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A five-field conformal technique with three-dimensional radiation therapy treatment planning (3-DRTP) has been shown to permit better definition of the target volume for lung cancer, while minimizing the normal tissue volume receiving greater than 50% of the target dose. In an initial study to confirm the safety of conventional doses, we used the five-field conformal 3-DRTP technique. We then used the technique in a second study, enhancing the therapeutic index in a series of 42 patients, as well as to evaluate feasibility, survival outcome, and treatment toxicity. Forty-two consecutive patients with nonsmall-cell lung carcinoma (NSCLC) were evaluated during the years 1993–1997. The median age was 60 years (range 34–80). The median radiation therapy (RT) dose to the gross tumor volume was 6,300 cGy (range 5,000–6,840 cGy) delivered over 6 to 6.5 weeks in 180–275 cGy daily fractions, 5 days per week. There were three patients who received a split course treatment of 5,500 cGy in 20 fractions, delivering 275 cGy daily with a 2-week break built into the treatment course after 10 fractions. The stages of disease were II in 2%, IIIA in 40%, IIIB in 42.9%, and recurrent disease in 14.3% of the patients. The mean tumor volume was 324.14 cc (range 88.3–773.7 cc); 57.1% of the patients received combined chemoradiotherapy, while the others were treated with radiation therapy alone. Of the 42 patients, 7 were excluded from the final analysis because of diagnosis of distant metastasis during treatment. Two of the patients had their histology reinterpreted as being other than NSCLC, 2 patients did not complete RT at the time of analysis, and 1 patient voluntarily discontinued treatment because of progressive deterioration. Median follow-up was 11.2 months (range 3–32.5 months). Survival for patients with Stage III disease was 70.2% at 1 year and 51.5% at 2 years, with median survival not yet reached. Local control for the entire series was 23.3 ± 11.4% at 2 years. However, for Stage III patients, local control was 50% at 1 year and 30% at 2 years. Patients who received concurrent chemotherapy had significantly improved survival (P = 0.002) and local control (P = 0.004), compared with RT alone. Late esophageal toxicity of ≥Grade 3 occurred in 14.1 ± 9.3% of patients (3 of 20) receiving combined chemoradiotherapy, but in none of the 15 patients treated with RT alone. Pulmonary toxicity limited to Grades 1–2 occurred in 6.8% of the patients, and none developed ≥Grade 3 pulmonary toxicity. Patients with locally advanced NSCLC, who commonly have tumor volumes in excess of 200 cc, present a challenge for adequate dose delivery without significant toxicity. Our five-field conformal 3-DRTP technique, which incorporates treatment planning by dose/volume histogram (DVH) was associated with minimal toxicity and may facilitate dose escalation to the gross tumor. Radiat. Oncol. Invest. 7:297–308, 1999. © 1999 Wiley-Liss, Inc.

A measurable improvement in the efficacy of the three-dimensional radiotherapy (RT) of primary lung cancer patients with unresectable disease will require the development of a technique that increases the therapeutic ratio of dose delivered to the tumor volume relative to functional lung. A full course of definitive RT dose was delivered to six consecutive primary lung cancer patients using multiple fields with treatment portals tightly conformed to the tumor shape in beams-eye-view, using multileaf collimation. For each patient, a treatment planning dose/volume histogram (DVH) was constructed considering the most anatomically normal tissues in both the ipsilateral and contralateral lungs. When compared to a standard anteroposterior-posteroanterior (AP-PA) treatment plan followed by parallel-opposed oblique fields with conventional blocks, the five-field conformal technique yielded a significantly lower integral lung dose as determined by cumulative DVH data. We compared the data for total lung capacity in cubic centimeters from the treatment planning DVH with that obtained by pulmonary function tests and found good concordance. The present RT technique and patient evaluation program should provide a valuable approach toward improving the quality of life in irradiated lung cancer patients, and may also guide efforts by which to escalate the dose to a tumor volume in the chest. © 1995 Wiley-Liss, Inc.

It is known experimentally that a wedge transmission factor depends upon the field size and depth of measurement in particular. Dependence of the transmission upon depth has been attributed to a hardening of the incident beam through the filter, which preferentially absorbs the low‐energy photon of the bremsstrahlung component of that beam. We have attempted to separate this hardening effect from that of increased phantom scatter due to dose gradient induced by the wedge filter. Using an experimental wedge machined from cerrobend, the filter transmission at depth is measured and redefined relative to an ‘‘equally hardened’’ beam, obtained by filtering through a flat slab of equal thickness at the center of the wedge. Results of the Co‐60, 4‐, and 8‐MV wedged beams indicate that nearly half of the increase in the transmission at depth is due to the effect of dose‐gradient scatter in polystyrene phantom. Based on a simple relationship between primary and scattering radiation, an algebraic presentation is indeed in support of the dose gradient resulting in apparent increase in the wedge factors, at depth. Key words: wedge factor, beam hardening, Co‐60, x ray, dose gradient

An exact formula used for determination of the magnification of the target using the conventional stereotactic biplane radiographic imaging has been derived for the stereotactic frame.

Abutment of unmodified electron fields to irradiate large areas can lead to significant dose inhomogeneities in the region of junction of the fields. In this paper we describe the design and dosimetric characteristics of a device developed to broaden the electron beam penumbra and thereby to improve the dose uniformity in the overlap region. The device is a high‐density triangular‐toothed comb capable of reducing the beam intensity without seriously degrading the beam energy. The effect of the comb is such that a single device will generate a beam penumbra which is broad and very nearly linear at all depths for all clinically used beam energies. Results are shown for various field configurations and energies. With a gap of 5.0 cm between the treatment cone and phantom surface the dose ‘‘ripple’’ in the region beneath the teeth was found not to exceed ±5% at 0.5‐cm depth.

Polyacrylamide-based tissue-equivalent phantoms simulating cortical bone and muscle are described. The equivalency is based upon similar elemental composition and density, and partial similarity in the morphology of bone. Satisfactory results were obtained when the phantoms were tested at low (20 keV) and high (15 MeV) gamma radiation. Applicability of this phantom material to neutron transport is discussed. The material can be molded and shaped and its composition is easily modified by altering the proportions of the constituents. Trace elements or radionuclides are easily added. Details of the physical and radiation characteristics of the formulated systems are given together with the manufacturing procedures.

Comments are given on the new TG‐21 protocol for the calibration of absorbed dose from electron beams. The technique for determining the energy of electron beams is discussed in detail and suggestions are made regarding removal of inconsistencies and ambiguities in the determination of electron beam energy. (AIP)