V Sathiaseelan

Evaluation of an ingestible telemetric temperature sensor for deep hyperthermia applications

We have investigated the potential of an ingestible thermometric system (ITS) for use with a deep heating system. The ingestible sensor contains a temperature-sensitive quartz crystal oscillator. The telemetered signal is inductively coupled by a radiofrequency coil system to an external receiver. The sensors, covered with a protective silicon coating, are 10 mm in diameter and 20 mm long and are energized by an internal silver-oxide battery. Experimental studies were carried out to investigate the accuracy of the system and the extent of reliable operation of these sensors in an electromagnetic environment. Different measurements were repeated for five sensors. Calibration accuracy was verified by comparison with a Bowman probe in the temperature range 30 degrees C to 55 degrees C. Linear regression analysis of individual pill readings indicated a correlation within +/- 0.4 degrees C at 95% prediction intervals in the clinical temperature range of 35 degrees C to 50 degrees C. Further work is required to improve this accuracy to meet the quality assurance guidelines of +/- 0.2 degrees C suggested by the Hyperthermia Physics Center. Response times were determined by the exponential fit of heat-up and cool-down curves for each pill. All curves had correlation coefficients greater than 0.98. Time (mean +/- SE) to achieve 90% response during heat-up was 115 +/- sec. Time to cool-down to 10% of initial temperature was 114 +/- 4 sec. The effect of the external antenna and sensor spacing and the angle of orientation of the sensor relative to the antenna plane were also studied. Electromagnetic interference effects were studied by placing the sensor with a Bowman probe in a cylindrical saline phantom for the tests in an annular phase array applicator. Different power levels at three frequencies--80, 100, and 120 MHz--were used. Accurate temperature readings could not be obtained when the electromagnetic power was on because of interference effects with the receiver. However, the temperatures read with the ITS immediately after the electromagnetic power was switched off correlated well with the Bowman probe readings across the power categories and the three frequencies used. The phantom was heated to steady state, with a Bowman probe placed at the central axis of the cylinder used as control. During the heat-up period and the steady state, the mean difference (+/- SE) between the ITS and Bowman probe was 0.12 degrees C (+/- 0.05 degrees C).(ABSTRACT TRUNCATED AT 400 WORDS)

Phase I/II trial of combined 131I anti‐CEA monoclonal antibody and hyperthermia in patients with advanced colorectal adenocarcinoma

This pilot project was undertaken to evaluate the toxicity of and tumor response to combined 131I anti–carcinoembryonic antigen monoclonal antibody (131I anti‐CEA RMoAb) and hyperthermia in patients with metastatic colorectal adenocarcinoma.

Initial results for automated computational modeling of patient-specific electromagnetic hyperthermia

The authors report the first highly automated CT image segmentation and interpolation scheme applied to model patient-specific EM hyperthermia. This novel system is based on sophisticated tools from the artificial intelligence, computer vision, and computer graphics disciplines. It permits CT-based patient-specific hyperthermia models to be constructed without tedious manual contouring on digitizing pads or CRT screens. The system permits in principle near-real-time assistance in hyperthermia treatment planning. The authors apply this system to interpret actual patient CT data, reconstructing a 3-D model of the human thigh from a collection of 29 serial CT images at 10 mm intervals. Then, using the finite-difference-time-domain (FD-TD) method, they obtain 2-D and 3-D models of EM hyperthermia of this thigh due to a waveguide applicator. They find that different results are obtained from the 2-D and 3-D models, and they conclude that full 3-D tissue models are required for future clinical usage.<<ETX>>

EFFICACY OF IRRADIATION AND EXTERNAL HYPERTHERMIA IN LOCALLY ADVANCED, HORMONE-REFRACTORY OR RADIATION RECURRENT PROSTATE CANCER: A PRELIMINARY REPORT

PURPOSE To present a preliminary report on the feasibility, efficacy, and toxicity of irradiation (RT) and hyperthermia (HT) in patients with locally advanced, hormone-refractory prostate cancer (LAHRPC) who may or may not have received prior RT. METHODS AND MATERIALS Between 1997 and 2002, 13 consecutive patients with LAHRPC or RT-recurrent prostate cancer were treated with RT and HT on a Phase I-II protocol. Eight patients had RT-recurrent LAHRPC (Group A) and 5 had LAHRPC without prior RT (Group B). All patients had large and clinically symptomatic tumors. The median RT dose was 39.6 Gy and 66.6 Gy in Groups A and B, respectively. External deep HT was delivered using a BSD-2000 Sigma-60 applicator. The median number of HT treatments was 8 in group A and 10 in group B. RESULTS The median follow-up was 14 and 13 months for Groups A and B, respectively. All patients achieved a complete or partial response (CR/PR) and complete palliation of symptoms. Eleven patients had follow-up CT scans that demonstrated a CR in six and a PR in five. Two patients, who died of metastasis, did not have CT scans and had a PR on digital rectal examination. Two patients demonstrated a biochemical CR. The median duration of the CR/PR among Group A patients was 12 months after therapy. Three patients in Group A developed tumor recurrence at 9, 17, and 27 months after repeat RT to doses of 39.6, 36, and 50 Gy, respectively. At last follow-up, no Group B patient developed local recurrence. Grade 1-2 rectal bleeding was noted in 3 patients. RT and HT were generally well tolerated by all patients who had not previously undergone RT. Of the 8 patients who had, 6 (75%) tolerated retreatment well with minimal or no complications. Two patients in the repeat RT group had severe complications. One patient with lymphoma and factor XI deficiency developed Grade 4 hemorrhagic cystitis. Another previously irradiated patient developed a rectovesical fistula 4 months after retreatment, after disappearance of a large, invasive, and necrotic tumor. CONCLUSION This preliminary report demonstrates the feasibility and efficacy of RT and HT in patients with LAHRPC, who may or may not have received prior RT. Presently, such patients who have undergone previous RT have no effective treatment options. RT and HT were generally well tolerated by patients who were not previously undergone RT. Of those who had been, most (6 of 8) tolerated retreatment well with minimal or no complications. The high-risk factors for treatment- and tumor regression-related side effects include the presence of large necrotic tumors, previous RT with a large dose/fraction, and the presence of bleeding disorders. Despite the size of these large tumors, RT and HT resulted in significant tumor shrinkage, rapid serum prostate-specific antigen decline, durable treatment responses, and durable palliation of symptoms. Additional clinical studies are warranted.

A Comprehensive Quality Assurance Program for Personnel and Procedures in Radiation Oncology: Value of Voluntary Error Reporting and Checklists

PURPOSE This report describes the value of a voluntary error reporting system and the impact of a series of quality assurance (QA) measures including checklists and timeouts on reported error rates in patients receiving radiation therapy. METHODS AND MATERIALS A voluntary error reporting system was instituted with the goal of recording errors, analyzing their clinical impact, and guiding the implementation of targeted QA measures. In response to errors committed in relation to treatment of the wrong patient, wrong treatment site, and wrong dose, a novel initiative involving the use of checklists and timeouts for all staff was implemented. The impact of these and other QA initiatives was analyzed. RESULTS From 2001 to 2011, a total of 256 errors in 139 patients after 284,810 external radiation treatments (0.09% per treatment) were recorded in our voluntary error database. The incidence of errors related to patient/tumor site, treatment planning/data transfer, and patient setup/treatment delivery was 9%, 40.2%, and 50.8%, respectively. The compliance rate for the checklists and timeouts initiative was 97% (P<.001). These and other QA measures resulted in a significant reduction in many categories of errors. The introduction of checklists and timeouts has been successful in eliminating errors related to wrong patient, wrong site, and wrong dose. CONCLUSIONS A comprehensive QA program that regularly monitors staff compliance together with a robust voluntary error reporting system can reduce or eliminate errors that could result in serious patient injury. We recommend the adoption of these relatively simple QA initiatives including the use of checklists and timeouts for all staff to improve the safety of patients undergoing radiation therapy in the modern era.

Effects of hyperthermia and iodine-131 labeled anticarcinoembryonic antigen monoclonal antibody on human tumor xenografts in nude mice

Background. Many studies have demonstrated synergistic interaction between hyperthermia and radiation. This study was undertaken to determine whether hyperthermia could enhance the effect of radioimmunotherapy (RIT) in the treatment of human colon adenocarcinoma xenografts in nude mice.

Unexpected physical phenomena indicated by FDTD modeling of the Sigma-60 deep hyperthermia applicator

We investigate the numerical convergence properties of two-dimensional (2-D) and three-dimensional (3-D) finite-difference time-domain (FDTD) models of the BSD-2000 Sigma-60 annular phased array used for deep hyperthermia. The FDTD modeling data indicate unexpected physical phenomena for the case of Sigma-60 excitation of an elliptical tissue phantom embedded in a circular water bolus. These phenomena include: (1) high-Q energy storage; (2) electromagnetic (EM) mode flipping within the water bolus/phantom; and (3) whispering-gallery transmission of energy to the opposite side of the phantom relative to the exciting dipole pair. We conclude that these phenomena substantially impact the FDTD numerical modeling of this system, and further conclude that the whispering-gallery effect can impact clinical applications of the Sigma-60.

Characteristics of improved microwave interstitial antennas for local hyperthermia

The heating potentials of two newly-developed microwave interstitial antennas are reported in this paper. The longitudinal (parallel to the antenna) and transverse (over a plane perpendicular to the antenna) specific absorption rate (SAR) distributions of single and an array of four parallel antennas were measured in a muscle equivalent phantom and their performance characterized at 915 MHz in terms of the following parameters: peak depth (location of the profile peak with respect to the surface), 50% HL (effective heating length over which SAR greater than 50% of the peak normalized SAR), dead length (axial length at the antenna tip with SAR less than 50% of peak normalized SAR), and the variations of the specific absorption rate pattern relative to the depth of insertion. The results are analyzed and discussed in terms of these parameters and other factors important in the clinical use of these antennas for effective interstitial hyperthermia.

Cardiac-Sparing Whole Lung IMRT in Children With Lung Metastasis

PURPOSE To demonstrate the dosimetric advantages of cardiac-sparing (CS) intensity modulated radiation therapy (IMRT) in children undergoing whole lung irradiation (WLI). METHODS AND MATERIALS Chest CT scans of 22 children who underwent simulation with 3-dimensional (n=10) or 4-dimensional (n=12) techniques were used for this study. Treatment planning was performed using standard anteroposterior-posteroanterior (S-RT) technique and CS-IMRT. Left and right flank fields were added to WLI fields to determine whether CS-IMRT offered any added protection to normal tissues at the junction between these fields. The radiation dose to the lung PTV, cardiac structures, liver, and thyroid were analyzed and compared. RESULTS CS-IMRT had 4 significant advantages over S-RT: (1) superior cardiac protection (2) superior 4-dimensional lung planning target volume coverage, (3) superior dose uniformity in the lungs with fewer hot spots, and (4) significantly lower dose to the heart when flank RT is administered after WLI. CONCLUSIONS The use of CS-IMRT and 4-dimensional treatment planning has the potential to improve tumor control rates and reduce cardiac toxicity in children receiving WLI.

Intra-operative pubic arch interference during prostate seed brachytherapy in patients with CT-based pubic arch interference of ≤1 cm

PURPOSE There are only a few reports on the frequency of intra-operative pubic arch interference (I-PAI) during prostate seed brachytherapy (PB). MATERIALS AND METHODS Two hundred and forty-three patients with a CT-based pubic arch interference (PAI) of < or =1 cm and a prostate volume of < or =50-60 cc underwent PB. Those patients requiring needle repositioning by > or =0.5 cm on the template were scored as having I-PAI. The incidence of I-PAI and its impact on biochemical control were analyzed. RESULTS Intra-operative PAI was encountered in 47 (19.3%) patients. Forty two patients (17.3%) had I-PAI in 1-2 needles, two (0.8%) had I-PAI in four needles and three patients (1.2%) had I-PAI in six needles. Overall, 1.4% of needles required repositioning due to I-PAI. BMI>27 kg/m(2) and wider (>75 mm) pubic bone separation at mid ramus (PS-ML) were associated with a lower incidence of I-PAI. At a median follow-up of 50.1 months, the 3- and 5-year bPFS was 97.3% and 95.2%, respectively. The 5-year bPFS rates for patients with and without I-PAI were 95.6% and 95%, respectively (p=0.28). CONCLUSIONS The use of CT-based PAI of < or =1cm as a selection criterion for PB is a simple and reliable method for minimizing the incidence of I-PAI and maintaining excellent biochemical control rates.