Daniel I. Rosenthal

Tissue ablation with radiofrequency: Effect of probe size, gauge, duration, and temperature on lesion volume

RATIONALE AND OBJECTIVES We evaluated the parameters affecting the size and distribution of thermal tissue damage produced by radiofrequency electrodes. METHODS Thermal lesions were produced by electrodes connected to a radiofrequency generator in specimens of liver (n = 143) and muscle (n = 20). Various combinations of probe tip exposure (0.5-8 cm), gauge (12-24 gauge), duration of treatment (0.5-12 min), and temperature (80-90 degrees C) were studied. The resulting volumes of tissue coagulation were measured and compared. RESULTS Lesions equal to or less than 1.6 cm in diameter were symmetrically distributed around the electrode. Lesion diameter (but not length) increased with probe gauge and duration of treatment to a maximum of 6 min. However, lesions with mean diameters larger than 1.6 cm could not be produced using a single probe with any technique. Lesion length correlated with probe tip exposure from 1 to 8 cm (r2 = .996). Over the limited range investigated, increased temperature had minimal effects, except for tip exposures greater than 5 cm, in which larger and more uniform lesions resulted. Lesions varied equal to or less than 3 mm in diameter and equal to or less than 5 mm in length for each combination of variables. CONCLUSION Radiofrequency ablation can accurately and reproducibly cause coagulative tissue necrosis. Necrosed tissue volume increases with length of exposed probe tip, larger probes, and sessions lasting at least 6 min.

Percutaneous radiofrequency coagulation of osteoid osteoma compared with operative treatment.

Osteoid osteoma, a benign bone tumor, has traditionally been treated with operative excision. A recently developed method for percutaneous ablation of the tumor has been proposed as an alternative to operative treatment. The relative outcomes of the two approaches to treatment have not previously been compared, to our knowledge. The rates of recurrence and of persistent symptoms were compared in a consecutive series of eighty-seven patients who were managed with operative excision and thirty-eight patients who were managed with percutaneous ablation with radiofrequency. Patients who had a spinal lesion were excluded. The minimum duration of follow-up was two years. There was a recurrence, defined as the need for subsequent intervention, after operative treatment in six (9 per cent) of sixty-eight patients who had been managed for a primary lesion and in two of nineteen who had been managed for a recurrent lesion. The average length of the hospital stay was 4.7 days for the patients who had a primary lesion and 5.1 days for those who had a recurrent lesion. There was a recurrence after percutaneous treatment in four (12 per cent) of thirty-three patients who had been managed for a primary lesion and in none of five who had been managed for a recurrent lesion. The average length of the hospital stay was 0.2 day for these thirty-eight patients. With the numbers available, we could detect no significant difference between the two treatments with regard to the rate of recurrence. The rate of persistent symptoms (that is, symptoms that did not necessitate additional treatment) was greater than the rate of recurrence. According to responses to a questionnaire, eight (30 per cent) of twenty-seven patients had persistent symptoms after operative treatment and six (23 per cent) of twenty-six patients had persistent symptoms after percutaneous treatment with radiofrequency. Two patients had complications after operative excision, necessitating a total of five additional operations. There were no complications associated with the percutaneous method. The results of the present study suggest that percutaneous ablation with radiofrequency is essentially equivalent to operative excision for the treatment of an osteoid osteoma in an extremity. The percutaneous method is preferred for the treatment of extraspinal osteoid osteoma because it generally does not necessitate hospitalization, it has not been associated with complications, and it is associated with a rapid convalescence.

Radiofrequency tissue ablation: importance of local temperature along the electrode tip exposure in determining lesion shape and size.

RATIONALE AND OBJECTIVES We determined whether heat distribution along a radiofrequency (RF) electrode would be uniform when longer tip exposures are used and whether local temperature effects would influence the shape of induced tissue coagulation. METHODS Thermistors were embedded within 18-gauge RF electrodes at both ends and in the middle of the exposed tip. The length of tip exposure varied from 1 to 7 cm. RF was applied in vitro to pig liver for 6 min using a constant tip temperature, which was varied in 10 degrees C increments from 60 degrees C to 110 degrees C. Experiments were performed in triplicate. The 3- and 5-cm probes were used at a 90 degrees C tip temperature to create lesions in live pig liver and muscle using similar parameters. Temperature was measured throughout the procedure. Observable coagulation necrosis was measured at the end of the treatment. Regression analysis was used to evaluate the local temperature-lesion diameter relationship. RESULTS Temperatures were not uniform along the tip exposure for any given trial. Temperature variation increased with higher tip temperatures and longer tip exposures. The diameter of local coagulation necrosis was a function of the local mean temperature. For in vitro trials, no coagulation was seen when the local temperature was less than 50 degrees C. Temperatures above this threshold resulted in progressively greater lesion diameter, with a minimum of 1 cm of necrosis occurring at 71 degrees C. Additional increases in lesion diameter (1.4-1.6 cm) were observed at approximately 90 degrees C. Mathematical modeling demonstrated a best-fit curve: lesion diameter (in cm) = ¿1.4 + 0.03 (tip exposure)¿ ¿1 - e [-0.067(local temp - 49.5 degrees C)]¿, r2 = .986, SD = 0.14 cm for each curve. In living tissue, less uniformity in the shape of coagulation necrosis was seen around the electrodes. Local temperature-lesion diameter data fit the same logarithmic relation, but the threshold for coagulation necrosis was 8.5 degrees C higher than for in vitro specimens. CONCLUSION Using a single-probe technique for RF-induced tissue necrosis, the diameter of tissue coagulation may be predicted by the local temperature along the exposed electrode. The uniformity of temperature decreases with increased tip exposures. This effect may be partially corrected by creating lesions at higher tip temperatures, where necrosis diameter is increased. Because effects are more pronounced in vivo, uniform volumes of tissue necrosis are limited to tip exposures of 3 cm or less.

Neoadjuvant chemotherapy and radiotherapy for large extremity soft-tissue sarcomas

PURPOSE Treatment of extremity soft-tissue sarcomas yields excellent local control, but distant failure is common with large, high-grade tumors. A regimen of preoperative chemotherapy consisting of mesna, adriamycin, ifosfamide, and dacarbazine (MAID) interdigitated with radiotherapy followed by resection and postoperative chemotherapy with or without radiotherapy was designed to improve treatment outcome. We report the mature outcome data on 48 treated patients and compare them with the data of an historical matched control patient population. METHODS AND MATERIALS Adult patients with high-grade extremity soft-tissue sarcomas >or=8 cm were treated with three cycles of preoperative chemotherapy combined with 44 Gy of radiotherapy followed by surgery. Three cycles of postoperative MAID were planned. For patients with positive surgical margins, 16 Gy was delivered postoperatively. RESULTS All 48 patients (M0) received the MAID protocol treatment, and their outcome was superior to that of the historical control patients. The 5-year actuarial local control, freedom from distant metastasis, disease-free survival, and overall survival rate was 92% and 86% (p = 0.1155), 75% and 44% (p = 0.0016), 70% and 42% (p = 0.0002), and 87% and 58% (p = 0.0003) for the MAID and control patient groups, respectively. Acute hematologic toxicity in the MAID group included febrile neutropenia in 12 patients (25%). Wound healing complications occurred in 14 (29%) of 48 MAID patients. One MAID patient developed late fatal myelodysplasia. CONCLUSION After aggressive chemoradiation and surgery, these patients showed a significant reduction in distant metastases, with a highly significant gain in disease-free and overall survival compared with a historical control group. On the basis of this experience, the Radiation Therapy Oncology Group conducted a multi-institutional trial.

Effect of computerized order entry with integrated decision support on the growth of outpatient procedure volumes: seven-year time series analysis.

PURPOSE To determine the effect of a computerized radiology order entry (ROE) and decision support (DS) system on growth rate of outpatient computed tomography (CT), magnetic resonance (MR) imaging, and ultrasonography (US) procedure volumes over time at a large metropolitan academic medical center. MATERIALS AND METHODS Institutional review board approval was obtained for this study of deidentified aggregate administrative data. The research was compliant with HIPAA; informed consent was waived. This was a retrospective study of outpatient advanced imaging utilization before, during, and after implementation of a Web-based ROE and DS system. Dependent variables were the quarterly volumes of outpatient CT, MR imaging, and US examinations from quarter 4 of 2000 through quarter 4 of 2007. Outpatient visits during each quarter were included as control variables. These data were analyzed as three separate time series with piecewise linear regression for simultaneous estimation of quarterly examination volume trends before and after ROE and DS system implementation. This procedure was repeated with log-transformed quarterly volumes to estimate percentage growth rates. RESULTS There was a significant decrease in CT volume growth (274 per quarter) and growth rate (2.75% per quarter) after ROE and DS system implementation (P < .001). For MR imaging, growth rate decreased significantly (1.2%, P = .016) after ROE and DS system implementation; however, there was no significant change in quarterly volume growth. With US, quarterly volume growth (n = 98, P = .014) and growth rate (1.3%, P = .001) decreased significantly after ROE implementation. These changes occurred during a steady growth in clinic visit volumes in the associated referral practices. CONCLUSION Substantial decreases in the growth of outpatient CT and US procedure volume coincident with ROE implementation (supplemented by DS for CT) were observed. The utilization of outpatient MR imaging decreased less impressively, with only the rate of growth being significantly lower after interventions were in effect.

Treatment of the patient with stage M0 soft tissue sarcoma.

During the period 1971 to 1985, 220 patients with soft tissue sarcoma of the extremities, torso, and head-neck region were managed by radiation and resectional surgery at the Massachusetts General Hospital (MGH). Actuarial 5-year local control and disease-free survival rates were 86% and 70%, respectively. The success rate improved during this time period. Namely, the local control rates for 1971 to 1975, 1976 to 1980, and 1981 to 1985 were 81%, 81%, and 94%, respectively. For the same time periods, the 5-year disease-free survival rates were 64%, 70%, and 76%. One hundred thirty-one patients were treated with postoperative radiation, and 89 with preoperative radiation. In the most recent 5-year period, the local control rates were 91% and 97% for the two groups (number of patients being 50 and 57 in the post- and preoperative groups, respectively). Treatment by preoperative radiation appears to have a major advantage for patients with very large sarcomas, ie, greater than 15 cm in maximum dimension. None of our patients with local control of grade 1 sarcoma have developed distant metastasis (DM). In contrast, among patients with grade 2 or 3 sarcomas, there is a relentless and progressive increase in the frequency of DM with size of the primary lesion, namely, 6% at less than or equal to 2.5 cm, congruent to 60% at 15 to 20 cm, and congruent to 80% at greater than 20 cm.

Cost Effectiveness of Screening Perimenopausal White Women for Osteoporosis: Bone Densitometry and Hormone Replacement Therapy

Bone mass measurement at menopause to identify and selectively prescribe hormone replacement therapy for women at high risk for fractures has seen limited clinical use. We used epidemiologic, clinical, and economic data in a decision-analytic model to compare the following clinical strategies for perimenopausal, asymptomatic, white women with intact uteri: no intervention; bone mineral density measurement followed by selective, long-term (15-year) estrogen-progestin therapy in women with low bone mass; and unselective, universal hormone replacement therapy. Life expectancy and direct medical cost per patient were estimated for each strategy. Strategies for screening and treating women with perimenopausal bone mineral density less than 0.9 g/cm2 or less than 1.0 g/cm2 would cost

Effects of Testosterone and Progressive Resistance Training in Eugonadal Men with AIDS Wasting: A Randomized, Controlled Trial

11,700 or

Stage IA and IIA supradiaphragmatic Hodgkin's disease: prognostic factors in surgically staged patients treated with mantle and paraaortic irradiation.

22,100, respectively, per year of additional life gained. If the cost of screening is less than

Controlled thermal injury of bone. Report of a percutaneous technique using radiofrequency electrode and generator.

84, then resource savings from hip fractures prevented would be more than the cost of screening and treatment. Universal treatment without screening would prevent additional fatal fractures but would expose many more women to the adverse effects of hormone replacement therapy and would cost an additional