Improvement of Accidental Coincidence Estimation for Scanditronix PC2048/4096 PET Scanners

正子放射斷層造影(positron emission tomography, PET)時隨機產生之意外偶合(accidental coincidence)，或稱隨機事件(randoms)，是降低造影精確度的原因之一。然而，與一般人所以為的情況相反的是，儘管已使用PET廠商所提供的軟／硬體作意外偶合校正，意外偶合仍可能對PET的定量造成顯著影響。本文研究Scanditronix正子斷層掃描儀原廠所提供意外偶合校正方式並提出簡單的修正，藉此求得更佳的結果。方法：以圓柱形做為假體，以兩種不同起始放射強度，但固定的短時間間隔連續收集多筆資料，每次共收集12小時。選擇不同時間區段內不同加總取像時間之所有資料相加的總和，可得八種不同長／短掃描時間及高／低事件計數之資料。藉此我們可以比較原廠方法所估測的隨機事件數與改良後所估測的隨機事件數。結果：當取像時間遠大於放射核種之半衰期時，原廠估測之隨機事件數遠不如修正後所估測之隨機事件數正確。結論：本文中對原廠提供方法所做的簡單修正，可明顯改善對意外偶合的估測。

關鍵字

正子放射斷層造影術；閃爍計數；演算法

並列摘要

Accidental coincidence (randoms) is one of the factors that degrade the accuracy of positron emission tomography (PET). In contrast to widely-held beliefs, we have previously shown that randoms can significantly affect quantitative PET even after current hardware/software randoms correction is applied. In order to have better estimation of randoms for our Scanditronix scanner, we investigated the limitation of the vendor-provided randoms estimation and proposed a simple modification. Methods: Multiple short-frame data of a homogeneous circular cylinder were collected over 12 hours. Summed data were generated by summing up selected frames. Randoms of the summed data estimated by the vendor-provided method and our modified method were compared. Results: The vendor-provided randoms estimation did not work as well as the modified method when frame duration is much larger than the half-life of the radioactive agent used. Conclusion: Our minimal modification of the vendor-provided method significantly improves randoms estimation.

並列關鍵字

Positron emission tomography ； Scintillation counting ； Algorithms

國際替代計量

Improvement of Accidental Coincidence Estimation for Scanditronix PC2048/4096 PET Scanners

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