Biomedical subjects

R J Tesser

Publications and source records attributed to R J Tesser.

3 recordsLinked to original sources

PubMed1991

Technical considerations in the use of 3-D beam arrangements in the abdomen.

The practical utilization of 3-D treatment planning to reduce doses to normal tissues in the abdomen is illustrated for irradiation of hepatic masses using fields with central axes rotated out of the transverse plane. The beams were arranged to go through the minimum amount of normal liver tissue, while exiting above or below a kidney. Although these beam arrangements were not coplanar with standard transverse body sections, they were designed for dose delivery through use of standard Megavoltage equipment. The planning process for these techniques illustrates the need for and use of several tools usually associated with 3-D treatment planning systems. Beam's eye-view planning with perspective display of the relevant anatomy in the projective beam geometry is required for designing the placement of focused blocks for these oblique fields. Three-dimensional volumetric dose calculations are required to evaluate dose distributions. Additionally, port-film-type radiographs, digitally reconstructed from the CT dataset, are found to be useful in understanding the correctness of simulation and verification films. The reduction in dose to normal tissues over that achievable using standard plans with beams entering the patient at right angles to the central axis of the body is illustrated using dose-volume histograms. These techniques have allowed the initiation of a radiation dose escalation protocol for tumors involving the liver and porta hepatis.

Abdomen↗

PubMed1990

An application of dose volume histograms to the treatment of intrahepatic malignancies with radiation therapy.

A clinical protocol was designed that used the dose volume histogram (DVH) of the normal liver to determine the dose of radiation to be delivered to patients with intrahepatic malignancies. The dose given to the tumor depended on the volume of normal liver that could be excluded from the boost field: 45 Gy if more than 50% of the normal liver could be excluded and 60 Gy if more than 75% of the normal liver could be excluded. Thus, dose prescription depended on the ability to perform, on a routine basis, three-dimensional (3-D) treatment planning with dose volume histogram generation. A total of 36 patients have been entered onto this study. Twenty-one of 25 patients (84%) with disease that could be delineated on CT scan were eligible for boost treatment. Successive planning attempts often produced plans which qualified for boost therapy when the initial estimate had been that boost treatment would not be possible. Patients with large tumors were sometimes able to receive boost treatment, demonstrating that individualized planning was required. These results show that intrahepatic tumors can be safely treated with high doses of radiation when dose prescription is guided by the dose volume histogram of the normal liver. Furthermore, this approach strongly promotes an active role in treatment planning, since creative planning often permitted the delivery of higher doses to the tumor.

Humans↗

PubMed1989

Boost treatment of the prostate using shaped, fixed fields.

Using a CT-based, 3-D treatment planning system and Beam's Eye-View (BEV) displays, shaped fixed-field techniques have been developed for external beam boost treatment of Stage C carcinoma of the prostate. The basic technique comprises three sets of opposing beams (laterals and +/- 45 degrees with respect to the lateral) into a 6-field arrangement. Target volumes together with bladder and rectal wall volumes are outlined on axial CT slices and combined to form 3-D volumes. For each field, an interactive BEV display is produced showing the target volume in its correct 3-D geometrical perspective and an auto-block routine is used to design focused blocks which conform to that volume. Full 3-D volume calculations computed for those plans on 17 patients were analyzed along with similar calculations for more traditional unblocked 4-field box and bilateral arc techniques. Compared to the 95% isodose volume for the 6-field conformational technique, traditional open beam full target coverage techniques typically produce high dose volumes which cover up to five times as much uninvolved tissue. Dose volume histograms illustrate that typically half as much bladder and rectal tissue is treated to high dose using the conformational boost techniques. From the dosimetric perspective of sparing normal tissues, shaped fixed-field boost techniques are shown to be clearly superior to traditional full coverage bilateral arc techniques. Smaller 8 cm X 8 cm arc techniques are shown to be quantitatively unacceptable for treatment of this advanced stage disease, as they typically misses 20-35% of the target volume.

Humans↗