Which of the following is the least sensitive in preoperative imaging of parathyroid in Primary hyperparathyroidism?
**Core Concept**
Primary hyperparathyroidism is often caused by a single parathyroid adenoma, and preoperative imaging plays a crucial role in localizing the abnormal gland. **Imaging modalities** such as ultrasound, sestamibi scan, CT, and MRI are used to identify the affected parathyroid gland.
**Why the Correct Answer is Right**
The correct answer is related to the sensitivity of various imaging modalities in detecting parathyroid adenomas. Generally, **ultrasound** and **sestamibi scan** are considered highly sensitive, while **MRI** and **CT** have varying degrees of sensitivity.
**Why Each Wrong Option is Incorrect**
**Option A:** Ultrasound is a highly sensitive and specific modality for parathyroid imaging, especially for adenomas located near the thyroid gland.
**Option B:** Sestamibi scan is also highly sensitive, especially when combined with single-photon emission computed tomography (SPECT).
**Option C:** CT scan, although less sensitive than ultrasound and sestamibi scan, can still be useful in certain cases, especially when ectopic glands are suspected.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that **ultrasound** is often the first-line imaging modality due to its high sensitivity, non-invasiveness, and lack of radiation exposure.
**Correct Answer:** D. MRI