Biomedical subjects
J F Hiehle
Publications and source records attributed to J F Hiehle.
Magnetization transfer effects in MR-detected multiple sclerosis lesions: comparison with gadolinium-enhanced spin-echo images and nonenhanced T1-weighted images.
PURPOSE: To define the relationship between magnetization transfer and blood-brain-barrier breakdown in multiple sclerosis lesions using gadolinium enhancement as an index of the latter. METHODS: Two hundred twenty lesions (high-signal abnormalities on T2-weighted images) in 35 multiple sclerosis patients were studied with gadolinium-enhanced spin-echo imaging and magnetization transfer. Lesions were divided into groups having nodular or uniform enhancement, ring enhancement, or no enhancement after gadolinium administration. For 133 lesions, T1-weighted images without contrast enhancement were also analyzed. These lesions were categorized as isointense or hypointense based on their appearance on the unenhanced T1-weighted images. RESULTS: There was no difference between the magnetization transfer ratio (MTR) of lesions as a function of enhancement. MTR of hypointense lesions on unenhanced T1-weighted images was, however, lower than the MTR of isointense lesions. CONCLUSION: We speculate that diminished MTR may reflect diminished myelin content and that hypointensity on T1-weighted images corresponds to demyelination. Central regions of ring-enhancing lesions had a lower MTR than the periphery, suggesting that demyelination in multiple sclerosis lesions occurs centrifugally. In addition, the short-repetition-time pulse sequence seems useful in the evaluation of myelin loss in patients with multiple sclerosis.
Correlation of spectroscopy and magnetization transfer imaging in the evaluation of demyelinating lesions and normal appearing white matter in multiple sclerosis.
Magnetization transfer imaging (MT) and localized proton spectroscopy (1H-MRS) were utilized in the evaluation of lesions (high signal abnormalities on T2-weighted images) and normal-appearing white matter (NAWM) in multiple sclerosis (MS). Eleven patients with a clinical diagnosis of MS were independently evaluated with both 1H-MRS and MT. The magnetization transfer ratio (MTR) of lesions was compared with the relative concentration of N-acetyl-aspartate (NAA) and a composite peak at 2.1 to 2.6 ppm termed "marker peaks." The MTR of white matter lesions in the MS patients was markedly decreased (6-34%; normal approximately 42%), and correlated well with increase in the marker peaks region (0.94-3.89). There was no correlation between the relative concentration of NAA and MTR. Increased resonance peaks in the 2.1 to 2.6 ppm range and marked decreases in MTR may be a relatively specific indicators of demyelination.
Prevalence of MR evidence of diffuse axonal injury in patients with mild head injury and normal head CT findings.
PURPOSE: To assess the prevalence of MR evidence for diffuse axonal injury at 1.5 T in patients with normal head CT findings after mild head injury. METHODS: Twenty consecutive patients with mild head injury (Glasgow Coma Scale, 13 to 15; no subsequent deterioration, loss of consciousness < 20 minutes) and normal head CT findings were examined with MR at 1.5 T. Pulse sequences included a conventional T2-weighted spin-echo sequence (2500-3000/30,80/1[repetition time/echo time/excitations]) and a T2*-weighted gradient-echo sequence (750/40/2, 10 degrees flip angle). Each sequence was read independently by two blinded readers. RESULTS: The readers agreed that abnormalities compatible with diffuse axonal injury were present in the white matter of 6 (30%) of 20 patients (95% confidence interval, 12% to 54%). Both readers agreed that foci of high signal intensity were present on the T2-weighted spin-echo sequence in 3 (15%) of the 20 cases (95% confidence interval, 3% to 38%) and that foci of hypointensity compatible with hemorrhagic shear injury were present on the T2*-weighted sequence in 4 (20%) of the 20 patients (95% confidence interval, 6% to 44%). Both types of abnormality were noted by the readers in one patient. CONCLUSIONS: MR shows evidence of diffuse axonal injury in some patients with normal head CT findings after mild head injury. These lesions may represent the pathologic substrate underlying the postconcussion syndrome that occurs in many patients with moderate to severe head injury.
Gastrointestinal toxicity of 5-FU and 5-FUDR: radiographic findings.
The authors describe two patients who suffered gastrointestinal toxicity after receiving chemotherapy for unresectable lesions in the liver that metastasized from colonic carcinoma. One patient had severe ileitis caused by intravenous administration of 5-fluorouracil; the other had severe duodenitis caused by infusion of 5-floxuridine into the hepatic artery by an implanted pump. The type of toxicity that occurred was directly related to the route of administration of these chemotherapeutic agents. Cessation of the chemotherapy led to a dramatic clinical response in these patients.
Magnetic resonance imaging of the hip with emphasis on avascular necrosis.
The hip has a primary role in weight bearing and gait. It is frequently involved in mechanical and inflammatory processes, leading to a painful joint. The pain is often nonspecific, requiring imaging studies for evaluation and diagnosis. Standard radiographs usually are the initial and often the only study required. Routine radiographs are insensitive to changes in the soft tissues and may not reveal changes in the medullary canal. The multiplanar capabilities and high contrast resolution of magnetic resonance imaging make it an ideal method for imaging the hip following standard radiography. Magnetic resonance imaging may be used to detect abnormalities in patients who have had normal radiographs or it can be used to evaluate the complications or stages of disease in patients who have had abnormal radiographs.
Laser balloon angioplasty: effect of constant temperature versus constant power on tissue weld strength.
Thermal fusion of intimal plaque with the arterial wall during coronary balloon angioplasty may significantly reduce the incidence of abrupt closure and may reduce the occurrence of delayed restenosis by improvement of luminal size and shape. Although Nd:YAG laser energy has been shown to be effective in the thermal fusion of plaque-arterial wall separations in vitro, the most efficient manner of energy delivery for rapid achievement of therapeutically useful equilibrium tissue temperature during laser exposure has not been defined. A comparison of weld strength achieved was therefore made between two formats of laser delivery: constant power vs. decremental power with an initial high dose followed by the minimal serial decrements necessary to maintain tissue temperature constant for 15 seconds. One hundred sixty-six tissue discs of human postmortem aorta of 11 mm diameter were studied. Intimal plaque was separated from the media, the two layers were juxtaposed, a force of 4 pounds was applied, and a fiberoptic-delivered laser beam was directed perpendicular to the tissue over a 3-mm-diameter nominal spot size. Weld strength was measured as the shear force required to separate completely the two tissue layers. The mean weld strength (75 g) achieved by use of the decremental power format was significantly higher (P less than .01) than the mean strength (32 g and 56 g) achieved by using constant power for 20 and 30 seconds, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Nd-YAG laser fusion of human atheromatous plaque-arterial wall separations in vitro.
The hypothesis that thermal fusion of disrupted layers of atheromatous arterial wall can be achieved with a neodymium-yttrium aluminum garnet (Nd-YAG) laser was tested. Fresh postmortem human atheromatous plaque was separated from the underlying arterial wall to simulate a dissection in 1-cm2 arterial wall sections. With the plaque and underlying arterial wall subsequently compressed between glass slides, 17 W of continuous-wave Nd-YAG laser radiation were delivered through an optical fiber to the luminal surface of the plaque over a 4-mm2 area. Fusion of the plaque to the underlying arterial wall invariably occurred when tissue compression was applied during lasing and a thin blood film was present between the tissues. The load supported by tissue welds depended on plaque thickness, plaque composition, and exposure duration and was as great as 25 g. In postmortem, blood-filled, whole-artery segments, in which plaque had been completely separated from the media, this technique was applied intraluminally during angioplasty with a prototype balloon catheter. Lateral dispersion of Nd-YAG radiation from the termination of an optical fiber within the balloon allowed fusion of plaque to the underlying arterial wall during balloon inflation to 2 atm. Histologic examination of laser-treated tissues showed coagulation of tissues at the junction between the intimal plaque and media. It is concluded that thermal fusion of separated layers of atheromatous arterial wall can be achieved with Nd-YAG laser irradiation. This concept may be useful in the treatment of arterial dissections.