Use of magnetic tape for recording radioactivity.

Abstract

Radioactive isotopes are frequently used as tracer material for diagnostic purposes. The principle employed for determining rate of blood flow is based on a dilution or elimination rate of the administered tracer dose. Activity rate is measured with a suitable detector and recording system. Interpretation of disappearance curves is at times rendered difficult because of a weak dose of radioactive material introduced into the system or inadequate settings of the rate meter as to scaling and time factors. To obviate loss of valuable data, a recording system that could register all impulses emitted by the detector probe would be of value. These could then be reproduced at leisure through a scaler or integrating rate meter. Commercial tape recorders have proved adaptable for registering radioactive disintegration impulses. Method A suitable detector probe is activated to the proper voltage level by an appropriate power supply source, either from a scaler or rate-meter unit. The output from the scaler or rate meter is directly attached to the microphone input of the tape recorder. The simultaneous use of tape recording does not interfere with the routine recording system obtained directly from a rate meter or while the counting of radioactivity is in progress. Rate Meter 1. Nuclear-Chicago Rate Meter, Labitron, or Survey Meter. The speaker leads, or phone plugs, are tapped and connected directly to the microphone input of the tape recorder (Fig. 1). 2. Picker Rate Meter. The amplifier output, contact point 8 on the J4 amplifier plug in the socket, is tapped and connected to the microphone input of the tape recorder. Settings of the rate meter, sensitivity, and scaling rate are immaterial for magnetic tape recording purposes (Fig. 2). Tape Speed for Recording Tape speed for recording is dependent on activity rate. A three-speed Norelco Phillips tape recorder offers wider flexibility in recording and for replay. Normally a 3 3/4 inch per second tape recording is adequate. Replay of Tape Recording Tape recordings can be replayed by simply connecting the tape recorder output to the input of the rate meter. For counting purposes, it may be connected to the input of a scaler. 1. Nuclear-Chicago Rate Meter (Model #1620): A small Fisher transistor preamplifier is employed. The tape recorder speaker output is connected to the preamplifier input and the preamplifier output to the scaler or rate-meter input (Fig. 3). 2. Nuclear-Chicago Labitron (Model #1619A): No preamplifier is necessary. The recorder output is directly connected to the input. 3. Picker Counting Rate Meter (Model #2805): Tape recorder output is attached directly to the rate-meter preamplifier input; contact point 2 on the J4 amplifier plug in socket. The count rate can be doubled or halved depending on the tape speed at which the recording is replayed. With a replay speed twice the recording speed, counts are doubled and counting time is halved.