Treatment planning after hydrogel injection during radiotherapy of prostate cancer

PURPOSE

Imaging for treatment planning shortly after hydrogel injection is optimal for practical purposes, reducing the number of appointments. The aim was to evaluate the actual difference between early and late imaging.

PATIENTS AND METHODS

Treatment planning computed tomography (CT) was performed shortly after injection of 10 ml hydrogel (CT1) and 1-2 weeks later (CT2) for 3 patients. The hydrogel was injected via the transperineal approach after dissecting the space between the prostate and rectum with a saline/lidocaine solution of at least 20-ml. Hydrogel volume and distances between the prostate and rectal wall were compared. Intensity-modulated radiotherapy (IMRT) plans up to a dose of 78 Gy were generated (rectum V70 < 20 %, rectum V50 < 50 %; with the rectum including hydrogel volume for planning).

RESULTS

A mean planning treatment volume of 104 cm(3) resulted for a prostate volume of 37 cm(3). Hydrogel volumes of 30 and 10 cm(3) were determined in CT1 and CT2, respectively. Distances between the prostate and rectal wall at the levels of the base, middle, and apex were 1.7 cm, 1.6 cm, 1.5 cm in CT1 and 1.3 cm, 1.2 cm, 0.8 cm in CT2, respectively, corresponding to a mean decrease of 24, 25, and 47 %. A small overlap between the PTV and the rectum was found only in 1 patient in CT2 (0.2 cm(3)). The resulting mean rectum (without hydrogel) V75, V70, V60, V50 increased from 0 %, 0 %, 0.6 %, 10 % in CT1 to 0.1 %, 1.2 %, 6 %, 20 % in CT2, respectively.

CONCLUSION

Treatment planning based on imaging shortly after hydrogel injection overestimates the actual hydrogel volume during the treatment as a result of not-yet-absorbed saline solution and air bubbles.

Analyses of the genomic methylation status of the human cyclin A1 promoter by a novel real-time PCR-based methodology

The role of CpG methylation in the regulation of tissue-specific gene expression is highly controversial. Cyclin A1 is a tissue-specifically expressed gene that is strongly methylated in non-expressing tumor cell lines. We have established a novel real-time PCR method to quantitate genomic CpG methylation of the cyclin A1 promoter. Genomic DNA samples from different human organs were treated with bisulfite and amplified with methylation-specific primers and with primers amplifying methylated as well as non-methylated DNA. PCR product quantitation was obtained by using a fluorogenic probe labeled with FAM and TAMRA. These analyses demonstrated that the human cyclin A1 promoter was methylated in kidney, colon, spleen, testis, and small intestine, but not in brain, liver, pancreas, or heart. Expression of cyclin A1 was predominantly found in testis. Low level expression of cyclin A1 was present in spleen, prostate, leukocytes, colon, and thymus. Taken together, our data provide evidence that CpG methylation patterns of the human cyclin A1 promoter in human organs do not generally correlate with cyclin A1 gene expression in vivo.

Provision of data for on-line simulation

A crucial factor for the quality and results of the on-line simulation of a municipal sewage treatment system is the provision of the requisite data in adequate quality and density. Since the measured data cannot be incorporated in a simulation model without prior processing, it should be prepared in such a way that it can be converted to the model-related input quantities. If individual input measuring signals fail, substitute value concepts must be developed which are based on the remaining information. With this it is possible to ensure the continuous provision of data. Various approaches are possible in seeking a solution to this problem. At the Wupperverband a detailed programme of investigation on the subject area of the processing of inflow data is being implemented as a component of future on-line simulation at Wuppertal-Buchenhofen STP.

Large-scale production and plaque titration of European Chlorella viruses

Viruses of the exsymbiotic green freshwater algae Chlorella, family Phycodnaviridae, appear to be distributed worldwide but those found in North American algae have been characterized in detail. The distinct European Chlorella viruses were studied and it was necessary to adapt both large scale purification and the plaque titration assay to the host organisms' different physiology and to our specific laboratory needs. In the virus purification scheme, a precipitation step with polyethylene glycol was introduced which allows high yield recovery of infective particles from large volumes by rapid low-speed centrifugation. In the plaque assay, a standardized algal culture was introduced. The influence of other factors, e.g. circadian rhythm, on plaque growth is also described.

Biosynthesis of mycothiol: elucidation of the sequence of steps in Mycobacterium smegmatis

Several members of the Actinomycetales, including the medically important mycobacteria, produce 1-D-myo-inosityl-2-(N-acetyl-L-cysteinyl)amino-2-deoxy-alpha-D- glucop yranoside (trivial name mycothiol) as their principal low-molecular-mass thiol. The pseudo-disaccharide component of mycothiol, 1-D-myo-inosityl-2-amino-2-deoxy-alpha-D-glucopyranoside (alpha-D-GI), was synthesized by ligation of 1-D,L-2,3,4,5, 6-penta-O-acetyl-myo-inositol to 3,4,6-tri-O-acetyl-2-deoxy- 2-(2,4-dinitrophenylamino)-alpha-D-glu- copyranosyl bromide to give, in the first instance, an isomeric mixture of alpha- and beta-linked pseudo-disaccharides. The alpha-coupled D,D and D,L isomers, alpha-D-GI and alpha-L-GI respectively, were purified from the mixture by TLC, followed by removal of the protecting groups. A cell-free extract of Mycobacterium smegmatis catalysed the ligation of cysteine, acetate and alpha-D-GI in the presence of ATP and Mg2+ to form mycothiol, as judged by HPLC. When no acetate was added to the incubation mixture, an additional thiol accumulated. In the presence of [14C]acetate no radiolabel was recovered in this species, but only in mycothiol. The additional thiol was isolated as the bimane derivative, and 1H and 1H-1H COSY NMR spectra confirmed its identity as desacetylmycothiol. A more complete conversion of desacetylmycothiol into mycothiol was achieved in the presence of acetyl-S-CoA. These results indicate that the biosynthesis of mycothiol proceeds by the sequential addition of cysteine and acetate to alpha-D-GI. The inositol moiety appears to be an important determinant of specificity, since alpha-L-GI was poorly utilized.