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SU‐FF‐T‐282: Development of a Multi Electrode Well Ionization Chamber to Be Used in Nuclear Medicine
Author(s) -
Takeda F,
Santos M,
Vieria J,
Calvo W,
Netto T Ghilardi,
Nicolucci P
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3181759
Subject(s) - ionization chamber , materials science , electrode , saturation (graph theory) , argon , analytical chemistry (journal) , ionization , linearity , voltage , volume (thermodynamics) , nuclear medicine , atomic physics , chemistry , ion , physics , medicine , mathematics , organic chemistry , combinatorics , chromatography , quantum mechanics
Purpose: Development and perform preliminary test of a multi electrode well ionization chamber to be used in Nuclear Medicine. Method and Materials: The well ionization chamber wall was constructed in stainless stell (ANSI 304). The well has 72mm‐diameter and 238mm‐height with a wall thickness of 0.5mm. The external dimensions are 168mm‐diameter and 300mm‐height. The sensitive volume is filled with high pure argon (0.3 Mpa). The electrodes are made with brass and have a multi‐layer paralel configuration allowing low voltage saturation. Sources of 57 Co (∼123MBq), 133 Ba (∼8MBq) e 137 Cs (∼7MBq) were used to study the variation of response with pressure of argon. 99 Tc (∼1GBq) and 131 I (1GBq) sources were used to study response saturation with polarizing voltage (10 to 500V). Sensitivity and linearity of response with activity was studied for 99 Tc (60MBq to 7GBq) and 131 I (220MBq to 4GB). Results: The tests performed with 57 Co, 133 Ba and 137 Cs sources showed that a voltage of 100V already saturates the chamber response. Similar result was also found when 99 Tc and 131 I sources were used. The chamber response is linear (r = 0.999) as a function of activity for the sources and range of activities used. The response repetitivity was better than 99.6% for the activities measured for the 99 Tc and better than 95.2% for the 131 I source. The chamber response in A/MBq was found to be doubled for 131 I when compared to the 99 Tc source. Also the relative sensitivity for the 131 I source was found to be 1.56% the relative sensitivity for the 99 Tc source. Conclusion: The preliminary tests performed show that the response of the developed well ionization chamber is adequate to allow its use in Nuclear Medicine. Aditional tests have still to be performed and Monte Carlo simulation will be used to study construction parameters to optimize its response.