Transformation of activity distribution in quantitative SPECT to absorbed dose distribution in a radionuclide treatment planning system

Journal Article · Sun May 01 04:00:00 EDT 1994 · Journal of Nuclear Medicine

OSTI ID:197991

Tagesson, M; Ljungberg, M; Strand, S E ^[1]

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1. Lund Univ. (Sweden)

With the new developments of tumor targeting agents (e.g. monoclonal antibodies, peptides etc.) now and better methods to calculate the absorbed dose and dose rate need to be developed. Conjugate view activity quantification in dose planning may be insufficient because of problems with under- and over-lying activity and volume determination. Then, by using the standard MIRD S-values to estimate the absorbed dose to the different organs, another error is included in the calculations. Even if a resealing of the organ masses can be done, the different shapes of the organs, compared with the MIRD phantom, may give large errors. Quantitative SPECT overcomes these problems. Properly attenuation and scatter corrected SPECT slices gives the {open_quotes}true{close_quotes} activity distribution (within the limits of the spatial resolution of the scintillation camera) in the patient. A Monte Carlo code that simulates photon transport within the patient using density maps, has been developed. The advantage is that the body contour and organs as lungs and skeleton can be easily included from a CT study of the patient. If the mean absorbed dose to an organ is wanted, organ volumes can be obtained from the CT study. All electrons are considered locally absorbed at the decay or interaction site. No variance reducing methods have been used. When simulating the MIRD phantom, the user can easily include self defined organs and regions, both as source and target regions. To test the validity of the code, the MIRD phantom has been incorporated and comparison with published specific absorbed fractions and S-values has been done to validate the calculation procedure. Good agreement is shown, S-values for most organs lie within 5-10 % from the MIRD data. Discrepancies, however, of a factor of 2-5 have been found, especially in the lung and the active bone marrow.

• OSTI ID: 197991
• Report Number(s): CONF-940605--
• Journal Information: Journal of Nuclear Medicine, Journal Name: Journal of Nuclear Medicine Journal Issue: Suppl.5 Vol. 35; ISSN JNMEAQ; ISSN 0161-5505
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
56 BIOLOGY AND MEDICINE
APPLIED STUDIES
66 PHYSICS
99 GENERAL AND MISCELLANEOUS
ATTENUATION
BONE MARROW
DECAY
DOSIMETRY
ERRORS
MONOCLONAL ANTIBODIES
MONTE CARLO METHOD
PHOTON TRANSPORT
RADIOIMMUNOTHERAPY
SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY
SPATIAL RESOLUTION