The relationship between administered radiopharmaceutical activity in myocardial perfusion scintigraphy and imaging outcome

• Published in: European journal of nuclear medicine and molecular imaging Vol. 35; no. 2; pp. 329 - 335
• Main Authors: Robinson, C. N., van Aswegen, A., Julious, S. A., Nunan, T. O., Thomson, W. H., Tindale, W. B., Tout, D. A., Underwood, S. R.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-02-2008; Springer Nature B.V
• Subjects: Aged; Cardiology; Clinical outcomes; Coronary Artery Disease - diagnostic imaging; Dose-Response Relationship, Drug; Female; Humans; Imaging; Male; Medical imaging; Medicine; Medicine & Public Health; Nuclear Medicine; Oncology; Organophosphorus Compounds - administration & dosage; Organotechnetium Compounds - administration & dosage; Original Article; Orthopedics; Pharmacology; Radiology; Radionuclide Imaging; Radiopharmaceuticals - administration & dosage; Reproducibility of Results; Sensitivity and Specificity; Statistics as Topic; United Kingdom > UK; Image quality; MPS; Activity; Radiopharmaceutical; Outcome
• ISSN: 1619-7070; 1619-7089
• DOI: 10.1007/s00259-007-0597-9

Introduction
Lower radiopharmaceutical activities are used for myocardial perfusion scintigraphy (MPS) in the UK than in other countries. There is no evidence to suggest that higher activities improve imaging or clinical outcome.
Materials and methods
We undertook a multicentre study of the relationship between radiopharmaceutical activity and imaging outcome. Fifty-one patients with clinical referrals for MPS followed a 2-day protocol with an injection of 1,000 MBq
99m
Tc-tetrofosmin for each of the stress and rest images. ECG-gated acquisition was performed in three rotations occupying 25, 35 and 40% of a standard acquisition, and rotations were summed to simulate administered activities of 250, 400, 750 and 1,000 MBq. Each set of images was reported by an experienced physician who was blinded to all clinical information and to the simulated activity. Scores were assigned for image quality, low count, attenuation and reconstruction artefact, segmental tracer uptake, segmental and global defect classification, and confidence in the global classification. The images were reported twice to assess intra-observer variability.
Results
Positive relationships were found between administered activity and overall image quality, observer confidence and intra-observer agreement of uptake score, and a negative relationship was found with low-count artefact. For the majority of comparisons, there was no additional improvement with increasing activity from 750 to 1,000 MBq. Intra-observer agreement was found to be better in female patients and in those below average body mass index.
Discussion
We conclude that higher administered radiopharmaceutical activities lead to better quality images and improved surrogate parameters for clinical outcome, but that activities above 750 MBq may be unnecessary in average patients.