Cardiac MRI

What it does

Cardiac MRI reads a complete CMR study: cine short-axis and long-axis stacks, late gadolinium enhancement and, when acquired, parametric maps, phase-contrast flow and first-pass perfusion. The run contours the left ventricle, myocardium and right ventricle on every cine phase, detects end-diastole and end-systole from the volume curve, and computes volumes, ejection fraction and mass indexed to body surface area.

Tissue characterisation is reported on the AHA 17-segment model: scar extent and transmurality on LGE with an ischaemic or non-ischaemic pattern, segmental native T1, T2 and extracellular volume, and perfusion defects. Flow, shunt ratio and strain complete the study, and the sections combine into a pattern-based differential, including the Lake Louise 2018 criteria for myocarditis.

Intended use

Decision support for physicians reporting CMR, where manual contouring is slow and basal-slice and papillary-muscle choices change EF and mass: reproducible volumes, segmental tissue values and a viability map after myocardial infarction.

Who it is for

Cardiologists and radiologists who report CMR, imaging fellows, heart-failure and cardiomyopathy clinics, and interventional teams who need segmental transmurality before revascularising a stenosed territory. Developers call the run to add CMR quantification to a cardiovascular PACS or registry.

Accepted input

• DICOM MR study (MR Image, Enhanced MR or Legacy Converted Enhanced MR) as a zip or by DICOMweb STOW-RS. Cine series are split by TriggerTime and CardiacNumberOfImages.
• Vendor maps: inline T1, T2 and quantitative perfusion maps are read when present.
• Each series is recognised as cine, LGE, T1 or T2 map, phase contrast or perfusion from its acquisition parameters.

Requirements

Requirement	Why
Short-axis cine stack covering both ventricles	Volumes, EF and mass
2-, 3- and 4-chamber cine (optional)	Atria, long-axis function and strain
LGE short-axis	Scar, transmurality and microvascular obstruction per segment
Native T1 and T2 maps (optional)	Segmental T1 and T2; post-contrast T1 with a haematocrit adds ECV
2D phase contrast with a valid VENC (optional)	Flow volumes, regurgitant fraction, Qp:Qs; aliasing is checked
Stress and rest first-pass perfusion (optional)	Segmental perfusion defects

Optional context

Height and weight index volumes and mass to body surface area. A same-day haematocrit is needed for ECV. The indication (chest pain, suspected myocarditis, cardiomyopathy, viability) shapes the differential. T1 and T2 values are compared with local normal ranges, because mapping values are scanner- and sequence-specific.

The result

Section	Content
Chamber segmentation	LV, myocardium and RV masks on every cine phase, plus atria on long-axis views
Ventricular function	LV and RV EDV, ESV, SV and EF, LV mass, indexed to BSA and flagged against reference ranges
Late gadolinium enhancement	Scar mask, scar as % of LV mass, transmurality per segment, ischaemic or non-ischaemic pattern, microvascular obstruction
T1, T2 and ECV mapping	Myocardial masks on the maps, per-segment native T1, T2 and ECV against local normal ranges
Stress perfusion	Perfusion defects per AHA segment; myocardial blood flow when vendor quantitative maps are supplied
Phase-contrast flow	Vessel contour, forward and backward volume, regurgitant fraction, peak velocity, Qp:Qs
Myocardial strain	Global and segmental longitudinal, circumferential and radial strain
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

Standards

• DICOM: multi-frame SEG for cine contours, SR TID 1500 with measurements per AHA segment, Parametric Map for T1, T2 and ECV, KOS key images and Encapsulated PDF. The result carries an aha_segments block.
• Post-processing: SCMR 2020 recommendations for contouring, volumes, LGE and flow.
• Mapping: SCMR 2017 T1/T2/ECV mapping consensus; Lake Louise 2018 criteria for myocarditis.
• Segments: AHA 17-segment model for LGE, mapping, perfusion and strain.

Reading the result

Volumes and mass are reported in absolute terms and, with height and weight, indexed to BSA. Quantitative maps are kept in physical units (ms for T1 and T2, % for ECV) and are never intensity-normalised.