FEASIBILITY STUDY OF USING PCXMC 2.0 TO ESTIMATE PATIENT DOSE ARISING FROM DEXA SCANS.

Patients undergoing dual energy X-ray absorption (DEXA) scans are exposed to small doses of ionizing radiation. Few papers have been published on the effective dose and organ dose for patients undergoing such scans on newer DEXA scanners. PCXMC 2.0 was used to calculate adult patient dose arising from DEXA scans. PCXMC 2.0 calculations were compared to published data and a discrepancy was noted for organ dose. Following this, effective and organ dose were measured on an anthropomorphic phantom using TLDs as a second comparison. The mean dose from 50 scans (minus background radiation) was measured. The dose calculated from PCXMC 2.0 compared to published data shows very good agreement for effective dose but a difference for organ dose. Our TLD data and PCXMC 2.0 data for organ dose have a closer agreement, within 20%. We are confident in using PCXMC 2.0 to calculate adult patient effective and organ dose arising from DEXA scans.

Combinatorial aid for underprivileged scaffolds: solution and solid-phase strategies for a rapid and efficient access to novel aza-diketopiperazines (Aza-DKP).

An efficient solution-phase synthesis of aza-diketopiperazines (aza-DKP, triazinediones) is reported. A structurally diverse collection of c-[aza-alkylGly-Pro] derivatives and yet unreported 2,4,5-trisubstituted-1,2,4-triazine-3,6-diones has been synthesized starting from Fmoc-l-Pro-OH and various Fmoc-l-amino acids. To extend the practical value of this class of dipeptidomimetics, a general solid-phase synthesis approach amenable to library production was developed on both Wang-PS and HMBA-PS resins. The final acidic treatment of the resins in TFA/water mixture at room temperature enabled the rapid and quantitative cyclization/release highly pure triazinediones. The conformational preferences and the spatial organization of the three substituents of a representative 2,4,5-trisubstituted-1,2,4-triazine-3,6-dione were investigated by X-ray diffraction and (1)H NMR spectroscopy.