(SMEs add content and update the text below. Thank you.)
Parametric Mapping is a way to measure relaxation time for longitudinal and transverse relaxation time along with extracellular volume. The Native T1 mapping or longitudinal (T1) relaxation time is the time constant which determines the rate at which excited protons return to equilibrium. It is a measure of the time taken for spinning protons to realign with the external magnetic field. The T2 mapping or transverse (T2) relaxation time constant which determines the rate at which excited protons reach equilibrium or go out of phase with each other. It is a measure of the time taken for spinning protons to lose phase coherence among the nuclei spinning perpendicular to the main field. The term "native" means contrast niave in this context. the T2 measurement is only done prior to contrast.
"T1 mapping stands for registering the course of recovery of longitudinal magnetism", this means the relaxation time after either the preparation step (saturation or inversion prepulse) followed by the acquisition of images at several time points during the T1 recover/relaxation. T1 value represents the time when recovery of magnetism has reached a percentage of its original state (63%). The recovery rate relates to the myocardial tissue properties that may be altered by pathological tissue presence (https://www.ahajournals.org/doi/10.1161/circresaha.116.307974). T1 mapping values increase with disease, and decrease post contrast.
- What is the difference between T1 and T2? Should there be any differences in the data collected for each of these? one is longitudinal relaxation time and the other is transverse relaxation time. The results vary by the physics of the MRI. It shows how the protocns relax after a period of excitation. 1.5 Tesla has a different constant than for another type of scanner. It detects edema/fibrosis. Transverse relaxation time - under 49 change to 40 to 50; 50,60 is high.
- Do we need minimum and maximum values? for SI mean, area, circumference, SI mean, SI min/max?- will change depending on the (also changes after contrast)- NA; in the context of research do they collect this - no. Not relevant.
For extracellular volume - use percent. Normal is under 28.5%; Abnormal is in the mid 30%; mid 20%
Post contrast longitudinal relaxation time is 400s to 500s
Post contrast transverse relaxation time is not done
Stopped here -
- Do we need timepoints for the T1 measurement or just the point in time of the final assessment? Not applicable
- Does Cardiac Motion correction need to be indicated? If yes, does the type need to be indicated (such as the modified LL (MOLLI) sequence)? If yes, should this be reflected on each result? (Alana/Jon/Diane - I am considering a "Cardiac Motion Correction Indicator" NSV if this is important)- MOLLI shMOLLI, SHASHA, too much in the weeds. not applicable.
- Three is a "gold" standard noted as the "T1 mapping based on the acquisition of single images by a T1 turbo spin-echo sequence". It is noted as the ultimate T1 mapping method. Does the method need to be called out by what kind of acquisition sequence was used? NA
- For the location does the intracellular compartment need to be noted? (myocytes, fibroblasts, endothelial cells, smooth muscle cells)
- Does the cardiac phase for the specific T1 segment need to be noted? (atrial systole-diastole; isovolumentric contraction-diastole; rapid ejection-systole; reduced ejection-systole; isovolumetric relaxation-diastole; rapid ventricular filling-diastole) - NA, done in diastole
- Is it important to record the "MRI scanner type" (Avanto, Siemens; Best, Philips; Acheiva, Philips), the "reception coil" (16-channel; 32-channel), "the T1 mapping sequence" (MOLLI; ShMOLLI)
The following example shows the parametric mapping (T1 mapping, T2 mapping, and extracellular volume) results for USUBJID 301. For brevity, after contrast a limited sample of tests were shown in this example.
The PR dataset shows the procedure of cardiac magnetic resonance imaging using the device associated with SPDEVID ABC001 and the PRREFID of 12345678. This information shows what CMR device is used for the procedure and the accession number or procedure reference identifier associated with the specific procedure for USUBJID 301. The SPDEVID variable is used to relate records by the device (in this case, the CMR machine). The Device Identifier (DI) dataset holds the device information details, the Device Properties (DO) dataset holds characteristics of the device that do not vary over the between subjects. The Device-In-Use (DU) dataset holds settings that are set on a device when it is used and may vary between participants.
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Notes for discussion
Interslice Distance - aligns with "Gap"
A minimum of 12 slices were performed, with 20 phases/slice... ?
Imaging protocol - would this be put somewhere? It seems like it would be helpful - would a GRPID be used and then defined somewhere? Or, would it be in the study protocol and not required in the data. If aggregating across studies, it seems like it would be helpful to have it in the data.
Number of excitations =2 for breath hold; 4 to 5 for free breathing (what would this DUTEST be?)
Radiofrequency flip angles were set between 50 degrees and 70 degrees
Grid tag spacing was 7 to 8 mm
TE/TR = 3ms/6.6 ms (by type of machiine)
views per segment = views/segment = 7 to 9 based on machine type (one was = 8)
Data analysis was via "standard planimetry techniques" using semi-automated computer software - this is where Medis is mentioned... is this perhaps what should be in ANMETH? Do we have a definition for "Feature Tracking" (in the Circum and Long Strain examples)
https://www.jacc.org/doi/abs/10.1016/j.jacc.2008.12.032 - article is for strain - find one for CMR and Parametric mapping .... if different parameters.
