NEET-PG 2013 Radiology MCQs — Questions 41–44 (Page 5 of 5)

Q: What is the standard radiation dose to point A in the cervix for brachytherapy in the treatment of cervical cancer?

8000 rad. ***8000 rad*** - The standard **total cumulative radiation dose** to **Point A** in the cervix for the treatment of cervical cancer is approximately **8000 rad (80 Gy)**. - This represents the **combined dose** from external beam radiation therapy (EBRT, typically 45-50 Gy) plus intracavitary brachytherapy (typically 30-40 Gy to Point A). - Point A is a classical reference point defined as **2 cm superior to the external cervical os and 2 cm lateral to the uterine canal**, representing the location where the uterine artery crosses the ureter. - This total dose aims to provide adequate tumor control while minimizing toxicity to surrounding organs like the bladder and rectum. *6000 rad* - A total dose of **6000 rad** is insufficient for definitive local control of cervical cancer. - This dose is below the therapeutic threshold and would result in significantly higher rates of local recurrence and treatment failure. - Adequate doses are essential for curative intent in cervical cancer management. *10000 rad* - A dose of **10000 rad** to Point A would be excessively high and significantly increase the risk of severe acute and late toxicities to surrounding tissues. - Such a high dose could lead to serious complications including **rectovaginal or vesicovaginal fistulas, proctitis, cystitis, bowel strictures, and tissue necrosis**. - The therapeutic window would be exceeded, causing more harm than benefit. *4000 rad* - A dose of **4000 rad** would be substantially lower than the standard therapeutic dose for cervical cancer. - This suboptimal dose would likely result in **inadequate tumor control and increased risk of local recurrence**. - It is far below the dose required for curative treatment of cervical cancer.

Q: Enhancement in CT contrast is due to -

Iodine. ***Iodine*** - **Iodine-based contrast agents** are commonly used in CT scans to enhance the visualization of blood vessels, organs, and certain lesions due to their **high atomic number** and ability to absorb X-rays. - The degree of enhancement observed on a CT image is directly proportional to the concentration of **iodine** in the tissue or blood. *Gadolinium* - **Gadolinium-based contrast agents** are predominantly used in **Magnetic Resonance Imaging (MRI)**, not CT scans. - Gadolinium works by altering the **magnetic properties** of water molecules in tissues, thereby improving MRI signal intensity. *Mercury* - **Mercury** is a highly toxic heavy metal and is **not used as a contrast agent** in any imaging modality due to its severe health risks. - While historically used in some medical applications, it has been replaced by safer alternatives. *Silver* - **Silver** is not used as a contrast agent in medical imaging; it has no suitable properties for enhancing images in CT or other common modalities. - It is known for its **antimicrobial properties** and is sometimes used in wound dressings.

Q: Normal prevertebral soft tissue thickness in adults at C3 level is

7 mm. ***7 mm*** * The normal prevertebral soft tissue thickness in adults at the **C3 level** is approximately **7 mm** (upper limit 5-7 mm) on a lateral cervical spine radiograph. * The **C1-C4 levels** have relatively thin prevertebral soft tissue as they lie above the hypopharynx and esophagus. * Exceeding this measurement can indicate **prevertebral hematoma, edema, abscess**, or other pathologies such as retropharyngeal abscess or cervical spine fracture with soft tissue swelling. *Incorrect: 15 mm* * A measurement of 15 mm at the **C3 level** would be considered **abnormal** and indicates prevertebral soft tissue swelling. * This value exceeds the normal limit by more than double and warrants further investigation. *Incorrect: 22 mm* * A measurement of 22 mm at the **C3 level** is significantly **abnormal** and highly suggestive of serious pathology such as retropharyngeal hematoma, abscess, or cervical spine injury. * Note that 22 mm may be within normal limits at the **C6-C7 level** where the esophagus widens the prevertebral space. *Incorrect: 30 mm* * 30 mm is severely abnormal at the **C3 level**. * While prevertebral soft tissue thickness can be greater at lower cervical levels (C5-C7) due to the esophagus, even at those levels 30 mm would suggest pathology. * Such measurements indicate significant conditions like large hematoma, abscess, or tumor.

Q: Flask shaped heart is seen in –

Pericardial effusion. ***Pericardial effusion*** - A **"flask-shaped"** or **"water bottle-shaped" heart** on chest X-ray is a classic finding in significant pericardial effusion. - This appearance results from the accumulation of a large amount of fluid in the **pericardial sac**, which causes the cardiac silhouette to enlarge symmetrically and assume a globular shape. *TOF (Tetralogy of Fallot)* - TOF typically presents with a **"boot-shaped" heart** (coeur en sabot) on chest X-ray due to right ventricular hypertrophy and a concave pulmonary artery segment. - This morphology is distinctly different from the flask-shaped appearance of pericardial effusion. *Ebstein anomaly* - Ebstein anomaly is characterized by apical displacement of the tricuspid valve, leading to **massive right atrial enlargement**. - On chest X-ray, this often results in a **markedly enlarged oval-shaped heart**, which can be quite massive but does not typically have the distinct flask/water bottle shape. *TAPVC (Total Anomalous Pulmonary Venous Connection)* - TAPVC can present with different X-ray findings depending on the type, but a classic finding for the supracardiac type is a **"snowman" or "figure-of-8" heart** in children. - This appearance is due to the dilated superior vena cava and anomalous veins draining to it, not a flask shape.

Q41

What is the standard radiation dose to point A in the cervix for brachytherapy in the treatment of cervical cancer?

Q42

Enhancement in CT contrast is due to -

Q43

Normal prevertebral soft tissue thickness in adults at C3 level is

Q44

Flask shaped heart is seen in –

NEET-PG 2013 — Radiology