Cardiac Amyloidosis Imaging, Part 2: Quantification and Technical Considerations

Area of Science:

• Nuclear Medicine
• Cardiology
• Radiology

Background:

• 99mTc-PYP imaging was initially used for myocardial infarction but is now crucial for diagnosing cardiac amyloidosis.
• Increased utilization has highlighted the need for standardized imaging and interpretation protocols.
• Expert consensus recommendations were developed to address procedural variability.

Purpose of the Study:

• To detail the evolution of 99mTc-PYP imaging procedures for cardiac amyloidosis.
• To describe image processing, quantification, and radiotracer kinetics.
• To discuss critical technical considerations like injection-to-imaging delay and imaging modalities (planar vs. SPECT).

Main Methods:

• Standardized protocol involves injecting 370-740 MBq (10-20 mCi) of 99mTc-PYP with imaging at 3 hours.
• Planar chest images (anterior, lateral) and SPECT images are acquired.
• Semiquantitative grading (0-3 scale) of myocardial uptake versus ribs, and heart-to-contralateral-lung ratio calculation.

Main Results:

• A SPECT grade of 2 or 3 is considered positive for cardiac amyloidosis.
• A heart-to-contralateral-lung ratio >1.3 at 3 hours aids in confirming the diagnosis when SPECT findings are positive.
• The standardized protocol aims to benefit most laboratories by optimizing parameters.

Conclusions:

• The standardized 99mTc-PYP imaging protocol, including specific timing and analysis, is essential for accurate cardiac amyloidosis diagnosis.
• Understanding radiotracer kinetics and technical parameters like injection-to-imaging delay is vital.
• This article is part of a series providing comprehensive guidance on cardiac amyloidosis imaging and interpretation.