Hyperthermia thermometry evaluation: criteria and guidelines.

Results of the evaluation of thermometry devices used during hyperthermia treatments at 14 different clinics in the USA are presented. Measurements were made by the Hyperthermia Physics Center (HPC, a national hyperthermia quality assurance program under NCI contract No. N01-CM-37512) according to a protocol. Our sample included thermocouples, fiberoptic thermometers, and high lead resistance thermistors. We found that only some but not all of the thermometers of each kind performed within the +/- 0.2 degrees C acceptability criteria of accuracy. The precision, stability, and response times achieved with each type of thermometer are presented. A summary of perturbations and artifacts typical for each system is presented together with suggested precautions to avoid them during clinical usage. We conclude that although the technology used with each thermometer system is capable of producing a temperature accuracy of 0.2 degrees C, this accuracy is clinically achievable only with a concerted effort and a constant alertness on the part of the investigator. Based on the combined experience of this survey, the clinical investigators we visited, and published reports, we present certain guidelines and procedures that can help to reduce the inaccuracies and improve the reliability of temperature data obtained in clinical hyperthermia trials.

Hyperthermia quality assurance guidelines.

These Hyperthermia Quality Assurance guidelines are a result of a joint workshop of the Hyperthermia Committee of the American College of Radiology and the Hyperthermia Physics Center, which is the national quality assurance program under Contract No. N01-CM-37512 with the National Cancer Institute. Hyperthermia technology presently lacks the kind of standardization in equipment, treatment procedures, patient monitoring, and treatment documentation available in radiotherapy. Therefore, preventing unacceptable variability in treatment data demands a strong commitment to in-house quality control procedures and to centralized quality assurance reviews in cooperative multi-institutional trials. This paper presents a set of test procedures necessary to ensure proper operation of equipment, suggests a frequency for such tests, and also includes guidelines on quality control procedures to be used during treatment to improve the safety, effectiveness, and reproducibility of hyperthermia treatments. A set of forms are presented to indicate the minimum data, albeit incomplete, that must be collected for acceptable documentation of treatment. These guidelines should be valuable not only to the new entrants in the field but also to those participating in multi-institutional cooperative hyperthermia trials. They have been approved by the Hyperthermia Committees of American College of Radiology, American Society for Therapeutic Radiology and Oncology, Radiation Therapy Oncology Group and the American Association of Physicists in Medicine.

Effects of nebulized morphine sulfate on the exercise tolerance of the ventilatory limited COPD patient.

We have shown previously that the administration of morphine (0.8 mg/kg) to patients with COPD increases the VO2max by 19.3 percent. A recent study demonstrated that the administration of low-dose nebulized morphine (approximately 2 mg) increased the endurance time of patients with severe lung disease by 1 min (35 percent) with few systemic side effects. This double-blind crossover study evaluated the effects of various doses of nebulized morphine (0, 1, 4, and 10 mg) on the exercise tolerance and the psychologic status of COPD patients. In the present study, eight COPD patients (FEV1 = 0.90 +/- 0.26 L, workload max = 76 +/- 29 W, VO2max = 950 +/- 264 ml, VEmax = 34 +/- 7 L), who were ventilatory limited were tested on four separate days. On each testing day, the patients underwent incremental exercise testing and psychologic testing before and 45 min after receiving the nebulized solution. The mean changes (+/- SD) in the exercise test results after each of the four different regimens were as follows: [table: see text] Although there tended to be larger increases in the workload, VO2max, and VEmax after the largest dose of morphine, none of the changes was statistically significant. Likewise, there were no significant differences in spirometry, resting metabolic measurements, or psychologic test scores after the four different regimens. We conclude that aerosolized morphine in the doses used in this study has no significant beneficial effect on the exercise tolerance of patients with COPD.

Timing of microcirculatory injury from ischemia reperfusion.

The low flow state that results from ischemia and reperfusion injury is a potentially reversible process that is important in numerous clinical situations. However, the point in time during the course of reperfusion where tissue injury becomes irreversible is unknown. This experiment evaluated the continuum of tissue damage in skeletal muscle after ischemic insult by quantifying the number of flowing capillaries and percentage muscle necrosis in a male Wistar rat skeletal muscle model. A gracilis muscle flap was raised on the vascular pedicle of 39 male Wistar rats and examined at 832x using intravital videomicroscopy. The numbers of flowing capillaries in five consecutive high-power fields were counted for baseline values. The flap was then subjected to 4 hours of global ischemia (except in sham animals, n = 7) by placing a microvascular clamp on the pedicle artery and vein. Upon reperfusion, flowing capillaries were counted in the same five high-power fields at intervals of 5, 15, 30, and 60 minutes, then at 2 to 8 (1-hour intervals), 24, and 48 hours. The gracilis muscle was then harvested at these intervals during reperfusion and assessed for viability. Compared with baseline, flowing capillaries from the ischemia and reperfusion group (mean +/- SEM) decreased significantly in the first 8 hours of reperfusion (7.7 +/- 0.2 to 3.2 +/- 0.3, p < 0.001) with minimal change noted from 8 to 48 hours. Percentage muscle necrosis increased progressively in ischemia and reperfusion preparations from 1 to 7 hours of reperfusion (16.5 +/- 2.6 percent to 38.9 +/- 1.2 percent, p < 0.001). No significant change in muscle necrosis in the ischemia and reperfusion group was noted between 7 and 48 hours. Sham preparations showed no change in the number of flowing capillaries through 3 hours of reperfusion, with a slight decrease at 24 hours. This rat gracilis microcirculation skeletal muscle model demonstrates a heterogeneous reperfusion injury. The decrease in flowing capillaries correlated with the increase in percentage necrosis and appeared to stabilize at the 7- to 8-hour interval. This finding may have important implications for the timing of interventions aimed at minimizing tissue damage from ischemia-reperfusion.

Hyperthermia quality assurance results.

The Hyperthermia Physics Center (HPC), under contract with the National Cancer Institute (NCI), has conducted review-type quality assurance (QA) measurements at the five Hyperthermia Equipment Evaluation Centers involved in evaluating the clinical efficacy of a variety of devices for delivering heat treatments to deep-seated human tumours. A summary of the QA protocol, results, testing procedures, standards, criteria, conclusions and recommendations are presented in this paper. The QA review measurements indicate (a) that 81.5 per cent of temperatures surveyed were within the 0.2 degrees C HPC criterion (91 per cent were within 0.4 degrees C), (b) that only 66 per cent of power indications were within the 10 per cent criterion, (c) that the heat patterns in a phantom produced by the BSD Annular Phased Array (AA) had significant variability, (d) that each treatment facility had at least a few potentially occupiable locations where the maximum permissible American National Standards Institute standards of electromagnetic leakage were exceeded, and (e) that these levels of accuracy and safety were achieved only after stringent inhouse QA efforts. From the combined data, it is concluded that the temperature accuracy in this cooperative trial was sufficient to justify a common analysis of clinical data as presented in this series. Also, stringent quality control of every parameter must continue to be stressed in all future hyperthermia trials.

Calorimetric evaluation of antennas used for microwave interstitial hyperthermia.

Several quasi-adiabatic calorimeters have been constructed for determining the heating efficiency of microwave antennas. The absorber is 0.9% saline which is stirred continuously, making equilibration times short (several seconds). Depth of insertion data have been obtained for standard BSD and CTC antennas at 915 MHz. Efficiency varies only slightly with insertion depth in the range 7-16 cm and can be as high as 65%. At shallower depths efficiency drops off, while reflected power and leakage fields increase. Data obtained in site visits conducted by the Hyperthermia Physics Center show that antenna efficiency of the BSD and CTC models can vary by as much as 35% within sets of functional 'identical' antennas.