We developed a prototype for a closed apparatus for assembling tissue-engineered vascular grafts (TEVGs) with the goal of creating a simple operator-independent method for making TEVGs to optimize safety and enable widespread application of this technology. The TEVG is made by seeding autologous bone marrowderived mononuclear cells onto a biodegradable tubular scaffold and is the first man-made vascular graft to be successfully used in humans. A critical barrier, which has prevented the widespread clinical adoption of the TEVG, is that cell isolation, scaffold seeding, and incubation are performed using an open method. To reduce the risk of contamination, the TEVG is assembled in a clean room. Clean rooms are expensive to build, complex to operate, and are not available in most hospitals. In this investigation, we used an ovine model to compare the safety and efficacy of TEVGs created using either a standard density centrifugation-based open method or the new filter-based closed system. We demonstrated no graft-related complications and maintenance of growth capacity in TEVGs created using the closed apparatus. In addition, the use of the closed system reduced the amount of time needed to assemble the TEVG by *50%. Adaptation of similar methodologies may facilitate the safe translation and the widespread use of other tissue engineering technologies.

Objectives To evaluate the feasibility and repeatability of applying blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging in the feet to quantify regional dynamic changes in tissue oxygenation during proximal cuff occlusion and reactive hyperemia. Subjects and Methods Ten healthy male subjects underwent BOLD and T1-weighted imaging of the feet on two separate occasions using a 3T scanner. Dynamic changes in BOLD signal intensity were assessed before and during proximal cuff occlusion of the thigh and during reactive hyperemia, and BOLD time course data was evaluated for the time-to-half ischemic minimum, minimum ischemic value, peak hyperemic value, time-to-peak hyperemia, time-to-half peak hyperemia, and end value. T1-weighted images were used for segmentation of volumes of interest (VOI) in anatomical regions of the foot (heel, toes, dorsal foot, medial and lateral plantar foot). Repeatability of vascular responses was assessed for each foot VOI using semi-automated image registration and quantification of serial BOLD images. Results The heel VOI demonstrated a significantly higher peak hyperemic response, expressed as percent change from baseline BOLD signal intensity, compared to all other VOIs of the foot (heel, 7.4±1.2%; toes, 5.6±0.8%; dorsal foot, 5.7±1.6%; medial plantar, 5.6±1.7%; lateral plantar, 5.6±1.5%; P<0.05). Additionally, the lateral plantar VOI had a significantly lower terminal signal intensity value (i.e., end value) when compared to all foot VOIs (P<0.05). BOLD MR imaging was repeatable between visits in all foot VOIs, with no significant differences between study visits for any of the evaluated functional indices. Conclusions BOLD MR imaging offers a repeatable technique for volumetric assessment of regional foot tissue oxygenation. Future application of BOLD imaging in the feet of patients with peripheral vascular disease may permit serial evaluation of regional tissue oxygenation and allow for improved assessment of therapeutic interventions targeting specific sites of the foot.

The authors demonstrate that the TEW method leads to overestimation in scatter and crosstalk for the CZT-based imaging system while the proposed scatter and crosstalk correction method can provide more accurate self-scatter and down-scatter estimations for quantitative single-radionuclide and dual-radionuclide imaging.

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