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The purpose of this work was to characterize three formulations of PRESAGE(®) dosimeters (DEA-1, DEA-2, and DX) and to identify optimal readout timing and procedures for accurate in-house 3D dosimetry. The optimal formulation and procedure was then applied for the verification of an intensity modulated radiation therapy (IMRT) and a volumetric modulated arc therapy (VMAT) treatment technique. PRESAGE(®) formulations were studied for their temporal stability post-irradiation, sensitivity, and linearity of dose response. Dosimeters were read out using a high-resolution optical-CT scanner. Small volumes of PRESAGE(®) were irradiated to investigate possible differences in sensitivity for large and small volumes ('volume effect'). The optimal formulation and read-out technique was applied to the verification of two patient treatments: an IMRT plan and a VMAT plan. A gradual decrease in post-irradiation optical-density was observed in all formulations with DEA-1 exhibiting the best temporal stability with less than 4% variation between 2-22 h post-irradiation. A linear dose response at the 4 h time point was observed for all formulations with an R(2) value >0.99. A large volume effect was observed for DEA-1 with sensitivity of the large dosimeter being ~63% less than the sensitivity of the cuvettes. For the IMRT and VMAT treatments, the 3D gamma passing rates for 3%/3 mm criteria using absolute measured dose were 99.6 and 94.5% for the IMRT and VMAT treatments, respectively. In summary, this work shows that accurate 3D dosimetry is possible with all three PRESAGE(®) formulations. The optimal imaging windows post-irradiation were 3-24 h, 2-6 h, and immediately for the DEA-1, DEA-2, and DX formulations, respectively. Because of the large volume effect, small volume cuvettes are not yet a reliable method for calibration of larger dosimeters to absolute dose. Finally, PRESAGE(®) is observed to be a useful method of 3D verification when careful consideration is given to the temporal stability and imaging protocols for the specific formulation used.

It has been recently shown that chestwall recurrence of breast cancer and many other superficial diseases can be successfully treated with the combination of radiation, chemotherapy and hyperthermia. Conformal microwave antenna array for hyperthermia treatment of large area superficial diseases can significantly increase patient comfort while at the same time facilitate treatment of larger and more irregularly shaped disease. A large number of small efficient antennas is preferable for improved control of heating, as the disease can be more accurately contoured and the lower power requirement correlates with system reliability, linearity and reduced cost. Thus, starting from the initially proposed square slot antennas, we investigated new designs for multi-fed slot antennas of several shapes that maximize slot perimeter while reducing radiating area, thus increasing antenna efficiency. Simulations were performed with commercial electromagnetic simulation software packages (Ansoft HFSS) to demonstrate that the antenna size reduction method is effective for several dual concentric conductor (DCC) aperture shapes and operating frequencies. The theoretical simulations allowed the development of a set of design rules for multi-fed DCC slot antennas that facilitate conformal heat treatments of irregular size and shape disease with large multi-element arrays. Independently on the shape, it is shown that the perimeter of 10cm at 915 MHz delivers optimal radiation pattern and efficiency. While the maximum radiation is obtained for a circular pattern the rectangular shape is the one that feels more efficiently the array space.

Catheter-based ultrasound applicators have been developed for delivering hyperthermia or high-temperature thermal ablation of cancer and benign disease of the prostate. These devices allow for control of heating along the length and angular expanse during therapy delivery. Four types of transurethral applicators were devised for thermal treatment of prostate combined with MR thermal monitoring: sectored tubular transducer devices with directional heating patterns and rotation; planar and curvilinear devices with narrow heating patterns and rotation; and multi-sectored tubular devices capable of dynamic angular control without applicator movement. Interstitial devices (2.4 mm OD) have been developed for percutaneous implantation with directional or dynamic angular control. In vivo experiments in canine prostate under MR temperature imaging were used to evaluate these devices and develop treatment delivery strategies. MR thermal imaging was used to monitor temperature and thermal dose in multiple slices through the target volume. Multi-sectored transurethral applicators can dynamically control the angular heating profile and target large regions of the gland in short treatment times without applicator manipulation. The sectored tubular, planar, and curvilinear transurethral devices produce directional coagulation zones, extending 15-20 mm radial distance to the outer prostate capsule. Sequential rotation under motor control and modulated dwell time can be used to tightly conform thermal ablation to selected regions. Interstitial implants with directional devices can be used to effectively ablate targeted regions of the gland while protecting the rectum. The MR derived 52 degrees C and lethal thermal dose contours (t43=240 min) effectively defined the extent of thermal damage and provided a means for real-time control of the applicators. Catheter-based ultrasound devices, combined with MR thermal monitoring, can produce relatively fast (5-40 min) and precise thermal ablation of prostate.