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Fiberglass limb phantoms: Fabrication and use for quantitative scintigraphy
Author(s) -
Bading James R.,
DiResta Gene R.,
Corbally Martin T.,
Conlon Kevin C.
Publication year - 1988
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 - 10.1118/1.596274
Subject(s) - scintigraphy , medical physics , fabrication , biomedical engineering , nuclear medicine , medical imaging , medicine , materials science , radiology , alternative medicine , pathology
Quantitative radionuclide scintigraphy often requires empirical calibration factors derived from phantoms which simulate the radioactivity distribution, tissue geometry and tissue composition of the region of interest. This paper describes a method in which casts made with fiberglass tape are used to form realistic, water‐fillable phantoms of the limbs. Phantoms were constructed for the hind legs of the dog and rabbit, species frequently used in developing new radioscintigraphic techniques. Leg bones removed from euthanized animals were mounted anatomically within the casts. The dimensions of the phantom cavities were determined by x‐ray computed tomography. A procedure was developed for orienting the phantoms to match the hind leg geometry of a given experimental setup. Use of the phantoms for image activity calibration is illustrated for a geometric‐mean counting technique used to determine 99 m Tc activity densities in soft‐tissue regions of the dog thigh. Generalization of the calibration technique to planar and tomographic imaging is straightforward. Insitu measurements of 99 m Tc activity density obtained by external counting were compared with in vitro radioassays of excised tissue. For 22 tissue samples obtained from four dogs, the in situ and in vitro data were linearly correlated ( r =0.98, p ≪0.001) over a 50‐fold range of activity density. The mean and standard deviation of the observed percent discrepancies [% discrepancy=100( in situ − in vitro )/ in vitro ] were (7.8±2.9) and (13.7±2.1), respectively. A supplementary investigation indicated that the discrepancies resulted from a combination of various, individually small sources of error. In conclusion, durable phantoms with cavities closely simulating the irregular outer contours of the limbs can readily be fabricated with fiberglass tape in the laboratory setting. Use of such phantoms permits measurement of regional activities in the limbs with an average error of <15%.