Biomedical subjects

A Akamune

Publications and source records attributed to A Akamune.

13 recordsLinked to original sources

PubMed2001

Reproducibility of the brain perfusion index for measuring cerebral blood flow using technetium-99m compounds.

We previously developed an alternative method for estimating the brain perfusion index (BPI) using technetium-99m compounds and spectral analysis (SA) for quantification of cerebral blood flow (CBF). In this study, we investigated the reproducibility of the BPI values obtained by SA (BPIS) using a double injection of technetium-99m ethyl cysteinate dimer without any intervention, and compared it with that of the BPI values obtained by graphical analysis (BPIG). The BPIS values in the first (x) and second sessions (y) correlated closely (y=0.921x+0.036; r=0.962; n=64; s.e.e.=0.058 min-1). Although the BPIG values in the first (x) and second sessions (y) also correlated (y=0.942x+0.040; r=0.916; n=64; s.e.e.=0.061 min-1), the correlation coefficient for BPIS was significantly higher than that for BPIG. The reproducibility was dependent on the injection dose ratio of the second session to the first (R). The difference in BPI between the first and second sessions tended to be smaller when 1.5<R<2.5 than when 0<R<1.5 or 2.5<R. These results suggest that the reproducibility of BPIS is satisfactory and that it can be applied to two sequential measurements of CBF using a double injection of 99mTc compounds. When applying our method to such measurements, it is recommended that R is taken as approximately 2.0.

Aged↗

PubMed1999

An alternative approach to estimation of the brain perfusion index for measurement of cerebral blood flow using technetium-99m compounds.

Cerebral blood flow (CBF) has been quantified non-invasively using the brain perfusion index (BPI) determined from radionuclide angiographic data generated by technetium-99m hexamethylpropylene amine oxime( )((99m)Tc-HMPAO) or technetium-99m ethyl cysteinate dimer( )((99m)Tc-ECD). The BPI is generally calculated using graphical analysis (GA). In the present study, BPI was measured using spectral analysis (SA), and its usefulness evaluated in comparison with GA. The BPI was calculated from the sum of spectral data obtained by SA. We applied this method to radionuclide angiographic data collected from the bilateral brain hemispheres of 20 patients with various brain diseases using (99m)Tc-HMPAO and from those of 20 patients using (99m)Tc-ECD. We also measured BPI using GA. The BPI values obtained by SA (BPI(S)) (x) and by GA (BPI(G)) (y) correlated closely (y=0.708x+0.038, r=0.945 for (99m)Tc-HMPAO and y=0.559x+0.093, r=0.931 for (99m)Tc-ECD). However, the BPI(G) values were underestimated by 22.9%+/-6.6% (mean+/-SD) for (99m)Tc-HMPAO and by 27.9%+/-7.5% for (99m)Tc-ECD as compared with the BPI(S) values. The extent of underestimation tended to increase with increasing BPI(S) values. These findings were considered to be a result of the BPI(G) values being affected by the first-pass extraction fraction of the tracer. We also compared the BPI(S) and BPI(G) values with those of CBF measured using N-isopropyl-p-[(123)I]iodoamphetamine (CBF(IMP)) in 16 patients (six for (99m)Tc-HMPAO and ten for (99m)Tc-ECD). Although both BPI(S) and BPI(G) values correlated significantly with the CBF(IMP) values, the correlation coefficient in BPI(S) was always better than that in BPI(G) (r=0.869 for (99m)Tc-HMPAO and r=0.929 for (99m)Tc-ECD in BPI(S), r=0.629 for (99m)Tc-HMPAO and r=0.856 for (99m)Tc-ECD in BPI(G)). These results suggest that SA can provide a more reliable BPI for quantifying CBF using (99m)Tc-HMPAO or (99m)Tc-ECD than the conventional method using GA. Our method will be useful especially when using a tracer with a low first-pass extraction fraction and/or when performing activation studies using pharmacological intervention.

Aged↗

PubMed1999

[Estimation of integral of input function for quantification of cerebral blood flow with N-isopropyl-p-[123I]iodoamphetamine using one-point venous blood sampling].

The present study was designed to investigate a possibility of substitution of the venous blood radioactivity counts sampled 26 min post injection for the octanol-extracted arterial blood radioactivity counts obtained at 5 min after the injection of N-isopropyl-p-[123I]iodoamphetamine (123I-IMP). Furthermore, we investigated whether the integral of input function can be estimated from the venous blood radioactivity counts sampled 26 min post injection and the whole-brain time-activity curves early after 123I-IMP injection. There was a good correlation between the arterial blood radioactivity counts sampled 5 min post injection (y) and those obtained at 26 min (r = 0.902; n = 91; y = 2.348x - 867.063). There was also a good correlation between the arterial (x) and venous blood radioactivity counts (y) sampled 26 min post injection (r = 0.954; n = 14; y = 0.761x + 924.336). The venous blood radioactivity counts sampled at 26 min (x) correlated well with the octanol-extracted arterial blood radioactivity counts sampled at 5 min (y) (r = 0.964; n = 32; y = 0.173x - 21.598). There was a good correlation between the integrals of input function obtained from the regression equation obtained above and the whole-brain time-activity curves acquired during 7 min post injection (y) and those obtained by 5-min continuous arterial blood sampling (x) (r = 0.965; n = 41; y = 0.957x + 2665.208). These results indicate that this noninvasive and simple method can estimate the integral of input function for quantification of cerebral blood flow using 123I-IMP.

Aged↗

PubMed1998

A method for estimating the integral of the input function for the quantification of cerebral blood flow with 123I-IMP using one-point arterial blood sampling.

We have developed a new method to replace the conventional method of quantitatively measuring cerebral blood flow (CBF), in which octanol-extracted radioactivity counts are measured in continuous arterial blood samples. With the new method, the whole-brain time-activity curves early after the intravenous injection of N-isopropyl-p-[123I]iodoamphetamine were first obtained by the least-squares curve-fitting method. The equation thus obtained was differentiated and the radioactivity counts were corrected by the 5-min octanol-extracted radioactivity counts of the arterial blood sample obtained at a single time point. In the present study, the value obtained by integrating the equation from 0 to 5 min, which was obtained by curve-fitting, was compared with the octanol-extracted radioactivity counts obtained by 5-min continuous arterial blood sampling in 160 patients with cerebrovascular disorders. The results showed good agreement between the values obtained by the two procedures (y = 1.049x - 1522.4; r = 0.987). Using the CBF obtained by the 5-min continuous arterial blood sampling as the standard, the errors using the present integral values of the input function were 7.1 +/- 4.9%. Measurements of the integral of the input function by the present one-point arterial blood sampling method has the potential for use in the routine measurement of CBF, because it is less invasive and more convenient than the conventional method, and it is unaffected by cardiopulmonary disease or smoking.

Arteries↗

PubMed1998

[Estimation of integral value of input function for the quantification of cerebral blood flow with 123I-IMP using one-point arterial blood sampling].

Cerebral blood flow (CBF) has been measured using a microsphere model with octanol-extracted radioactivity counts (integral value of input function). We developed a new method estimating the integral value of input function. First, we fitted the whole brain time-activity curves early after intravenous injection of N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) by the least-squares method. Second, we differentiated this equation. Third, we calibrated it using octanol-extracted radioactivity counts of the arterial blood sampled at 5 min. Finally, we integrated it. A significant correlation was found between the integral values obtained using a new method and those obtained using the continuous arterial blood sampling data (y = 1.048x-1206, r = 0.984). The errors between the CBF values obtained using a new method and those obtained using the 5-min continuous arterial blood sampling was 6.88 +/- 4.78%. Measurement of integral values of the input function using a new method with one-point arterial blood sampling is less invasive and convenient, and is not influenced by cardiopulmonary disease or smoking. Therefore, it would be useful for the routine measurement of CBF.

Amphetamines↗

PubMed1998

[Simplified method to quantitate regional cerebral blood flow by 123I-IMP microsphere model: validity of input counts by using the whole brain time-activity curve and one point arterial blood sampling].

We developed a new microsphere method using 123I-IMP in which arterial blood is collected at one time point early after 123I-IMP injection instead of conventional continuous arterial blood sampling, and the input count is estimated using a whole brain time-activity curve until that time point. The differential curve dCb(t)/dt of the brain time-activity curve Cb(t) early after 123I-IMP injection (when the microsphere model is established) approximates the arterial time-activity curve Ca(t) as an input function. The input count as the integral value of Ca(t) at 0-5 min was estimated using the 50 min whole brain activity Cb(5 min) and the differential value dCb(5 min/dt and the 5-min octanol-extracted count of arterial samples obtained at one time point Ca(5 min). The input counts calculated by this method were very closely correlated with measurement values obtained by continuous arterial sampling. This method is more convenient and less invasive than the continuous arterial sampling method.

Amphetamines↗

PubMed1998

[Investigation on feasibility of using a gamma camera for the measurement of blood radioactivity].

The present study was undertaken to determine whether gamma cameras can be used to measure radioactivity in samples, e.g. in blood. Aqueous 123I solution with a concentration of 10.3 MBq/ml was infused at a volume of one ml into a blood-sampling vial having an internal diameter of 22.5 mm. Various concentrations of radioactivity were generated by leaving the vial and taking radioactive decay into account. Static images were acquired for five minutes with a gamma camera using a 64 x 64 matrix to measure radioactivity counts, and the regions of interest with 7 x 7 pixels (21 mm x 21 mm) were defined on the image. The results showed that there was a good linear correlation between the radioactivity counts measured with the gamma camera without collimator and those measured with the well-type scintillation counter in the range between 0.032 kBq/ml and 279 kBq/ml. It therefore appears that gamma cameras can be substituted for well-type scintillation counters in the measurement of radioactivities in samples.

Blood↗

PubMed1998

Measurement of blood radioactivity for quantification of cerebral blood flow using a gamma camera.

OBJECTIVE: This study was designed to determine whether gamma cameras can be substituted for well-type scintillation counters in measuring blood radioactivity counts to be used as an input function for the quantitative measurement of cerebral blood flow (CBF). METHODS: Twelve different aqueous 123I solutions were prepared by serial dilution of the original concentration of 281.9 kBq/ml, and the radioactivity count of each dilution was measured with a gamma camera with the collimator removed, and with a well-type scintillation counter. When measuring the radioactivity counts with a gamma camera, static images were acquired using a 128 x 128 matrix for 5 min, and the regions of interest with 14 x 14 pixels (21 mm x 21 mm) were defined. RESULTS: There was a good correlation between the results obtained by these two procedures in the range of concentration between 0.008 kBq/ml and 281.9 kBq/ml (y = 4.245x-2.549, r = 1.0, n = 12, s.e.e. = 7.217 kcpm). There was good agreement between the CBF values (ml/100 g/min) obtained using the cross-calibration factor (CCF) and blood radioactivity counts measured with the two procedures (y = 0.990x + 0.552, r = 0.990, n = 231, s.e.e. = 1.340 ml/100 g/min). CONCLUSION: The results suggest that gamma cameras can be substituted for well-type scintillation counters in the quantitative measurement of CBF, and make it unnecessary to measure CCF after routine calibration of a SPECT apparatus.

Brain↗

PubMed1997

[Compton-scatter correction using the triple energy window (TEW) method in conventional single photon emission computed tomography without TEW acquisition hardware].

We devised a method which allowed the triple energy window (TEW) method to be applied for Compton-scatter correction in conventional single photon emission computed tomography (SPECT) systems without any hardware for TEW acquisition. In this method, the data within two subwindows located at both sides of the main window were acquired together. The effectiveness of this method was investigated by phantom experiments. The integral and differential uniformities measured using a flood phantom filled with 123I were minimized when the energy width of subwindows was 5 keV (5.8% and 4.2%, respectively). When this method was applied to a brain phantom filled with 123I in which the relative activities in white and gray matter were assigned as 1: 4.3, the ratio of SPECT values between them was more accurate (1:4.26) than that obtained without this method (1:208). This method appears to be useful for Compton-scatter correction in SPECT, because it can be applied to conventional SPECT systems without any hardware for TEW acquisition and is available for routine clinical use for its simplicity.

Brain↗

PubMed1995

[A time-saving approach for quantifying regional cerebral blood flow and application to split-dose method with 123I-IMP SPECT using a single-head rotating gamma-camera].

We have proposed a modified early method, which can shorten the total time required for the quantitative regional cerebral blood flow (rCBF) measurement with N-isopropyl-p(-)[123I]iodoamphetamine (123I-IMP) using single-head rotating gamma-camera and the continuous arterial sampling method. Between 7 to 25 minutes after the intravenous injection of 123I-IMP, brain activity increases linearly, the SPECT data acquisition is being performed, and during which detector is rotating continuously. Then the rCBF values based on the microsphere model were calculated using the planar images obtained before and after the above acquisition and 5 min after the injection, and input counts obtained by the continuous arterial sampling. A good correlation (r = 0.951) was observed between the rCBF values obtained by this method and the traditional method, in which the SPECT data acquisition started about 30 min after injection. Applying this method to the quantitative rCBF measurements at rest and during stress with Diamox by the split dose method of 123I-IMP, we could evaluate the rCBF at rest and cerebral perfusion reserve in the same day. We conclude that this method can shorten the total time required for the standard normal microsphere method and can be applied to the split dose method, and this method provide the rCBF values not so much affected by washout of the tracer from the brain.

Acetazolamide↗

PubMed1992

In vitro and in vivo effects of diethylene triamine penta-acetic acid on the distribution of indium-111 monoclonal antibody metabolism.

The effects of diethylene triamine penta-acetic acid (DTPA) on indium-111 monoclonal antibody (MoAb) metabolism were examined. Sequential analysis of 111In-MoAb incubated in serum at 37 degrees C by high performance liquid chromatography (HPLC) and electrophoresis revealed that the radioactivity gradually moved from the MoAb to a 70-90 kDa molecular weight fraction. DTPA inhibited the transchelation of 111In to this fraction. It also decreased 111In uptake by isolated rat hepatocytes but did not remove 111In incorporated in hepatocytes. The daily in vivo administration of DTPA (0.5-2.0 mg/mouse daily) to athymic mice after 111In-MoAb injection significantly reduced the 111In uptake in the liver and kidney. The tumour uptake was decreased somewhat but not significantly. The serum radioactivity in the 70-90 kDa fraction was also decreased. Scintigraphic examination demonstrated a decreased liver uptake in the DTPA-treated group of mice. Our results show that 111In released from the DTPA-MoAb conjugate in serum binds to molecules of 70-90 kDa and that DTPA decreases the 111In uptake in this fraction, which induces a decrease of 111In accumulation in normal tissues.

Animals↗

PubMed1992

[Potential application of DTPA for improving the image quality in radioimmunoscintigraphy with 111In labeled monoclonal antibodies].

Studies on application of diethylenetriamine-pentaacetic acid (DTPA) to decrease the non-specific localization of 111In-labeled antibodies (111In-MoAb) to the liver were performed. The transchelation of 111In to the molecule of M.W. 70,000-90,000 by the incubation of 111In-MoAb in human serum was inhibited by adding DTPA. These in vitro findings were also demonstrated by serum analysis after 111In-MoAb injection to the normal mice and postinjection of DTPA. By addition of DTPA, the uptake of 111In-MoAb by isolated rat hepatocytes was inhibited, but the 111In-release was unaffected. The addition of DTPA had no effect on uptake of 111In-MoAb and 111In-release in tumor cells. These results suggest that DTPA administration following 111In-MoAb injection may inhibit transchelation of 111In to transferrin or other serum proteins, so decrease non-specific liver localization of 111In and give rapid blood clearance.

Animals↗

PubMed1991

[Intraoperative radiation therapy of carcinoma of the pancreas].

From May 1978 to December 1989, 54 patients with pancreatic carcinoma underwent electron beam intraoperative radiotherapy (IORT). Three died of preoperative complications within a month. In 19 patients, liver metastasis and/or peritoneal dissemination became obvious at laparotomy. They therefore underwent IORT with palliative intent. Relief of pain was obtained in 12 of the 14 patients with pain (85.7%), although three of them were treated in combination with splanchnic nerve block. Thirty-two patients with localized carcinoma underwent IORT with curative intent (total tumor resection in 6, partial resection in 6, and no tumor resection in 20). With additional IORT treatment, their survival was significantly (p less than 0.05 during the 18th month) longer than that of 40 patients without IORT (total tumor resection in 13, partial resection in 9, and no tumor resection in 18). Among the patients without tumor resection, the 20 patients who underwent IORT survived significantly (p less than 0.05 during the 7th month) longer than the 18 patients who did not. Twelve patients who underwent total pancreatectomy died earlier than the 23 patients treated with IORT in combination with partial tumor resection or no tumor resection (not significant). In 26 patients with partial tumor resection or no tumor resection, either additional external irradiation or IORT using a small field within a large field significantly (p less than 0.05 during the 7th and 8th month) improved survival compared with IORT using a single field. Of the 20 patients without tumor resection, relief from pain was obtained in 18 of 19 patients with pain (94.7%), although two of them were treated in combination with splanchnic nerve block. In terms of adverse effects possibly caused by IORT in 26 patients who survived longer than 6 months, gastrointestinal problems were serious in several (gastric ulcer in 2, duodenal stenosis in 1, gastric ulcer and duodenal stenosis in 1, and duodenal perforation and duodenal ulcer in 1). In conclusion, our experience suggests that IORT can relieve patients of serious pain and improve survival in patients with localized pancreatic carcinoma.

Adult↗