John T. Lyman

Optimization of radiation therapy, III: a method of assessing complication probabilities from dose-volume histograms

To predict the likelihood of success of a therapeutic strategy, one must be able to assess the effects of the treatment upon both diseased and healthy tissues. This paper proposes a method for determining the probability that a healthy organ that receives a non-uniform distribution of X-irradiation, heat, chemotherapy, or other agent will escape complications. Starting with any given dose distribution, a dose-cumulative-volume histogram for the organ is generated. This is then reduced by an interpolation scheme (involving the volume-weighting of complication probabilities) to a slightly different histogram that corresponds to the same overall likelihood of complications, but which contains one less step. The procedure is repeated, one step at a time, until there remains a final, single-step histogram, for which the complication probability can be determined. The formalism makes use of a complication response function C(D, V) which, for the given treatment schedule, represents the probability of complications arising when the fraction V of the organ receives dose D and the rest of the organ gets none. Although the data required to generate this function are sparse at present, it should be possible to obtain the necessary information from in vivo and clinical studies. Volume effects are taken explicitly into account in two ways: the precise shape of the patients histogram is employed in the calculation, and the complication response function is a function of the volume.

Treatment planning for heavy ion radiotherapy

A computerized treatment planning system based on quantitative information in computerized tomographic (CT) scans has been developed for the heavy ion radiotherapy trials at the Lawrence Berkeley Laboratory. The CT number of each pixel is converted to a water equivalent length and used in the calculation of isoeffect dose distributions from multiport heavy charged particle irradiation. The water equivalent length of pixels in the beam path has also been histogrammed and used in quantitatively studying the range shortening effects by inhomogeneities. Treatment plans for representative lesions of the pelvis, abdomen, and thorax are presented.

Comparison of different radiation types and irradiation geometries in stereotactic radiosurgery

Recent interest in stereotactic radiosurgery of intracranial lesions, and the development of stereotactic irradiation techniques has led to the need for a systematic and complete comparison of these methods. A method for conducting these comparisons is proposed and is applied to a set of currently-used stereotactic radiosurgical techniques. Three-dimensional treatment planning calculations are used to compare dose distributions for several different radiation types and irradiation geometries. Calculations were performed using charged particles (H, He, C, and Ne ions) and the irradiation geometry currently used at Lawrence Berkeley Laboratory. Photons in the Gamma Knife configuration and the Heidelberg Linac arc method are used. The 3-dimensional dose distributions were evaluated by means of dose-volume histograms and integral doses to the target volume and to normal brain. The effects of target volume, shape and location are studied. The charged particle dose distributions are more favorable than those of the photon methods. The differences between charged particles and photons increase with increasing target volume. The differences between different charged particle species are small, as are the effects of target shape and location.

Early and late effects of accelerated charged particles on normal tissues.

Abstract The response of skin and spinal cord to accelerated charged particle irradiation has been examined. For skin, irradiation with helium or neon ions in the plateau region of ionization yields RBE values (compared to 230 kV X-rays) of about 1.0 and 1.5 respectively. Irradiation with helium or neon ions in a therapeutically modified (“spread-out”) Bragg peak region of ionization yields RBE values of about 1.3 and 2.2–2.5 respectively. After exposure to divided doses of either helium or neon ions in the spread-out Bragg peak region of ionization, the amount of dose recovered appeared to be decreased by about 30% (as compared to the amount of dose recovered after exposure to divided doses of X-rays given over an interval of 24 hr) for the helium ion irradiations, and appeared to be decreased by about 75% for the neon ion irradiations. For effects on spinal cord, the degree of myelopathy appeared to be similar after irradiation with helium ions in either the plateau or spread-out Bragg peak regions of ionization; while after exposure to neon ions in the plateau region of ionization, the RBE appeared to be about 1.3.

Isah: A versatile treatment positioner for external radiation therapy

Mechanical features, control philosophy, and operational characteristics are described for the computer‐controlled patient positioner, „ISAH (Irradiation Stereotaxic Apparatus for Humans). The positioner is currently being used with the 910‐MeV helium‐ion beam from the 184”︁ Cyclotron at the Lawrence Berkeley Laboratory. It is capable of positioning a patient to 0.1‐mm accuracy in three dimensions. It can simultaneously or selectively translate the patient in three orthogonal axes and rotate him about two perpendicular axes. ISAH is used to deliver a therapeutic dose of radiation to an arbitrarily determined volume within the patients body during irradiation, so as to minimize exposure to surrounding tissues. The motions are under online control by a PDP‐8/1 computer which directs the necessary motions and verifies the positioning. The computer also controls the intensity and the depth of penetration of the heavy‐ion beam.

Some considerations regarding w values for heavy charged‐particle radiotherapy

The AAPM recommendations regarding the w values for heavy charged‐particles radiotherapy are discussed. (AIP)

Results of tumor treatments with alpha particles and heavy ions at Lawrence Berkeley Laboratory

Abstract A clinical trial, starting with 934 MeV helium ions produced at the 184-inch cyclotron, has been underway at Lawrence Berkeley Laboratory since 1975. Eighty-five patients have been treated in a pilot series with the helium ion beam. Treatment techniques have been developed for large field, fractionated, spread out Bragg peak charged particle radiotherapy. A treatment planning computer routine has been developed to compute physical and biological isodoses for charged particle beams taking into account beam perturbations by varying tissue densities as determined by CT scanning in the region of interest. An RBE of 1.2 for fractionated helium ion therapy has been clinically confirmed using daily doses of 200 photon equivalent rad per fraction, four fractions per week to total doses of 6000 rad. Pilot studies with heavier ions such as carbon and neon are just beginning at the Bevalac. Patients with locally advanced malignancies not amenable to conventional therapy will be selected for pilot irradiation with carbon and neon ions to determine clinical RBEs, normal tissue reaction and tumor regression. The goal of these pilot studies is a prospective clinical trial utilizing helium ions to evaluate the advantages of improved dose localization, and carbon or neon ions to study the increased biological effect and improved dose localization available with heavy charged particle therapy.

Biological response across a ridge filter carbon ion Bragg peak.

The dose distribution of carbon ion beams was modified to cover 14 cm peak width using a ridge filter suitable for clinical application. The results of cell survival as a function of depth of penetration of carbon ions and the mouse skin (foot) response at the proximal-, mid-, and distal-peak positions using four daily fractions are reported. The objective of these studies is to verify whether the dose distribution in the peak region is properly compensated to produce uniform biological effect. The implications of the shape of the dose distribution in the peak region to radiotherapy application are discussed.