P. Stauffer, Oana Craciunescu, P. Maccarini, Cory Wyatt, K. Arunachalam, O. Arabe, V. Stakhursky, B. Soher, J. MacFall, Z. Li, William Joines, S. Rangarao, K. Cheng, S. Das, Carlos Martins, Cecil Charles, Mark Dewhirst, T. Wong, E. Jones, Z. Vujaskovic
A critical need has emerged for volumetric thermometry to visualize 3D temperature distributions in real time during
deep hyperthermia treatments used as an adjuvant to radiation or chemotherapy for cancer. For the current effort,
magnetic resonance thermal imaging (MRTI) is used to measure 2D temperature rise distributions in four cross sections
of large extremity soft tissue sarcomas during hyperthermia treatments. Novel hardware and software techniques are
described which improve the signal to noise ratio of MR images, minimize motion artifact from circulating coupling
fluids, and provide accurate high resolution volumetric thermal dosimetry. For the first 10 extremity sarcoma patients,
the mean difference between MRTI region of interest and adjacent interstitial point measurements during the period of
steady state temperature was 0.85°C. With 1min temporal resolution of measurements in four image planes, this noninvasive
MRTI approach has demonstrated its utility for accurate monitoring and realtime steering of heat into tumors at
depth in the body.
This work reports the ongoing development of a combination applicator for simultaneous heating of superficial tissue
disease using a 915 MHz DCC (dual concentric conductor) array and High Dose Rate (HDR) brachytherapy delivered
via an integrated conformal catheter array. The progress includes engineering design changes in the waterbolus, DCC
configurations and fabrication techniques of the conformal multilayer applicator. The dosimetric impact of the thin
copper DCC array is also assessed. Steady state fluid dynamics of the new waterbolus bag indicates nearly uniform flow
with less than 1°C variation across a large (19×32cm) bolus. Thermometry data of the torso phantom acquired with
computer controlled movement of fiberoptic temperature probes inside thermal mapping catheters indicate feasibility of
real time feedback control for the DCC array. MR (magnetic resonance) scans of a torso phantom indicate that the
waterbolus thickness across the treatment area is controlled by the pressure applied by the surrounding inflatable
airbladder and applicator securing straps. The attenuation coefficient of the DCC array was measured as 3± 0.001% and
2.95±0.03 % using an ion chamber and OneDose dosimeters respectively. The performance of the combination
applicator on patient phantoms provides valuable feedback to optimize the applicator prior use in the patient clinic.
Oana Craciunescu, Ellen Jones, Kimberly Blackwell, Terence Wong, Eric Rosen, Zeljko Vujaskovic, James MacFall, Vlayka Liotcheva, Michael Lora-Michiels, Leonard Prosnitz, Thaddeus Samulski, Mark Dewhirst
At Duke University Medical Center, selective LABC patients were treated on a protocol using neoadjuvant Myocet/Paclitaxel (ChT) and HT. With the purpose of generating perfusion/permeability parametric maps and to use gadolinium (Gd) enhancement curves to score and predict response to neoadjuvant treatment, a study was designed to acquire 3 sets of DE-MRI images along the 4 cycles of combined ChT and HT. A T1-weighted three-dimensional fast gradient echo technique was used over 30 minutes following bolus injection of Gd-based contrast agent. Perfusion/permeability maps were generated by fitting the signal intensity to a double exponential curve that generates washin (WiP) and washout (WoP), parameters that are associated with the tumors vascularity/permeability and cellularity. Based on the values of the WiP, the tumors were divided in lowWI (WiP < 100), mediumWI (100 200). During the HT treatments temperatures in the breast were measured invasively via a catheter inserted under CT guidance. Although minimum sampled temperatures give a crude indication of the temperature distribution, several thermal dose metrics were calculated for each of the HT fractions (e.g. T90, T50, T10). As expected, tumors that were more vascularized (i.e. higher WiP) heated less than tumors with low WiP, a degree on average. The adjuvant treatment also changed the shape and inhomogeneity of the perfusion/permeability maps, with dramatic changes after the first fraction in responders. The correlation between the thermal metrics and pathological response will be discussed, as well as possible correlation with other tumor physiology parameters. In conclusion, the Gd-enhancement analysis of DE-MRI images is able to generate information related to the tumor vascularity, permeability and cellularity that can correlate with the tumor's response to the neoadjuvant treatment in general, and to HT in particular. Work supported by a grant from the NCI CA42745.
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