Intracavitary brachytherapy using the Manchester system is planned for carcinoma of the cervix. Point A, the classical prescription reference point for dose calculation, is defined as:

• A 2 cm above the external os in the uterine cavity
• B 5 cm lateral to the midline at the level of the sacral promontory
• C Midpoint of the vaginal ovoids on the anterior vaginal wall
• D 2 cm lateral and 2 cm above the external os, in the parametrium ✓

Explanation

In the Manchester system, point A lies 2 cm superior to the external cervical os and 2 cm lateral to the midline, in the region of the uterine artery crossing, approximating where the paracervical parametrial tissues receive dose. Point D lies 3 cm further laterally at the same level, near the pelvic sidewall nodes. The sacral promontory point relates to midline sagittal dosimetry, not the prescription point.

Reference: Hall and Giaccia, Radiobiology for the Radiologist, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.