Automatic total kidney volume measurement on follow-up magnetic resonance images to facilitate monitoring of autosomal dominant polycystic kidney disease progression.
BACKGROUND
Renal imaging examinations provide high-resolution information about the anatomic structure of the kidneys and are used to measure total kidney volume (TKV) in autosomal dominant polycystic kidney disease (ADPKD) patients. TKV has become the gold-standard image biomarker for ADPKD progression at early stages of the disease and is used in clinical trials to characterize treatment efficacy. Automated methods to segment the kidneys and measure TKV are desirable because of the long time requirement for manual approaches such as stereology or planimetry tracings. However, ADPKD kidney segmentation is complicated by a number of factors, including irregular kidney shapes and variable tissue signal at the kidney borders.


METHODS
We describe an image processing approach that overcomes these problems by using a baseline segmentation initialization to provide automatic segmentation of follow-up scans obtained years apart. We validated our approach using 20 patients with complete baseline and follow-up T1-weighted magnetic resonance images. Both manual tracing and stereology were used to calculate TKV, with two observers performing manual tracings and one observer performing repeat tracings. Linear correlation and Bland-Altman analysis were performed to compare the different approaches.


RESULTS
Our automated approach measured TKV at a level of accuracy (mean difference ± standard error = 0.99 ± 0.79%) on par with both intraobserver (0.77 ± 0.46%) and interobserver variability (1.34 ± 0.70%) of manual tracings. All approaches had excellent agreement and compared favorably with ground-truth manual tracing with interobserver, stereological and automated approaches having 95% confidence intervals ∼ ± 100 mL.


CONCLUSIONS
Our method enables fast, cost-effective and reproducible quantification of ADPKD progression that will facilitate and lower the costs of clinical trials in ADPKD and other disorders requiring accurate, longitudinal kidney quantification. In addition, it will hasten the routine use of TKV as a prognostic biomarker in ADPKD.
Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN, USA.
Timothy L
TL
Kline
Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN, USA.
Panagiotis
P
Korfiatis
Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA.
Marie E
ME
Edwards
Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN, USA.
Joshua D
JD
Warner
Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA.
Maria V
MV
Irazabal
Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN, USA.
Bernard F
BF
King
Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA.
Vicente E
VE
Torres
Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN, USA.
Bradley J
BJ
Erickson
D000328:Adult; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D009929:Organ Size; D016891:Polycystic Kidney, Autosomal Dominant / Q000175:diagnosis*; D011379:Prognosis; D012372:ROC Curve
autosomal dominant polycystic kidney disease; magnetic resonance imaging; planimetry; registration; segmentation; stereology