Study on the propagation of ultra-short pulse light in cylindrical optical phantoms

A detailed study about ultra-short pulse light propagation inside cylindrical scattering and absorbing phantoms is presented. Some comparisons between a Monte Carlo code and the analytical solution of diffusion equation for a delta(t) source and point-like detectors placed at different angles of detection are shown. To better quantify the agreement between the temporal profiles obtained from the two different methods of calculation, a fitting procedure based on the Levenberg-Marquardt algorithm has been implemented. Some examples on the retrieval of the optical properties for both the Monte Carlo and experimental data are presented. In the case of inhomogeneous cylindrical phantoms, some comparisons between the results of the time-domain 3D model of finite element method and 3D Monte Carlo are also shown.

Estimation of internal absorbed dose of L-[methyl-11C]methionine using whole-body positron emission tomography

L-[Methyl-11C]-methionine (11C-methionine) is proposed as a useful radiotracer for tumour diagnosis. Human biodistribution data of cumulated activities and absorbed doses estimated by the MIRD (medical internal radiation dosimetry) method for 11C-methionine are not available in the literature. In this study we measured the organ activity for 11C-methionine by using whole-body positron emission tomography (PET) and estimated the absorbed doses to 25 organs by the MIRD method. Whole-body dynamic PET scans were performed on five normal volunteers to measure the time course of the organ activity concentration (activity/volume) after intravenous administration of 11C-methionine. Cumulated activities of the ten source organs were calculated from the time-activity curves, obtained from the dynamic PET data. Absorbed dose estimates were performed by the MIRD method for the Caucasian reference man and for the Japanese reference man. The organs which received the highest absorbed doses for the Caucasian reference man were found to be the bladder wall (2.7x10(-2) mGy/MBq), the pancreas (1.9x10(-2) mGy/ MBq), the liver (1.8x10(-2) mGy/MBq) and the kidney (1.1x10(-2) mGy/MBq). The effective doses for the Caucasian reference man and the Japanese reference man were calculated as 5.2x10(-3) and 5.0x10(-3) mSv/MBq, respectively.

Evaluation of fluorimetrically estimated serum bile acid in liver disease

Fasting serum bile acid (SBA) was measured by the enzymic fluorimetric method coupled with the NAD-resazurin system in 23 controls, 35 asymptomatic carriers of HIs antigen including 4 e antigen carriers and 91 patients with various liver diseases. All GHBs and e antigen carriers showed SBA within the normal range. SBA was most significantly correlated with serum bilirubin (gamma=0.74) and was a more sensitive index for impaired liver function than bilirubin or alkaline phosphatase in 164 radomly chosen samples from the liver disease group. In serial determinations of SBA with reference to GOT, GPT, changing patterns of these two parameters were classified into the parallel type and the discrepant type. Thirty two out of 40 cases with chronic liver disease belonged to the parallel type. SBA remained abnormal even after the normalization of transaminase in 12 out of 20 resolving episodes in cases of the parallel type, regardless of diagnosis. Since SBA changes according to the stage of the disease activity, serial and simultaneous estimation of SBA and GOT, GPT was found to be helpful in the observation of liver diseases. Maximum values of SBA elevation in an endogenous bile acid tolerance test after eating two egg yolks were higher than controls in 4 out of 7 cases with liver disease, who were associated with normal fasting SBA.