Radiation dosimetry of (68)Ga-PSMA-11 (HBED-CC) and preliminary evaluation of optimal imaging timing.
OBJECTIVE
The clinical introduction of (68)Ga-PSMA-11 ("HBED-CC") ligand targeting the prostate-specific membrane antigen (PSMA) has been regarded as a significant step forward in the diagnosis of prostate cancer (PCa). In this study, we provide human dosimetry and data on optimal timing of PET imaging after injection.


METHODS
Four patients with recurrent PCa were referred for (68)Ga-PSMA-11 PET/CT. Whole-body PET/CTlow-dose scans were conducted at 5 min, and 1, 2, 3, 4 and 5 h after injection of 152-198 MBq (68)Ga-PSMA-11. Organs of moderate to high uptake were used as source organs; their total activity was determined at all measured time points. Time-activity curves were created for each source organ as well as for the remainder. The radiation exposure of a (68)Ga-PSMA-11 PET was identified using the OLINDA-EXM software. In addition, tracer uptake was measured in 16 sites of metastases.


RESULTS
The highest tracer uptake was observed in the kidneys, liver, upper large intestine, and the urinary bladder. Mean organ doses were: kidneys 0.262 ± 0.098 mGy/MBq, liver 0.031 ± 0.004 mGy/MBq, upper large intestine 0.054 ± 0.041 mGy/MBq, urinary bladder 0.13 ± 0.059 mGy/MBq. The calculated mean effective dose was 0.023 ± 0.004 mSv/MBq (=0.085 ± 0.015 rem/mCi). Most tumor lesions (n = 16) were visible at 3 h p.i., while at all other time points many were not qualitatively present (10/16 visible at 1 h p.i.).


CONCLUSIONS
The mean effective dose of a (68)Ga-PSMA-11 PET is 0.023 mSv/MBq. A 3-h delay after injection was optimal timing for (68)Ga-PSMA-11 PET/CT in this patient cohort.
Department of Nuclear Medicine, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany. a.afshar@gmx.de.|Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center, INF 280, 69120, Heidelberg, Germany. a.afshar@gmx.de.
Ali
A
Afshar-Oromieh
Division of Medical Physics in Radiology, German Cancer Research Center, INF 280, 69120, Heidelberg, Germany.
Henrik
H
Hetzheim
Division of Radiation Protection and Dosimetry, German Cancer Research Center, INF 280, 69120, Heidelberg, Germany.
Wolfgang
W
Kübler
Department of Nuclear Medicine, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany.
Clemens
C
Kratochwil
Department of Nuclear Medicine, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany.
Frederik L
FL
Giesel
Department of Radiology and Biomedical Imaging, University of California, 505 Parnassus Avenue, M-391, Box 0628, San Francisco, CA, 94143, USA.
Thomas A
TA
Hope
Division of Radiopharmaceutical Chemistry, German Cancer Research Center, INF 280, 69120, Heidelberg, Germany.
Matthias
M
Eder
Division of Radiopharmaceutical Chemistry, German Cancer Research Center, INF 280, 69120, Heidelberg, Germany.
Michael
M
Eisenhut
Division of Radiopharmaceutical Chemistry, German Cancer Research Center, INF 280, 69120, Heidelberg, Germany.
Klaus
K
Kopka
Department of Nuclear Medicine, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany.|Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center, INF 280, 69120, Heidelberg, Germany.
Uwe
U
Haberkorn
D000368:Aged; D004492:Edetic Acid / Q000031:analogs & derivatives*; D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging*; D011874:Radiometry; D012008:Recurrence; D012189:Retrospective Studies; D013997:Time Factors; D051598:Whole Body Imaging
D005709:Gallium Isotopes; D005710:Gallium Radioisotopes; D009842:Oligopeptides; C000718244:gallium 68 PSMA-11; D004492:Edetic Acid
Dosimetry; HBED-CC; PET/CT; PSMA-11; Prostate cancer; Prostate-specific membrane antigen