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Background <p>Technetium-99m-pyrophosphate (<sup>99m</sup>Tc-PYP) planar scintigraphy, a core modality of cardiac amyloid radionuclide imaging (CARI), is a widely established noninvasive technique for diagnosing transthyretin cardiac amyloidosis (ATTR-CA). However, the diagnostic contribution of semi-quantitative uptake indices and extracardiac tracer distribution remains incompletely defined.</p> Objective <p>To evaluate the diagnostic performance of semi-quantitative planar <sup>99m</sup>Tc-PYP scintigraphy in patients with suspected ATTR-CA, including analysis of extracardiac uptake and temporal stability.</p> Methods <p>In this retrospective study, 174 consecutive patients referred for <sup>99m</sup>Tc-PYP scintigraphy were analyzed. Inclusion was based on heart failure symptoms and echocardiographic findings suggestive of CA (e.g., wall thickness ≥ 12&#xa0;mm). Heart-to-contralateral lung (H/CL) and heart-to-mediastinum (H/M) ratios were measured from anterior and left-lateral planar images at 1 and 3&#xa0;h post-injection. Extracardiac tracer uptake was quantified using soft tissue-to-rib ratios at shoulder, elbow, axilla, and liver sites. Final diagnosis was determined by histopathology and/or validated non-biopsy clinical criteria.</p> Results <p>H/CL and H/M ratios demonstrated excellent diagnostic performance for identifying ATTR-CA, with AUCs of 0.97 and 0.88, respectively (0.98 and 0.93 in the histologically confirmed subgroup). Both indices were strongly correlated (<i>r</i> &gt; 0.8). H/M values were stable across timepoints (<i>p</i> = 0.22), while H/CL showed a slight but statistically significant decline (1.4 vs. 1.3, <i>p</i> = 0.01). Patients with confirmed ATTR-CA had significantly higher myocardial and selected extracardiac uptake ratios (e.g., elbow/rib, axilla/rib) compared with non-ATTR individuals (<i>p</i> &lt; 0.05).</p> Conclusion <p>Semi-quantitative <sup>99m</sup>Tc-PYP planar scintigraphy provides high diagnostic accuracy for ATTR-CA, with the 1-h H/CL ratio showing the highest performance. Lateral H/M projections offer stable measures that improve confidence in cases with sternal overlap. While extracardiac uptake reflects systemic involvement, it currently serves as a hypothesis-generating marker. Incorporating these semi-quantitative metrics into routine workflows supports objective, clinically actionable assessment and may reduce the need for invasive histological confirmation.</p>

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Diagnostic utility of semi-quantitative planar scintigraphy in ATTR cardiac amyloidosis: timepoint analysis and extracardiac tracer distribution

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月7日

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  • Aiganym Imakhanova,
  • Reiko Ideguchi,
  • Moldir Zhapparova,
  • Hiroaki Kawano,
  • Koji Maemura,
  • Takashi Kudo

摘要

Background

Technetium-99m-pyrophosphate (99mTc-PYP) planar scintigraphy, a core modality of cardiac amyloid radionuclide imaging (CARI), is a widely established noninvasive technique for diagnosing transthyretin cardiac amyloidosis (ATTR-CA). However, the diagnostic contribution of semi-quantitative uptake indices and extracardiac tracer distribution remains incompletely defined.

Objective

To evaluate the diagnostic performance of semi-quantitative planar 99mTc-PYP scintigraphy in patients with suspected ATTR-CA, including analysis of extracardiac uptake and temporal stability.

Methods

In this retrospective study, 174 consecutive patients referred for 99mTc-PYP scintigraphy were analyzed. Inclusion was based on heart failure symptoms and echocardiographic findings suggestive of CA (e.g., wall thickness ≥ 12 mm). Heart-to-contralateral lung (H/CL) and heart-to-mediastinum (H/M) ratios were measured from anterior and left-lateral planar images at 1 and 3 h post-injection. Extracardiac tracer uptake was quantified using soft tissue-to-rib ratios at shoulder, elbow, axilla, and liver sites. Final diagnosis was determined by histopathology and/or validated non-biopsy clinical criteria.

Results

H/CL and H/M ratios demonstrated excellent diagnostic performance for identifying ATTR-CA, with AUCs of 0.97 and 0.88, respectively (0.98 and 0.93 in the histologically confirmed subgroup). Both indices were strongly correlated (r > 0.8). H/M values were stable across timepoints (p = 0.22), while H/CL showed a slight but statistically significant decline (1.4 vs. 1.3, p = 0.01). Patients with confirmed ATTR-CA had significantly higher myocardial and selected extracardiac uptake ratios (e.g., elbow/rib, axilla/rib) compared with non-ATTR individuals (p < 0.05).

Conclusion

Semi-quantitative 99mTc-PYP planar scintigraphy provides high diagnostic accuracy for ATTR-CA, with the 1-h H/CL ratio showing the highest performance. Lateral H/M projections offer stable measures that improve confidence in cases with sternal overlap. While extracardiac uptake reflects systemic involvement, it currently serves as a hypothesis-generating marker. Incorporating these semi-quantitative metrics into routine workflows supports objective, clinically actionable assessment and may reduce the need for invasive histological confirmation.