Does the presence of high levels of free Sn۲+ in PYP kit causes in vivo red blood cell radiolabeling and high blood pool radioactivity?

Introduction: Technetium-۹۹m-pyrophosphate scintigraphy (TPS) is a highly effective method for diagnosing transthyretin cardiac amyloidosis (ATTR-CA). It may eliminate the need for endomyocardial biopsy. However, the detection of radioactivity in the blood pool (BP) during these scans can make it difficult to interpret planar images. This often leads to the necessity for longer and repeated scanning sessions.Methods: We conducted a prospective study involving unique patients who underwent TPS. The initial group of ۵۸ patients used a pyrophosphate (PYP) kit labeled with ۳۰ mCi (PYP-۳۰) of radioactivity, while the subsequent group had a kit labeled with ۹۰ mCi (PYP-۹۰), although the administrated dose remained constant. This study aimed to assess how varying radioactivity levels in the kits affected BP activity visualization.Results: Univariable analysis showed creatinine level of the patients and added radioactivity amount in the PYP kits affected BP activity (p<۰.۰۵), while gender, age, and BMI did not (p>۰.۰۵). Multivariable analysis confirmed creatinine (OR<۰.۰۰۱) and added radioactivity (OR=۰.۰۰۵) significantly influenced BP visualization. Patients with creatinine<۱.۵ showed a significant difference in BP activity between two groups (PYP-۳۰ and PYP-۹۰), but those with creatinine ≥۱.۵ did not.Conclusion: These findings emphasize the significance of considering the levels of radioactivity in PYP kits, which may be linked to the concentration of free Sn²⁺ in the prepared kit, as well as the patient’s kidney function. These factors are essential for optimizing imaging quality and improving diagnostic accuracy in cases of cardiac amyloidosis.

کلیدواژه ها:

Transthyretin cardiac amyloidosis ، [۹۹mTc]Tc-PYP ، Blood pool activity ، Sn۲+