Afterloading source

It has been proposed that NO mediates the myocardial depression associated with sepsis (F6, L14). NO synthesis induced by endotoxin blunts beta-adrenergic responsiveness (B2). In vivo, the use of NO synthase inhibitors led to conflicting results (M26), with a general decreased cardiac output and oxygen delivery being observed. NO synthase inhibition improved left ventricular contractility in endo-toxemic pigs but also increased ventricular afterloads, which ultimately is detrimental to cardiac function (H20). Possible sources of NO in the heart may be the vascular cells, the endothelial cells, and the cardiac myocytes (P6). 

Brachytherapy Sources. The first 252cf sources for radiotherapy research were prepared at SRL about fourteen years ago (4 5). Initially, these sources resembled the classical radium needles familiar in clinical radiotherapy. Eventually, afterloading cells and applicator tubes were supplied to medical evaluators, and all medical sources were improved by the use of californium-palladium cermet wire sheathed in Pt - 10% Ir alloy (6, 7). The most recent designs for medical sources produced in quantity for therapy research are line sources and point sources containing a range of Cf from iess than 1 yg to 200 yg (Figures 9 and 10). 

The purpose of the development work at SRL is to prepare physically small, yet intense 252 f sources for remote afterloading brachytherapy research. Remote afterloading is used by many hospitals to avoid radiation exposure to medical and hospital personnel. 

Typically, a remote afterloader is a shielded cell or treatment room. Long cables pass through the wall of the room from an operating station outside the room to a patient treatment position inside the room. Radioactive sources are attached to the cables at the patient treatment position. With the patient in the treatment room and the shielded room door closed, the sources are advanced to the treatment position in previously installed applicators by means of the cables and a mechanism in the control system outside the treatment room wall. Our goal was to adapt sources containing up to 200 yg of 252 f to use in these remote afterloaders. 

Using the same process, we prepared and shipped three nominal 200 yg 252cf sources to the Keio University School of Medicine in Tokyo, Japan for evaluation in the Toshiba Electric Co., Ltd. afterloader. Three additional sources are currently being fabricated for the same evaluator. 

Permar, P. H. Walker, V. W. "Californium-252 Radiotherapy Sources for Interstitial Afterloading," USAEC Report CONF-760436, Proceedings of the Paris Symposium of the International Symposium on Californium-252 Utilization,... 

The heart is the energy source that is responsible for pumping the total blood flow (Q) around the body. As stated above, the preload, afterload, cardiac con-... 

To overcome these technical limitations of lORT we developed a technique for high-dose-rate (HDR) irradiation of liver metastases using an afterloading method with a iridium source sited using CT-guided percutaneous applicator placement with dosimetry using three-dimensional CT data sets. 

---