Irradiators: Digital Research Irradiator

Stellarray’s Digitally Addressable Research Irradiator (DARI) is a multi-spot x-ray system that will accelerate experimentation and enrich data sets in radiobiology, radiochemistry and medical research. DARI allows the researcher to selectively irradiate samples in any well in a 96-well plate with variation of the energy, dose, dose rate and exposure time between wells. Existing isotope and x-ray tube irradiators don’t allow variation between wells, and the actual dose to each is affected by the contents of adjacent cells, distance from the radiation source and other factors, so it’s hard to know what the dose really is for each sample. This wastes time, diminishes accuracy and makes it cumbersome to develop relative biological effectiveness curves, since each point on the curve requires separate sample preparation and exposure.

With DARI, researchers will place a standard 96-well plate on top of a collimator in the sample chamber. The collimator includes alignment features to precisely register the location of each well and ensure that the collimated x-ray flux beam for each gets to the right well. The sample chamber may be configured with temperature and atmosphere controls to maintain the environment of biological samples. The user can program the system with a touch screen or a PC interface to irradiate the wells individually, sequentially or in user-programmed groups. X-ray filters can be placed on top of the collimator, across the entire 96-spot array or at individual spots.

The heart of DARI is the specially designed Research Irradiator X-ray Source (RIXS). The DARI-96 irradiator uses a source made with an 8 x 12 spot format, with up to 100 kV (later 160 kV) and 2 mA per x-ray spot. Each spot has a 7 mm flux exit diameter and the pitch between spots is 9 mm, corresponding to the standard format of a 96-well plate. X-ray flux to the wells can be pulsed or delivered in DC mode for prolonged periods. In the small volumes of a micro-well, high doses can be delivered very quickly. Air-cooling with internal fans transfers heat from the anode, through the source module and out the cabinet. DARI features a built-in high voltage power supply and control system. Dose readings are provided by precise voltage and current feedback for each spot. Verification can be with alanine, film or ion chamber dosimeters. The standard shielded cabinet for DARI-96 is being made so it can easily fit on a desk or bench. Sources and collimators for other well-plate or sample array formats can also be made.