Biomedical subjects

Natarajan V Raman

Publications and source records attributed to Natarajan V Raman.

3 recordsLinked to original sources

PubMed2005

Effects of field parameters on IMRT plan quality for gynecological cancer: a case study.

Traditional external beam radiotherapy of gynecological cancer consists of a 3D, four-field-box technique. The radiation treatment area is a large region of normal tissue, with greater inhomogeneity over the treatment volume, which could benefit more with intensity-modulated radiation therapy (IMRT). This is a case report of IMRT planning for a patient with endometrial cancer. The planning target volume (PTV) spanned the intrapelvic and periaortic lymph nodes to a 33-cm length. Planning and treatment were accomplished using double isocenters. The IMRT plan was compared with a 3D plan, and the effects of field parameters were studied. Delineated anatomical contours included the intrapelvic nodes (PTV), bone marrow, small bowel, bladder, rectum, sigmoid colon, periaortic nodes (PTV), spinal cord, left kidney, right kidney, large bowel, liver, and tissue (excluding the PTVs). Comparisons were made between IMRT and 3D plans, 23-MV and 6-MV energies, zero and rotated collimator angles, different numbers of segments, and opposite gantry angle configurations. The plans were evaluated based on dosevolume histograms (DVHs). Compared with the 3D plan, the IMRT plan had superior dose conformity and spared the bladder and sigmoid colon embedded in the intrapelvic nodes. The higher energy (23 MV) reduced the dose to most critical organs and delivered less integral dose. Zero collimator angles resulted in a better plan than "optimized" collimator angles, with lower dose to most of the normal structures. The number of segments did not have much effect on isodose distribution, but a reasonable number of segments was necessary to keep treatment time from being prohibitively long. Gantry angles, when evenly spaced, had no noticeable effect on the plan. The patient tolerated the treatment well, and the initial complete blood count was favorable. Our results indicated that large-volume tumor sites may also benefit from precise conformal delivery of IMRT.

Adenocarcinoma↗

PubMed2005

Cell-phone interference with pocket dosimeters.

Accurate reporting of personal dose is required by regulation for hospital personnel that work with radioactive material. Pocket dosimeters are commonly used for monitoring this personal dose. We show that operating a cell phone in the vicinity of a pocket dosimeter can introduce large and erroneous readings of the dosimeter. This note reports a systematic study of this electromagnetic interference. We found that simple practical measures are enough to mitigate this problem, such as increasing the distance between the cell phone and the dosimeter or shielding the dosimeter, while maintaining its sensitivity to ionizing radiation, by placing it inside a common anti-static bag.

Artifacts↗

PubMed2005

Prostate motion and isocenter adjustment from ultrasound-based localization during delivery of radiation therapy.

PURPOSE: To study prostate motion from 4,154 ultrasound alignment fractions on 130 prostate patients treated with conformal radiotherapy or intensity-modulated radiation therapy at the University of Nebraska Medical Center. METHODS AND MATERIALS: Each prostate patient was immobilized in a vacuum cradle. Daily treatment was verified by ultrasound scan after laser setup with skin marks and before radiation delivery by the same physician responsible for anatomic delineation during planning. Directional statistics were employed to test the significance of shift directions. RESULTS: Polar histograms showed the prevalence of prostate motion in superior-posterior directions. The average direction was about 27 degrees from the superior axis. The average changes of prostate position in superior to inferior (SI), anterior-posterior (AP), and left to right (LR) directions and in radial distance were 0.25, -0.13, 0.03, and 0.92, cm respectively. Our data indicated that prostate motion was not patient specific, and its average magnitude remained virtually unchanged over time. Recommended planning target volume (PTV) margins for use without ultrasound localization were 0.90 cm in SI, 1.02 cm in AP, and 0.80 cm in LR directions. CONCLUSION: Ultrasound localization revealed a predominance of prostate shift from planning position in the superior-posterior direction, with an average closer to the superior axis. The motion data provides recommended margins for PTV.

Algorithms↗