Computer-aided segmentation on MRI for prostate radiotherapy, Part I: Quantifying human interobserver variability of the prostate and organs at risk and its impact on radiation dosimetry

Jeremiah W Sanders; Henry Mok; Alexander N Hanania; Aradhana M Venkatesan; Chad Tang; Teresa L Bruno; Howard D Thames; Rajat J Kudchadker; Steven J Frank

doi:10.1016/j.radonc.2021.12.011

Computer-aided segmentation on MRI for prostate radiotherapy, Part I: Quantifying human interobserver variability of the prostate and organs at risk and its impact on radiation dosimetry

Radiother Oncol. 2022 Apr:169:124-131. doi: 10.1016/j.radonc.2021.12.011. Epub 2021 Dec 16.

Authors

Jeremiah W Sanders¹, Henry Mok², Alexander N Hanania³, Aradhana M Venkatesan⁴, Chad Tang², Teresa L Bruno², Howard D Thames⁵, Rajat J Kudchadker⁶, Steven J Frank²

Affiliations

¹ Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, USA. Electronic address: jsanders1@mdanderson.org.
² Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA.
³ Department of Radiation Oncology, Baylor College of Medicine, Houston, USA.
⁴ Department of Diagnostic Radiology, The University of Texas MD Anderson Cancer Center, Houston, USA.
⁵ Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, USA. Electronic address: hthames@gmail.com.
⁶ Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, USA.

PMID: 34921895
DOI: 10.1016/j.radonc.2021.12.011

Abstract

Background and purpose: Quantifying the interobserver variability (IoV) of prostate and periprostatic anatomy delineation on prostate MRI is necessary to inform its use for treatment planning, treatment delivery, and treatment quality assessment.

Materials and methods: Twenty five prostate cancer patients underwent MRI-based low-dose-rate prostate brachytherapy (LDRPBT). The patients were scanned with a 3D T2-weighted sequence for treatment planning and a 3D T2/T1-weighted sequence for quality assessment. Seven observers involved with the LDRPBT workflow delineated the prostate, external urinary sphincter (EUS), seminal vesicles, rectum, and bladder on all 50 MRIs. IoV was assessed by measuring contour similarity metrics, differences in organ volumes, and differences in dosimetry parameters between unique observer pairs. Measurements from a group of 3 radiation oncologists (G1) were compared against those from a group consisting of the other 4 clinical observers (G2).

Results: IoV of the prostate was lower for G1 than G2 (Matthew's correlation coefficient [MCC], G1 vs. G2: planning-0.906 vs. 0.870, p < 0.001; postimplant-0.899 vs. 0.861, p < 0.001). IoV of the EUS was highest of all the organs for both groups, but was lower for G1 (MCC, G1 vs. G2: planning-0.659 vs. 0.402, p < 0.001; postimplant-0.684 vs. 0.398, p < 0.001). Large differences in prostate dosimetry parameters were observed (G1 maximum absolute prostate ΔD90: planning-76.223 Gy, postimplant-36.545 Gy; G1 maximum absolute prostate ΔV100: planning-13.927%, postimplant-8.860%).

Conclusions: While MRI is optimal in the management of prostate cancer with radiation therapy, significant interobserver variability of the prostate and external urinary sphincter still exist.

Keywords: Brachytherapy; Dosimetry; Interobserver variability; Low-dose-rate; MRI; Prostate.

MeSH terms

Brachytherapy*
Computers
Humans
Magnetic Resonance Imaging
Male
Observer Variation
Organs at Risk / diagnostic imaging
Prostate / diagnostic imaging
Prostatic Neoplasms* / diagnostic imaging
Prostatic Neoplasms* / radiotherapy
Radiometry
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted