Simplified TRS398 dosimetry protocol for dose determination in high-energy electrons beams.

A method is proposed to simplify the IAEA TRS398 dosimetry code of practice in respect to dose determination of high-energy electron beams. The proposed method eliminates the use of the intermediate beam quality Q(int) (and beam quality correction factor k(Q,Q(int))) applicable for cross calibration and subsequent use of the user's chamber for dose determination in water for high-energy electron beams. This method allows calculation of the dose to water calibration factor for the user's instrument at the reference beam quality N(D)(w,Q0) directly from a cross calibration in a high-energy electron beam of quality Q(cross) at the user's institute.

Age related preservation and loss in optimized brain SPECT.

Background: Recent single photon emission computed tomography (SPECT) studies have reported age related increases in regional brain perfusion (called preservation here) as well as losses.

Aim: To apply optimized SPECT processing to better define and understand both age related preservation and loss in brain SPECT.

Methods: Brain SPECT was performed on 85 healthy subjects using Tc hexamethylpropylene amine oxime (HMPAO), processed using findings from recent optimization work, and subjected to voxel based statistical analysis.

Optimisation of brain SPET and portability of normal databases.

Use of a normal database in quantitative regional analysis of brain single-photon emission tomography (SPET) facilitates the detection of functional defects in individual or group studies by accounting for inter-subject variability. Different reconstruction methods and suboptimal attenuation and scatter correction methods can introduce additional variance that will adversely affect such analysis. Similarly, processing differences across different instruments and/or institutions may invalidate the use of external normal databases.