Which is true about Lipoma on USG, MRI & CT
**Question:** Which is true about Lipoma on USG, MRI & CT
A. Lipoma appears as a well-defined, homogeneous, and isoechoic (equally echogenic) lesion on ultrasound (USG)
B. Lipoma does not show enhancement on MRI
C. Lipoma appears as a well-defined, homogeneous, and isointense (same signal intensity) lesion on MRI
D. Lipoma appears as a well-defined, heterogeneous, and hyperintense (higher signal intensity) lesion on T1-weighted MRI sequences
**Correct Answer:** C. Lipoma appears as a well-defined, homogeneous, and isointense (same signal intensity) lesion on MRI
**Core Concept:**
Lipomas are benign, slow-growing tumors derived from adipose tissue. They are characterized by their well-defined borders, homogeneous appearance, and the presence of adipocytes. These tumors consist of mature adipocytes and are typically isointense on MRI sequences.
**Why the Correct Answer is Right:**
MRI is the most reliable imaging modality to visualize lipomas due to their specific characteristics. On MRI, lipomas appear as well-defined, homogeneous, and isointense (same signal intensity) lesions. The isointensity is a result of the presence of fat within the tumor, which has a similar signal intensity to adjacent fat tissue.
**Why Each Wrong Option is Incorrect:**
A. Lipomas are not described as having a homogeneous and isoechoic (equal echogenicity) appearance on ultrasound (USG), making this option incorrect. Lipomas are typically not visualized on USG due to their location (usually subcutaneous or intramuscular) and the limited ability of USG to visualize adipose tissue.
B. Lipomas do not show enhancement on MRI, but they are not described as heterogeneous and hyperintense (higher signal intensity) on T1-weighted MRI sequences, making this option incorrect. Lipomas show a homogeneous signal intensity on T1-weighted sequences, not hyperintensity.
D. Lipomas are not described as heterogeneous and hyperintense (higher signal intensity) on T1-weighted MRI sequences, making this option incorrect. Lipomas show a homogeneous signal intensity on T1-weighted sequences, not hyperintensity.
**Clinical Pearl:**
MRI is the preferred imaging modality for evaluating lipomas, as it can accurately depict their signal intensity and borders. Ultrasound and computed tomography (CT) scans are less sensitive in detecting lipomas due to their low signal intensity on these modalities. However, ultrasound may occasionally be useful in assessing the size and borders of the tumor.