Data_Sheet_1_Measurement of T1 Mapping in Patients With Cardiac Devices: Off-Resonance Error Extends Beyond Visual Artifact but Can Be Quantified and Corrected.docx

Background: Measurement of myocardial T1 is increasingly incorporated into standard cardiovascular magnetic resonance (CMR) protocols, however accuracy may be reduced in patients with metallic cardiovascular implants. Measurement is feasible in segments free from visual artifact, but there may still be off-resonance induced error.Aim: To quantify off-resonance induced T1 error in patients with metallic cardiovascular implants, and validate a method for error correction for a conventional MOLLI pulse sequence.Methods: Twenty-four patients with cardiac implantable electronic devices (CIEDs: 46% permanent pacemakers, PPMs; 33% implantable loop recorders, ILRs; and 21% implantable cardioverter-defibrillators, ICDs); and 31 patients with aortic valve replacement (AVR) (45% metallic) were studied. Paired mid-myocardial short-axis MOLLI and single breath-hold off-resonance field maps were acquired at 1.5 T. T1 values were measured by AHA segment, and segments with visual artifact were excluded. T1 correction was applied using a published relationship between off-resonance and T1. The accuracy of the correction was assessed in 10 healthy volunteers by measuring T1 before and after external placement of an ICD generator next to the chest to generate off-resonance.Results: T1 values in healthy volunteers with an ICD were underestimated compared to without (967 ± 52 vs. 997 ± 26 ms respectively, p = 0.0001), but were similar after correction (p = 0.57, residual difference 2 ± 27 ms). Artifact was visible in 4 ± 12, 42 ± 31, and 53 ± 27% of AHA segments in patients with ILRs, PPMs, and ICDs, respectively. In segments without artifact, T1 was underestimated by 63 ms (interquartile range: 7–143) per patient. The greatest error for patients with ILRs, PPMs and ICDs were 79, 146, and 191 ms, respectively. The presence of an AVR did not generate T1 error.Conclusion: Even when there is no visual artifact, there is error in T1 in patients with CIEDs, but not AVRs. Off-resonance field map acquisition can detect error in measured T1, and a correction can be applied to quantify T1 MOLLI accurately.

背景：心肌T1的测量正日益纳入标准心血管磁共振（CMR）协议中，然而，在植入金属心血管植入物的患者中，测量的准确性可能会降低。在无视觉伪影的部位进行测量是可行的，但仍可能存在共振失谐引起的误差。目标：量化金属心血管植入物患者中共振失谐引起的T1误差，并验证一种用于传统MOLLI脉冲序列的误差校正方法。方法：对24例装有心脏植入式电子设备（CIEDs：46%永久性心脏起搏器，PPMs；33%植入式环状记录器，ILRs；和21%植入式心脏除颤器，ICDs）的患者以及31例进行主动脉瓣置换术（AVR）（45%为金属）的患者进行了研究。在1.5T下获取了成对心肌中轴MOLLI和单次呼吸保持下的共振失谐场图。通过AHA分段测量T1值，并排除具有视觉伪影的分段。使用已发表的共振失谐与T1之间的关系进行T1校正。通过在胸部外部放置ICD发生器并在旁边产生共振失谐来检测校正的准确性，在10名健康志愿者中进行测量。结果：与健康志愿者相比，装有ICD的健康志愿者的T1值低估了（分别为967 ± 52 ms和997 ± 26 ms，p = 0.0001），但校正后相似（p = 0.57，残留差异2 ± 27 ms）。在ILRs、PPMs和ICDs患者的AHA分段中，可见伪影的比例分别为4 ± 12%，42 ± 31%，和53 ± 27%。在无伪影的分段中，每位患者的T1值低估了63 ms（四分位数范围：7–143）。ILRs、PPMs和ICDs患者的最大误差分别为79 ms、146 ms和191 ms。存在AVR不会产生T1误差。结论：即使在无视觉伪影的情况下，装有CIEDs的患者T1测量仍存在误差，但AVR则无。共振失谐场图获取可以检测测量T1中的误差，并可应用校正以准确量化T1 MOLLI。