Biomedical subjects

D L Burk

Publications and source records attributed to D L Burk.

57 records · Page 4Linked to original sources

PubMedDate not supplied

Marrow infarction in sickle cell anemia: correlation with marrow type and distribution by MRI.

Ischemic necrosis of bone is believed to occur exclusively in areas of predominantly fatty marrow. Sickle cell disease is unusual in that marrow infarction occurs in areas of active hematopoiesis. MR images of long bone obtained in ten patients with sickle cell anemia (SCA) were analyzed to correlate the distribution and appearance of marrow infarction with the type of marrow. While the hematopoietic marrow predominated in metaphyseal and diaphyseal regions of femurs and tibias, the fatty or mixed marrow was the most common pattern in epiphyses. Infarcts occurred in fatty as well as hematopoietic marrow. Marrow infarcts were isointense or minimally hyperintense on T1 weighted images with the hematopoietic marrow and therefore difficult to detect. On T2 weighted images, the infarcts showed very high signal. T2 weighted images are essential for detection of marrow infarction. Soft tissue changes seen as low signal on T1 and high signal on T2, may be secondary to intramuscular injections of analgesics or muscle ischemia occurring during sickle crisis.

Adult↗

PubMedDate not supplied

Improvement in signal-to-noise ratio and reduction of chemical shift and motion-induced artifacts by summation of gradient and spin echo data acquisition.

Narrow bandwidth magnetic resonance (MR) imaging allows an increase of signal-to-noise ratio (SNR) but causes increased chemical shift and motion-induced artifacts. To obtain MR images with SNR approximately equal to that obtained with narrow bandwidth but with less chemical shift and motion-induced artifact, we introduced triple readout gradient reversal centered around the spin echo. As a result, signals from two gradient echoes and a single spin echo can be collected and summed. Phantom, knee, shoulder, and abdominal MR images were obtained using a 1.5 T GE Signa System at sampling rates ranging from 10 to 60 kHz. Since the bandwidth per pixel was tripled, chemical shift misregistration was reduced by the same factor. The summation image of two gradient echoes and one spin echo had an SNR comparable with that of a single spin echo acquired within the same total sampling interval. Data acquisition at a high sampling ratio also minimizes the dispersion of T2* weighting among three echoes. In addition, summation of the three resulting images decreases motion artifact by effective averaging.

Abdomen↗

PubMedDate not supplied

Hepatocellular tumors with high signal on T1-weighted MR images: chemical shift MR imaging and histologic correlation.

We reviewed conventional and chemical shift MR images and histologic findings of seven proven primary hepatic masses that had higher signal than liver on T1-weighted images to determine if this necessarily indicates fat and if the presence of fat indicates malignancy. These seven masses included five hepatocellular carcinomas (HCCs), one focal nodular hyperplasia (FNH), and one fatty dysplastic nodule. An eighth solitary high signal mass without histologic proof had evidence of abundant fat on each of two chemical shift MR images 25 months apart. Only one of the five HCCs had chemical shift or histologic evidence of fat, while the FNH and dysplastic nodule each had both chemical shift and histologic confirmation of fat. The dysplastic nodule became more dysplastic and grew significantly within 14 months, but remained benign. The unproven fatty lesion decreased in size over 25 months and is therefore presumably benign. Although no statistical inferences can be drawn from this small correlative study, we have shown that HCC may have higher signal intensity than liver on T1-weighted images, whether or not it contains fat. Chemical shift techniques can confirm the presence of intratumoral fat and thus indicate a mass of hepatocellular origin, but the mass may be benign or malignant.

Biopsy↗