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Biomedical subjects

D G Mitchell

Publications and source records attributed to D G Mitchell.

At least 199 records · Page 11Linked to original sources
PubMed1986

Osteopetrosis: MR characteristics at 1.5 T.

Four patients with proved osteopetrosis (three with the infantile malignant form and one with the benign form) were examined with magnetic resonance imaging at 1.5 T. All patients were studied in the coronal and sagittal planes using both short and long repetition time/echo time sequences. The infantile malignant form was characterized by a complete lack of signal from the marrow alternating with a signal intensity equivalent to that of the intervertebral disks, resulting in a "stepladder" appearance. In the benign form or after successful marrow transplantation in the infantile malignant form, intermediate or high signal intensity in the vertebrae was noted, suggesting the presence of some marrow elements.

Child, Preschool↗
PubMed1986

Avascular necrosis of the femoral head: morphologic assessment by MR imaging, with CT correlation.

To better understand the morphologic appearance of avascular necrosis (AVN) of the femoral head on magnetic resonance (MR) images (1.5 T) and computed tomographic (CT) scans, the records of 21 lesions were reviewed retrospectively. All MR imaging studies included T1-weighted images (T1WI) (repetition times [TR] of 400-1,000 msec, and echo times [TE] of 20-25 msec), and 15 included T2-weighted images (T2WI) (TR = 2,000-2,500 msec; TE = 60-80 msec). MR signal features of the lesions were compared with features on the corresponding CT scans. Abnormalities in the superoanterior aspect of the femoral head were noted on both image types in all 21 lesions but were more obvious on MR images in two. A characteristic margin of peripheral sclerosis seen on CT scans in 95% (20 of 21) of lesions corresponded to a line of low intensity on MR images. Fractures complicating AVN were seen in eight lesions at CT scanning. On T1WI, fractures were not clearly delineated. On T2WI, fractures were of high intensity but were depicted less clearly than on CT scans. Central signal intensity of the lesions on T1WI correlated with the presence or absence of fracture: 88% (seven of eight) of the lesions with fractures appeared less intense than fat, compared with only 8% (one of 13) of lesions without fractures (P less than .005). While MR imaging is a sensitive method for early diagnosis of AVN, CT scanning can more accurately identify fractures and is thus important for staging.

Adult↗
PubMed1986

MRI of hemorrhagic renal cysts in polycystic kidney disease.

Nine patients with polycystic kidney disease were examined by MRI, CT, and sonography. MRI distinguished among simple cysts, cysts complicated by prior hemorrhage, and coexistent renal cell carcinoma. On T1-weighted spin-echo images, simple renal cysts appeared as round, homogeneous, low-signal regions with smooth outer margins and a distinct interface with remaining normal renal parenchyma or adjacent cysts. Hemorrhagic cysts were seen as homogeneous medium- to high-signal intensity regions, and about half of them correlated with hyperdense cysts by CT. In five cases, fluid-iron levels were evident by dependent high-intensity layering within the cysts. Renal cell carcinomas occasionally show high intensity because of hemorrhage, but intratumoral fluid-iron levels have not yet been described. These results suggest that MRI is useful in differentiating between simple cysts, hemorrhagic cysts, and neoplasms when CT and sonography are indeterminate.

Adult↗
PubMed1986

MRI of joint fluid in the normal and ischemic hip.

MR images in 36 hips with documented avascular necrosis and 80 hips without evidence of joint disease were studied to determine the amount and appearance of fluid in the joint. All MRI examinations were done on a 1.5-T machine and included coronal images made with relative T2 weighting (repetition times = 2000-2500 msec, echo delays = 60-100 msec). The amount of joint fluid, which had an intense signal higher than fat, was graded from 0 to 3 and analyzed with respect to the patient's age and radiographic stage of avascular necrosis. Joint fluid was seen in 84% of presumed normal hips. Only four (5%) of 80 had enough fluid to surround the femoral neck (grade 2), and none had sufficient fluid to distend the joint capsule (grade 3). In comparison, 21 (58%) of 36 hips with avascular necrosis had grade-2 or grade-3 effusions (p less than 0.005), and some fluid was seen in all. Grade-3 effusions were seen in seven (50%) of 14 hips with flattening of the femoral head, compared with only one (5%) of 20 in which the femoral contour was normal. It is concluded that small amounts of fluid are present in both normal hips and those with avascular necrosis. In avascular necrosis, increased joint fluid may be present before radiographic abnormalities occur, but it is greatest after there is flattening of the femoral head. MRI is a highly sensitive method for detecting fluid in the hip joint.

Adolescent↗
PubMed1985

Xanthogranulomatous perinephritis: unusual cause of renal vein and vena caval thrombosis.

Xanthogranulomatous pyelonephritis is an uncommon form of chronic renal infection which can be confused clinically, radiographically, and pathologically with renal carcinoma. Occasionally, xanthogranulomatous changes are more prominent in perinephric tissue than in the renal parenchyma itself. We present a case of locally invasive xanthogranulomatous perinephritis associated with thrombosis of the renal vein and inferior vena cava. With this constellation of findings, infections as well as malignant etiologies should be considered in the differential diagnosis.

Female↗
PubMed1985

Hepatic excretion of urographic contrast medium: use in delineating intrahepatic cholangiocarcinoma on scans delayed for 2 hours.

Vicarious excretion of urographic contrast media by the liver has been detected by conventional radiographic methods in patients with renal impairment or unilateral obstruction. It occurs in patients with normal renal function, however, and can be detected by delayed postcontrast computed tomography scans. A case is presented in which an intrahepatic cholangiocarcinoma was best depicted on scans delayed for 2 hours. After 2 hours, the contrast medium remained within hepatic parenchyma but was virtually cleared from the vascular and interstitial spaces.

Adenoma, Bile Duct↗
PubMed1985

Viscosity of iodinated contrast agents: significance for peripheral venous injection.

The meglumine salt of a urographic contrast agent is significantly more viscous than the comparable sodium salt. To noninvasively deliver a bolus to some patients it is often necessary to use a 21-gauge needle. The inherent resistance of a 21-gauge scalp needle results in approximately a 60% increase in injection time for the meglumine salt as opposed to the sodium salt.

Contrast Media↗
PubMed1985

Intraperitoneal hepatocellular carcinomatosis.

The sonographic and computed tomographic features of liver involvement with hepatocellular carcinoma are well known. The extrahepatic manifestations of hepatocellular carcinoma are not uncommon, but have received little attention in the radiologic literature. We present a case in which intraperitoneal carcinomatosis and portal vein thrombosis were the dominant findings on sonography and computed tomography.

Aged↗
PubMed1985

Effect of bias in hematofluorometer measurements of protoporphyrin in screening programs for lead poisoning.

Values for erythrocyte protoporphyrin (EP), measured in our laboratory after extraction with ethyl acetate-acetic acid, were compared with hematofluorometer measurements made in 21 other laboratories. We found that: (a) for samples of patients' blood, hematofluorometer results were 11 to 28% lower than the extraction-based values, depending on the concentration of EP and the mathematical model used; (b) hematofluorometers had mean errors of 0 to 3% for federal proficiency-testing samples; (c) there were no performance differences between fresh and shipped blood for the six laboratories that were analyzing both; (d) a hematofluorometer with a 20% low bias at an EP concentration of 500 micrograms per liter of whole blood (by the extraction method) will not detect about a third of the children whose EP concentration exceeds that cutoff value; and (e) at this same cutoff value for EP, the extraction tests detects about 45% of children whose blood lead exceeds 300 micrograms/L, whereas a 20% low-bias hematofluorometer detects only about 37%.

Blood Specimen Collection↗
PubMed1984

Problems in the determination of erythrocyte protoporphyrin by ethyl acetate-acetic acid extraction.

Three problems with the ethyl acetate-acetic acid method of protoporphyrin analysis were identified: (1) protoporphyrin extraction from whole blood may yield low recoveries in comparison with extraction from prediluted blood; (2) recovery of protoporphyrin is low with some batches of ethyl acetate, but such unsatisfactory reagent can be identified by an iodide oxidation test; (3) protoporphyrin standards prepared with deionised water may be unstable. However, glass-distilled water is satisfactory.

Acetates↗
PubMed1974

Lead content of foodstuffs.

The lead content of a number of foodstuffs, particularly baby fruit juices and milk, is reported. Samples were analyzed in quadruplicate by using an automated Delves cup atomic absorption procedure. A large proportion of the products examined contained significant amounts of lead. Of 256 metal can examined, the contents of 62% contained a lead level of 100 mug/l. or more, 37% contained 200 mug/l. or more and 12% contained 400 mug/l. lead or more. Of products in glass and aluminum containers, only 1% had lead levels in excess of 200 mug/l. Lead levels of contents also correlate with the seam length/volume ratio of the leaded seam can. A survey of bulk milk showed a mean lead level of 40 mug/l. for 270 samples; for canned evaporated milk the mean level was 202 mug/l. These data indicate a potential health hazard.

Animals↗