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Identifying MRI markers associated with early response following laser ablation for neurological disorders: preliminary findings.

Tiwari P, Danish S, Madabhushi A - PLoS ONE (2014)

Bottom Line: Although highly promising, the long-term effects of laser ablation as a viable treatment option for neurological disorders have yet to be rigorously studied and quantified.In this work, we present a quantitative framework for monitoring per-voxel thermal-induced changes post-LITT over time on multi parametric MRI.On a cohort of six GBM studies we found that (a) it may be important for the initial treatment-related changes to subside to more reliably capture MRI markers relating to tumor recurrence, and (b) T1w MRI and T2-GRE may better differentiate changes that may correspond to tumor recurrence from patients with no recurrence, as compared to T2w-MRI, and FLAIR.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America.

ABSTRACT
There is a renewed interest in MR-guided laser interstitial thermal therapy (LITT) as a minimally invasive alternative to craniotomy for local treatment of various brain tumors and epilepsy. LITT allows for focused delivery of laser energy monitored in real time by MRI, for precise ablation of the lesion. Although highly promising, the long-term effects of laser ablation as a viable treatment option for neurological disorders have yet to be rigorously studied and quantified. In this work, we present a quantitative framework for monitoring per-voxel thermal-induced changes post-LITT over time on multi parametric MRI. We demonstrate that voxel-by-voxel quantification of MRI markers over time can enable a careful and accurate (a) characterization of early LITT-related changes (if and when they are exaggerated and when they subside), and (b) identification and monitoring of MRI markers that potentially allow for better quantification of response to LITT therapy. The framework was evaluated on two distinct cohorts of patients (GBM, epilepsy), who were monitored post-LITT at regular time-intervals via multi-parametric MRI. On a cohort of six GBM studies we found that (a) it may be important for the initial treatment-related changes to subside to more reliably capture MRI markers relating to tumor recurrence, and (b) T1w MRI and T2-GRE may better differentiate changes that may correspond to tumor recurrence from patients with no recurrence, as compared to T2w-MRI, and FLAIR. Similarly, our preliminary analysis of four epilepsy studies suggests that (a) early LITT changes (attributed to swelling, edema) appear to subside within 4-weeks post-LITT, and (b) ADC may be more reflective of early treatment changes (up to 1 month), while T1w may be more reflective of early delayed treatment changes (1 month, 3 months), while T2-w and T2-FLAIR appeared to be more sensitive to late treatment related changes (6-months post-LITT) compared to the other MRI protocols under evaluation.

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Related in: MedlinePlus

Illustration of intensity drift between pre- (red) and post-LITT at different time points (shown in blue, green, yellow, magenta, and cyan) for T1w MRI, by plotting the corresponding distributions along the same axis.Note that after intensity standardization, the distributions across different time-points are no longer misaligned, suggesting successful correction of the drift artifact.
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pone-0114293-g003: Illustration of intensity drift between pre- (red) and post-LITT at different time points (shown in blue, green, yellow, magenta, and cyan) for T1w MRI, by plotting the corresponding distributions along the same axis.Note that after intensity standardization, the distributions across different time-points are no longer misaligned, suggesting successful correction of the drift artifact.

Mentions: When the histograms for T1w MRI at (red) and at different time-points (blue, green, yellow, magenta, cyan respectively) are plotted together (Fig. 3a)), it is clear they have different intensity ranges and are not in alignment. In order to quantitatively compare the changes in MRI markers between pre- and post-LITT acquisitions, an intensity standardization scheme developed by Nyul and Udupa [20] was implemented in-house using a Matlab software package and was used to automatically identify corresponding landmarks on each of the histograms, and subsequently non-linearly map them to one other. As a result of intensity standardization, the histograms are aligned (Fig. 3(b)) and the MRI markers can be directly compared across different time-points. Intensity standardization was performed for corresponding pairs of MRI markers (T1w, T2w, GRE, FLAIR intensities) between pre- and post-LITT MRI acquisitions at different time-points. Since ADC is a standardized quantitative measure (obtained from DWI) across acquisitions, no intensity standardization was performed for ADC images.


Identifying MRI markers associated with early response following laser ablation for neurological disorders: preliminary findings.

Tiwari P, Danish S, Madabhushi A - PLoS ONE (2014)

Illustration of intensity drift between pre- (red) and post-LITT at different time points (shown in blue, green, yellow, magenta, and cyan) for T1w MRI, by plotting the corresponding distributions along the same axis.Note that after intensity standardization, the distributions across different time-points are no longer misaligned, suggesting successful correction of the drift artifact.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263602&req=5

pone-0114293-g003: Illustration of intensity drift between pre- (red) and post-LITT at different time points (shown in blue, green, yellow, magenta, and cyan) for T1w MRI, by plotting the corresponding distributions along the same axis.Note that after intensity standardization, the distributions across different time-points are no longer misaligned, suggesting successful correction of the drift artifact.
Mentions: When the histograms for T1w MRI at (red) and at different time-points (blue, green, yellow, magenta, cyan respectively) are plotted together (Fig. 3a)), it is clear they have different intensity ranges and are not in alignment. In order to quantitatively compare the changes in MRI markers between pre- and post-LITT acquisitions, an intensity standardization scheme developed by Nyul and Udupa [20] was implemented in-house using a Matlab software package and was used to automatically identify corresponding landmarks on each of the histograms, and subsequently non-linearly map them to one other. As a result of intensity standardization, the histograms are aligned (Fig. 3(b)) and the MRI markers can be directly compared across different time-points. Intensity standardization was performed for corresponding pairs of MRI markers (T1w, T2w, GRE, FLAIR intensities) between pre- and post-LITT MRI acquisitions at different time-points. Since ADC is a standardized quantitative measure (obtained from DWI) across acquisitions, no intensity standardization was performed for ADC images.

Bottom Line: Although highly promising, the long-term effects of laser ablation as a viable treatment option for neurological disorders have yet to be rigorously studied and quantified.In this work, we present a quantitative framework for monitoring per-voxel thermal-induced changes post-LITT over time on multi parametric MRI.On a cohort of six GBM studies we found that (a) it may be important for the initial treatment-related changes to subside to more reliably capture MRI markers relating to tumor recurrence, and (b) T1w MRI and T2-GRE may better differentiate changes that may correspond to tumor recurrence from patients with no recurrence, as compared to T2w-MRI, and FLAIR.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America.

ABSTRACT
There is a renewed interest in MR-guided laser interstitial thermal therapy (LITT) as a minimally invasive alternative to craniotomy for local treatment of various brain tumors and epilepsy. LITT allows for focused delivery of laser energy monitored in real time by MRI, for precise ablation of the lesion. Although highly promising, the long-term effects of laser ablation as a viable treatment option for neurological disorders have yet to be rigorously studied and quantified. In this work, we present a quantitative framework for monitoring per-voxel thermal-induced changes post-LITT over time on multi parametric MRI. We demonstrate that voxel-by-voxel quantification of MRI markers over time can enable a careful and accurate (a) characterization of early LITT-related changes (if and when they are exaggerated and when they subside), and (b) identification and monitoring of MRI markers that potentially allow for better quantification of response to LITT therapy. The framework was evaluated on two distinct cohorts of patients (GBM, epilepsy), who were monitored post-LITT at regular time-intervals via multi-parametric MRI. On a cohort of six GBM studies we found that (a) it may be important for the initial treatment-related changes to subside to more reliably capture MRI markers relating to tumor recurrence, and (b) T1w MRI and T2-GRE may better differentiate changes that may correspond to tumor recurrence from patients with no recurrence, as compared to T2w-MRI, and FLAIR. Similarly, our preliminary analysis of four epilepsy studies suggests that (a) early LITT changes (attributed to swelling, edema) appear to subside within 4-weeks post-LITT, and (b) ADC may be more reflective of early treatment changes (up to 1 month), while T1w may be more reflective of early delayed treatment changes (1 month, 3 months), while T2-w and T2-FLAIR appeared to be more sensitive to late treatment related changes (6-months post-LITT) compared to the other MRI protocols under evaluation.

Show MeSH
Related in: MedlinePlus