ESTIMATION OF ORGAN DOSES AND EFFECTIVE DOSES BASED ON IN-PHANTOM DOSIMETRY FOR PAEDIATRIC DIAGNOSTIC CARDIAC CATHETERISATION.

The present study evaluated the organ doses, effective doses and conversion factors from the dose-area product to effective dose in pediatric diagnostic cardiac catheterization performed by in-phantom dosimetry and Monte Carlo simulation. The organ and effective doses in 5-y-olds during diagnostic cardiac catheterizations were evaluated using radiophotoluminescence glass dosemeters implanted into a pediatric anthropomorphic phantom and PCXMC software. The mean effective dose was 3.8 mSv (range: 1.8-7.5 mSv). The conversion factors from the dose-area product to effective dose were 0.9 and 1.6 mSv (Gy cm2)-1 for posteroanterior and lateral fluoroscopy, respectively, and 0.9 and 1.5 mSv (Gy cm2)-1 for posteroanterior and lateral cineangiography, respectively. Effective doses evaluated using the pediatric dosimetry system agreed with those obtained using PCXMC software within 12%. The dose data and conversion factors evaluated may guide the estimation of exposure doses in children undergoing diagnostic cardiac catheterization.

Thermodynamics of partitioning of phenothiazine drugs between phosphatidylcholine bilayer vesicles and water studied by second-derivative spectrophotometry.

The partition coefficients (Kps) of phenothiazine drugs (trifluoperazine, triflupromazine, chlorpromazine and promazine) between phosphatidylcholine (PC) small unilamellar vesicles (SUV) and water were determined over the temperature range of 10-40 degrees C by a second-derivative spectrophotometric method. The second derivative spectra of each drug solution containing various amounts of SUV showed distinct derivative isosbestic points confirming the entire elimination of the residual background signal effects of the SUV. The Kp values were calculated from the derivative intensity change of the drugs induced by the addition of SUV to the drug buffer solutions (pH 7.4) and obtained with the R.S.D. below 10% (n=3). The van't Hoff analysis of the temperature dependence of Kp values revealed negative deltaH(w-->l) and positive deltaS(w-->l), suggesting an enthalpy/entropy driven mechanism for the phenothiazine partitioning. The negative deltaH(w-->l) implies that the electrostatic interaction, positively charged alkyl amino groups of phenothiazine drugs with negatively charged phosphate groups on the surface of PC SUV, partly contributes to the partitioning. The existence of halogen atom(s) on the phenothiazine ring at position C-2 enhanced the Kp value (Hl) value (Hl) increase is considered to be enhancement of disorder in the hydrophobic acyl chain regions of PC SUV membranes derived from the phenothiazine ring insertion and thus depends on the bulkiness of the substituent. The enthalpy-entropy correlation analysis yielding a good linear relationship also suggests that the phenothiazine drugs studied have identically an enthalpy-entropy compensation mechanism for the partitioning.