PubMed Health⌕ Search

PubMed · 12162523

Radiotherapy prostheses.

Abstract

The orofacial region performs the essential functions of mastication and speech, as well as that of appearance, which for better or worse evokes an instant and instinctive response in other people. In this region, tissue loss caused by surgical resection of a malignant tumor has a tremendous negative impact on the patient's quality of life, with deep mental and psychological repercussions. Therefore, from the standpoint of preserving form and function, radiotherapy has a major role to play in the treatment of malignant tumors in the orofacial region. That said, important organs, such as sensory organs, are present in close proximity to each other in this small region. During the irradiation process, therefore, it is important to ensure that the lesion is sufficiently irradiated while simultaneously protecting the surrounding normal tissue. In certain cases of radiotherapy of malignant tumors of the orofacial region, the use of radiotherapy prostheses can help to satisfy a basic principle of radiotherapy: that of delivering a lethal dose to the tumor while minimizing irradiation to normal tissue. In recent years, medical and dental experts have taken a team approach to creating and employing a variety of radiotherapy prostheses, working towards improving the treatment record for malignant tumors as well as reducing complications in surrounding normal tissue. As a result, patients treated with radiotherapy prostheses are now able to receive post-radiotherapy prosthodontic treatment in a dramatically safer and more rapid manner. It is clear that radiotherapy prostheses contribute significantly to the improvement of these patients' quality of life.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

H Taniguchi. 2000. Radiotherapy prostheses.. https://pubmed.ncbi.nlm.nih.gov/12162523/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Intraoperative dural irradiation by customized 192iridium and 90yttrium brachytherapy plaques.

PURPOSE: After vertebral or paravertebral tumor resection, tumor cells may remain on the dura. Because a tumoricidal dose is difficult to achieve using external beam radiotherapy without exceeding the spinal cord tolerance, we developed intraoperative applicators to deliver additional dose to the dura. METHODS AND MATERIALS: Eight patients with vertebral or paravertebral tumor underwent conformal external beam radiotherapy, tumor resection, and intraoperative radiotherapy to the dura involved by tumor. At surgery, vertebra, soft tissue, and epidural tumor were resected. A radioactive applicator plaque was placed on the dura to deliver 7.5-15 Gy, and then removed. Vertebral reconstruction and stabilization was completed. Chemotherapy was administered for large, high-grade sarcomas. RESULTS: We progressed through three plaque designs, initially (192)Ir, subsequently liquid (90)Y, and finally (90)Y foil in a semicylindrical polycarbonate plaque, in the treatment of 8 patients. The low-energy (90)Y beta-emissions provided a more attractive depth dose profile than that achievable with iridium and gave negligible staff radiation exposure. The (90)Y depth dose measured 29% at 2 mm and 9% at 4 mm from the surface of the foil plaque, with acceptable surface dose homogeneity. The average surface dose rate ranged from 18.7 to 47.6 cGy/min for the iridium plaques and 45.2 to 187.5 cGy/min for the (90)Y plaques. The treatments have been without acute or late neurologic complications. The disease of 6 of 8 patients was locally controlled at median potential follow-up of 24 months. CONCLUSIONS: The (90)Y foil applicator is technically elegant, easy to use, and superior to the earlier models. It has been incorporated into a protocol for spinal tumor treatment.

Brachytherapy↗

Is it necessary to eliminate the posterior dose margin in prostate brachytherapy to achieve an acceptably low risk of late rectal morbidity?

PURPOSE: The use of a posterior dose margin in (125)I prostate brachytherapy is controversial. The posterior margin is often eliminated to lower the risk of late rectal morbidity (Radiation Therapy Oncology Group protocols 9805 and P-0019), but this may compromise the posterior prostate dose coverage. The purpose of this work is to determine whether it is necessary to eliminate the posterior margin to achieve an acceptably low risk of Grade 2 (bleeding/ulceration) late rectal morbidity. METHODS AND MATERIALS: The present work is an extension of a previous study in which we reported the probability of Grade 2 late rectal morbidity (bleeding/ulceration) as a function of the maximum rectal dose. Here, we define the relationship between the maximum rectal dose and the width of the posterior dose margin. From this relationship, and the probability of late morbidity determined earlier, we assessed the probability of late rectal morbidity as a function of the width of the posterior dose margin. The present work was based on the preplans of 15 permanent (125)I prostate seed implants having volumes ranging from 19 to 78 cm(3). All used peripheral loading with (125)I sources in the range 0.35-0.45 mCi. The maximum rectal dose was taken to be the isodose line coincident with the posterior edge of the prostate. The maximum rectal dose and the corresponding margin width were determined from the isodose distribution. The sensitivity of the relationship between the maximum rectal dose and the margin width to the prostate volume, the seed density, and the distance of the most posterior seeds from the posterior edge of the prostate was investigated. RESULTS: The maximum rectal dose is directly proportional to the margin width. This relationship is relatively insensitive to the prostate volume and the seed density, but is sensitive to the location of the posterior seeds relative to the posterior edge of the gland. Moving the seeds from 5 mm to 3 mm from the edge typically increased the maximum rectal dose by 17%. With the posterior seeds 3 mm from the edge, the maximum rectal doses that corresponded to 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm margins were 187 +/- 6 Gy, 222 +/- 8 Gy, 257 +/- 11 Gy, 292 +/- 14 Gy, and 327 +/- 17 Gy, respectively. The corresponding probabilities that a patient will experience late rectal morbidity are < or =1%, < or =2%, < or =3%, < or =5%, and < or =7%, respectively. CONCLUSIONS: Our results indicate that a 2-3-mm posterior dose margin can be used in prostate brachytherapy with a relatively low (2-3%) risk of Grade 2 (bleeding/ulceration) late rectal morbidity, provided the sources in the posterior row are implanted at least 3 mm from the edge of the prostate. A practical guideline is to keep the maximum rectal dose below 150% of the target dose.

Brachytherapy↗