The combined use of the natural and the cumulative dose-volume histograms in planning and evaluation of permanent prostatic seed implants.

BACKGROUND AND PURPOSE: To investigate prostate dose coverage and overdosage in planned and realized permanent iodine seed prostate implants and to explore the use of the natural dose-volume histogram (NDVH) and the cumulative dose-volume histogram (CDVH) as tools to optimize prostate implants. MATERIALS AND METHODS: The optimal prescription dose (PD) or natural prescription dose (NPD) was derived from the NDVH. The mismatch between the NPD and the given PD was called the natural dose ratio (NDR). For an ideal implant the NDR should be 1. The target is overdosed if NDR >1 and underdosed if NDR <1. The NDR and prostate coverage were evaluated in implants of nine patients. Prostate coverage was determined from the CDVH based on pre-implant ultrasound or post-implant MRI for the planned and realized implants, respectively. The use of the NDVH to further optimize the planned prostate implants was also explored. RESULTS: The mean values of the NDRs were 1.30+/-0.34 (range 0.76-1.79), 1.22+/-0.31 (0.76-1.74) and 1.22+/-0.12 (0.98-1.33) for the planned, realized and optimized seed distributions, respectively. The realized prostatic implants showed smaller prostate coverage than the planned implants. The prostate volume fractions receiving 100% of the prescription dose were V(100)=79+/-6% and V(100)=97+/-3% for the realized and the planned implants, respectively. CONCLUSIONS: The NDVH and the CDVH proved to be valuable tools in plan evaluation. The NDVH and its derived parameter NDR quantify the risk of under or overdosage for a given PD. The CDVH is valuable in evaluation of prostate coverage realized prostate. Our strategy to implant just the prostate and not the prostate plus a margin led to NDR values between 1.1 and 1.3 and a prostate coverage of V(100)=79+/-6% in the nine patients. The planned coverage of V(100)=95% was not realized, mainly due to inadequate coverage of the base of the prostate.

High-dose-rate brachytherapy for primary carcinomas of the oral cavity and oropharynx.

OBJECTIVE: Local control for patients treated with primary radiation therapy for tumors of the oral cavity is improved using low-dose-rate brachytherapy. Oropharyngeal carcinomas have also been treated with brachytherapy. The few reports in the literature regarding high-dose-rate brachytherapy (HDRBT) for head and neck cancer involve small numbers of patients and often contain a mix of palliative and curative cases. The purpose of this study is to evaluate the feasibility of HDRBT in the largest reported cohort of primary head and neck cancer patients treated with primary radiation therapy. STUDY DESIGN: This is a prospective nonrandomized study. METHODS: Fifty-five patients with primary untreated squamous cell carcinomas of the oral cavity and oropharynx were analyzed. There were 16 patients with T1, 26 with T2, 8 with T3, and 5 with T4 tumors. All patients received external-beam radiotherapy (EBRT) followed by HDRBT. Thirty-eight patients received hyperfractionated (twice daily) EBRT followed by HDRBT two or three times daily. Patients with cervical adenopathy also received hyperthermia and an electron boost to the site(s) of positive nodes. Median follow-up was 2.7 years. Toxicity and local control were analyzed. Data were analyzed by the Kaplan-Meier life-table method with statistical significance determined by the X2 and log-rank tests. RESULTS: High-dose-rate brachytherapy was extremely well tolerated. Only 9 patients (16%) developed a complication. Four patients developed osteoradionecrosis, and five developed soft tissue necrosis, all of which healed with conservative medical management. No complication required surgical intervention or hospitalization. Actuarial 2-year local control for the entire cohort was 79%. Local control was 87% for patients with T1 (15/16) and T2 (22/26) tumors versus 47% for T3 (5/8) and T4 (2/5) tumors (P < .01). CONCLUSIONS: High-dose-rate brachytherapy is feasible as a boost for patients with primary squamous cell carcinomas of the oral cavity and oropharynx. Patients with T1 and T2 tumors fared exceptionally well; those with advanced tumors may require more aggressive treatment, such as higher radiation doses, surgical resection, or systemic chemotherapy. The use of HDRBT both shortens the overall treatment time and limits the volume of tissue exposed to high doses of radiation therapy. In the future, as more patients treated with HDRBT are evaluable, we hope to identify potential factors that predict for local control so that we may select patients optimally for this treatment.

A computerized rotating laminar radionuclide camera.

We have constructed a radionuclide camera that embodies a unique detector-collimator concept and provides a radically new approach to imaging. The heart of the instrument is a linear array of semiconductor detectors separated by thin tungsten plates that confine the field of view of each detector to one dimension. This collimator design has a higher collection efficiency than the standard parallel-hole collimator but cannot directly produce a two-dimensional image. When multiple measurements are taken as the array rotates through 180 degrees, a computerized image restoration algorithm can then produce two-dimensional images with resolution determined by the width of the detectors. A small prototype camera has produced images with resolution superior to conventional Anger cameras.