單次閉氣心臟T1圖譜:Hybrid MOLLI與MOLLI53之比較

Abstract

心肌T1弛緩時間在多種疾病病程中會產生轉變，因此對原始T1數值作定量也許能提供有用的資訊去偵測與評估心肌疾病。目前有許多方法可應用於心肌T1數值的定量，每一種方法都能提供不同的優勢。在本研究中，我們提出一個新的hybrid MOLLI技術，旨在探討新技術與典型MOLLI53技術於影像品質以及T1量測精確度的比較。 此研究中提出新型的hybrid MOLLI是由反轉脈衝與飽和脈衝所組成，藉由反轉脈衝與飽和脈衝的組合，解決磁矩回復時間的需求，進而在T1弛緩曲線上，快速完成影像收取或者獲取更多影像資訊。為了評估與原始MOLLI53序列的優劣，針對仿體與健康受試者進行一系列實驗驗證。 根據實驗結果，hybrid MOLLI與MOLLI53在仿體T1數值的估計上展現良好的精確度，雖然T1數值低估的情況依舊存在，但得到的T1精確度仍能提供足夠的靈敏度去偵測疾病。在心肌T1圖譜上，三種MOLLI技術都能在單次閉氣中完成，而且定量出相似的T1數值並與文獻上的數值一致。而針對特定圈選出來的心肌部分，三種方法在T1精確度上的比較，大約只有百分之三的誤差。 本研究中提出的hybrid MOLLI技術在單次閉氣下展現良好的心臟T1圖譜，並且在仿體和健康受試者的影像品質上與傳統的MOLLI53方法相當。因此，結合反轉脈衝與飽和脈衝的新技術對於廣泛應用的MOLLI序列而言，可提供一個有效的替代方案於T1數值定量上。

Myocardial T1 relaxation time could be altered in various disease states. Therefore, characterization of the native T1 values may provide useful information to detect and assess cardiomyopathies. Numerous approaches have been suggested for quantifying myocardial T1, and each of them provides a different profile of advantages. In this study, we propose a new hybrid MOLLI technique to investigate the image quality and the precision of T1 measurements compared with classical MOLLI53 technique. A novel hybrid MOLLI method introduced in this study comprises an inversion pulse, followed by a saturation pulse. A combination of inversion and saturation pulses can eliminate the need for sufficient recovery of magnetization, thus permitting fast image acquisition or more images to be acquired along the longitudinal relaxation curve. Phantom and healthy subject experiments were performed to evaluate the proposed sequences against the original MOLLI53 sequence. Both hybrid MOLLI and MOLLI53 displayed T1 estimations with good precision which were reproducible when repeating the controlled protocols in phantoms. Although underestimation was visible, the precision of apparent T1 still allowed disease detection with sufficient sensitivity. All three MOLLI techniques had the ability to achieve T1 mapping in a single breath-hold, and yielded similar quantitative values which were consistent with the literature values. Regions-of-interest within the myocardium showed comparable precisions at the level of about 3% errors for the three methods. The hybrid MOLLI techniques proposed in this study have been shown to yield precise T1 mapping in a single breath-hold, with quality comparable to that shown in the conventional MOLLI53 method on phantoms and healthy subjects. It is concluded that the proposed techniques incorporating saturation recovery and inversion recovery are an effective alternative to the widely used MOLLI53 sequence for quantitative T1 mapping in the myocardium.