Stereotaxic irradiation with a linear accelerator

At least two fundamental requirements must subsist for every stereotaxic radiotherapy treatment: 1) a capacity to administer extremely high doses of radiation to small areas which have been precisely defined in three dimensions; 2) the presence of a steep gradient between adjacent isodose curves so that damage to the tissues close to the target may be reduced to the minimum. The authors have built a special stereotaxic device for the fixing of the head of the patient (together with the chosen intracranial target), once the indispensable neuroradiological evaluations and bioptic controls have been effected, at the isocenter of a linear accelerator (Varian Clinac 4). Once the dimensions of the collimator have been chosen in accordance with the volume and the three dimensional conformation of the target and the dose to be administered has been decided upon in accordance with the histological nature of the lesion, both the linear accelerator and the patient are rotated about the isocenter of the therapy unit. It this way it is possible to reach extremely high dosages with very steep isodose gradients, centered exclusively upon the target ("gamma knife"). The procedure employed is described in full. The dosimetric evaluations which preceded the use of the set-up in clinical practice are illustrated as well. The advantages that this technique offers when compared with interstitial brachytherapy and/or Leksell's radiosurgical procedures are stressed. The described procedure, which is entirely bloodless and thus applicable also to high vascularized lesions, has so far been used in a limited series of cases.     

Radiation dose to the eyes using a "German helmet" field with the 4-MV linear accelerator.

A "German helmet" field defined by depleted uranium or Asarcola blocks was used to reduce the dose to the lens. With the uranium blocks, the lenticular dose was reduced to about 60% of the central axis dose (CAD). The Asarcola blocks reduced the lenticular dose to about 43% of the CAD. Even further reduction (15% CAD) was achieved by tilting the gantry 5 degrees or 10 degrees.     

Therapeutic irradiation of the central nervous system using intrathecal 90Y--DTA.

The erdication of established neuroleukaemia is often difficult, and with subsequent relapses even harder. The use of an intrathecally-injected beta emitting isotope has the advantage of preserving the bone-marrow of the vertebral column and cranium whislt irradiating the meninges. The value of intrathecal 90Y-DTPA(diethylene-triamine penta-acetic acid) has been investigated in nine patients with neuroleukaemia or CNS involvement in malignant lymphoma. Measurements of retention of the isotope in the whole body, spinal, and intracranial subarachnoid spaces have been made, together with blood levels, and are reported. The clinical results are presented. In three out of five evaluable patients 90Y-DTPA failed to maintain a chemotherapy-induced CNS remission and in two out of two evaluable patients malignant cells were not dispersed from the CNS with a single intrathecal injection of 90Y-DTA. It is concluded, therefore, that with this agent and the doses used no useful clinical result is gained.     

微波致中枢神经系统损伤研究进展

目的 综述近年来有关微波致中枢神经系统损伤的研究进展。资料来源与选择 国内外该领域的研究论文及论著。资料引用 引用国内外学术刊物上发表的研究论文及论著。资料综合 就微波导致中枢神经系统损伤的生物效应中的非热效应进行讨论，并在此基础上提出了今后研究所需关注的方面。结论 中枢神经系统对微波的反应比较敏感，长期受其低强度反复作用后，中枢神经系统功能将发生改变，常引起一系列的神经紊乱症状，多数研究结果表明微波对大脑的作用是抑制过程占优势。     

Stereotactic irradiation using a linear accelerator with helmet-type shell

A new method is proposed for external stereotactic and three-dimensional irradiation for a small target in the skull. In this method, we use a special long tube collimator, helmet-type shell (guiding rods are attached to the shell using the CT-stereotactic apparatus) and 10 MV linear accelerator. The patient's head is fixed conservatively by the helmet-type shell. In the phantom experiment, the 90% isodose area was 10 mm in diameter, and the error between the geometrical center of the target and the irradiated center was 2 mm.     

Applications of the intravoxel coherent motion technique to the central nervous system

Phase difference images, obtained by comparing data from motion-sensitized and -unsensitized spin-echo sequences, can be used to study intravoxel coherent motions. The resulting images, which have been routinely used to study fast flowing blood, may potentially yield information about perfused flows and bulk tissue motion. The likely limitations and potential of this technique applied to the central nervous system are reviewed with reference to parallel studies of intravoxel incoherent motion.     

Effects of prophylactic irradiation of acute lymphoblastic leukemia in the central nervous system of children

The development of prophylactic therapy for acute lymphoblastic leukemia (ALL) in the central nervous system in children has resulted in an improvement of the prognosis and prolongation of patients' lives. On the other hand, late irradiation effects have increased with the improvement of the prognosis. Therefore, there is now an important need to lessen these late effects without deteriorating the prognosis. We have investigated the recurrence rate, the survival rate and the cause of death of ALL patients who were divided into a none prophylactic irradiation group and 15 Gy, 20 Gy and 24 Gy irradiation groups. The results show that the effect of prophylactic irradiation has been more effective in the 20 Gy group than that of the 24 Gy group. Furthermore, brain atrophy and leukoencephalopathy, which were investigated by X-ray CT in long-term survivors of post-prophylactic irradiation without recurrence, have been less in the 20 Gy group than in that of the 24 Gy group. This report presents the result that the most favorable dose for prophylactic irradiation for central nervous system leukemia of ALL in children is 20 Gy by a step-up method.     

Isolated central nervous system vasculitis manifesting as a pseudotumor

Vasculitis is characterized by inflammation of the vessel walls, with or without necrosis, that causes narrowing and occasionally obstruction of the vessels. Vasculitis can be a primary process or it can occur secondary to other disease. Isolated central nervous system vasculitis (ICNSV) is a rare type of primary vasculitis that predominately affects the supratentorial regions. The clinical presentation and imaging findings are unspecific and diagnosis is made by exclusion and biopsy. We present a case manifesting as a pseudotumor in the posterior fossa on computed tomography and magnetic resonance imaging. The diagnosis was after biopsy, and the patient evolved favorably after treatment.     

Femoral-facial syndrome with malformations in the central nervous system

The femoral hypoplasia-unusual facies syndrome (FFS) is a very rare association of femoral and facial abnormalities. Maternal diabetes mellitus has been mainly involved as the causal agent. We report the second case of FFS with anomalies in the central nervous system (CNS) including corticosubcortical atrophy, colpocephaly, partial agenesis of corpus callosum, hypoplasia of the falx cerebri and absent septum pellucidum. The psychomotor development has been normal. We propose that the CNS defects observed in these patients are part of the spectrum of abnormalities in the FFS.