Splenic T1-mapping: a novel quantitative method for assessing adenosine stress adequacy for cardiovascular magnetic resonance

Background: perfusion cardiovascular magnetic resonance (cmr) performed with inadequate adenosine stress leads to false-negative results and suboptimal clinical management. the recently proposed marker of adequate stress,the splenic switch-off sign,detects splenic blood flow attenuation during stress perfusion (spleen appears dark),but can only be assessed after gadolinium first-pass,when it is too late to optimize the stress response. reduction in splenic blood volume during adenosine stress is expected to shorten native splenic t1,which may predict splenic switch-off without the need for gadolinium. methods: two-hundred and twelve subjects underwent adenosine stress cmr: 1.5 t (n = 104; 75 patients,29 healthy controls); 3 t (n = 108; 86 patients,22 healthy controls). native t1spleen was assessed using heart-rate-independent shmolli prototype sequence at rest and during adenosine stress (140 μg/kg/min,4 min,iv) in 3 short-axis slices (basal,mid-ventricular,apical). this was compared with changes in peak splenic perfusion signal intensity (δsispleen) and the “splenic switch-off” sign on conventional stress/rest gadolinium perfusion imaging. t1spleen values were obtained blinded to perfusion δsispleen,both were derived using regions of interest carefully placed to avoid artefacts and partial-volume effects. results: normal resting splenic t1 values were 1102 ± 66 ms (1.5 t) and 1352 ± 114 ms (3 t),slightly higher than in patients (1083 ± 59 ms,p = 0.04; 1295 ± 105 ms,p = 0.01,respectively). t1spleen decreased significantly during adenosine stress (mean δt1spleen ~ −40 ms),independent of field strength,age,gender,and cardiovascular diseases. while δt1spleen correlated strongly with δsispleen (rho = 0.70,p < 0.0001); neither indices showed significant correlations with conventional hemodynamic markers (rate pressure product) during stress. by roc analysis,a δt1spleen threshold of ≥ −30 ms during stress predicted the “splenic switch-off” sign (auc 0.90,p < 0.0001) with sensitivity (90%),specificity (88%),accuracy (90%),ppv (98%),npv (42%). conclusions: adenosine stress and rest splenic t1-mapping is a novel method for assessing stress responses,independent of conventional hemodynamic parameters. it enables prediction of the visual “splenic switch-off” sign without the need for gadolinium,and correlates well to changes in splenic signal intensity during stress/rest perfusion imaging. δt1spleen holds promise to facilitate optimization of stress responses before gadolinium first-pass perfusion cmr. © 2017 the author(s).