Advances in progenitor cell therapy using scaffolding constructs for central nervous system injury.

Traumatic brain injury (TBI) is a major cause of morbidity and mortality in the United States. Current clinical therapy is focused on optimization of the acute/subacute intracerebral milieu, minimizing continued cell death, and subsequent intense rehabilitation to ameliorate the prolonged physical, cognitive, and psychosocial deficits that result from TBI. Adult progenitor (stem) cell therapies have shown promise in pre-clinical studies and remain a focus of intense scientific investigation. One of the fundamental challenges to successful translation of the large body of pre-clinical work is the delivery of progenitor cells to the target location/organ. Classically used vehicles such as intravenous and intra arterial infusion have shown low engraftment rates and risk of distal emboli. Novel delivery methods such as nanofiber scaffold implantation could provide the structural and nutritive support required for progenitor cell proliferation, engraftment, and differentiation. The focus of this review is to explore the current state of the art as it relates to current and novel progenitor cell delivery methods.

The effect of shoulder variation on IMRT and SmartArc for Head and Neck Cancer

Purpose: First, to determine an average and maximum displacement of the shoulder relative to isocenter over the course of treatment. Second, to establish the dosimetric effect of shoulder displacements relative to correct isocenter alignment on the dose delivered to the target and the surrounding structures for head and neck cancer patients. Method and Materials: The frequency of shoulder shifts of various magnitudes relative to isocenter was assessed for 4 patients using image registration software. The location of the center of the right and left humeral head relative to isocenter (usually C2) was found daily from CT on rails scans, and was compared to the location of the humeral heads relative to isocenter on the initial simulation CT. Three Baseline head and neck IMRT and SmartArc plans were generated in Pinnacle based on simulation CTs. The CT datasets (external contour and boney structures) were then modified to represent shifts of the shoulder (relative to isocenter) between 3 mm and 15 mm in the SI, AP, and LR directions. The initial plans were recalculated on the image sets with shifted shoulders. Results: On average, shoulder variation was 2-5 mm in each direction, although displacements of over 1 cm in the inferior and posterior directions occurred. Shoulder shifts induced perturbations in the dose distribution, although generally only for large shifts. Most substantially, large, superior shifts resulted in coverage loss by the 95% isodose line for targets in the lower neck. Inferior shifts elevated the dose to the brachial plexus by 0.6-4.1 Gy. SmartArc plans showed similar loss of target coverage as IMRT plans. Conclusions: The position of the shoulder can have an impact on target coverage and critical structure dose. Shoulder position may need to be considered for setup of head and neck patients depending on target location.