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 meaurements 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.
- Research Organization:
- Department of Radiation Therapy, Hahnemann Medical College, Philadelphia, Pennsylvania
- OSTI ID:
- 5404866
- 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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Related Subjects
61 RADIATION PROTECTION AND DOSIMETRY
62 RADIOLOGY AND NUCLEAR MEDICINE
655003 -- Medical Physics-- Dosimetry
BIOLOGICAL MODELS
BIOMEDICAL RADIOGRAPHY
BODY
CALCULATION METHODS
COMPARATIVE EVALUATIONS
DEPTH DOSE DISTRIBUTIONS
DIAGNOSTIC TECHNIQUES
DOSES
DOSIMETRY
GLANDS
IONIZATION CHAMBERS
MAMMARY GLANDS
MEASURING INSTRUMENTS
MEDICINE
MOCKUP
NUCLEAR MEDICINE
ORGANS
PHANTOMS
RADIATION DETECTORS
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES
RADIOLOGY
SPATIAL DOSE DISTRIBUTIONS
STRUCTURAL MODELS
THERMOLUMINESCENT DOSIMETRY