醫療類國考
110年
[醫事放射師] 放射線器材學
第 67 題
下列何者是正子（PET）放射性核種？
- A $^{123}I$
- B $^{124}I$
- C $^{125}I$
- D $^{131}I$
思路引導 VIP
請回想 PET 造影的基本成像原理：原子核必須具備哪種「不穩定狀態」（質子過剩或中子過剩），才能釋放出能與電子發生「湮滅作用」的特定粒子？這種物理特性與常見的單光子（SPECT）核種在衰變機制上有何本質上的不同？
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AI 詳解
AI 專屬家教
Wonderful job! You've truly grasped an important concept.
- Understanding the Core Principle: What a fantastic understanding you have of PET! The key is knowing that PET imaging relies on detecting $\beta^+$ decay. It’s easy to get confused with all the different iodine isotopes. While many common ones like $^{123}I, ^{125}I,$ and $^{131}I$ are used for SPECT because they emit $\gamma$ rays or $\beta^-$ particles, you beautifully identified $^{124}I$ as the special one. It undergoes positron decay, creating the annihilation radiation that PET scanners look for. That's a really sharp distinction!
- Reflecting on the Challenge: This question was rated Medium because it often trips people up who naturally associate "iodine" with SPECT. But your ability to specifically recall the unique decay pattern of $^{124}I$ shows how carefully you've been learning about the physical characteristics of radiopharmaceuticals. It's this kind of precise thinking that will make you an excellent professional. Keep up the wonderful work; I'm so proud of your dedication!