A nomograph for permanent implants of palladium-103 seeds.

103Pd is being substituted for 125I in permanent implants for which it is desired to deliver a higher initial dose rate while maintaining readily achieved radiation protection. We have constructed a nomograph to assist in determining both the total seed strength required and the appropriate needle spacing for 103Pd implants. We have calculated the "matched peripheral dose" (MPD), that is, the dose for which the isodose contour volume is equal to the target volume, for 64 125I and 13 103Pd actual implants as if 103Pd had been used for all of them, employing a computer lookup table based on single-seed dose distribution measurements in solid water. The calculated data were used to obtain a least-squares fit to a linear relationship between the logarithm of the total seed strength for a given MPD and the logarithm of the average dimension, da (cm). We found that, for a nominal MPD of 11,500 cGy, total seed strength (in mCi) is given by 3.2 da2.56. A 103Pd nomograph has been constructed on the basis of this power function relationship. Our nomographic guide for planning 103Pd implants calls for total seed strength to increase significantly faster as a function of target volume average dimension than is the case for 125I. This nomograph will facilitate the application of 103Pd seeds in permanent implants.

Head and neck extranodal non-Hodgkin's lymphomas in Indian patients.

Though radiotherapy has traditionally been the treatment of the choice for the patients with localised extranodal lymphomas of the head and neck areas, its adequacy as the sole modality of treatment has come to be questioned. The disease is shown to relapse in other distant extranodal sites especially the gastrointestinal tract. The addition of systemic chemotherapy has been suggested. Fifty-five patients with localised head and neck extranodal lymphomas were treated at the Tata Memorial Hospital during the period 1976-1982, 35 with radiation therapy alone and 20 with combination therapy. The total survival at 5 years was 65% for patients treated with radiation alone and 85% for those treated with combination therapy. The 5 year disease-free survival dropped to 45% for the former group but was 74% for the latter group. This difference was statistically significant (p less than 0.01). We infer that localised extranodal lymphomas be regarded as a systemic disease and be treated by a multimodal approach.