Total body irradiation using helical tomotherapy: Set-up experience and in-vivo dosimetric evaluation

PURPOSE

Helical Tomotherapy (HT) appears as a valuable technique for total body irradiation (TBI) to create highly homogeneous and conformal dose distributions with more precise repositioning than conventional TBI techniques. The aim of this work is to describe the technique implementation, including treatment preparation, planning and dosimetric monitoring of TBI delivered in our institution from October 2016 to March 2019.

MATERIAL AND METHOD

Prior to patient care, irradiation protocol was set up using physical phantoms. Gafchromic films were used to assess dose distribution homogeneity and evaluate imprecise patient positioning impact. Sixteen patients' irradiations with a prescribed dose of 12Gy were delivered in 6 fractions of 2Gy over 3 days. Pre-treatment quality assurance (QA) was performed for the verification of dose distributions at selected positions. In addition, in-vivo dosimetry was carried out using optically stimulated luminescence dosimeters (OSLD).

RESULTS

Planning evaluation, as well as results of pre-treatment verifications, are presented. In-vivo dosimetry showed the strong consistency of OSLD measured doses. OSLD mean relative dose differences between measurement and calculation were respectively +0,96% and -2% for armpit and hands locations, suggesting better reliability for armpit OSLD positioning. Repercussion of both longitudinal and transversal positioning inaccuracies on phantoms is depicted up to 2cm shifts.

CONCLUSION

The full methodology to set up TBI protocol, as well as dosimetric evaluation and pre-treatment QA, were presented. Our investigations reveal strong correspondence between planned and delivered doses shedding light on the dose reliability of OSLD for HT based TBI in-vivo dosimetry.

[Presence of the bacterial kidney disease in salmonid fish in Quebec (author's transl)]

Presence of the bacterial kidney disease in salmonid fish in Quebec During the summers of 1979 and 1980, wild and hatchery fish were analysed for the presence of the bacterial kidney disease (BKD) agent in salmonid fish in Quebec by the indirect immunofluorescence technique. The causative agent of BKD was detected in all hatcheries tested. Ten to 25% of the fish were positive. The presence of this agent was independent of age and species. We were unable to detect the BKD in fish from the rivers in the northern part of Quebec (over the 50th parallel). The first detection of BKD in Quebec was made in the spring of 1979 in a hatchery. A high mortality occurred in fish over a year old. The majority of the fish were positive by immunofluorescence and the bacteriun was isolated from some fish. Three weeks before the disease appeared, six ponds received fish from this hatchery. No mortality was observed in those ponds and in the middle of the summer the percentage of carrier fish by immunofluorescence was approximately 20%.

[Fantasy activity in advantaged and disadvantaged children: development at age 4 to 6 years, latency and learning]

1) In the context of research on disadvantaged children, the authors have concentrated their efforts on the study of the fantasy life of both advantaged and disadvantaged children, at age 4, 5 and 6.

Using a scale of development inspired by Anna Freud's concept of developmental lines, they have found statistically significant major differences in the evolution of the two groups, in studying both their libidinal and ego organizations. Such differences are consistently evident, although in varying degrees through the three years of observation. A minority of the disadvantaged children show good emotional resources in their first nursery years (age 4), and their development remains adequate through first grade. Most of them however present an inadequate development all along and continue in first grade to function at the level of a preœdipal phantasy life which they should have repressed or transformed.

2) A study of plastic productions in first grade (drawings) and of the learning indices which they reflect also reveals important disparities between the two groups. Advantaged children reach a state of serenity which allows them to enter easily into the world of formal learning and latency. Disadvantaged children are still too often under the domination of a dangerous phantasy world which delays their entry into formal learning and makes it problematic.

3) The review of recent literature suggests a pessimistic view about early intervention with disadvantaged children; the authors, however, believe in the necessity of tenaciously pursuing observations of such early interventions and long-term evaluations of results.