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T V Samulski

Publications and source records attributed to T V Samulski.

At least 37 records · Page 2Linked to original sources
PubMed1993

Intraperitoneal cisplatin and regional hyperthermia for ovarian carcinoma.

PURPOSE: To review the theoretical basis and results of a Phase I study of concurrent intraperitoneal cisplatin and hyperthermia in the treatment of ovarian carcinoma. METHODS AND MATERIALS: Previously treated patients with epithelial ovarian carcinoma received intraperitoneal instillation of cisplatin and 60 minutes of regional hyperthermia, with a goal temperature of 41.5 degrees C. Cisplatin dose started at 20 mg/m2 with escalation to the maximally tolerated dose. Six such cycles given every 3 weeks were planned. Pharmacokinetic studies with and without hyperthermia were performed. RESULTS: Fifteen patients receiving 17 courses of treatment were evaluable. The maximally tolerated dose of cisplatin was between 80 and 120 mg/m2. The dose limiting toxicity was nephrotoxicity in all but one course. The median intraperitoneal temperature was 40.7 degrees C; the majority of treatments in which the goal temperature was not reached had power limited by patient discomfort. No major toxicities attributable to hyperthermia were noted. Pharmacokinetic studies noted no significant differences between treatments with vs. without hyperthermia, with intraperitoneal to plasma area under the curve ratios being 30-35. Ten patients had a decline in their CA-125 count during treatment, although in only two patients did this response persist beyond their course of treatment. CONCLUSION: Intraperitoneal cisplatin and regional hyperthermia can be performed with reasonable toxicity. The maximally tolerated dose of 80-120 mg/m2 in pretreated patients (which is similar to those reported with cisplatin alone) and median intraperitoneal temperatures of 40.7 degrees C, however, are felt to be too low to be efficacious in a significant percentage of women with bulky recurrent disease. Further study using intravenous thiosulfate and controlled analgesia is being performed.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1993

Cumulative minutes with T90 greater than Tempindex is predictive of response of superficial malignancies to hyperthermia and radiation.

PURPOSE: To better define thermal parameters related to tumor response in superficial malignancies treated with combined hyperthermia and radiation therapy. METHODS AND MATERIALS: Patients were randomized to receive one or two hyperthermia treatments per week with hyperthermia given during each week of irradiation. Hyperthermia was given for 60 min with treatments begun within 1 hr following irradiation. Power was increased to patient tolerance or normal tissue temperature of 43.0 degrees C. Irradiation was generally given 5 times per week with doses prescribed to normal tissue tolerance (generally 24-70 Gy at 1.8-2.5 Gy per fraction). Multipoint thermometry was used with temperatures obtained every 5 min. RESULTS: One hundred eleven individual treatment fields containing 1 or more tumor nodules were completely evaluable. The complete and overall response rates were 46% and 80%, respectively. Forty-one percent of all treatment fields (51% of responding lesions) remained controlled at 2 years. Multivariate analysis revealed that the cumulative minutes that the temperature achieved by 90% of the measured tumor sites (T90) was > or = 40.0 degrees C, tumor histology, tumor volume, and radiation dose were significantly associated with complete tumor response. The complete response rate was not significantly affected by the number of hyperthermia treatments given per week. The incidence of clinically significant complications was low. CONCLUSIONS: These results support the usefulness of the cumulative minute system in describing time-temperature relationships. The significance of thermal variables with regard to tumor response strongly supports the contention that hyperthermia can be a useful adjunct to irradiation for the local control of cancer.

Adult↗
PubMed1993

Sensitivity of hyperthermia trial outcomes to temperature and time: implications for thermal goals of treatment.

PURPOSE: In previous work we have found that the cumulative minutes of treatment for which 90% of measured intratumoral temperatures (T90) exceeded 39.5 degrees C was highly associated with complete response of superficial tumors. Similarly, the cumulative time for which 50% of intratumoral temperatures (T50) exceeded 41.5 degrees C was highly associated with the presence of > 80% necrosis in soft tissue sarcomas resected after radiotherapy and hyperthermia. In the present work we have calculated the time for isoeffective treatments with T90 = 43 degrees C and T50 = 43 degrees C, respectively, using published thermal isoeffective dose formulae. The purpose of these calculations was to determine the sensitivity of treatment outcome to variations in thermal isoeffective dose. METHODS AND MATERIALS: The basis for the calculations were the thermal parameters and treatment outcomes in three patient populations: 44 patients with moderate or high grade soft tissue sarcoma treated preoperatively with hyperthermia and radiation; 105 patients with superficial tumors treated with hyperthermia and radiation, and 59 patients with deep tumors treated with hyperthermia and radiation. RESULTS: The thermal dose values calculated are strongly associated with outcome in multivariate logistic regression analysis. Simple dose-response equations result from the analysis, and we use these equations to assess the sensitivity of outcome upon variations in thermal dose. This information, in turn, allows us to estimate the number of patients required in Phase II and III trials of hyperthermia and radiation therapy. CONCLUSIONS: For regimens of 5 to 10 hyperthermia treatments, improvements in median T90 (superficial tumors) and T50 (deep tumors) parameters by 1.2-1.5 degrees C could result in response rates high enough (compared to radiotherapy alone) to justify Phase III trials. A similar improvement in response rates would require an increase in overall duration of treatment by a factor of 3 to 5. This would be difficult to achieve while also avoiding thermal tolerance induction. Achieving these temperature goals may be possible with improvements in hyperthermia technology. Alternatively, there may be ways to increase the sensitivity of cells to temperatures that can be achieved currently, such as pH reduction or chemosensitization.

Combined Modality Therapy↗
PubMed1993

Theoretical and measured electric field distributions within an annular phased array: consideration of source antennas.

The magnitude of E-field patterns generated by an annular array prototype device has been calculated and measured. Two models were used to describe the radiating sources: a simple linear dipole and a stripline antenna model. The stripline model includes detailed geometry of the actual antennas used in the prototype and an estimate of the antenna current based on microstrip transmission line theory. This more detailed model yields better agreement with the measured field patterns, reducing the rms discrepancy by a factor of about 6 (from approximately 23 to 4%) in the central region of interest where the SEM is within 25% of the maximum. We conclude that accurate modeling of source current distributions is important for determining SEM distributions associated with such heating devices.

Absorption↗
PubMed1992

Use of nitroprusside to increase tissue temperature during local hyperthermia in normal and tumor-bearing dogs.

The present study investigates the effects of nitroprusside, a potent vasodilating agent, on tissue temperature during local hyperthermia in five normal and five tumor-bearing dogs. Caudal thigh muscles were heated in normal dogs and muscle temperatures were recorded during hyperthermia. Tumor-bearing dogs received two hyperthermia treatments during a course of radiation therapy. Temperatures were recorded in tumor and surrounding normal tissues. Mean arterial pressure was decreased by approximately 40-45% during nitroprusside infusion and was associated with a compensatory increase in heart rate and increases in tissue temperature. In normal dogs, muscle temperatures increased an average of 1.7 degrees C with nitroprusside administration. When nitroprusside was administered at the beginning of local hyperthermia to induce step-down heating, approximately 48% of the measured positions in caudal thigh muscle achieved a temperature greater than or equal to 43 degrees C, sufficient to induce step-down heating, during the hyperthermia episode. In tumor-bearing dogs, there was a significant increase in tumor and normal tissue temperatures during nitroprusside administration. Estimated T90 and T50 descriptors increased by 0.9 degrees C and 1.6 degrees C, respectively, for tumor tissue and by 0.4 degrees C and 1.2 degrees C, respectively, for normal tissue. Despite the increase in normal tissue temperatures no toxicity was observed in these dogs. Nitroprusside may be a useful agent for manipulation of tumor temperatures during the entire hyperthermia treatment or for a short time period at the initiation of treatment to induce step-down heating.

Animals↗
PubMed1992

Feasibility of estimating the temperature distribution in a tumor heated by a waveguide applicator.

The feasibility of using a 2-dimensional (2D) modeling approach for retrospectively describing complete temperature distributions in the midplane of a tumor during a clinical hyperthermia treatment was tested. An experimental treatment, using a 915-MHz waveguide applicator to heat a large melanoma in a dog, was modeled. Detailed measurements of temperatures were made during the treatment. The steady-state blood flow distribution at the midplane was imaged by positron emission tomography (PET), and these data were used to prescribe the modeled perfusion pattern. A 2D finite element method (FEM) was used to approximate the solution to Maxwell's Equations to obtain the specific absorption rate (SAR) distribution. The blood-flow estimates, assumed material properties, SAR distribution, and temperature boundary conditions were then used with the same mesh in a second FEM program to obtain a solution to the bioheat transfer equation. This latter routine was embedded in a state-and-parameter-estimation program that systematically varied selected parameters until the differences between computed and measured temperatures were minimized. Optimizations were performed independently for three subsets of the measured temperature data to assess the sensitivity of the predicted temperature field to the number of measurements. The calculated temperature distributions that resulted were similar to each other, and the predicted temperatures at the sensor points excluded from these optimizations were in reasonable agreement with the measurements. However, lack of unique blood flow values following optimization indicates that the methods of estimating blood flow will need to be improved or that there are problems with model mismatch. This work is a clinical case study of an evolving 2D system of thermal dosimetry which relies on both empirical and theoretical concepts. The methodology is being evaluated for its ability to generate prognostically significant descriptors of the treatment temperature field.

Animals↗
PubMed1992

Phase I/II study of external radio frequency phased array hyperthermia and external beam radiotherapy in the treatment of prostate cancer: technique and results of intraprostatic temperature measurements.

As part of an ongoing Phase I/II study at Duke University Medical Center investigating the toxicity and efficacy of external beam radiotherapy plus hyperthermia for deep-seated, locally advanced or recurrent solid tumors, 12 patients with prostate malignancies (adenocarcinoma--11, leiomyosarcoma--1) were treated with radiotherapy plus hyperthermia. Hyperthermia was given after radiotherapy using a Radio Frequency Phase/Amplitude Control Sigma 60 annular phased array device. All patients had simultaneous temperature measurements made in the rectal lumen and within the prostate during at least one hyperthermia session. Intraprostate thermometers were placed via a unique method described herein using both computerized tomography scan and a rigid sigmoidoscope for guidance. We were able to achieve the desired tumor temperature of > or = 42.5 degrees C in only 1/28 (3.5%) of hyperthermia treatments. Subjective symptoms of pain and/or pressure limited power deposition in 79% of hyperthermia treatments. Higher temperatures were achieved in the distal rectum than in the prostate in all treatments, although the differences were not statistically significant. This temperature differential could not be compensated by using phase and amplitude steering. Rectal temperatures adjacent to the prostate were predictive of prostate temperatures. We conclude that using this regional heating technique we were unable to demonstrate an ability to get an advantageous temperature differential between the prostate and normal tissue. This technique is not useful as an adjuvant to radiation therapy for prostate cancer. The usefulness of other regional heating techniques and devices should be explored.

Adenocarcinoma↗
PubMed1991

RTOG quality assurance guidelines for clinical trials using hyperthermia administered by ultrasound.

Clinical quality assurance guidelines are established for RTOG hyperthermia protocols in which unfocused planar ultrasound may be used to administer hyperthermia. Measurement of temperature at a few fixed points is no longer considered to be adequate. Thermal mapping is required to obtain profiles of the temperature across the tumor dimensions, including margins of normal tissue. The thermometry strategies established for microwaves are to be adhered to with oblique insertion of the probes recommended. Two types of errors arise which are generally not present with microwaves. A measurement error, commonly referred to as a temperature artifact, arises because of absorption and/or viscous heating of the probe. Another error arises when thermocouples are used due to the conduction of heat along the wire leads, especially the copper wire. Several thermometry systems are evaluated with regard to the expected artifact and conduction errors. Acceptable systems include: a) indexing a polyurethane sheathed single sensor thermocouple in a polyurethane catheter, b) indexing a fiberoptic probe in a steel needle, c) indexing a single sensor thermocouple in a steel needle, and d) use of manganin-constantan multisensor thermocouples. Unacceptable systems include: a) fixed or static probes that do not provide profiles of the temperature across the tumor dimensions, b) copper-constantan multisensor thermocouples, and c) teflon sheathed thermocouples inserted into a teflon catheter.

Clinical Protocols↗
PubMed1990

Effects of hyperthermia and irradiation on the growth of mouse melanoma tumors following immunotherapy.

Recent investigations suggest that adjuvant hyperthermia enhances the response of human malignant melanoma to ionizing radiation. A study was undertaken to explore the effect of radiation and hyperthermia on the responsiveness of melanoma following active immunization with lethally irradiated B16 melanoma cells in C57 BL 6 mice. Two groups of mice were treated: group 1 received immunotherapy on days 2-5 following tumor inoculation, and group 2 received immunotherapy on days 15-18 following tumor inoculation. The mice in each group were subsequently randomized into one of three subgroups: 1) no further treatment; 2) radiation therapy alone (6 Gy in a single fraction); 3) radiation therapy and regional hyperthermia (43 degrees C x 1 hour). Tumor sizes were measured regularly, and between day 52 and 63 the animals were sacrificed and the lungs sectioned for counting of metastatic tumors. Results from this study show that the immunomodulated B16 murine melanoma is responsive to radiation therapy alone and that this responsiveness is enhanced by the addition of adjuvant regional hyperthermia. There did not appear to be any significant effect of radiation therapy or radiation therapy plus hyperthermia on the development of lung metastases in this tumor model system.

Animals↗
PubMed1990

Interstitial 192Ir flexible catheter radiofrequency hyperthermia treatments of head and neck and recurrent pelvic carcinomas.

Since September 1983, five patients with head and neck cancers and five patients with pelvic or perineal recurrences of colorectal neoplasms received 192Ir interstitial implants through flexible afterloading catheters that were modified to allow RF hyperthermia treatments of the tumor within 1 hr pre- and post-brachytherapy. Local control in the implant volume was obtained in three of the patients with head and neck cancers (base tongue--2/4; floor of mouth--1/1) with follow-up of 9 to 42 months. Two patients had local recurrences after disease-free periods of 8 and 24 months. Two of the five patients treated for pelvic recurrences had complete responses lasting less than 3 months; prolonged stabilization (12 months) of a presacral mass in a third patient also occurred, but the neoplasm eventually regrew. Average temperatures of 39.2 degrees C to 43.7 degrees C were obtained in the implant volumes of these patients during the 45 minute heating periods which took place prior to loading, and just after removal, of the 192Ir seeds in each patient. No instances of intra or post-operative hemorrhage or necrosis of bone or soft tissues occurred in these patients. However, one individual required a permanent tracheostomy for persistent epiglottic edema after implantation as part of a base-tongue brachytherapy procedure. Interstitial RF hyperthermia in conjunction with brachytherapy appears to be a relatively safe and effective modality, but must be tested prospectively to compare its efficacy to interstitial irradiation alone.

Adult↗
PubMed1990

Spiral microstrip hyperthermia applicators: technical design and clinical performance.

Spiral microstrip microwave (MW) antennas have been developed and adapted for use as clinical hyperthermia applicators. The design has been configured in a variety of forms including single fixed antenna applicators, multi-element arrays, and mechanically scanned single or paired antennas. The latter three configurations have been used to allow an expansion of the effective heating area. Specific absorption rate (SAR) distributions measured in phantom have been used to estimate the depth and volume of effective heating. The estimates are made using the bioheat equation assuming uniformly perfused tissue. In excess of 500 treatments of patients with advanced or recurrent localized superficial tumors have been performed using this applicator technology. Data from clinical treatments have been analyzed to quantify the heating performance and verify the suitability of these applicators for clinical use. Good microwave coupling efficiency together with the compact applicator size have proved to be valuable clinical assets.

Equipment Design↗
PubMed1990

Two or six hyperthermia treatments as an adjunct to radiation therapy yield similar tumor responses: results of a randomized trial.

From March 1984 to February 1988, 70 patients with 179 separate treatment fields containing superficially located (less than 3 cm from surface) recurrent or metastatic malignancies were stratified based on tumor size, histology, and prior radiation therapy and enrolled in prospective randomized trials comparing two versus six hyperthermia treatments as an adjunct to standardized courses of radiation therapy. A total of 165 fields completed the combined hyperthermia-radiation therapy protocols and were evaluable for response. No statistically significant differences were observed between the two treatment arms with respect to tumor location; histology; initial tumor volume; patient age and pretreatment performance status; extent of prior radiation therapy, chemotherapy, hormonal therapy, or immunotherapy; or concurrent radiation therapy. The means for all fields of the averaged minimum, maximum, and average measured intratumoral temperatures were 40.2 degrees C, 44.8 degrees C, 42.5 degrees C, respectively, and did not differ significantly between the fields randomized to two or six hyperthermia treatments. The treatment was well tolerated with an acceptable level of complications. At 3 weeks after completion of therapy, complete disappearance of all measurable tumor was noted in 52% of the fields, greater than or equal to 50% tumor reduction was noted in 7% of the fields, less than 50% tumor reduction was noted in 21% of the fields, and continuing regression (monotonic regression to less than 50% of initial volume) was noted in 20% of the fields. No significant differences were noted in tumor responses at 3 weeks for fields randomized to two versus six hyperthermia treatments (p = 0.89). Cox regression analyses were performed to identify pretreatment or treatment parameters that correlated with duration of local control. Tumor histology, concurrent radiation doses, and tumor volume all correlated with duration of local control. The mean of the minimum intratumoral temperatures (less than 41 degrees C vs. greater than or equal to 41 degrees C) was of borderline prognostic significance in the univariate analysis, and added to the power of the best three covariate model. Neither the actual number of hyperthermia treatments administered nor the hyperthermia protocol group (two versus six treatments) correlated with duration of local control. The development of thermotolerance is postulated to be, at least in part, responsible for limiting the effectiveness of multiple closely spaced hyperthermia treatments.

Adult↗
PubMed1989

Preoperative hyperthermia and radiation for soft tissue sarcomas: advantage of two vs one hyperthermia treatments per week.

As part of an ongoing Phase II trial at Duke University Medical Center (DUMC), patients with Stage IIB-IVA soft tissue sarcomas (STS) potentially amenable to wide local excision were treated with preoperative hyperthermia (HT) plus radiation therapy (RT), with HT randomized to one versus two treatments per week, stratified with respect to tumor volume. 17 patients were treated and analyzed. HT was given 30-60 minutes after RT, with heating maintained for 1 hour after 42.0 degrees C was reached. In patients treated with 2 HT per week, treatments were separated by 48 hrs. Concurrent RT was given with 180-200 cGy fractions, five treatments per week, to a nominal tumor dose of 5000-5040 cGy. Surgical extirpation was performed 4 weeks after completion of HT/RT. Treatment effect was evaluated by histopathologic examination of the resected lesions, according to a previously reported system. The mean number of HT given in the 1 and 2/wk groups was 4.4 and 7.3, respectively (p less than 0.01). Tmax for the 1 and 2 HT/wk groups was 42.4 +/- 2.1 degrees C and 43.5 +/- 1.8 degrees C, and T min was 38.1 +/- 0.8 degrees C and 38.6 +/- 0.5 degrees C, respectively. The increase in T min from first to last treatment was 0.5 +/- 1.2 degrees C and 1.0 +/- 0.8 degrees C, respectively. The T min from the best treatment was 39.1 +/- 1.2 degrees C and 40.0 +/- 1.0 degrees C, and the Tmax from the best treatment was 44.5 +/- 3.4 degrees C and 45.4 +/- 2.5 degrees C for the 1 and 2 HT/wk groups, respectively. There were no statistically significant differences between the 2 treatment groups for any of the above temperature parameters. Severe histopathologic changes were found in 71% (12 of 17) of the lesions. T min and Tmax and highest T min and Tmax were between 0.4-1.1 degrees C higher in patients with severe changes (p = NS). All 9 patients in the 2 HT/wk group had extensive changes, versus only 3 of the 8 patients in the 1 HT/wk group. This difference was highly statistically significant (p = 0.009, two-tailed Fisher's exact test). These findings suggest an advantage to twice weekly, as opposed to weekly, HT in the setting of this study. Whether there is a corresponding therapeutic gain, or whether these results can be extrapolated to other settings requires further investigational efforts. It is recommended that treatment parameters, particularly temperature parameters, continue to be examined in Phase II trials.

Adult↗
PubMed1989

Tumor temperature distributions predict hyperthermia effect.

Review of clinical hyperthermia (HT) trial results shows that there previously has not been a robust model relating efficacy of HT treatments to characteristics of the temperature distribution. Lack of a model has been an impediment in Phase II trials; these trials must include defining the prescription for HT treatment, optimizing the schedule of HT treatments, and defining quality assurance procedures. We propose a model that is based upon noting that the majority of a tumor volume is contained in the outermost "shell" of a solid tumor, across which shell the radial temperature distribution is assumed to be linear. Any linear distribution can be defined by coordinates of a point and a slope, and we choose the temperature at the radiographically defined edge of a tumor and the slope (dT/dr) across the outer shell as these determinants of the linear radial temperature distribution. A discriminant analysis of success or failure of treatment can then be based upon these two descriptors (Tedge, dT/dr). We have tested this model using data from patients with soft tissue sarcoma (Stage IIB or greater) that have entered an ongoing prospective trial of conventional preoperative radiotherapy (5000 cGy/25 Fx/5 wk) together with HT, the latter randomized to be given once or twice weekly during the 5 week course. Wide local excision of the primary tumor is done 1 month after completion of radiotherapy, and the extent of histologic change in the resected specimen is scored. Our model has an 86% predictive value for lack of complete or nearly complete necrosis in the resected specimen according to whether the time-averaged Tedge and slope during each HT treatment satisfy the equation Tedge + 1.2 (slope in degree C/cm) less than or equal to 40.6 degrees C in all but one treatment at most. Conversely, in 85% of cases with complete or nearly complete tumor necrosis, temperature distributions satisfied Tedge + 1.2 (slope in degree C/cm) greater than 40.6 degrees C during at least one HT treatment. Requiring greater than or equal to one third of treatments of a patient to satisfy the preceeding discriminant equation resulted in 80% of patients being correctly classified as a responder or nonresponder, with only one false positive prediction (patient incorrectly classified as a responder). The model can reveal systematic changes in the edge temperature distribution during the treatment course that are consistent with tumor perfusion changes inferred and measured by independent means.(ABSTRACT TRUNCATED AT 400 WORDS)

Body Temperature↗
PubMed1989

Improved coupling of ultrasound hyperthermia applicators to patients.

Coupling ultrasound (US) hyperthermia (HT) applicators to patients requires an acoustical medium conforming to both applicator and patient that allows for rapid, reproducible set-up for each treatment and prevents drift or misalignment of the applicator during treatments. We describe a technique that uses a commercially available immobilization foam to create a rigid, conforming foam block that kinematically positions the US applicator over the tumor area. The central volume of the foam block is removed and filled with a plastic bag of degassed water or with US gel during treatments. We also describe a technique for positioning surface and interstitial thermometry sensors in alignment with individual elements of a multi-element US applicator. Using these techniques, relative movement between patient and applicator is minimized, correct thermometry sensor location relative to each US element is confirmed, and efficient transmission of the acoustical power into the target volume is assured. These techniques are particularly important when using multi-element applicators with complex temperature-power control algorithms.

Humans↗
PubMed1989

Thermal conduction effects associated with temperature measurements in proximity to radiofrequency electrodes and microwave antennas.

The smearing effects due to thermal conduction along various, nonenergized, interstitial devices were quantified in a flow cell-thermal step gradient. An insulated cylindrical flow cell with a high (ca 45 degrees C, 1.12 cm i.d., 1.6 cm o.d.) temperature region surrounded by a low (ca 37 degrees C) temperature region was used to compare temperature profiles measured with a thermocouple sensor inside a Stanford radiofrequency (RF) hyperthermia/brachytherapy catheter, a BSD instrumented microwave (MW) antenna (i.e., thermistor integrated into a dipole antenna) and a Dartmouth MW antenna with a juxtaposed optical sensor. Two parameters were used to quantify the thermal smearing of each interstitial device in the flow cell: (a) the maximum temperature difference (MTD) and (b) the full- width- half-maximum (FWHM) of the high temperature region. The "true" temperature maximum (45.4 degrees C) and distribution (FWHM = 1.65 +/- 0.06 cm) were measured with an optical sensor. These data indicate that the BSD instrumented MW antenna significantly smeared the true temperature profile (MTD = 2.7 degrees C, FWHM = 2.1 cm), as did the Dartmouth MW antenna (MTD = 1.5 degrees C, FWHM = 1.7 cm). The Stanford RF catheter, when insulated, resulted in minimal smearing (MTD = 0.3 degrees C, FWHM = 1.9 cm). Moreover, when the insulation was removed so the RF electrode was exposed to the thermal step gradient, smearing was again minimal (MTD = 0.3 degrees C, FWHM = 1.9 cm).

Brachytherapy↗
PubMed1987

Correlations of thermal washout rate, steady state temperatures, and tissue type in deep seated recurrent or metastatic tumors.

The rates of cooling ("thermal washout") in selected sites in tumor and adjacent normal tissues following the completion of clinical hyperthermia sessions were analyzed in ten patients treated with combined radiation and hyperthermia for deep seated recurrent or metastatic tumors. The temperatures were recorded at 10 second intervals for at least 2 minutes after the cessation of microwave power at the end of the 30-60 minute duration hyperthermia treatments. These thermal washouts were characterized by the slope of a log-linear relation between temperature elevation above the oral baseline temperature and time. Washout rates (expressed as a perfusion rate in ml/100g-min) significantly correlated with tissue categories as noted on CAT scan (i.e., tumor, normal tissue, tumor/normal tissue interface, hypodense tumor areas). Relationships between thermal washout rate and steady-state temperature elevation were tested and also showed significant correlations in general and for some specific tissue categories. The implications of these findings in explaining inhomogeneities in heating patterns, and in hyperthermia treatment modeling will be presented.

Combined Modality Therapy↗