Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology
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The purpose of this investigation was to determine the irradiation tolerance level and complication rates of the proximal vagina to combined external irradiation and low dose rate (LDR) brachytherapy. Also, the mucosal tolerance for fractionated high dose rate (HDR) brachytherapy is further projected based on the biological equivalent dose (BED) of LDR for an acceptable complication rate. ⋯ The traditional 150 Gy LDR tolerance dose (single source plus external irradiation) can be relaxed to 175 Gy or equivalently a full mucosal dose of 238 Gy (all sources plus external irradiation) for a nominal 5% Grade 3 complication rate. Higher fractionation is necessary with four to six fractions in HDR therapy for similar rates of sequelae. The mucosal surface dose from a single ovoid, which can be readily computed, remains a convenient tolerance check for treatment planning purposes.
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The aim of this analysis is to evaluate the feasibility of inverse treatment planning and intensity modulated radiation therapy (IMRT) for head and neck cancer in daily clinical routine. A step and shoot IMRT approach was developed which allows the treatment of large target volumes without the need to use a split beam technique. By using the IMRT approach better protection of different organs at risk in the head and neck region may be achieved and an escalation of the dose in the tumor should be possible. We evaluated the feasibility of the treatment technique and the patient tolerance to the treatment. First clinical results are reported. ⋯ The use of an inversely-planned and intensity-modulated step and shoot approach is feasible in clinical routine for head and neck tumors. Treatment could be applied as planned and no increased toxicity was found. Compared to other IMRT approaches for the head and neck region the used technique allows the treatment of the primary tumor and the lymph nodes level I-VI with only one intensity modulated treatment volume. The presented technique avoids to match conventional radiotherapy fields and IMRT fields, and therefore, reduce the risk of overdosage or underdosage at the matching line. Compared to conventional treatment techniques IMRT shows advantages in tumor dose and dose at the organs at risk.
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To assess the influence of patient repositioning and organ motion on dose distribution within the prostate and the seminal vesicles (clinical target volume, (CTV)). ⋯ Precise targeting of prostate radiotherapy is primarily dependent on careful daily set-up and on random changes in rectal geometry. Margins no less than 10 mm around the prostate and at least 15 mm around the seminal vesicles are probably necessary to insure adequate target coverage with a six-field technique.
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The shrinking effect of 3-month neoadjuvant androgen deprivation (NAD) on preradiotherapy prostate gland volume is well documented. However, recently, it has been shown that the cancerous prostate gland keeps shrinking up to 12 months after NAD start. Thus, if such a reduction is not taken into account, a larger than planned portion of the surrounding normal tissues might shift in the high-dose region during conformal radiotherapy (3DCRT) course. The present study was undertaken to quantify this issue. ⋯ For patients who undergo plCT and 3DCRT shortly after AD start, prostate gland shrinkage may be substantial. In some of these patients, this might lead to an unexpected increase of the percentage of rectal wall exposed to intermediate doses.
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To assess the feasibility, and potential implications, of using intra-prostatic fiducial markers, rather than bony landmarks, for the co-registration of computed tomography (CT) and magnetic resonance (MR) images in the radiation treatment planning of localized prostate cancer. ⋯ Prostate contouring on MR is associated with less inter-observer variation than on CT. In addition, we have demonstrated the feasibility of using intra-prostatic fiducial markers, rather than bony landmarks, for the co-registration of CT and MR images in the radiation treatment planning of localized prostate cancer. This technique, together with on-line correction of treatment set-up according to the fiducial marker position on electronic portal imaging, may enable a reduction in the planning target volume (PTV) margin needed to account for inter-observer error in target delineation, and for prostate motion.