3D Conformal Radiotherapy for Nephroblastoma: Unusual Technique in Dalal Jamm Hospital

Nephroblastoma is the most common kidney tumor in children, accounting for 6% of all pediatric tumors. This tumor most commonly occurs between one and five years of age with a peak incidence around three and a half years. Multidisciplinary treatment combining neo-adjuvant chemotherapy followed by surgery and radiotherapy has achieved an overall survival of 90% at 10 years. This radiotherapy is optimal when it makes it possible to deliver an optimal dose of radiation while preserving the healthy developing organs in this subject. Conformational intensity modulation radiotherapy (IMRT) by linear accelerator or helical tomotherapy and hadrontherapy make it possible to respect this principle. These irradiation techniques were not available in our practice setting. We used a three-dimensional conformational radiotherapy technique for pan-abdominal irradiation of a nephroblasm while respecting the dosimetric constraints required in IMRT. Indeed, a rigorous optimization of three-dimensional conformational radiotherapy by a good delineation of the volumes of interest and a multiplication of the irradiation beams makes it possible to approach new radiotherapy techniques in terms of dose coverage, compliance with dosimetric constraints with reduction secondary cancer risk associated with low doses.

Evaluation of Nonradiative Clinical Imaging Techniques for the Longitudinal Assessment of Tumour Growth in Murine CT26 Colon Carcinoma

Background and Objectives. To determine the most appropriate technique for tumour followup in experimental therapeutics, we compared ultrasound (US) and magnetic resonance imaging (MRI) to characterize ectopic and orthotopic colon carcinoma models. Methods. CT26 tumours were implanted subcutaneously (s.c.) in Balb/c mice for the ectopic model or into the caecum for the orthotopic model. Tumours were evaluated by histology, spectrofluorescence, MRI, and US. Results. Histology of CT26 tumour showed homogeneously dispersed cancer cells and blood vessels. The visualization of the vascular network using labelled albumin showed that CT26 tumours were highly vascularized and disorganized. MRI allowed high-resolution and accurate 3D tumour measurements and provided additional anatomical and functional information. Noninvasive US imaging allowed good delineation of tumours despite an hypoechogenic signal. Monitoring of tumour growth with US could be accomplished as early as 5 days after implantation with a shorter acquisition time (<5 min) compared to MRI. Conclusion. MRI and US afforded excellent noninvasive imaging techniques to accurately follow tumour growth of ectopic and orthotopic CT26 tumours. These two techniques can be appropriately used for tumour treatment followup, with a preference for US imaging, due to its short acquisition time and simplicity of use.

Characterizing and Comparing Fretting Fatigue and Pitting in Low-Amplitude Reciprocating Contact

Fretting fatigue has consistently been described as an “insidious” fracture process due to the difficulty in modeling and predicting fretting-induced crack initiation. Components can develop fretting fatigue cracks even when they are designed for minimal relative motion, as in the case of a turbine blade root. Vibrations that are typically small enough to be considered negligible in engineering analysis can cause cracks that will lead to component failure. The sliding distance for fretting to occur is loosely defined as tens to hundreds of micrometers. To date, there has not been a good delineation between the fretting motion and gross-sliding regimes. Likewise, it is not well understood when a given component will experience fretting fatigue or pitting (which is associated with gross sliding and is often seen in gear components). Preliminary data suggest that pitting-like cracks can initiate in a hemisphere-on-flat linear reciprocating configuration at a low number of cycles (104) and fretting-sized displacements (200–300μm). Because of the differences between the mechanisms for failure in fretting and pitting, new insight must be developed to determine parameters under which to expect either failure mode. This work seeks to characterize these two forms of failure and to determine the conditions under which fretting or pitting becomes dominant to develop a new tool for the prediction and prevention of moving components.