臺灣冷凍大體PMCT影像異常與退冰因素之實驗分析

Abstract

本研究的動機來自影像中心在實務中觀察到的現象：許多冷凍大體在退冰後未能完全解凍，這情況經常讓影像判讀變得困難，有時甚至影響最終診斷結果。目前對於如何處理這類問題，尚缺乏一致標準，導致大體退冰操作與結冰影像判讀缺少清晰的指引。為深入了解這方面的問題，本研究整理並分析影像中心累積的相關案例資料，同時設計動物實驗，探討冷凍時間、退冰時間、體表溫度與實際退冰狀態之間的關聯，期望能為實務工作提供參考。 研究內容分為兩部分，第一階段回顧分析影像中心的冷凍案例，記錄體表溫度，並與相應器官的影像密度進行比對，觀察體表溫度變化與內部解凍狀態的關係；第二階段使用不同冷凍時間的豬隻樣本，在退冰過程中監測體表溫度，並進行死後電腦斷層掃描（PMCT），比較冷凍前後的組織密度、是否出現分層現象及冰晶的變化。實驗結果顯示，退冰不完全的影像中可見異常的密度分層與冰晶，這些現象可能模糊器官邊界、影響密度判讀的準確性。體表溫度主要反映表層情況，在評估深層組織的解凍程度上，參考價值有限。雖然研究結果指出，冷凍時間與退冰時間呈現正相關，即冷凍時間越長，退冰所需時間也越長，但動物實驗的結果尚難直接推論至人體案例，解釋時需要格外謹慎。 綜合上述發現，為了避免冷凍保存對影像品質造成的不利影響，本研究的結論是，在實務操作中處理需影像分析的大體時，應以冷藏保存取代冷凍保存以最大程度確保判讀的準確性。

This study stemmed from an observation in practice at the imaging center: many frozen cadavers don't fully thaw after defrosting. This condition often complicates image interpretation and can even affect diagnostic outcomes. Standardized protocols for these issues are currently lacking, which leads to unclear guidelines for cadaver defrosting procedures and for interpreting images from subjects that are frozen or incompletely thawed. To address this, this study analyzed accumulated case data from the imaging center and conducted animal experiments to explore the connections between freezing duration, thawing duration, body surface temperature, and actual thawing status, aiming to offer practical guidance. The study had two parts. Part one retrospectively analyzed frozen cadaver cases from the imaging center, correlating recorded body surface temperatures with the imaging densities of their corresponding organs to examine the relationship between surface temperature changes and internal thawing progress. Part two used porcine samples with varying freezing times. During thawing, their surface temperatures were monitored, and Postmortem Computed Tomography (PMCT) was performed to compare tissue densities before and after freezing, the presence of stratification, and changes in ice crystals. The results indicated that incompletely thawed images showed abnormal density stratification and ice crystals, which could obscure organ boundaries and affect the accuracy of density interpretation. Body surface temperature mainly reflected surface conditions and had limited value in assessing the thawing state of deep tissues. While the results suggested a positive correlation between freezing and thawing times (longer freezing meaning longer thawing), the extrapolation of animal experiment findings to human cases requires great caution. In conclusion, to reduce the negative effects of frozen storage on image quality and ensure the best possible interpretive accuracy, this study recommends choosing refrigerated storage over frozen storage for cadavers that require imaging analysis in practice.