Surface coil MR imaging of abdominal viscera. Part III. The pancreas

Eight healthy volunteers and 11 patients with pancreatic abnormalities were studied using a conventional body coil and a prototype magnetic resonance (MR) surface coil. Final pathologic diagnoses included carcinoma of the head (six), body (one), and tail of the pancreas (two) and chronic pancreatitis (two). In surface coil images of the volunteers, the body and tail of the pancreas was visualized in all cases but one, and the pancreatic duct was seen in five of eight cases. In-plane spatial resolution of 0.9 X 0.9 mm and 5-mm section thickness was obtained. At the same time, pancreatic surface coil images had a twofold improvement in the signal-to-noise ratio (SNR) compared with body coil images. T1-weighted spin-echo images gave greater SNR, reduced motion artifacts, provided superior anatomic detail, and offered more diagnostic information than comparable T2-weighted images. Significant abnormalities detected only by surface coil imaging included a small tumor surrounded by reactive edema and periglandular tumor invasion. This study demonstrates that surface coil imaging of the pancreas not only is feasible but provides an improved method for examining the pancreas by MR.     

Metallic hip implants: CT with multiplanar reconstruction

Thirty consecutive patients with metallic implants in the hip were evaluated with both standard transaxial computed tomography (CT) and multiplanar reconstruction (MPR) to assess the contribution of MPR. The metallic devices included total hip replacements (n = 6), one or more surgical plates with screws (n = 9), acetabular pins or screws (n = 9), and Knowles pins (n = 6). The metallic implants were on the side of interest in 25 hips and in the contralateral hip in five cases. One patient had bilateral hardware. MPR reformats axially acquired data into other planes. The reconstruction program weights the true signal over the randomly distributed artifacts by integrating adjacent axial images. Examination using standard transaxial imaging was graded as excellent in five cases, adequate in 15 cases, and inadequate in ten cases. After MPR, 19 studies were classified as excellent, 11 were classified as adequate, and none were classified as inadequate. It is concluded that MPR significantly reduced artifacts caused by metal present in transaxial images.     

Surface coil MR imaging of abdominal viscera. Part I. Theory, technique, and initial results

Prototype surface coil magnetic resonance (MR) images were obtained from phantoms and 42 subjects at 0.6 T to assess the feasibility of imaging relatively deep abdominal structures. Surface coil images demonstrated a two- to fourfold improvement in signal-to-noise ratio (SNR) when compared with whole-body coil images with the same resolution elements. This improvement in SNR allowed us to obtain images with thinner sections, higher in-plane resolution, or, alternatively, a decrease in image time. Compared with body images, surface coil images demonstrated greater anatomic detail and reduction in motion artifacts. Despite the limited field of view in very large patients, the use of surface coils improves the diagnostic capability of MR imaging of the abdomen.     

Magnetic resonance imaging and spectroscopy of hepatic iron overload

Experimental animals that had been given excess iron in their diet were studied by magnetic resonance (MR) imaging in vivo and by magnetic resonance (MR) spectroscopy in vitro. Hepatic iron overload in patients with transfusional iron excess was studied by MR imaging, and isolated iron protein fractions were studied in vitro by MR spectroscopy. The spin echo image intensity of livers with iron overload was decreased because of the extreme decreases in T2 compared with normal; T1 was decreased only moderately. The relaxation rates 1/T2 and 1/T1 both showed a linear relationship to hepatic iron levels. Ferritin solutions showed moderate decreases in T2 and mild decreases in T1. The T2 relaxivity of ferritin, which is due to the iron core rather than the apoferritin protein shell, does not appear sufficient to account for the extreme decrease in T2 observed in hepatic iron overload. Low molecular weight cytosol iron is present in lower concentrations than ferritin but potentially has much greater relaxivity and may contribute to the MR findings. These techniques may be useful in other studies of iron metabolism.     

Suspected testicular torsion and ischemia: evaluation with color Doppler sonography

Color Doppler sonography was performed in 32 patients with a painful scrotum in whom testicular ischemia from torsion or postherniorrhaphy was clinically suspected. Surgical correlation was available in 15 patients, and scintigraphic correlation was available in 17 patients. Seven of the 32 patients were diagnosed as having testicular ischemia from torsion. Color Doppler flow imaging demonstrated a lack of intratesticular flow in six of the seven testes with torsion and relatively normal intratesticular flow in one of the patients with acute torsion. Normal or increased intratesticular flow was demonstrated by color Doppler in all 57 of the nonischemic testes. Using the single criterion of presence or absence of identifiable intratesticular flow, the authors found that color Doppler was 86% sensitive, 100% specific, and 97% accurate in the diagnosis of torsion and ischemia in the painful scrotum. Color Doppler sonography is an accurate, noninvasive means of rapidly assessing perfusion of the testis in the painful scrotum.