Comparison of ion chamber and TLD dosimetry in mammography
An ionization chamber method has been developed to measure exposure vs depth in a uniform BR 12 ''average breast'' phantom. It employs a Memorial mammography chamber for exit exposure measurements; resulting data is then corrected for backscatter as well as for the exceptionally thin window of this chamber. A careful comparison has then been made with relative exposure vs depth curves obtained using TLD at several mammography beam qualities, for identical exposure factors and SSD values. Use of a correction for residual and background TL signals significantly improved agreement between TLD and ion chamber curves in the 28 to 35 kVp/0.03 mm Mo range of beam quality. Agreement was within +- 5% for the Mo target tube, but TLD readings were 4%--8% higher than ion chamber values for the W/Mo target tube. At Xeromammography energies (45 kVp/1.6 mm Al), corrected TLD curve readings were 6% higher at depth than ion chamber curve values. TLD measurements with 28 to 35 kVp/0.03 mm Mo beams tend to underestimate dosage to the midbreast parenchyma. For example, in a 5 cm ''average breast'', the underestimation ranges from 2%--10% for corrected, 10%--16% for uncorrected TLD readings. Key words: Mammography dosimetry, mammography, thermoluminescent dosimetry, ion chamber dosimetry
- Research Organization:
- Department of Radiation Therapy and Nuclear Medicine, Hahnemann Medical College and Hospital, Philadelphia, Pennsylvania 19102
- OSTI ID:
- 6018643
- Journal Information:
- Med. Phys.; (United States), Journal Name: Med. Phys.; (United States) Vol. 8:6; ISSN MPHYA
- Country of Publication:
- United States
- Language:
- English
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46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
BODY
COMPARATIVE EVALUATIONS
CORRECTIONS
DEPTH DOSE DISTRIBUTIONS
DOSEMETERS
DOSES
DOSIMETRY
GLANDS
IONIZATION CHAMBERS
LUMINESCENT DOSEMETERS
MAMMARY GLANDS
MEASURING INSTRUMENTS
MOCKUP
ORGANS
PHANTOMS
RADIATION DETECTORS
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES
SPATIAL DOSE DISTRIBUTIONS
STRUCTURAL MODELS
THERMOLUMINESCENT DOSEMETERS
X-RAY DOSIMETRY