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B Erickson

Publications and source records attributed to B Erickson.

At least 19 recordsLinked to original sources
PubMed2001

Comparision of four different dose specification methods for high-dose-rate intracavitary radiation for treatment of cervical cancer.

PURPOSE: To compare the dose delivered to target tissues and dose-limiting structures as defined by specific dose points with high-dose-rate intracavitary brachytherapy using tandem and ring or tandem and ovoids applicators, and to provide a reasonable approach to dose optimization. METHODS AND MATERIALS: Dosimetry was obtained using four different dose specifications: (1) 100% of the dose prescribed in a tapered fashion along the tandem and 140% at the ovoid/ring surface, (2) 100% of the dose prescribed along the tandem and 100% at the ovoid/ring surface, (3) 100% of the dose prescribed to point A without any additional applicator specification points, and (4) nonoptimized plan using relative dwell weighting to simulate classic Fletcher low-dose-rate (LDR) loading with the dose specified at point A. Point doses were recorded at A, B, and T (cervical tumor point), ICRU rectum, and ovoid/ring surface. RESULTS: For the tandem and ovoids applicators, significant differences were found among the four different dose specification methods for point T and vaginal mucosal doses. When the dose was optimized to point A alone, the ovoid dwell weights were reduced, resulting in higher point T doses and underdosing of the vaginal mucosa. Fixed weighting based on Fletcher LDR loading specifications resulted in higher vaginal mucosa doses. For the tandem and ring applicators, significant differences were observed for vaginal mucosal doses and the ICRU rectal dose. Optimization to point A alone resulted in widely varying dosimetric distributions and vaginal mucosa doses up to 632% of the prescription dose. With nonoptimized fixed weighting, the vaginal wall dose and ICRU rectal dose were increased. CONCLUSION: Prescribing to dose optimization points in a tapered fashion along the tandem and at the ovoid/ring surface results in a pear-shaped dose distribution resembling classic LDR systems. The other dose specification methods may result in underdosing of important target tissues or overdosing of adjacent dose-limiting structures.

Brachytherapy↗
PubMed2001

Comparison of traditional low-dose-rate to optimized and nonoptimized high-dose-rate tandem and ovoid dosimetry.

PURPOSE: Few dose specification guidelines exist when attempting to perform high-dose-rate (HDR) dosimetry. The purpose of this study was to model low-dose-rate (LDR) dosimetry, using parameters common in HDR dosimetry, to achieve the "pear-shape" dose distribution achieved with LDR tandem and ovoid applications. METHODS AND MATERIALS: Radiographs of Fletcher-Suit LDR applicators and Nucletron "Fletcher-like" HDR applicators were taken with the applicators in an idealized geometry. Traditional Fletcher loadings of 3M Cs-137 sources and the Theratronics Planning System were used for LDR dosimetry. HDR dosimetry was performed using the Nucletron Microselectron HDR UPS V11.22 with an Ir-192 source. Dose optimization points were initially located along a line 2 cm lateral to the tandem, beginning at the tandem tip at 0.5-cm intervals, ending at the sail, and optimized to 100% of the point A dose. A single dose optimization point was also placed laterally from the center of each ovoid equal to the radius of the ovoid (ovoid surface dose). For purposes of comparison, dose was also calculated for points A and B, and a point located 1 cm superior to the tandem tip in the plane of the tandem, (point F). Four- and 6-cm tandem lengths and 2.0-, 2.5-, and 3.0-cm ovoid diameters were used for this study. Based on initial findings, dose optimization schemes were developed to best approximate LDR dosimetry. Finally, radiographs were obtained of HDR applications in two patients. These radiographs were used to compare the optimization schemes with "nonoptimized" treatment plans. RESULTS: Calculated doses for points A and B were similar for LDR, optimized HDR, and nonoptimized HDR. The optimization scheme that used tapered dose points at the tandem tip and optimized a single ovoid surface point on each ovoid to 170% of point A resulted in a good approximation of LDR dosimetry. Nonoptimized HDR resulted in higher doses at point F, the bladder, and at points lateral to the tandem tip than both the optimized plan or the LDR plan. CONCLUSION: Optimized HDR allows specification of dose to points of interest, can approximate LDR dosimetry, and appears superior to nonoptimized HDR treatment planning, at least at the tandem tip. An optimization scheme is presented that approximates LDR dosimetry.

Brachytherapy↗
PubMed2001

Selective irradiation for the treatment of recurrent ovarian carcinoma involving the vagina or rectum.

OBJECTIVE: The aim of this study was to evaluate the role of selective irradiation in the management of recurrent or persistent ovarian carcinoma involving the vagina or rectum after initial surgery or surgery and chemotherapy. METHODS: Twenty-eight patients with recurrent or persistent vaginal and/or perirectal disease from ovarian carcinoma received selective irradiation and were evaluated for local control, survival, and quality of life. Seventy-nine percent had previously received various combinations of chemotherapy after initial surgery. At recurrence, 68% of the 28 patients were treated with external beam irradiation only, 7% with brachytherapy only, and 18% with both external beam irradiation and brachytherapy. In addition, 50% of the patients received various combinations of chemotherapy before or after radiotherapy and 3 patients received additional surgery. RESULTS: Vaginal bleeding was controlled in all patients and a complete symptomatic response was achieved in 79% of the symptomatic patients. Survival after recurrence at 2 years was 57% for patients who had no liver or extra-abdominal metastasis at the time of radiotherapy (21 patients) and 0% for patients who had liver or extra-abdominal metastases (7 patients). Median survival of 5 patients with abdominal and pelvic disease and 16 patients with no extrapelvic disease at the time of recurrence was 2.16 (0.16-10.67) and 2.08 (0.58-27) years, respectively, after recurrence. Fifty percent of the 16 patients without extrapelvic disease had a complete response to radiotherapy (CR group) and the remaining had a partial response or stable disease (non-CR group). The 1-year survival after salvage irradiation in this same group was 100% in the CR group and 37.5% in the non-CR group (P < 0.0001). There are 4 long-term survivors in the CR group who are still alive in excess of 5 years after salvage radiotherapy. Thirty-five percent (5/14) of the patients with pelvic disease only recurred in the unirradiated upper abdomen. CONCLUSIONS: Radiation can be considered an effective treatment option for patients with vaginal and/or perirectal recurrences of ovarian carcinoma. It offers excellent palliation to patients with disseminated disease and may result in both local control and long-term survival in patients with nondisseminated disease. This location may represent a sanctuary site from chemotherapy. Pelvic irradiation alone may be effective salvage and the addition of brachytherapy may improve local control, particularly in patients with disease confined to the pelvis who undergo debulking or chemotherapy.

Adult↗
PubMed2001

Can imaginary head tilt shorten postrotatory nystagmus?

In healthy subjects, head tilt upon cessation of a constant-velocity yaw head rotation shortens the duration of postrotatory nystagmus. The presumed mechanism for this effect is that the velocity storage of horizontal semicircular canal inputs is being discharged by otolith organ inputs which signal a constant yaw head position when the head longitudinal axis is no longer earth-vertical. In the present study, normal subjects were rotated head upright in the dark on a vertical-axis rotational chair at 60 degrees/s for 75 s and were required to perform a specific task as soon as the chair stopped. Horizontal position of the right eye was recorded with an infra-red video camera. The average eye velocity (AEV) was measured over a 30-s interval following chair acceleration/deceleration. The ratios (postrotatory AEV/perrotatory AEV) were 1.1 (SD 0.112) when subjects (N=10) kept their head erect, 0.414 (SD 0.083) when subjects tilted their head forward, 1.003 (SD 0.108) when subjects imagined watching a TV show, 1.012 (SD 0.074) when subjects imagined looking at a painting on a wall, and 0.995 (SD 0.074) when subjects imagined floating in a prone position on a lake. Thus, while actual head tilt reduced postrotatory nystagmus, the imagination tasks did not have a statistically significant effect on postrotatory nystagmus. Therefore, velocity storage does not appear to be under the influence of cortical neural signals when subjects imagine that they are floating in a prone orientation.

Acceleration↗
PubMed2000

The American Brachytherapy Society recommendations for high-dose-rate brachytherapy for carcinoma of the endometrium.

PURPOSE: To develop recommendations for use of high-dose-rate (HDR) brachytherapy in patients with endometrial cancer. METHODS: A panel of members of the American Brachytherapy Society (ABS) performed a literature review, supplemented their clinical experience, and formulated recommendations for endometrial HDR brachytherapy. RESULTS: The ABS endorses the National Comprehensive Cancer Network (NCCN) guidelines for indications for radiation therapy for patients with endometrial cancer and the guidelines on HDR quality assurance of the American Association on Physicists in Medicine (AAPM). The ABS made specific recommendations for HDR applicator selection, insertion techniques, target volume definition, dose fractionation, and specifications for postoperative adjuvant vaginal cuff therapy, for vaginal recurrences, and for medically inoperable primary endometrial cancer patients. The ABS recommends that applicator selection should be based on patient and target volume geometry. The dose prescription point should be clearly specified. The treatment plan should be optimized to conform to the target volume whenever possible while recognizing the limitations of computer optimization. Suggested doses were tabulated for treatment with HDR alone, and in combination with external beam radiation therapy (EBRT), when applicable. For intravaginal brachytherapy, the largest diameter applicator should be selected to ensure close mucosal apposition. Doses should be reported both at the vaginal surface and at 0.5-cm depth irrespective of the dose prescription point. For vaginal recurrences, intracavitary brachytherapy should be restricted to patients with nonbulky (< 0.5-cm thick) disease. Patients with bulky (> 0.5-cm thick) recurrences should be treated with interstitial techniques. For medically inoperable patients, an appropriate applicator that will allow adequate irradiation of the entire uterus should be selected. CONCLUSION: Recommendations are made for HDR brachytherapy for endometrial cancer. Practitioners and cooperative groups are encouraged to use these recommendations to formulate their treatment and dose reporting policies. This will lead to meaningful comparisons of reports from different institutions and lead to advances and appropriate use of HDR.

Brachytherapy↗
PubMed2000

The American Brachytherapy Society recommendations for high-dose-rate brachytherapy for carcinoma of the cervix.

PURPOSE: This report presents guidelines for using high-dose-rate (HDR) brachytherapy in the management of patients with cervical cancer, taking into consideration the current availability of resources in most institutions. METHODS: Members of the American Brachytherapy Society (ABS) with expertise in HDR brachytherapy for cervical cancer performed a literature review, supplemented their clinical experience to formulate guidelines for HDR brachytherapy of cervical cancer. RESULTS: The ABS strongly recommends that definitive irradiation for cervical carcinoma must include brachytherapy as a component. Each institution should follow a consistent treatment policy when performing HDR brachytherapy, including complete documentation of treatment parameters and correlation with clinical outcome, such as pelvic control, survival, and complications. The goals are to treat Point A to at least a total low-dose-rate (LDR) equivalent of 80-85 Gy for early stage disease and 85-90 Gy for advanced stage. The pelvic sidewall dose recommendations are 50-55 Gy for early lesions and 55-65 Gy for advanced ones. The relative doses given by external beam radiation therapy (EBRT) vs. brachytherapy depend upon the initial volume of disease, the ability to displace the bladder and rectum, the degree of tumor regression during pelvic irradiation, and institutional preference. As with LDR brachytherapy, every attempt should be made to keep the bladder and rectal doses below 80 Gy and 75 Gy LDR equivalent doses, respectively. Interstitial brachytherapy should be considered for patients with disease that cannot be optimally encompassed by intracavitary brachytherapy. While recognizing that many efficacious HDR fractionation schedules exist, some suggested dose and fractionation schemes for combining the EBRT with HDR brachytherapy for each stage of disease are presented. These recommendations are intended only as guidelines, and the suggested fractionation schemes have not been thoroughly tested. The responsibility for the medical decisions ultimately rests with the treating radiation oncologist. CONCLUSION: Guidelines are established for HDR brachytherapy for cervical cancer. Practitioners and cooperative groups are encouraged to use these guidelines to formulate their treatment and dose-reporting policies. These guidelines will be modified, as image-based treatment becomes more widely available.

Antineoplastic Agents↗