Biomedical
Inter- and intra-rater reproducibility of quantitative T1 measurement using semiautomatic region of interest placement in myometrium
Peer Reviewed
Abstract
Purpose
This study aimed to investigate the inter- and intraobserver reproducibility of quantitative T1 (qT1) measurements using manual and semiautomatic region of interest (ROI) placements. We hypothesized the usefulness of the semiautomatic method, which utilizes a three-dimensional (3D) anatomical relationship between the myometrium and other tissues, for minimizing ROI placement variation, thereby improving qT1 reproducibility compared to the manual approach. The semiautomatic approach, which considered anatomical relationships, was expected to enhance reproducibility by reducing ROI placement variabilities.
Materials and Methods
This study recruited 23 healthy female volunteers. Data with variable flip angle (VFA) and inversion recovery were acquired using 3D-spoiled gradient echo and spin echo sequences, respectively. T1 maps were generated with VFA. Manual and semiautomatic ROI placements were independently conducted. Mean qT1 values were calculated from the T1 maps using the corresponding pixel values of the myometrial ROI. Inter- and intraobserver reproducibility of qT1 values was investigated. The inter- and intraobserver reproducibility of qT1 values was evaluated by calculating the coefficient of variation (CoV). Further, reproducibility was evaluated with inter- and intraobserver errors and intraclass correlation coefficients (ICCs). Bland–Altman analysis was utilized to compare the results, estimate bias, and determine the limits of agreement.
Results
The mean inter- and intraobserver CoV of the qT1 values for semiautomatic ROI placement was significantly lower than those for manual ROI placement (p < 0.05 and p < 0.01, respectively). ICCs for semiautomatic ROI placement were greater than those for manual ROI placement. Further, the mean inter- and intraobserver errors for semiautomatic ROI placement were significantly lower than those for manual ROI placement (p < 0.05 and p < 0.01, respectively).
Conclusion
Semiautomatic ROI placement demonstrated high reproducibility of qT1 measurements compared with manual methods. Semiautomatic ROI placement may be useful for evaluating uterine qT1 with high reproducibility.
Key Questions
1. How does semiautomatic ROI placement compare to manual placement in T1 mapping?
The study found that semiautomatic ROI placement demonstrated significantly higher reproducibility of qT1 measurements compared to manual methods, with lower coefficient of variation and inter- and intraobserver errors.
2. What are the advantages of the proposed semiautomatic ROI placement method?
The semiautomatic method utilizes 3D anatomical relationships between the myometrium and other tissues, minimizing ROI placement variation without the need for contrast agents, potentially improving reproducibility in quantitative MRI.
3. How was the reproducibility of T1 measurements evaluated in this study?
Reproducibility was assessed using coefficient of variation (CoV), inter- and intraobserver errors, intraclass correlation coefficients (ICCs), and Bland-Altman analysis to compare results, estimate bias, and determine limits of agreement.
4. What were the key findings regarding intraclass correlation coefficients (ICCs)?
ICCs for semiautomatic ROI placement were greater than those for manual ROI placement, with excellent inter- and intraobserver reproducibility (>0.98) for the semiautomatic method.
5. What are the potential clinical applications of this improved T1 mapping technique?
The semiautomatic ROI placement method may be useful for evaluating uterine qT1 with high reproducibility, potentially aiding in the assessment of various uterine conditions and improving quantitative tissue characterization in gynecological MRI.
