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The two types of correction of absorbed dose estimates for internal emitters
Article first published online: 12 FEB 2002
Copyright © 2002 American Cancer Society
Supplement: Eighth Conference on Radioimmunodetection and Radioimmunotherapy of Cancer
Volume 94, Issue Supplement 4, pages 1231–1234, 15 February 2002
How to Cite
Williams, L. E., Liu, A., Yamauchi, D. M., Lopatin, G., Raubitschek, A. A. and Wong, J. Y. C. (2002), The two types of correction of absorbed dose estimates for internal emitters. Cancer, 94: 1231–1234. doi: 10.1002/cncr.10290
- Issue published online: 12 FEB 2002
- Article first published online: 12 FEB 2002
- Manuscript Accepted: 14 NOV 2001
- Manuscript Received: 31 OCT 2001
- National Institutes of Health. Grant Numbers: Cancer Center Core Grant 33527, Program Project Grant PO1 CA43904
- absorbed dose;
- Medical Internal Radiation Dose (MIRD);
- internal emitters
Two types of correction for absorbed dose (D̄) estimates are described for clinical applications of internal emitters. The first is appropriate for legal and scientific reasons involving phantom-based estimates; the second is patient-specific and primarily intended for radioimmunotherapy (RIT).
The Medical Internal Radiation Dose (MIRD) relationship (D̄) = S Ã is used, where S is a geometric matrix factor and Ã is the integral of source organ activities. Internal consistency of the data and the size of organ systems in the humanoid phantom must be assured in both types of estimation.
The first dose estimate correction (I) is one whereby computations refer to one or another standard (e.g., MIRD-type) phantom. In this case the S value remains as given, but the measured patient Ã data must be standardized. The correction factor is the phantom's ratio of organ mass to whole-body mass divided by the same ratio for the volunteer or patient. The second dose estimate correction (II) is patient-specific. While the Ã value is unchanged for this application, a correction term is provided for the phantom-derived S matrix. The dominant (nonpenetrating radiation) component of this correction factor can be obtained via the ratio of the patient to phantom organ masses. In both corrections, we recommend that true organ sizes, necessary in each method of estimation, be determined in a separate sequence of anatomic images.
In both dose estimation corrections, true sizes of the patient's or volunteer's internal organs must be obtained. Correction due to organ mass size can be severalfold and is probably the dominant uncertainty in the internal emitter absorbed dose calculation process. Cancer 2002;94:1231–4. © 2002 American Cancer Society.