Radiographic and anatomic basis for prostate contouring errors and methods to improve prostate contouring accuracy

Area of Science:

• Radiation oncology
• Medical imaging
• Anatomy

Background:

• Conformal radiation therapy for prostate cancer risks overtreatment of normal tissues and undertreatment of the prostate.
• Accurate target delineation is crucial for effective prostate cancer treatment.

Purpose of the Study:

• To analyze the radiographic and anatomic basis of common errors in computed tomography (CT) contouring for prostate cancer.
• To suggest methods for correcting these contouring errors to improve treatment accuracy.

Main Methods:

• Retrospective analysis of 300 prostate cancer patients' CT and magnetic resonance imaging (MRI) data.
• Independent delineation of the prostate on CT and MRI datasets.
• Comparison of CT and MRI contours using deformable registration to identify and analyze delineation errors.

Main Results:

• Common CT contouring errors identified at the prostatic apex, mid gland, and base.
• Specific anatomical structures (e.g., genitourinary diaphragm, fasciae, bladder) and prostate variations (e.g., hypertrophy) contribute to over- and underestimation.
• Errors include overestimation at the apex and mid-gland due to surrounding structures, and at the base due to bladder and anterior fascia.

Conclusions:

• CT contouring errors can be detected by inspecting lateral views for deviations from the expected prostate shape.
• Recognizing specific anatomical structures visible on MRI but also on CT aids error identification.
• Many CT prostate contouring errors can be improved by understanding anatomy, without direct MRI data integration.