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Biomedical subjects

B E Demas

Publications and source records attributed to B E Demas.

29 records · Page 2Linked to original sources
PubMed1986

Sclerosing cholangitis associated with hepatic arterial FUDR chemotherapy: radiographic-histologic correlation.

During a 2-year period, cholangiography was performed on 17 patients with clinical evidence of cholestasis who were receiving hepatic intraarterial floxuridine (IA-FUDR) infusions for treatment of metastatic colorectal adenocarcinoma. The development of cholestasis was associated with persistently elevated alkaline phosphatase, but serial CT examinations of the liver showed no progression of the tumor. All patients had cholangiographic abnormalities (by endoscopic retrograde cholangiopancreatography, percutaneous transhepatic cholangiography, or operative cholangiography) of the biliary ductal system similar to those in idiopathic sclerosing cholangitis. Certain features, however, appear specific to IA-FUDR-induced cholestasis. All patients studied had segmental involvement at the common hepatic duct bifurcation. The cystic duct and gallbladder were often involved, but the distal common bile duct was spared. Histologic features of periportal and periductal fibrosis were present in specimens obtained from percutaneous liver biopsy in three patients, cholecystectomy in four patients, and autopsy in two patients. When clinical signs of hepatic dysfunction occur in the absence of tumor progression, biliary sclerosis must be suspected.

Cholangiography↗
PubMed1985

Theoretical considerations for optimizing intensity differences between primary musculoskeletal tumors and normal tissue with spin-echo magnetic resonance imaging.

In the radiographic assessment of primary musculoskeletal tumors, it is important for therapy planning to accurately define the extent of a tumor. Using a double spin-echo pulse sequence, the T1 and T2 relaxation times and relative hydrogen densities of several neoplastic tissues and of several normal tissues in four patients were measured. Neoplasms measured included one fibrosarcoma, two osteosarcomas, and one giant cell tumor. Normal tissues measured included normal muscle, fat, and bone marrow. Using a mathematical model of the double spin-echo pulse sequence, the intensity difference between each tumor and each normal tissue for multiple values of TR and TE was calculated. These calculated intensity differences were then used to plot isodifference contour curves for each tissue pair. These plots enabled us to pick combinations of TR and TE that optimized the signal difference between tumor and normal tissue. When comparing tumor with predominantly fatty tissue such as marrow or subcutaneous fat, optimal signal difference in our imager occurred at a TR of 600 to 800 msec and a very short TE. When comparing tumor with muscle, optimal signal difference occurred with very long TR times, and TE times ranging from 30 to 90 msec. These preliminary results suggest that an optimal scanning protocol for primary musculoskeletal tumors should contain at least two different pulse sequences with widely separated TR values (500 and 2000 msec in our instrument), and short to intermediate values of TE (28 and 56 msec in our instrument). It is believed that analysis of isodifference contour plots is a useful method for optimizing intensity differences between any two tissue types.

Bone Neoplasms↗
PubMed1985

Magnetic resonance imaging diagnosis of hepatic metastases in the presence of negative CT studies.

While magnetic resonance imaging (MRI) is not a screening examination in the search for metastatic disease, it has already demonstrated its value when performed as a carefully directed study to detect focal hepatic lesions. In the past 18 months we have encountered nine patients (six men, three women--ages 14-66) with a variety of primary tumors (renal cell carcinoma, two; colon carcinoma, two; hepatocellular carcinoma, two; pancreatic carcinoma, one; pheochromocytoma, one; rhabdomyosarcoma, one) whose MR scans revealed hepatic metastases after normal or nondiagnostic computed tomographic (CT) scans. The lesions were most clearly demonstrated using spin echo (SE) technique with recovery times (TR) of 2.0 seconds and delay times (TE) of 56 msec; metastases usually imaged with greater signal intensity than surrounding liver parenchyma. Lesions were solitary in three patients, multiple in six, and were found in all hepatic lobes without any specific location predominating. Pathologic confirmations of MR diagnoses were available in six of nine patients. In two patients, CT scans were of poor technical quality because streak artifacts from surgical clips obscured portions of the liver. In one patient iodinated contrast medium could not be given. In the remaining six patients CT scan quality was acceptable. This report is not a comparison study of the two modalities. We simply present nine patients in whom metastases were not detected by CT for various reasons but were found by MRI using SE technique.

Adolescent↗
PubMed1985

Magnetic resonance imaging in the diagnosis and staging of renal and perirenal neoplasms.

Thirty-one adult patients underwent magnetic resonance (MR) imaging after CT scans had demonstrated findings consistent with renal cell carcinoma. MR images were interpreted prospectively and independently of the CT findings. Because the CT scanning was performed at multiple institutions by many examiners, this study was not a direct comparison of CT versus MR. The preoperative diagnoses and staging of the neoplasms, as judged by MR, were compared with those obtained at laparotomy (n = 28), autopsy (n = 1), or biopsy (n = 2). Correct preoperative diagnoses were rendered in 31 patients (100%) on the basis of MR findings. The anatomic staging of 27 renal cell carcinomas was correctly performed by MR in 26 patients (86%). When compared with results of previous studies of the value of CT in the diagnosis and staging of renal neoplasms, MR appears to have several advantages in determination of the origin of the mass; the evaluation of vascular patency; the detection of perihilar lymph node metastases; and the evaluation of direct tumor invasion of adjacent organs. MR is sensitive in determining the extent of tumor thrombus and in evaluating invasion of the inferior vena caval wall. MR should assume an important role in the diagnosis and staging of renal neoplasms.

Adult↗
PubMed1985

Gallbladder bile: an experimental study in dogs using MR imaging and proton MR spectroscopy.

Magnetic resonance (MR) imaging, proton MR spectroscopy, and biochemical analysis were performed to investigate MR signal intensity (SI) differences between concentrated and dilute gallbladder bile of seven fasting and five sincalide-treated dogs. MR images revealed high SI from bile of fasting dogs and low to medium SI in sincalide-treated dogs when spin-echo (SE) pulse sequences with repetition rates of 0.5 and 2.0 sec were used. Proton MR spectra were similar for fasting and sincalide-treated dogs. In fasting dogs, water content in the bile was slightly lower, and cholesterol, phospholipid, and bile acid concentrations were higher. More than 90% of proton signals in all Fourier transform free induction decay spectra emanated from water molecules, and no lipid proton resonances were detected in Fourier transform SE spectra after tau delays of 7 msec. These results indicate that the differences in SI are caused by alterations in relaxation times of water protons, possibly resulting from the interactions of water protons and macromolecules.

Animals↗
PubMed1985

Magnetic resonance imaging in the evaluation of urologic malignancies.

Although MRI has been available for clinical use for only a short time it has already proven its value in the diagnosis and staging of renal malignancies and has shown promise in evaluation of malignancies of the lower urinary tract. Its excellent tissue contrast discrimination, ease of evaluation of vascular structures and perivascular lymph nodes and its capability for multiplanar imaging contribute to this promise. Its dependence on multiple tissue and imaging parameters allows manipulation of images to permit evaluation of a variety of structures for anatomic and physiologic abnormalities. Its lack of ionizing radiation and the absence of requirement for intravenous contrast agents are attractive features in evaluation of genitourinary structures. Clinical experience with MRI in diagnosis and staging of urologic malignancies is growing in a number of academic centers, and MRI units are being installed in many private hospitals. It is anticipated that the importance of MRI in the evaluation of the genitourinary tract will increase rapidly as this technology becomes widely available.

Adenocarcinoma↗
PubMed1984

Computed tomographic diagnosis of complications of transhepatic cholangiography and percutaneous biliary drainage.

Over a 12-month period we evaluated, using computed tomography, 11 patients suspected of having developed complications of biliary interventional procedures. CT scans revealed 3 hepatic abscesses, 3 intrahepatic or subcapsular hematomas, 3 bilomas, of which 2 were infected, 1 pancreatic abscess, and 1 case of extension of tumor along a biliary catheter tract. Computed tomography provided information which allowed very specific preoperative diagnoses and which guided plans for further evaluation and treatment.

Abscess↗
PubMed1984

Combined use of double- and single-contrast barium enema in the evaluation of suspected colonic disease.

Although controversy has surrounded the use of single- and double-contrast barium enemas for many years, a growing opinion exists that these studies are complementary, each possessing advantages in different clinical settings. We have found that when interpretation of double-contrast studies is difficult because suspected abnormalities are subtle or because technical quality of examinations is less than ideal, single-contrast enemas can be helpful. We have been able to obtain high-quality single-contrast studies using low-viscosity, low-density barium suspensions administered immediately following evacuation after initial air contrast evaluation.

Barium Sulfate↗
PubMed1984

Computed tomography of visceral infarction due to coagulopathy.

The computed tomographic (CT) appearance of pancreatic infarction has not been described previously. We report a case in which pancreatic infarction associated with multiple visceral infarcts was detected by CT. In addition, CT revealed extensive, progressive arterial and venous thrombosis due to the patient's known deficiency of antithrombin III.

Antithrombin III Deficiency↗