Intracranial dural arteriovenous fistulas with retrograde cortical venous drainage: assessment with cerebral blood volume by dynamic susceptibility contrast magnetic resonance imaging.

BACKGROUND AND PURPOSE: Retrograde cortical venous drainage (RCVD) is the most major risk factor for aggressive behavior of intracranial dural arteriovenous fistulas (DAVF). The purpose of this study was to assess the efficacy of relative cerebral blood volume (rCBV) map for RCVD in patients with DAVF. METHODS: Ten patients with angiographically proven DAVF with RCVD, 2 reference patients with DAVF without RCVD, and 10 control subjects underwent examinations with dynamic susceptibility contrast (DSC)-MR imaging. Four patients with DAVF with unilateral RCVD were evaluated, before and after treatment. The calculation of mean rCBV ratio was performed on a hemispheric basis. The mean rCBV ratio was defined as the value on one side (higher value side) divided by that on the other side (lower value side). RESULTS: In all patients with DAVF with RCVD, the rCBV map showed an increase in rCBV of the angiographically proved affected hemisphere. In 2 reference patients with DAVF without RCVD and all control subjects, the rCBV map showed no increase of rCBV. The mean rCBV ratio in patients with DAVF with RCVD was significantly higher than that of control subjects (P = .0002). Treatment response for RCVD was indicated by a decrease of CBV on the rCBV map and by a decrease of 22% in the mean rCBV ratio. CONCLUSIONS: Increased rCBV by DSC-MR correlated with RCVD in patients with DVAF. The assessment with rCBV for RCVD may be more quantitative than that with angiogram.

Comparison of fluid-attenuated inversion-recovery MR imaging with CT in a simulated model of acute subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Because MR imaging is becoming integral to the evaluation and treatment of very early stroke, it is critical to prove that MR imaging is at least as sensitive to acute subarachnoid hemorrhage (SAH) as is CT. The present study was conducted to evaluate the possibility of detecting a small amount of acute SAH diluted by CSF not revealed by CT but identified on fluid-attenuated inversion-recovery (FLAIR) MR images in an in vitro study. METHODS: Acute SAH was simulated with mixtures of artificial CSF and arterial blood (hematocrit [Hct], 45%) ranging from 0% to 100% by volume. We scanned these phantoms with CT and turbo-FLAIR MR imaging (9000/119 [TR/effective TE]; inversion time, 2200 ms; echo train length, 7), and we measured T1 and T2 relaxation times of these phantoms at temperatures within 36 degrees C to 37 degrees C. Plots of CT value from the different blood/water mixture ratios versus Hct were generated and correlated with the average CT value from normal cortex. We measured T1 and T2 relaxation times of these phantoms and normal cortex and generated T2 relaxation curves as a function of effective TE for a specific inversion time (2200), and determined the TR (9000) for the turbo-FLAIR sequence by using a theoretical equation for the turbo inversion recovery signal intensity. RESULTS: Above a Hct of 27% blood, the mixture was denser on CT scans than was the normal cortex. At a selected time longer than an effective TE of 120, above a Hct of 22.4% blood, the mixture was more hyperintense than the normal cortex on turbo-FLAIR images. At selected times longer than an effective TE of 160, above a Hct of 9% blood, the mixture was more hyperintense than was the normal cortex. CONCLUSION: FLAIR imaging is more sensitive than CT in the detection of a small amount of acute SAH diluted by CSF at selected appropriate TE, as determined in an in vitro study.

Sequential subtraction scintigraphy with 99Tcm-RBC for the early detection of gastrointestinal bleeding and the calculation of bleeding rates: phantom and animal studies.

To improve the detectability of gastrointestinal (GI) bleeding, we have developed a new method, 'sequential subtraction scintigraphy' (SSS) with 99Tcm-labelled red blood cells (RBC). Sequential subtraction scintigrams were obtained by subtracting 5 min interval images from each other using a digital gamma camera. With this method, we are able to detect the bleeding site and calculate the bleeding rate earlier because of the lower background activity. The results of the present study demonstrate that the minimum detectable bleeding rate was 0.05 ml min-1 in both a phantom and an animal model. The minimum detectable activity volumes within 10 min were 0.5 ml by SSS and more that 3 ml by conventional non-subtraction scintigraphy (CNS). The bleeding rates calculated with the subtraction method correlated well with the actual syringe pump rates. The detectability of GI bleeding by SSS and CNS in animal models was compared using the area under receiver operator characteristic (ROC) curves. The results showed that SSS significantly increased the area under the ROC curves from 0.55 +/- 0.05 to 0.79 +/- 0.04 for the 10 min image set and from 0.65 +/- 0.05 to 0.83 +/- 0.04 for the 30 min image set (Z = 5.45, P < 0.0001 and Z = 4.36, P < 0.0001, respectively). These results suggest that sequential subtraction scintigraphy with 99Tcm-RBC is an effective method for the early detection of GI bleeding when compared with the conventional non-subtraction method.

Reproducibility of 99Tcm-MAG3 clearance in normal volunteers with the two-sample method: comparison with 131I-OIH.

The aim of this study was to evaluate the reproducibility of 99Tcm-mercaptoacetyltriglycine (99Tcm-MAG3) clearance and to compare it with that of 131I-orthoiodohippurate (131I-OIH), which is widely used in clinical practice. Twelve young healthy volunteers with a mean age of 23.4 years (range 19-28) were enrolled in the study. The investigations were repeated at an interval of 1 month under similar physiological conditions. Each volunteer received a simultaneous injection of 99Tcm-MAG3 and 131I-OIH that was commercially available in an already labelled form. Blood samples were obtained at 44 and 104 min post-injection. Clearance values were calculated using the two-sample method. The mean (+/- S.D.) change from the first to the second measurement was -7.1 +/- 11.1% for 99Tcm-MAG3 and 1.7 +/- 13.6% for 131I-OIH. There were no significant differences between the first and the second measurements of 99Tcm-MAG3 and 131I-OIH clearance, respectively. 99Tcm-MAG3 clearance was shown to be very similar to that of 131I-OIH in healthy volunteers.

Extensive soft-tissue involvement of dermatomyositis detected by whole-body scintigraphy with 99mTc-MDP and 201TL-chloride.

The authors present a case of extensive soft-tissue radioactivity visualized on both 99mTc-MDP and 201Tl-chloride scintigrams in a patient with dermatomyositis and colon cancer. Incidentally, diffuse and intense uptake of 99mTc-MDP was observed in the shoulder girdles, anterior chest wall, psoas muscles, both proximal thighs and right lower limb, corresponding to the sites of symptomatic muscles, even though skin lesions were limited and no calcification was detected on radiographs. Moreover, 201Tl-chloride was also intensely accumulated in nearly the same sites as the symptomatic muscles as shown on the 99mTc-MDP bone scintigrams. Whole-body scintigraphy with 99mTc-MDP and 201Tl-chloride is a useful tool to detect occult muscle lesions with dystrophic calcification and hyperemia in dermatomyositis.

Fundamental study on gas monitoring in CELSS.

A mass spectrometer and computer system was developed for conducting a fundamental study on gas monitoring in CELSS. Respiration and metabolism of the hamster and photosynthesis of the Spirulina were measured in a combination system consisting of a hamster chamber and a Spirulina cultivator. They are connected through a membrane gas exchanger. Some technical problems were examined. In the mass spectrometric gas monitoring, a simultaneous multi-sample measurement was developed by employing a rotating exchange valve. Long term precise measurement was obtained by employing an automatic calibration system. The membrane gas sampling probe proved to be useful for long term measurement. The cultivation rate of the Spirulina was effectively changed by controlling CO2 and light supply. The experimental results are helpful for improving the hamster-spirulina system.

Malignant melanoma imaging with Tl-201.

Two patients with malignant melanoma were evaluated using Tl-201 scintigraphy. Planar scintigraphy showed tumor accumulation, and SPECT Tl-201 imaging revealed exact tumor localization. The findings indicate the utility of Tl-201 to detect the primary lesion and to identify postoperative recurrence in malignant melanoma.

Intracranial dural arteriovenous fistula with retrograde cortical venous drainage: use of susceptibility-weighted imaging in combination with dynamic susceptibility contrast imaging.

BACKGROUND AND PURPOSE: SWI is a new MR imaging method that maximizes sensitivity to magnetic susceptibility effects with phase information for visualizing small cerebral veins. The purpose of this study was to report the use of SWI in combination with DSC in examining related RCVD in patients with intracranial DAVFs. MATERIALS AND METHODS: Ten patients with angiographically confirmed DAVFs with RCVD underwent conventional MR imaging, SWI, and DSC. The ability of SWI to depict dilated cerebral veins was evaluated and then compared with DSC. The hemispheres of patients with DAVFs were grouped into affected (with RCVD) or nonaffected (without RCVD) categories by angiography. Four patients had bilaterally affected hemispheres. A total of 14 affected hemispheres in patients with DAVFs with RCVD were evaluated. RESULTS: SWI showed dilated cerebral veins on the surface of the brain in all (100%) of the 14 affected hemispheres in patients with DAVFs with RCVD and deep in the brain in 9 (64%). T2-weighted imaging showed prominent flow-voids on the surface of the brain in 10 (71%) of the 14 affected hemispheres in patients with DAVFs with RCVD and deep in the brain in 5 (36%). DSC showed increased cerebral blood volume in all of the 14 affected hemispheres. The SWI findings regarding dilated veins on the surface of the brain corresponded well with the areas of increased cerebral blood volume. CONCLUSIONS: SWI in combination with DSC could be used to characterize the presence of RCVD in patients with DAVFs.

Evaluation of static work load in a helium-oxygen saturation dive at 31 ATA.

The purpose of the present study is to evaluate the static work load as a model work in Submersible Decompression Chamber (SDC) during a deep sea saturation dive with helium-oxygen gas mixture. Heart rate (HR) and electromyogram (EMG) power spectrum changes were studied during a 7-minute static work, half-rising posture or flexed knee posture in four healthy male subjects. During the static work, EMG of the rectus femoris was recorded with surface electrodes, and changes in the EMG power spectrum were presented in the ratio of a high-frequency to low-frequency band (H/L ratio) after the Fourier transform analysis. The HR decreased at 31 ATA and increased remarkably after the decompression to 1 ATA. HR at post-decompression was higher than pre-compression. The lowering phenomena of EMG presented by H/L ratios during the static work were similarly observed in all three conditions. But the changes of the high and low frequency components were different in the post-decompression condition from the pre-compression and 31 ATA conditions. HR as a parameter of static work load might underestimate the work load at the hyperbaric environment due to hyperbaric bradycardia and overestimate it after decompression by "decompression tachycardia." The EMG lowering phenomenon observed after decompression might not be caused by the same mechanism as seen in the pre-compression and hyperbaric environments. Extreme care must be taken to evaluate the static work load not only at hyperbaric helium-oxygen environments but after decompression from a deep saturation dive.