Biomedical subjects
Publications and source records attributed to Y Inagaki.
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OBJECTIVE: Cardiac PET imaging offers the potential capability for the noninvasive measurement of arterial input function. This capability is somewhat limited, however, because of partial volume and spillover effects. The purpose of this study was to validate arterial tracer concentration measurements using PET images by assigning a region of interest (ROI) to the left ventricle, left atrium (LA), and ascending aorta. MATERIALS AND METHODS: We selected [11C]CO and [13N]ammonia as tracers, because the activity of [11C]CO is primarily in the blood pool and that of [13N]ammonia primarily in myocardial tissue. Six [11C]CO and 11 [13N]ammonia PET scans were obtained in 17 subjects. Arterial tracer concentrations determined by PET were compared with those measured by well counting of arterial blood sampling obtained at the midpoint of each image acquisition. RESULTS: Arterial tracer concentrations as determined by LA-PET imaging correlated closely with those measured by blood sampling (r = 0.996, slope = 1.00 for [11C]CO; r = 0.841, slope = 0.974 for [13N]ammonia). Partial volume and spillover effects were minimized by assigning an ROI to the LA. CONCLUSION: Arterial tracer concentrations can be measured noninvasively with cardiac PET.
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We assessed percent changes of regional myocardial blood flow (RMBF) after infusion of dipyridamole (0.56 mg/kg) with dynamic N-13 ammonia PET and the first-pass flow model. Positron emission tomography (PET) was performed at rest and after infusion of dipyridamole in 17 participants [five normal subjects, five patients with hypertrophic cardiomyopathy (HCM), and seven patients with coronary artery disease]. Dipyridamole increased RMBF 126 +/- 69% (mean +/- SD) in normal subjects and 55 +/- 43% in the patients with HCM. In the cases of coronary artery disease, the percent changes of RMBF were +19 +/- 19% in ischemic areas and +76 +/- 23% in nonischemic areas. These results demonstrate that N-13 ammonia dynamic PET study is useful in assessing the percent changes of RMBF induced by dipyridamole infusion.
It is very important to prevent skin exit site infections in order to continue continuous ambulatory peritoneal dialysis (CAPD) safely over the long-term. The silicon material conventionally used can result in sinus formation between the skin and the catheter, and may trigger exit site infections. To resolve this problem, we employed a bioinert, rigid, and nonporous transcutaneous connector made of alumina ceramic. Earlier long-term animal experiments with alumina ceramic placed in soft tissue demonstrated the outstanding biocompatibility of this material. The transcutaneous connector was designed with a simple cylindrical configuration; in order to make sufficient contact between this connector and the patient, a silicon tube was made into a swan neck catheter with a disk-shaped Dacron cuff at the upper position in order to reinforce adhesion to soft tissue. Ten CAPD patients (maximum time on dialysis of 14 months) have used the new CAPD catheter system with no exit site infections to date. Furthermore, there has been virtually no downgrowth of the skin around the connector, while the connector and tissue have remained in very close contact.
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Ten hemodialysis (HD) patients with normal liver function received disopyramide (DP) therapy in the steady state. DP, mono-N-dealkyldisopyramide (MND) and alpha-1-acid glycoprotein (AAG) were measured before and after HD. Ten patients with normal renal and liver function were selected as controls. The DP concentration was 2.08 +/- 0.39 micrograms/ml (mean +/- SD) in the control group, and the pre and post HD levels were 2.40 +/- 1.08 micrograms/ml and 1.73 +/- 0.87 micrograms/ml, respectively, in the HD group. The MND concentration was 0.42 +/- 0.23 microgram/ml in controls, 1.53 +/- 0.52 micrograms/ml in pre HD and 1.08 +/- 0.32 microgram/ml in post-HD. Although DP and MND are both classified as small molecular weight substances, the average decrease in plasma concentration from pre to post HD was under 30% with both agents. The MND/DP ratio in the HD group was higher than in controls, but there was no significant difference between pre and post HD. The AAG level was 75 +/- 5 mg/dl in controls and 109 +/- 11 mg/dL before HD in the HD group (p < 0.001). In conclusion, an MND accumulation was observed in HD patients receiving DP therapy. Because the anticholinergic effect of MND is 24 times that of DP, MND is thought to contribute in some way to the hypoglycemia induced by DP in renal failure.
To determine the prognostic factors for splenectomy in patients with chronic idiopathic thrombocytopenic purpura (ITP), 26 consecutive patients who had undergone splenectomy as a treatment for ITP in the last 20 years were investigated retrospectively. Predictive values of age, sex, the interval between diagnosis and surgery, presence of antiplatelet antibodies or accessory spleen, bleeding time, response to corticosteroids, response to high-dose immunoglobulin, weight of spleen, serum platelet-associated immunoglobulin G, preoperative maximal platelet count, and preoperative minimal platelet count were examined with multivariate analysis by multiple regression. Age less than 50 years at surgery, platelet count of 100 x 10(9)/l or more in response to high-dose immunoglobulin, and a maximal platelet count of 100 x 10(9)/l or more before splenectomy were favorable prognostic factors (p < 0.05). The correlation coefficient, sensitivity, specificity, and positive-predictive value of the analyzed multiple regression based on prognostic factors were 0.885, 68.8%, 85.7% and 91.7%, respectively. In conclusion, splenectomy is an effective treatment for younger patients, large maximal preoperative platelet counts and preoperative immunoglobulin dependence. Multivariate function analysis was useful for predicting outcome.