient, and both a pancreaticopleural fistula and a mediastinal pseudocyst in two patients. Chest radiography showed pleural fluid collections in eight patients. CT demonstrated a fluid-containing fistula in all nine patients. MR and MRCP depicted a fistula extending from the abdomen to the pleural space in the two patients with MR correlation. ERCP showed pancreatic ductal changes characteristic of chronic pancreatitis in the six patients with ERCP correlation but failed to demonstrate the fistula in two of the six patients. CONCLUSION: The CT, MR, MRCP, or ERCP finding of a fluid-filled tract extending from the pancreas to the thorax is characteristic of a thoracopancreatic fistula, particularly when identified in a patient who presents with pulmonary symptoms and a history of chronic pancreatitis.

Imaging features of radiation-induced changes in the abdomen.

After external-beam radiation therapy, radiation-induced changes may be observed in abdominal and pelvic organs at imaging. In the liver, an area of low attenuation corresponding to the radiation port (or an area of hyperattenuation if the underlying liver tissue shows fatty change) can be seen at computed tomography (CT) performed within 3-6 months after therapy. Later, the liver may be fibrotic and contracted. In the stomach, small intestine, and colon, wall thickening and edema are early manifestations. Ulcers may also be observed. Long-term complications include strictures and fistulas. After irradiation of the kidneys, altered attenuation of the renal parenchyma may be seen at CT. Ureteral strictures, typically involving the distal ureter, may be observed after pelvic irradiation. The bladder may be small and contracted with a thickened wall after radiation exposure. Fistulas between the bladder and other pelvic organs sometimes occur. Typical musculoskeletal changes include growth abnormalities in skeletally immature patients, fatty replacement of bone marrow, and radiation osteitis. Radiation-induced neoplasms are also recognized after therapy.

Intraoperative monitoring and postoperative imaging of hepatic cryosurgery.

Because intraoperative sonography displays segmental anatomy, allows discovery of more lesions than previously suspected from preoperative imaging, surgical inspection, or palpation, and permits more certain diagnosis of problematic masses, it facilitates surgical decision-making when liver resection or cryoablation is anticipated. Intraoperative sonography provides a guidance modality to accurately place cryosurgery probes in liver masses. More precise treatment of metastatic and primary tumors of the liver is possible with cryoablation because intraoperative sonography provides a means of monitoring the growth of the enlarging freeze zone to insure adequate surgical margins. Postoperative detection of acute complications after cryosurgery is best done with computed tomography. Normally cryosurgery defects shrink with time and lose the peripheral contrast opacification seen after surgery. Gas collections, seen as a result of tissue necrosis, must be discriminated from infection. Tumor recurrence can be detected well with computed tomography or magnetic resonance imaging following hepatic cryosurgery.

Half-Fourier RARE MR cholangiopancreatography: experience in 300 subjects.

PURPOSE: To determine prospectively the clinical applications and diagnostic accuracy of half-Fourier rapid acquisition with relaxation enhancement (RARE) magnetic resonance (MR) cholangiopancreatography (MRCP) in a large patient population. MATERIALS AND METHODS: Breath-hold, heavily T2-weighted half-Fourier RARE MRCP was performed in 265 patients with suspected pancreaticobiliary disease and in 35 control patients without symptoms or signs referrable to the biliary tract or pancreatic duct. MRCP findings were correlated with those at direct cholangiography, pathologic examination, cross-sectional imaging, and clinical follow-up. RESULTS: Diagnostic MRCP examinations were obtained in 299 (99.7%) subjects. MRCP yielded an accuracy of 100% in determining the presence of pancreaticobiliary disease, the presence and level of biliary obstruction, and obstruction due to bile duct calculi. The accuracy of MRCP and MR imaging in determining the presence and level of malignant obstruction was 98.2%. MRCP obviated endoscopic retrograde cholangiopancreatography (ERCP) by excluding choledocholithiasis in patients with acute pancreatitis (n = 13) and nonspecific abdominal pain (n = 82). In patients with sclerosing cholangitis and acquired immunodeficiency syndrome cholangiopathy, MRCP depicted the biliary tract as clearly as did ERCP (n = 9). After failed ERCP, MRCP delineated the pancreaticobiliary tract and helped determine therapeutic options (n = 27). CONCLUSION: Half-Fourier RARE MRCP enables accurate evaluation of pancreaticobiliary disease and obviates ERCP in some patients.