Nuclear Cardiology (MPI and Cardiac Amyloid)

What it does

Nuclear Cardiology reads the two families of cardiac nuclear exams. Stress/rest myocardial perfusion imaging (MPI) with SPECT or PET is one of the most frequent nuclear-medicine studies and is often read by cardiologists in training. Tc-99m PYP, DPD or HMDP scintigraphy can establish transthyretin cardiac amyloidosis (ATTR-CM) without a biopsy when a monoclonal protein has been excluded.

For an MPI study, the run scores perfusion on the 17-segment model and by coronary territory, separates ischaemia from scar, measures gated left-ventricular function and transient ischaemic dilation and, for dynamic PET, quantifies myocardial blood flow and flow reserve. For an amyloid scan, it returns the Perugini grade, the heart-to-contralateral (H/CL) ratio and the likelihood of ATTR-CM.

Intended use

Decision support for the reader of an MPI or amyloid study: reproducible summed scores and a segment map to check a visual read, and a quantified Perugini grade and H/CL ratio for the heart-failure clinic. Breast and diaphragmatic attenuation, balanced ischaemia in three-vessel disease, extracardiac activity and blood-pool uptake that mimics myocardial PYP uptake are the known pitfalls of these exams.

Who it is for

Nuclear cardiologists, cardiology fellows, nuclear-medicine physicians and radiologists; heart-failure and amyloidosis teams who order PYP, DPD or HMDP scans.

Accepted input

• MPI SPECT: DICOM NM gated and ungated tomographic series for the stress and the rest acquisition.
• MPI PET: DICOM PET stress and rest series, gated, and dynamic series for flow quantification.
• Cardiac amyloid scan: planar anterior chest view plus SPECT or SPECT/CT after PYP, DPD or HMDP.

Requirements

Requirement	Why
Both stress and rest series for MPI	Reversible (ischaemia) versus fixed (scar) defects need the pair
Gated acquisitions	LVEF, volumes, wall motion and thickening
Dynamic acquisition from injection onward (PET)	Myocardial blood flow needs the arterial input and tissue curves
SPECT in addition to the planar view (amyloid)	Separates myocardial uptake from blood-pool activity
Radiopharmaceutical recorded in the header	Tracer-specific normal limits and thresholds

The normal database used for perfusion scores is named with its version in the result.

Optional context

Stress protocol (exercise or pharmacological), symptoms, known coronary disease and prior revascularisation can be passed in clinical_context; they are used in the guidance.

The result

Section	Content
Myocardial perfusion	SSS, SRS and SDS, total perfusion deficit, 17-segment defects, ischaemia versus scar per coronary territory
Gated LV function	LVEF, end-diastolic and end-systolic volumes, transient ischaemic dilation ratio, regional wall motion and thickening
Myocardial blood flow	Stress and rest myocardial blood flow and flow reserve per territory from dynamic PET
Cardiac amyloid scintigraphy	Perugini grade 0–3, H/CL ratio and ATTR-CM likelihood
Draft report	Opt-in (options.report): an English narrative that interprets the result for the reader (findings, impression, limitations); every number is checked against the findings

An MPI study returns the perfusion and function sections, plus blood flow when a dynamic PET is included; an amyloid scan returns the amyloid section.

Standards

• DICOM: SR TID 3300 Stress Testing Report with TID 3307 NM/PET Perfusion Measurement Group and TID 3926 Myocardial Perfusion Analysis; segment coding with CID 3717 Left Ventricle Myocardial Wall 17 Segment Model; stress, rest and reversibility polar maps; Encapsulated PDF.
• Guidelines: ASNC SPECT myocardial perfusion guideline (2016); ASNC/SNMMI PET myocardial perfusion guideline (2016); AHA 17-segment model (2002).
• Cardiac amyloidosis: Perugini grade; H/CL ratio per ASNC; multisociety cardiac amyloidosis imaging consensus (2019/2021).

Scoring notes

Summed scores add the segmental defect scores of the 17-segment model at stress (SSS) and rest (SRS); their difference (SDS) expresses reversible ischaemia. For PYP, an H/CL ratio of 1.5 or more at one hour supports ATTR-CM, and the Perugini grade compares cardiac uptake with rib uptake. Light-chain amyloidosis can also take up these tracers, so the result is read together with the serum and urine tests for a monoclonal protein.

Related models

• nm/bone-scan: flags incidental cardiac uptake on routine bone scans, a common route to a dedicated amyloid scan.