Development of diffusion-weighted image using a 0.3T open MRI.

The purpose of this study was to develop a new technique for diffusion-weighted MRI (DWI) with a low-field scanner. DWI is becoming important for assessment of acute stroke. Until recently DWI required expensive technology. We developed multishot-DWI sequence for 0.3T open type MR imager. We prospectively studied forty patients on this 0.3T MRI and compared this DWI to single-shot-DWI by 1.5T-MRI. Group A: Twenty-four patients with acute cerebral infarctions detected by 1.5T-DWI were re-examined using 0.3T-DWI within 24 hours. Sixteen patients with acute cerebral infarctions detected by 0.3T-DWI were re-examined using 1.5T-DWI within 24 hours. In 22 (92%) of 24 cases, 0.3T-DWI showed high signal. In the other two patients, motion artifact distorted 0.3T-DWI. Group B: In all 16 patients, all infarctions detected by 0.3T-DWI showed high signal on 1.5T-DWI. These preliminary data show that, as long as the patient is able to keep still, multishot-DWI can be acquired successfully on a 0.3T open type MRI system.

[A quantitative approach to the rCBF response to acetazolamide using 99mTc-HMPAO and graphical analysis].

A simple noninvasive method for a quantitative measurement of brain perfusion is presented using intravenous radionuclide angiography with 99mTc-hexamethylpropylene amine oxime (HMPAO). Graphical analysis was employed for the evaluation of the unidirectional influx constant (ku) of the tracer from the blood to the brain and the initial distribution volume (Vn) for the tracer, which is the volume of the exchangeable region plus the plasma space. The ku and Vn values were standardized to provide objective and comparable values, brain perfusion indices (BPI) and corrected Vn (Corr. Vn), between subjects by setting the size ratio of ROI(brain) to ROI(aorta) at 10 and 1, respectively. BPI and Corr. Vn of the whole brain were measured before and 20 min after injection of 1 g acetazolamide. After acetazolamide administration, BPI and Corr. Vn increased in all eight subjects with cerebrovascular diseases and one with a pituitary adenoma, by a mean of x 1.26 and 1.24, respectively. Increase of BPI showed a significant correlation with increase of Corr. Vn. This technique is easy to apply as an adjunct to SPECT and may be helpful in the measurement of brain perfusion changes in the acetazolamide test.

[Acetazolamide effect on vascular response in crossed cerebellar diaschisis as measured by 99mTc-HMPAO SPECT].

We studied the effect of acetazolamine (DIAMOXR) on vascular response in areas with crossed cerebellar diaschisis (CCD) using consecutive 99mTc-hexamethyl-propyleneamine oxime (HMPAO) SPECT studies before and after DIAMOX administration with a subtraction method. Regions of interest were drawn over the bilateral cerebellar cortices and interhemispheric asymmetry indices (IAI) were obtained. Eleven of 14 patients with CCD at baseline showed decrease of IAI after DIAMOX administration. Although there is a possibility of underestimation of increase in perfusion in unaffected cerebellar hemisphere, this result suggests a greater increase in perfusion in the affected cerebellar hemisphere as compared with in the contralateral unaffected one and suggests more dilatation of the arterioles in areas with CCD post-DIAMOX than in areas without CCD. However nonsignificant correlation between IAI at baseline and difference of IAI from baseline to post-DIAMOX did not support the hypothesis of more dilatation post-DIAMOX of more constricted arterioles.

Hepatocellular carcinoma: the diagnostic difficulties of ultrasonography and analysis of risk factors in MHTS.

Thirty-nine cases of hepatocellular carcinoma (HCC) out of 55,135 examinees were examined. The diagnostic problems of ultrasonography (US) in detecting HCC and the risk value of 10 factors in HCC were discussed. We also propose the surveillance programs for HCC in Multiphasic Health Testing and Services (MHTS). US will be performed at 3-, or 6 monthly intervals in conjunction with AFP monitoring for the examinees over 50 males and over seventy females with liver dysfunction (GOT > 38 IU/ml) is recommended.

Delayed visualization of gallbladder with in vivo labeled Tc-99m-red blood cell scintigraphy for gastrointestinal bleeding.

A case of a 78-year-old man with delayed visualization of the gallbladder during in vivo labeling for 99mTc-red blood cell scintigraphy for gastrointestinal bleeding is reported. The patient had several episodes of renal failure, melena, anemia, blood transfusion, and hemodialysis. The mechanism of this unusual phenomenon is not clear; however, excess binding of heme and 99mTc-pertechnetate caused by autohemolysis and oliguria are suggested to be the main factor in this phenomenon.