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Biomedical subjects

M Goitein

Publications and source records attributed to M Goitein.

At least 55 records · Page 3Linked to original sources
PubMed1986

Visual outcome after proton beam irradiation of uveal melanoma.

Prognostic factors for visual loss following proton irradiation of uveal melanoma were evaluated for 440 eyes treated from 1975 to 1984, with visual acuity 20/200 or better before treatment. Analysis involved Kaplan-Meier survival curves and Cox proportional hazards analysis with visual outcome defined as worse than 20/200. Prognostic factors were tumor height: rate ratio (ratio of rate of visual loss for one category of the variable relative to the rate of visual loss for a reference category of that variable) of 5.26 (95% confidence interval, 2.66-10.39) for tumors greater than 5 mm compared to tumors 3.0 mm or less in height; distance of tumor from the optic disc and fovea: rate ratio 2.59 (1.63-4.11) for tumors 2DD or less from both the optic disc and fovea compared to those greater than 2 DD from these structures. Also predictive of visual loss were tumor location close to disc only, or close to fovea only, macular detachment, worse pretreatment vision, and higher radiation doses delivered to both the disc and fovea, and lens. Regression analysis using a visual acuity scale gave similar results.

Adolescent↗
PubMed1986

Degradation of the Bragg peak due to inhomogeneities.

The rapid fall-off of dose at the end of range of heavy charged particle beams has the potential in therapeutic applications of sparing critical structures just distal to the target volume. Here we explored the effects of highly inhomogeneous regions on this desirable depth-dose characteristic. The proton depth-dose distribution behind a lucite-air interface parallel to the beam was bimodal, indicating the presence of two groups of protons with different residual ranges, creating a step-like depth-dose distribution at the end of range. The residual ranges became more spread out as the interface was angled at 3 degrees, and still more at 6 degrees, to the direction of the beam. A second experiment showed little significant effect on the distal depth-dose of protons having passed through a mosaic of teflon and lucite. Anatomic studies demonstrated significant effects of complex fine inhomogeneities on the end of range characteristics. Monoenergetic protons passing through the petrous ridges and mastoid air cells in the base of skull showed a dramatic degradation of the distal Bragg peak. In beams with spread out Bragg peaks passing through regions of the base of skull, the distal fall-off from 90 to 20% dose was increased from its nominal 6 to well over 32 mm. Heavy ions showed a corresponding degradation in their ends of range. In the worst case in the base of skull region, a monoenergetic neon beam showed a broadening of the full width at half maximum of the Bragg peak to over 15 mm (compared with 4 mm in a homogeneous unit density medium). A similar effect was found with carbon ions in the abdomen, where the full width at half maximum of the Bragg peak (nominally 5.5 mm) was found to be greater than 25 mm behind gas-soft-tissue interfaces. We address the implications of these data for dose computation with heavy charged particles.

Humans↗
PubMed1985

The effects of pre-enucleation irradiation on the development of metastases from intraocular Greene melanoma in hamsters.

Using intraocular Greene melanoma in a hamster model, we studied the effect of pre-enucleation irradiation on the development of melanoma metastases. One group (No. = 111) was treated with 1,210 to 1,600 rads of cobaltous chloride Co 60 gamma irradiation before enucleation and the second group (No. = 100) received no irradiation. The groups did not differ with respect to presence of metastases in the 106 days after tumor implantation (chi 2 = 3.05; P = .08). However, Kaplan-Meier survival curves gave a longer time to melanoma-related death in the irradiated animals compared with the controls (log rank test, P = .0008).

Animals↗
PubMed1985

Future prospects in planning radiation therapy.

Recent advances in imaging, especially computed tomography and magnetic resonance imaging, and in the power and capabilities of reasonably priced computers and image display devices will permit a substantial extension of the scope of computer programs designed to help plan cancer therapy. All available diagnostic studies could be incorporated into the process of assessing the patient's disease, picking a treatment modality, and determining details of the selected treatment. Fully three-dimensional simulation of any possible treatment will be possible and methods for comparing and choosing between possible rival plans will be developed. Monitoring of the treatment machine and verification of the adequacy of the delivered treatment will be facilitated, and the follow-up of the patient and statistical analysis of the results of treatment can be incorporated into the overall programming system.

Humans↗
PubMed1985

Accuracy of radiation field alignment in clinical practice.

We present an analysis of simulator and portal films of 71 patients. Twenty-five were analyzed retrospectively, 39 prospectively, but without changing routine filming practice, and 7 had daily portal films taken. Treatment-to-treatment variations in anatomy with respect to the field were determined by comparing sequential portal films. The standard deviation of the variations was approximately normally distributed with an average value of 3 mm independent of site and field shaping technique. Discrepancies between the portal and simulator films were greater and depended on the site of treatment. The mean worst-case discrepancy averaged over all sites was 7.7 mm; the lowest value was 3.5 mm in the head and neck region; the highest value was 9.2 mm in the thorax.

Humans↗
PubMed1985

A diagnostic X ray field verification device for a 10 MV linear accelerator.

The quality of portal films taken at megavoltage energies is frequently poor, despite the use of various techniques such as lead screens to improve the image. When critical structures, such as the spinal cord, are to be blocked out of the treatment field, it is frequently difficult to determine whether the block is correctly placed. To solve this problem, a diagnostic X ray source has been mounted on the side of a 10 MV linear accelerator to provide accurate verification of patient positioning and location of shielding blocks. The coincidence between the mechanical, 10 MV and diagnostic X ray isocenters is about 1 mm. The system has been designed so that procedures to monitor this coincidence, and adjustment procedures to maintain it, are easily performed.

Humans↗
PubMed1985

Strategies for treating possible tumor extension: some theoretical considerations.

When there is a small possibility of cancer having extended to a region some distance from the main bulk of disease, it may be unclear whether to include that region in the target volume and, if so, what dose should be delivered to it. We have constructed a theoretical model that includes dose and volume relationships for both diseased and normal tissue. With this model one can calculate the change in tumor control probability (TCP) when varying doses are delivered to the regions of known and suspected disease. Values of TCP as a function of dose to the region of suspected disease have been calculated for a wide range of the variables on which the model depends. We conclude that the strategy of treating the region of suspected disease to about 70% of the dose delivered to the region of known disease is almost always better than not treating it at all, or treating both regions to a uniform but reduced dose designed to keep the probability of complication the same. The gain in TCP could be from 5 to 15% for situations of clinical interest.

Humans↗
PubMed1985

Current results of proton beam irradiation of uveal melanomas.

Proton beam irradiation has been used for the treatment of 241 uveal melanomas over the past 7 1/2 years. Twelve melanomas (5%) were small, 99 (41%) medium, 103 (43%) large and 27 (1%) extra-large melanomas. The mean length of follow-up was 21 months and the median 15 months. Ninety-four percent of the treated lesions with a follow-up more than two years and 65% of tumors with shorter follow-up showed regression. The most recent visual acuity was 20/40 or better in 47% and 20/100 or better in 66%. Ten eyes were enucleated because of complications (9) or continued tumor growth (1). Thirteen patients developed metastases from 4 to 50 months of treatment. Our data indicate that proton irradiation can be used to treat melanomas of various sizes and in a variety of locations, and preliminary results suggest that proton therapy has no deleterious effect on the likelihood of the development of metastases.

Adolescent↗
PubMed1985

Proton therapy at Harvard.

Fractionated precision high-dose proton radiotherapy has been carried out at the Harvard Cyclotron Laboratory (HCL) since 1973, in a collaborative effort with the Radiation Medicine Department of Massachusetts General Hospital (MGH) and the Retina Service of the Massachusetts Eye and Ear Infirmary (MEEI). This paper will discuss proton treatment in general, treatment planning procedures, and results to date in major patient categories. 846 patients have been treated with fractionated proton therapy at the Harvard Cyclotron, with normal tissue and tumor responses consistent with an RBE of 1.1 for the proton beam. Proton beam therapy is the treatment of choice for patients with uveal melanomas, and chordomas and chondrosarcomas involving the skull base and cervical spine. Improved dose distribution possible with protons have allowed greater doses than are given conventionally to be delivered to patients with prostatic carcinoma, head and neck malignancies, ano-rectal cancers, and retroperitoneal tumors. Doses employed have been usually 10 to 20% greater than normally would be delivered in our department to such tumors. Generally, local control rates have been good.

Animals↗
PubMed1985

Progress in low-LET heavy particle therapy: intracranial and paracranial tumors and uveal melanomas.

The Harvard Cyclotron Laboratory in collaboration with the Department of Radiation Medicine of the Massachusetts General Hospital and the Retina Service of the Massachusetts Eye and Ear Infirmary provides low-LET heavy particle therapy with 160 MeV protons. The improved dose distribution of protons results from their physical characteristics. A total of 965 patients have been treated as of December 31, 1984. Dose is expressed in units of cobalt gray equivalent (CGE) which is the dose in Gy multiplied by the RBE (1.1) for modulated protons relative to 60Co radiation. Sixty-seven patients with chordomas or low-grade chondrosarcomas of the base of skull or cervical spine have received proton treatment. Forty-three of these patients have been followed for at least 8 months with a median follow-up of 27 months. The median dose is 69 CGE. The 3-year actuarial local control rate is 89%. Seven patients with gliomas, eight with craniopharyngiomas, and six with meningiomas have also received proton radiation treatments. A total of 615 patients with uveal melanomas have received a median dose of 70 CGE in five fractions. Tumor regression has been seen in 94% with 66% having vision of 20/100 or better.

Actuarial Analysis↗
PubMed1985

Potential for low-LET charged-particle radiation therapy in cancer.

The current and likely future status of low-LET charged-particle therapy of cancer is reviewed with regard to both physical and clinical aspects. We conclude that such therapy has reached the stage at which clinical implementation is practical and that a broader program is needed if the clinical advantages of improved dose distributions are to be determined.

Clinical Trials as Topic↗
PubMed1984

Relative biological effectiveness of modulated proton beams in various murine tissues.

The relative biological effectiveness (RBE) of proton beams produced by Harvard University 160 MeV synchrocyclotron was studied in various murine tissues. Reference radiation was Cobalt-60 gamma-rays from a teletherapy unit at the Massachusetts General Hospital. Animals were C3Hf/Sed mice derived from our defined flora mouse colony. Test tissues are: lens, lung, testes and tail vertebrae. The RBE of the third generation isotransplants of a spontaneous mouse mammary carcinoma was also investigated. The proton and Cobalt-60 irradiations were carried out simultaneously by 2 teams. The dose response curves obtained for testes weight loss and growth stunting of tail vertebrae indicated that the RBE for our protons was independent of radiation dose in the range of 0.4 to 16 Gy. This finding was identical to our previous studies of the murine fibrosarcoma, skin and small intestine. The RBE values for lens and lung tissues were obtained by determining radiation dose to result in a complete cataract in half the irradiated eyes in 210 days and a 50% mortality in 180 days respectively. We have studied proton RBE in 7 normal tissues and 2 tumors including previously reported results. The RBE values for these tissues were found to fall between 1.09 and 1.32. No significant differences in the proton RBE were found between the several normal and tumor tissues studied.

Animals↗
PubMed1984

Compensating for heterogeneities in proton radiation therapy.

Our method for predicting, and compensating for, the effects of surface irregularities and tissue heterogeneities in proton radiation therapy was evaluated by comparing the predicted and measured dose distributions. Two heterogeneity configurations in a D-shaped water-filled phantom were handled in exactly the same way as patients. Target volumes were designated on thin-section CT scans, a single en face portal was defined, compensating boli were designed and made, and the dose distribution behind the phantom measured and compared with that intended. The compensation was accurate to within 1 mm for the phantom with a single air heterogeneity and to within 2.5 mm for the phantom with multiple bone and air heterogeneities. The bolus and phantom were misaligned by 3 mm and the dramatic change in the dose distribution demonstrated the need to address the problems of patient motion and imperfect immobilisation through compensator design. A philosophy of 'expanding' the bolus is described, and dose distributions measured with the 'expanded' boli indicate that target volume treatment can be assured within prespecified repositioning and motion uncertainties. The uncertainty in the alignment of bolus and heterogeneities leads to corresponding uncertainty in the penetration of the protons. Ranges within which they will stop are calculated and shown to encompass adequately the measured distributions in both the aligned and misaligned cases.

Humans↗
PubMed1984

Preliminary results of proton beam irradiation of macular and paramacular melanomas.

Proton beam irradiation has been used for the treatment of 60 eyes with choroidal melanomas located 3 mm or less from the fovea. The average follow-up period was 18 months. 86% of the treated lesions showed regression at the time of this analysis, and the 14% that did not were followed up for less than a year. Visual acuity remained the same in 47% of the treated eyes, improved in 20%, and deteriorated in 33%. 58% of the treated eyes had visual acuity of 20/100 or better at the last follow-up examination. Radiation vasculopathy with macular oedema was the most common complication, and it was observed in 22% of the treated eyes. These preliminary observations suggest that proton beam irradiation may be a reasonable alternative to enucleation even for this group of choroidal melanomas, which is considered unfavourable in respect of the preservation of visual function.

Adolescent↗
PubMed1983

Protons or megavoltage X-rays as boost therapy for patients irradiated for localized prostatic carcinoma. An early phase I/II comparison.

A total of 180 patients with carcinoma of the prostate limited to the pelvis were treated with one of two external beam irradiation techniques between 1972 and 1979. One hundred and sixteen patients were treated with conventional pelvic megavoltage x-ray therapy. Sixty-four patients were treated with combined pelvic x-ray therapy plus a perineal proton beam boost to a carefully defined prostatic tumor volume. A 160 MeV proton beam has been modified to irradiate patients with localized tumors by using conventional treatment schedules. This proton beam has the physical advantage over megavoltage x-rays of reducing the dose to normal tissues adjacent to the tumor volume. By using the proton beam boost we have delivered an increased prostatic tumor dose of 500 to 700 cGy without increasing treatment morbidity at all. The two groups are actuarially analyzed for patient survival, disease-free survival and local recurrence-free survival, and thus far, no significant differences have been noted. Because of the minimal complications observed in the proton group despite a 10% increase in dose, a randomized clinical trial comparing these two treatment techniques is studied.

Clinical Trials as Topic↗
PubMed1983

Multi-dimensional treatment planning: I. Delineation of anatomy.

We discuss the scope of a multi-dimensional treatment program designed to assist in planning radiation therapy. It includes: synthesis of diagnostic information; techniques for the assessment and delineation of anatomy; fully three-dimensional simulation of therapy; calculation and assessment of dose distributions; verification of treatment delivery; and assessment of the patient during and after treatment. In this paper we present details of techniques for the assessment and delineation of anatomy, including the display of CT information in three dimensions and the ability to draw on and edit the image displays.

Computers↗
PubMed1983

Multi-dimensional treatment planning: II. Beam's eye-view, back projection, and projection through CT sections.

Three features of a fully three-dimensional treatment planning program are presented: (1) The beam's-eye-view provides the user with an accurate reproduction of anatomic features from the viewpoint of a treatment source. The source can be moved to any feasible position relative to the patient, permitting a choice which allows sensitive organs to be excluded from the beam. In this view a field defining aperture can readily be designed. (2) Back-projection of such an aperture shows the parts of the original transverse CT sections, or reconstructed sagittal or coronal sections, which may be covered by the selected beam. (3) Projection through the CT data from any desired origin provides an alignment film simulation which can be used to confirm accuracy of treatment, as well as help establish anatomic relationships relative to the margins of a treatment field.

Computers↗