Clinical Dosemeter
Introduction
It comprises of a 0.2cm3 air equivalent ionization chamber detector coupled by a 2� metre long low noise triaxial cable to a solid state electrometer using an ultra-low bias current (75 fA) operational amplifier. The low current from the chamber ( 10-13 to 10-11 A) is measured and calibrated in terms of gamma exposure rate on three ranges : 0 -50 R/hr; 0-150R/hr; 0-250 R/hr. The graduated and specially shaped stiffening tube over the detector and part of cable enables easy insertion and monitoring at any position in the rectum.
The required voltages for the amplifier are obtained from a DC-DC converter. The instrument operates on standard flashlight batteries.
Specifications
Detector |
: |
Ionization chamber of volume 0.2 cc (approx), connected to the end of a 2� metre long triaxial cable. A graduated metallic stiffening tube is provided over the chamber and part of the cable. |
Range of exposure rate |
: |
Three linear ranges of 50,150 and 250 R/hr full scale. |
Display |
: |
0-50 micro amp. moving coil meter |
Accuracy |
: |
� 10% of full scale for Co-60 gamma rays. |
Response Time |
: |
15 Sec.(appro). For full scale |
Batteries |
: |
3 x 1.5 V cells (Eveready type 1050 or equivalent) |
Battery life |
: |
Practically shelf life for intermittent use. |
Accessory |
: |
Stiffening tube to protect the chamber especially while inserting into body cavity. |
Application Areas
- To measure dose rates in bladder and rectum of patients undergoing treatment with Cobalt or Cesium implants for carcinoma of uterine cervix.
- To measure dose rates in other body cavities.
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For further information please contact
Head, Technology Transfer & Collaboration Division,
Bhabha Atomic Research Centre,
Trombay, Mumbai- 400 085
Tel : 091-022-25593897
Fax : 091-022-25505151 / 25519613
Email : headttcd@barc.gov.in
