THE BRAGG PEAK OF A PROTON BEAM IN INTRACRANIAL THERAPY OF TUMORS
Results are reported on four patients with tumors treated by intracranial irradiation with the Bragg peak of a proton beam from the 160-Mev Harvard cyclotron, as well as radiobiological investigations in 100 monkeys demonstrating experimentally the feasibility of the method. Protons, emerging from the portal of the cyclotron at great speeds, can be directed in nearly straight lines so that at the end of their range (the Bragg peak) they stop at the brain target and liberate greater amounts of ionizing radiation than elsewhere along their path. Combining the Bragg peak with multiple portals of entry permits large doses of radiation, up to 20,000 rad, to be delivered to an intracranial target while surrounding zones receive a significantly lower dose. Use of the Bragg peak has advantages over the full penetration techniques. The fact that the beam penetrates only to target, combined with the greater ionizing energy yield of the Bragg peak, reduces by approximates 1/3--1/6 the dose to nontarget portions of the brain produced by a full-penetration method. Furthermore, a variety of portals can be selected because no emerging beam threatens radiosensitive structures such as the eyes, gonads, or blood-forming tissues. Cebus monkeys were used to assess such factors as the total dose and dose rate. The technique permits focal cerebral destructtons through skin, bone, and brain without making any opening along the path of the beam. To ensure that the brain target is superimposed on the Bragg peak, a precise stereotactic system is required. An instrument was designed that provides bony fixation to the small by tiny drill rods that enter the outer table of the skall to maintain the head position most firmly. The brain target is identified by bone landmarks or encephalography. The instrument is adjusted to bring the centers of rotation of the instrument precisely on the brain target, and the Bragg peak is precisely superimposed on the center of instrument rotation. Thus, the patient's head is rotated around Lhe two axes, permitting a large number of beam path portals while the brain target remains on the Bragg peak. A telescoping water absorber permits the proper penetration into the brain after a small correction is made to compensate for the difference in absorption of brain and bone from water. The technique makes it possible to irradiate malignant brain tumors (gliomas), tumors of the pituitary region, and vascular malformations. Hypophysectomy can be done with reduced risk to surrounding structures in an awake, comfortable patient. Successful results are reported in three patients with intracranial malignancies and one who underwent palliative hypophysectomy for breast cancer. Its use in alleviation of Parkinson's disease is planned. (BBB)
- Research Organization:
- Massachusetts General Hospital, Boston
- NSA Number:
- NSA-18-003668
- OSTI ID:
- 4131373
- Journal Information:
- Transactions of the American Neurological Association (U.S.), Vol. Vol: 87; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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