**Core Concept**
The treatment of cervical cancer often involves radiation therapy, including brachytherapy and external beam radiation. Point B is a specific technique used in brachytherapy for cervical cancer, where a radioactive source is placed near the tumor. This approach allows for high doses of radiation to be delivered directly to the tumor while minimizing exposure to surrounding healthy tissues.

**Why the Correct Answer is Right**
Point B refers to a specific technique in brachytherapy where a radioactive source, usually cesium-137 or iridium-192, is placed in a specific location within the pelvis. The source is typically implanted near the obturator lymph nodes, which are a common site for metastasis in cervical cancer. This placement allows for optimal delivery of radiation to the tumor while minimizing exposure to surrounding tissues. The obturator lymph nodes are located in the pelvis, near the obturator internus muscle, and are involved in the lymphatic drainage of the cervix.

**Why Each Wrong Option is Incorrect**
**Option A:** Mackenrodt's ligament, also known as the cardinal ligament, is a fibromuscular band that supports the cervix and uterus. While it is an important anatomical structure in the pelvis, it is not directly related to the placement of radioactive sources in point B brachytherapy.
**Option C:** The ischial tuberosity is a bony prominence located on the pelvis, where the hamstring muscles attach. It is not a relevant landmark for point B brachytherapy.
**Option D:** The round ligament of the uterus is a fibromuscular band that connects the uterus to the labia majora. It is not directly related to the placement of radioactive sources in point B brachytherapy.

**Clinical Pearl / High-Yield Fact**
In cervical cancer treatment, brachytherapy is often used in combination with external beam radiation to deliver high doses of radiation to the tumor while minimizing exposure to surrounding tissues. The specific placement of radioactive sources, such as in point B, is critical to achieving optimal treatment outcomes.

**✓ Correct Answer: B. Obturator Lymph node**