**Question:** All of the following investigations are used in FIGO staging of carcinoma cervix except:

A. Chest X-ray
B. Computed Tomography (CT) scan
C. Ultrasonography (USG)
D. Magnetic Resonance Imaging (MRI)

**Core Concept:**
FIGO staging is a system used to stage cancer, specifically cervical cancer. The staging system is based on the International Federation of Gynecology and Obstetrics (FIGO) and provides a standardized method to classify the extent and severity of the disease. In cervical cancer staging, various investigations are used to assess the tumor's size, location, and involvement of nearby structures.

**Why the Correct Answer is Right:**
The correct answer, **Option A: Chest X-ray**, is not used in the FIGO staging of cervical cancer because it primarily evaluates the lungs and mediastinum and does not provide information about the cervix or surrounding structures. Chest X-rays are primarily utilized to detect distant spread of cancer to other organs.

**Why Each Wrong Option is Incorrect:**

**Option B: Computed Tomography (CT) scan**
While CT scans can provide detailed information about the extent of the tumor, its invasion into surrounding structures, and detection of distant spread, they are not specific to staging cervical cancer. CT scans are often used in conjunction with other staging investigations like MRI and PET-CT. As a result, CT is not a standalone method for cervical cancer staging.

**Option C: Ultrasonography (USG)**
USG is a valuable tool for evaluating the size of the tumor, presence of parametrial involvement, and detection of lymph node enlargement. However, USG is limited in assessing the depth of cervical stromal invasion and detecting distant spread. These aspects are crucial for accurate staging of cervical cancer, making USG an incomplete method for staging.

**Option D: Magnetic Resonance Imaging (MRI)**
MRI provides detailed anatomic information, including the depth of cervical stromal invasion, the extent of parametrial involvement, and the detection of vaginal invasion, lymph node enlargement, and distant spread. MRI is more sensitive than CT in detecting the extent of tumor involvement and is considered the gold standard imaging modality for cervical cancer staging. This makes MRI essential for accurate staging and effective treatment planning.

**Why the Correct Answer is Right:**
In the context of cervical cancer staging, MRI is essential as it provides detailed information about the depth of cervical stromal invasion, vaginal involvement, and lymph node status. Additionally, MRI helps assess the presence of distant spread, which is crucial for proper treatment planning and patient management.

**Clinical Pearl:**
MRI should be performed in conjunction with other staging investigations, such as PET-CT, to achieve the most accurate staging of cervical cancer. This comprehensive staging helps in determining the appropriate treatment plan for the patient, including surgery, radiation therapy, and chemotherapy, improving patient outcomes and survival rates.