RT Journal Article
SR Electronic
T1 In Vivo Evaluation and Dosimetry of <sup>123</sup>I-2-Iodo-<span class="sc">d</span>-Phenylalanine, a New Potential Tumor-Specific Tracer for SPECT, in an R1M Rhabdomyosarcoma Athymic Mouse Model
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 2104
OP 2111
VO 46
IS 12
A1 Veerle Kersemans
A1 Bart Cornelissen
A1 Klaus Bacher
A1 Ken Kersemans
A1 Hubert Thierens
A1 Rudi A. Dierckx
A1 Bart De Spiegeleer
A1 Guido Slegers
A1 John Mertens
YR 2005
UL http://jnm.snmjournals.org/content/46/12/2104.abstract
AB Earlier reports described the preferential uptake of d-amino acids in tumor-bearing mice. Moreover, it was shown that in tumor cells in vitro the l-amino acid transporter system seemed to lack stereospecificity. Because of the successful results with 123/125I-2-iodo-l-phenylalanine, 123/125I-2-iodo-d-phenylalanine was developed, and its tumor-detecting characteristics were evaluated in vivo. Methods: 123I labeling of 2-iodo-d-phenylalanine was performed with a kit formulation by use of Cu1+-assisted nucleophilic exchange. 123I-2-Iodo-d-phenylalanine was evaluated in R1M tumor–bearing athymic mice by dynamic planar imaging (DPI) and dissection. The in vivo stability of the tracer was tested by high-performance liquid chromatography. Tumor tracer retention and tracer contrast were evaluated as a function of time. Two-compartment blood modeling from DPI results and dosimetric calculations from biodistribution results were carried out. Moreover, 125I-2-iodo-d-phenylalanine and 18F-FDG uptake in acute inflammation was investigated. Results: 123I-2-Iodo-d-phenylalanine was metabolically stable. Fast, high, and specific tumor retention was observed. Two-compartment modeling confirmed the fast clearance of the tracer through the kidneys to the bladder, as observed by DPI and dissection. Moreover, compared with the l-isomer, 123I-2-iodo-d-phenylalanine demonstrated faster clearance and faster uptake in the peripheral compartment. No accumulation in the abdomen or in the brain was noted. Dosimetry revealed that 123I-2-iodo-d-phenylalanine demonstrated a low radiation burden comparable to those of 123I-2-iodo-l-phenylalanine and 123I-2-iodo-l-tyrosine. Although 123I-2-iodo-d-phenylalanine showed a tumor retention of only 4%, the tumor contrast was increased up to 350% at 19 h after injection. Conclusion: 123I-2-Iodo-d-phenylalanine is a promising tracer for diagnostic oncologic imaging because of its high, fast, and specific tumor uptake and fast clearance from blood.