Conformity Of Dose Distribution Research Articles

Lung trajectory mapping

Purpose: Breathing motion has limited the use of intensity modulated radiation therapy (IMRT) for lung cancer treatments. We propose a method for directly measuring the complex three-dimensional motion of the entire lung during breathing (lung trajectory) for the purpose of optimizing IMRT treatment plans and improving the spatial resolution and small-lesion detectability of nuclear medicine imaging, principally positron emission tomography (PET). For IMRT, patient-specific knowledge of lung motion will enable the study of the compromise between dose distribution conformality (associated with fluence modulation complexity and margin size), dose delivery accuracy, and dose delivery efficiency (gating). We propose to measure patient-specific lung trajectory maps by combining gated CT images with automated deformable image registration techniques. This study investigates the feasibility and utility of this technique.

Whole-body dose from tomotherapy delivery

Purpose: To measure whole-body dose in tomotherapy of the head and neck region resulting from internal patient scatter and linear accelerator leakage. Methods and Materials: Treatments are performed using a commercial computer-controlled intensity modulated radiation therapy planning and delivery system (Peacock, NOMOS Corp.) and a 6-MV linear accelerator (Clinac 6/100, Varian Corp.). The patient dose outside the treatment field is measured in a water-equivalent phantom using thermoluminescent dosimetry. The whole-body dose components from internal scatter and leakage are separately determined. The use of fixed-portal leakage and scattered radiation measurements to estimate the whole-body dose from tomotherapy is evaluated. Results: The internally scattered dose is significant near the target, but becomes negligible relative to the leakage dose beyond 15 cm from the target. Dose at 10 cm from the target volume, due to internal scatter and leakage, is approximately 2.5% of the total target dose, reducing to 0.5% at 30 cm. The measured dose is relatively uniform throughout the phantom. Conclusion: The whole-body dose equivalent from a tomotherapy treatment is greater than that from conventional radiation therapy. Further studies are required to assess the trade-off between improved dose distribution conformality and a possible slight increase in radiation-induced fatal malignancies. The accuracy of using fixed-portal leakage and scattered dose measurements to estimate the whole-body dose from tomotherapy treatments is adequate, if the appropriate fixed-portal field size equivalent is used.

Conformation of dose distribution by pulsed (PDR) Afterloading

Conformation of dose distribution by pulsed (PDR) Afterloading

Examination of the Genital Organs in the Prepubescent and in the Adolescent Girl

To report the technical aspects of customized high-dose-rate brachytherapy for vaginal rhabdomyosarcoma using MRI- and CT-based planning in a 20-month-old girl.An impression of the vaginal cavity at the resection site was taken after adequate lubrication of the vagina with lidocaine jelly. The impression was processed in the dental laboratory to obtain an MRI-compatible device with three imbedded catheters 0.4 mm apart, assuring tumor coverage. An MRI- and CT-based simulation under anesthesia with the applicator in place were performed, and the images were registered for contouring and planning to deliver 40 Gy in 10 fractions daily. Dose to the ovaries was limited to a mean dose less than 4 Gy. Treatment was delivered daily under anesthesia with no acute complications.Brachytherapy using a customized applicator has many advantages over prefabricated vaginal cylinders for young girls. It allows greater dose distribution conformality with the possibility of contralateral vaginal wall sparing and more reproducible daily positioning. MRI-based planning is mainly performed to facilitate delineation of the target volume and the ovaries, which are easily identified on MRI.The customized applicator offers many advantages of which treatment reproducibility, inherent MRI compatibility, and excellent dose distribution conformality. Our brachytherapy technique using MRI and CT scan planning allows precise tumor and normal tissues delineation resulting in excellent tumor coverage and normal tissues sparing.