Bayesian estimation of changes in transverse relaxation rates

Walker‐Samuel, Simon; Orton, Matthew; McPhail, Lesley D.; Boult, Jessica K.R.; Box, Gary; Eccles, Suzanne A.; Robinson, Simon P.

doi:10.1002/mrm.22478

Cited by 28 publications

(37 citation statements)

References 33 publications

(45 reference statements)

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“…The accuracy of measured

T_{2}^{*}

values can also depend on the choice of echo times and type of data processing. In general, the signal‐to‐noise ratio (SNR) in the VOI should be adequate for images acquired using all echo times 27. Tissues characterized by short transverse relaxation times suffer from low SNR in the longer echo time images, which may lead to a subsequent overestimation of

T_{2}^{*}

.…”

Section: Discussionmentioning

confidence: 99%

“…These effects are not likely to significantly affect the relatively long mean

T_{2}^{*}

values measured at 3T in HNSCC nodal and primary tumor sites (23.6 and 18.7 msec, respectively). The noise bias should not be neglected when calculating relaxation times of tissues with short

T_{2}^{*}

, or in the case of subregional voxel‐based analysis, in which case Bayesian or data truncation methods might be required 27. The number of echoes used herein was a result of using in‐phase fat and water signal with echoes acquired with the same gradient polarity, together with SNR threshold.…”

Section: Discussionmentioning

confidence: 99%

“…In addition to the tumor vascular microenvironment, quantitation of

T_{2}^{*}

is also dependent on physiochemical and methodological parameters 14, 26, 27. Macroscopic magnetic field homogeneity resulting from the iterative shimming process affects the repeatability of

T_{2}^{*}

measurements.…”

mentioning

confidence: 99%

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Repeatability and sensitivity of measurements in patients with head and neck squamous cell carcinoma at 3T

Panek

Welsh

Dunlop

et al. 2016

Magnetic Resonance Imaging

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PurposeTo determine whether quantitation of T2* is sufficiently repeatable and sensitive to detect clinically relevant oxygenation levels in head and neck squamous cell carcinoma (HNSCC) at 3T.Materials and MethodsTen patients with newly diagnosed locally advanced HNSCC underwent two magnetic resonance imaging (MRI) scans between 24 and 168 hours apart prior to chemoradiotherapy treatment. A multiple gradient echo sequence was used to calculate T2* maps. A quadratic function was used to model the blood transverse relaxation rate as a function of blood oxygenation. A set of published coefficients measured at 3T were incorporated to account for tissue hematocrit levels and used to plot the dependence of fractional blood oxygenation (Y) on T2* values, together with the corresponding repeatability range. Repeatability of T2* using Bland–Altman analysis, and calculation of limits of agreement (LoA), was used to assess the sensitivity, defined as the minimum difference in fractional blood oxygenation that can be confidently detected.Results T2* LoA for 22 outlined tumor volumes were 13%. The T2* dependence of fractional blood oxygenation increases monotonically, resulting in increasing sensitivity of the method with increasing blood oxygenation. For fractional blood oxygenation values above 0.11, changes in T2* were sufficient to detect differences in blood oxygenation greater than 10% (Δ T2* > LoA for ΔY > 0.1).ConclusionQuantitation of T2* at 3T can detect clinically relevant changes in tumor oxygenation within a wide range of blood volumes and oxygen tensions, including levels reported in HNSCC. J. Magn. Reson. Imaging 2016;44:72–80.

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“…The accuracy of measured

T_{2}^{*}

T_{2}^{*}

.…”

Section: Discussionmentioning

confidence: 99%

“…These effects are not likely to significantly affect the relatively long mean

T_{2}^{*}

values measured at 3T in HNSCC nodal and primary tumor sites (23.6 and 18.7 msec, respectively). The noise bias should not be neglected when calculating relaxation times of tissues with short

T_{2}^{*}

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Repeatability and sensitivity of measurements in patients with head and neck squamous cell carcinoma at 3T

Panek

Welsh

Dunlop

et al. 2016

Magnetic Resonance Imaging

Self Cite

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“…MGE data were analyzed using a Bayesian maximum a posteriori approach (19). This modeled the MGE signal magnitude as a single exponential decay and took into account its Rician distribution.…”

Section: Mri Data Analysismentioning

confidence: 99%

“…It was hypothesized that negative DR 2 * carbogen and positive DR 2 * USPIO would show strong spatial colocalisation and be the primary tumor response to the CUSPIO protocol. This novel imaging protocol has been coupled with a Bayesian analysis method providing a robust statistical framework with which to determine whether on a pixelby-pixel basis DR 2 * significantly changed following both carbogen and USPIO challenges (19).…”

mentioning

confidence: 99%

Investigating temporal fluctuations in tumor vasculature with combined carbogen and ultrasmall superparamagnetic iron oxide particle (CUSPIO) imaging

Burrell

Walker‐Samuel

Baker

et al. 2011

Magnetic Resonance in Med

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A combined carbogen ultrasmall superparamagnetic iron oxide (USPIO) imaging protocol was developed and applied in vivo in two murine colorectal tumor xenograft models, HCT116 and SW1222, with established disparate vascular morphology, to investigate whether additional information could be extracted from the combination of two susceptibility MRI biomarkers. Tumors were imaged before and during carbogen breathing and subsequently following intravenous administration of USPIO particles. A novel segmentation method was applied to the image data, from which six categories of R 2 * response were identified, and compared with histological analysis of the vasculature. In particular, a strong association between a negative DR 2 * carbogen followed by positive DR 2 * USPIO with the uptake of the perfusion marker Hoechst 33342 was determined. Regions of tumor tissue where there was a significant DR 2 * carbogen but no significant DR 2 * USPIO were also identified, suggesting these regions became temporally isolated from the vascular supply during the experimental timecourse. These areas correlated with regions of tumor tissue where there was CD31 staining but no Hoechst 33342 uptake. Significantly, different combined carbogen USPIO responses were determined between the two tumor models. Combining DR 2 * carbogen and DR 2 * USPIO with a novel segmentation scheme can facilitate the interpretation of susceptibility contrast MRI data and enable a deeper interrogation of tumor vascular function and architecture. Magn Reson Med 66:227-234,

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Non‐invasive in vivo imaging of vessel calibre in orthotopic prostate tumour xenografts

Walker‐Samuel

Boult

McPhail

et al. 2011

Intl Journal of Cancer

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Susceptibility contrast magnetic resonance imaging (MRI), utilising ultrasmall superparamagnetic iron oxide (USPIO) particles, was evaluated for the quantitation of vessel size index (R v , lm), a weighted average measure of tumour blood vessel calibre, and fractional tumour blood volume (fBV, %), in orthotopically propagated murine PC3 prostate tumour xenografts. Tumour vascular architecture was assessed in vivo by MRI prior to and 24 hr after treatment with 200 mg/kg of the vascular disrupting agent ZD6126. A Bayesian hierarchical model (BHM) was used to reduce the uncertainty associated with quantitation of R v and fBV. Quantitative histological analyses of the uptake of Hoechst 33342 for perfused vasculature, and haematoxylin and eosin staining for necrosis, were also performed to qualify the MRI data. A relatively large median R v of 40.3 lm (90% confidence interval (CI 90 ) 5 37.4, 44.0 lm) and a high fBV of 5.4% (CI 90 5 5.3, 5.5%) were determined in control tumours, which agreed with histologically determined vessel size index. Treatment with ZD6126 significantly (p < 0.01) reduced tumour R v (34.2lm, CI 90 5 31.2, 38.0 lm) and fBV (3.9%, CI 90 5 3.8, 4.1%), which were validated against histologically determined significant reductions in perfusion and vessel size, and increased necrosis. Together these data (i) highlight the use of a BHM to optimise the inferential power available from susceptibility contrast MRI data, (ii) provide strong evaluation and qualification of R v and fBV as non-invasive imaging biomarkers of tumour vascular morphology, (iii) reveal the presence of a different vascular phenotype and (iv) demonstrate that ZD6126 exhibits good anti-vascular activity against orthotopic prostate tumours.Generic biomarkers, including those afforded by functional imaging techniques, are being increasingly used for the evaluation of novel therapeutics and new targets in oncology. The importance of imaging biomarkers in oncology drug development has been recognised by the FDA, and such biomarkers require evaluation and qualification before they can be deployed in clinical trials. 1 The new generation of targeted cancer therapeutics typically elicit a cytostatic response, and hence a negligible associated change in tumour volume that can be evaluated using standard radiological approaches (i.e. RECIST negative).2 With the clinical development of such agents has come the need to investigate emerging biomarkers afforded by novel imaging methods. These may further aid in interpretation and provide additional data to help characterise key hallmarks of tumour pathophysiology prior to and during a pharmacological response. Susceptibility contrast magnetic resonance imaging (MRI), which incorporates the use of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, is one of a number of imaging approaches being evaluated preclinically for the assessment of tumour angiogenesis.3,4 USPIO particles, which remain within the circulation and present negligible vascular leakage, enable the steady state determi...

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Bayesian estimation of changes in transverse relaxation rates

Cited by 28 publications

References 33 publications

Repeatability and sensitivity of measurements in patients with head and neck squamous cell carcinoma at 3T

Repeatability and sensitivity of measurements in patients with head and neck squamous cell carcinoma at 3T

Investigating temporal fluctuations in tumor vasculature with combined carbogen and ultrasmall superparamagnetic iron oxide particle (CUSPIO) imaging

Non‐invasive in vivo imaging of vessel calibre in orthotopic prostate tumour xenografts

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