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Bdaiwi AS, Niedbalski PJ, Hossain MM, Willmering MM, Walkup LL, Wang H, Thomen RP, Ruppert K, Woods JC, Cleveland ZI. Improving hyperpolarized 129 Xe ADC mapping in pediatric and adult lungs with uncertainty propagation. NMR IN BIOMEDICINE 2022; 35:e4639. [PMID: 34729838 PMCID: PMC8828677 DOI: 10.1002/nbm.4639] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 09/30/2021] [Accepted: 10/01/2021] [Indexed: 06/13/2023]
Abstract
RATIONALE Hyperpolarized (HP) 129 Xe-MRI provides non-invasive methods to quantify lung function and structure, with the 129 Xe apparent diffusion coefficient (ADC) being a well validated measure of alveolar airspace size. However, the experimental factors that impact the precision and accuracy of HP 129 Xe ADC measurements have not been rigorously investigated. Here, we introduce an analytical model to predict the experimental uncertainty of 129 Xe ADC estimates. Additionally, we report ADC dependence on age in healthy pediatric volunteers. METHODS An analytical expression for ADC uncertainty was derived from the Stejskal-Tanner equation and simplified Bloch equations appropriate for HP media. Parameters in the model were maximum b-value (bmax ), number of b-values (Nb ), number of phase encoding lines (Nph ), flip angle and the ADC itself. This model was validated by simulations and phantom experiments, and five fitting methods for calculating ADC were investigated. To examine the lower range for 129 Xe ADC, 32 healthy subjects (age 6-40 years) underwent diffusion-weighted 129 Xe MRI. RESULTS The analytical model provides a lower bound on ADC uncertainty and predicts that decreased signal-to-noise ratio yields increases in relative uncertainty (ϵADC) . As such, experimental parameters that impact non-equilibrium 129 Xe magnetization necessarily impact the resulting ϵADC . The values of diffusion encoding parameters (Nb and bmax ) that minimize ϵADC strongly depend on the underlying ADC value, resulting in a global minimum for ϵADC . Bayesian fitting outperformed other methods (error < 5%) for estimating ADC. The whole-lung mean 129 Xe ADC of healthy subjects increased with age at a rate of 1.75 × 10-4 cm2 /s/yr (p = 0.001). CONCLUSIONS HP 129 Xe diffusion MRI can be improved by minimizing the uncertainty of ADC measurements via uncertainty propagation. Doing so will improve experimental accuracy when measuring lung microstructure in vivo and should allow improved monitoring of regional disease progression and assessment of therapy response in a range of lung diseases.
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Affiliation(s)
- Abdullah S. Bdaiwi
- Center for Pulmonary Imaging Research, Division of
Pulmonary Medicine, Children’s Hospital Medical Center, Cincinnati, OH
45229
- Department of Biomedical Engineering, University of
Cincinnati, Cincinnati, OH 45221
| | - Peter J. Niedbalski
- Center for Pulmonary Imaging Research, Division of
Pulmonary Medicine, Children’s Hospital Medical Center, Cincinnati, OH
45229
| | - Md M. Hossain
- Division of Biostatistics and Epidemiology, Cincinnati
Children’s Hospital Medical Center, Cincinnati, OH 45229
| | - Matthew M. Willmering
- Center for Pulmonary Imaging Research, Division of
Pulmonary Medicine, Children’s Hospital Medical Center, Cincinnati, OH
45229
| | - Laura L. Walkup
- Center for Pulmonary Imaging Research, Division of
Pulmonary Medicine, Children’s Hospital Medical Center, Cincinnati, OH
45229
- Department of Biomedical Engineering, University of
Cincinnati, Cincinnati, OH 45221
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45221
| | - Hui Wang
- Philips Healthcare, Cincinnati, OH, USA
| | - Robert P. Thomen
- Center for Pulmonary Imaging Research, Division of
Pulmonary Medicine, Children’s Hospital Medical Center, Cincinnati, OH
45229
| | - Kai Ruppert
- Center for Pulmonary Imaging Research, Division of
Pulmonary Medicine, Children’s Hospital Medical Center, Cincinnati, OH
45229
| | - Jason C. Woods
- Center for Pulmonary Imaging Research, Division of
Pulmonary Medicine, Children’s Hospital Medical Center, Cincinnati, OH
45229
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45221
| | - Zackary I. Cleveland
- Center for Pulmonary Imaging Research, Division of
Pulmonary Medicine, Children’s Hospital Medical Center, Cincinnati, OH
45229
- Department of Biomedical Engineering, University of
Cincinnati, Cincinnati, OH 45221
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45221
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Diffusion MRI with Semi-Automated Segmentation Can Serve as a Restricted Predictive Biomarker of the Therapeutic Response of Liver Metastasis. Magn Reson Imaging 2015; 33:1267-1273. [PMID: 26284600 DOI: 10.1016/j.mri.2015.08.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 04/13/2015] [Accepted: 08/08/2015] [Indexed: 12/26/2022]
Abstract
PURPOSE To assess the value of semi-automated segmentation applied to diffusion MRI for predicting the therapeutic response of liver metastasis. METHODS Conventional diffusion weighted magnetic resonance imaging (MRI) was performed using b-values of 0, 150, 300 and 450s/mm(2) at baseline and days 4, 11 and 39 following initiation of a new chemotherapy regimen in a pilot study with 18 women with 37 liver metastases from primary breast cancer. A semi-automated segmentation approach was used to identify liver metastases. Linear regression analysis was used to assess the relationship between baseline values of the apparent diffusion coefficient (ADC) and change in tumor size by day 39. RESULTS A semi-automated segmentation scheme was critical for obtaining the most reliable ADC measurements. A statistically significant relationship between baseline ADC values and change in tumor size at day 39 was observed for minimally treated patients with metastatic liver lesions measuring 2-5cm in size (p=0.002), but not for heavily treated patients with the same tumor size range (p=0.29), or for tumors of smaller or larger sizes. ROC analysis identified a baseline threshold ADC value of 1.33μm(2)/ms as 75% sensitive and 83% specific for identifying non-responding metastases in minimally treated patients with 2-5cm liver lesions. CONCLUSION Quantitative imaging can substantially benefit from a semi-automated segmentation scheme. Quantitative diffusion MRI results can be predictive of therapeutic outcome in selected patients with liver metastases, but not for all liver metastases, and therefore should be considered to be a restricted biomarker.
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Jha AK, Kupinski MA, Rodríguez JJ, Stephen RM, Stopeck AT. Task-based evaluation of segmentation algorithms for diffusion-weighted MRI without using a gold standard. Phys Med Biol 2012; 57:4425-46. [PMID: 22713231 DOI: 10.1088/0031-9155/57/13/4425] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In many studies, the estimation of the apparent diffusion coefficient (ADC) of lesions in visceral organs in diffusion-weighted (DW) magnetic resonance images requires an accurate lesion-segmentation algorithm. To evaluate these lesion-segmentation algorithms, region-overlap measures are used currently. However, the end task from the DW images is accurate ADC estimation, and the region-overlap measures do not evaluate the segmentation algorithms on this task. Moreover, these measures rely on the existence of gold-standard segmentation of the lesion, which is typically unavailable. In this paper, we study the problem of task-based evaluation of segmentation algorithms in DW imaging in the absence of a gold standard. We first show that using manual segmentations instead of gold-standard segmentations for this task-based evaluation is unreliable. We then propose a method to compare the segmentation algorithms that does not require gold-standard or manual segmentation results. The no-gold-standard method estimates the bias and the variance of the error between the true ADC values and the ADC values estimated using the automated segmentation algorithm. The method can be used to rank the segmentation algorithms on the basis of both the ensemble mean square error and precision. We also propose consistency checks for this evaluation technique.
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Affiliation(s)
- Abhinav K Jha
- College of Optical Sciences, University of Arizona, Tucson, AZ, USA.
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