When your MR linac is down: Can an automated pipeline bail you out of trouble?

PURPOSE: The unique treatment delivery technique provided by magnetic resonance guided radiotherapy (MRgRT) can represent a significant drawback when system fail occurs. This retrospective study proposes and evaluates a pipeline to completely automate the workflow necessary to shift a MRgRT treatment to a traditional radiotherapy linac. MATERIAL AND METHODS: Patients undergoing treatment during the last MRgRT system failure were retrospectively included in this study. The core of the proposed pipeline was based on a tool able to mimic the original MR linac dose distribution. The so obtained dose distribution (AUTO) has been compared with the distribution obtained in the conventional radiotherapy linac (MAN). Plan comparison has been performed in terms of time required to obtain the final dose distribution, DVH parameters, dosimetric indices and visual analogue scales scoring by radiation oncologists. RESULTS: AUTO plans generation has been obtained within 10 min for all the considered cases. All AUTO plans were found to be within clinical tolerance, showing a mean target coverage variation of 1.7% with a maximum value of 4.3% and a minimum of 0.6% when compared with MAN plans. The highest OARs mean variation has been found for rectum V60 (6.7%). Dosimetric indices showed no relevant differences, with smaller gradient measure in favour of AUTO plans. Visual analogue scales scoring has confirmed comparable plan quality for AUTO plans. CONCLUSION: The proposed workflow allows a fast and accurate generation of automatic treatment plans. AUTO plans can be considered equivalent to MAN ones, with limited clinical impact in the worst-case scenario.

Conservation genetics of endangered fish populations in Arizona.

Genetic diversity in remnant populations of the Sonoran topminnow Poeciliopsis occidentalis (Pisces: Poeciliidae) from Arizona, where the species is endangered, is compared with that in populations from Sonora, Mexico, where the fish is widespread and abundant. Geographically peripheral Arizona populations contain substantially lower levels of genetic variation than do Mexican populations near the center of the species' range. Allelic differences among three genetically and geographically distinct groups are responsible for 53 percent of the total genetic diversity in this species, 26 percent is due to differences among local populations within the groups, and 21 percent is due to heterozygosity within local populations. Recommendations for conservation and restocking efforts in Arizona are based on these genetic findings.

Enzyme polymorphism in Ascaris suum (Nematoda).

The potential of multilocus electrophoretic studies for providing insight into the population biology of parasitic organisms was studied using the swine parasite Ascaris suum suum. Thirty-eight loci encoding enzymatic or nonenzymatic proteins have been resolved in extracts of adult worms by starch-gel electrophoresis. A preliminary study of variation in Ascaris from eastern Iowa revealed an average heterozygosity of 6.6%. Allele frequencies at six polymorphic loci were similar in males and females and genotypic frequencies were in accord with those expected in a single, randomly mating population; however, the significant linkage disequilibrium between Pep-2 and Es-3 suggested that there may be some genetic substructuring within Ascaris from Iowa. Genetic comparisons of Ascaris from Iowa with Ascaris from New Jersey and Maryland indicated slight differences between eastern and midwestern populations, as well as between the east coast localities. Larger samples from more locations are needed before any statistical significance can be attached to these differences; however, qualitative comparisons suggest that the differentiation is a biological reality. Knowledge of the population biology of this and other parasites may contribute to planning effective control programs.