A voxel-based analysis of cerebral blood flow abnormalities in obsessive-compulsive disorder using pseudo-continuous arterial spin labeling MRI

Daichi Momosaka; Osamu Togao; Akio Hiwatashi; Koji Yamashita; Kazufumi Kikuchi; Hirofumi Tomiyama; Tomohiro Nakao; Keitaro Murayama; Yuriko Suzuki; Hiroshi Honda

doi:10.1371/journal.pone.0236512

Peer Review History

Original SubmissionFebruary 27, 2020
6 May 2020 Decision Letter - Xi Chen, Editor PONE-D-20-05758 A voxel-based analysis of cerebral blood flow abnormalities in obsessive-compulsive disorder using pseudo-continuous arterial spin labeling MRI A cerebral blood flow analysis of obsessive-compulsive disorder using MRI PLOS ONE Dear Dr. Momosaka, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. We would appreciate receiving your revised manuscript by Jun 20 2020 11:59PM. When you are ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. 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Please amend either the title on the online submission form (via Edit Submission) or the title in the manuscript so that they are identical. [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: Yes ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 3. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: No ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ******** 5. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: Momosaka and colleagues identified regions of frontal operculum, midcingulate cortex and putamen with lower rCBF in OCD patients using ASL imaging. Moreover, these significant brain regions mostly targeted in the cortico-striatal-thalamic circuit, which provides more evidence of CSTC physiological disruption through ASL modality. It's a very interesting study. The analysis methods appeared to be sound and thus the group differences are very robust. I also have a couple of additional suggestions to improve this manuscript. Major comments: 1, In the inclusion criteria of OCD patients, the authors did not mention whether the patients have the comorbidity of depression and anxiety symptoms, as comorbidity issue is very common in the clinically psychiatric diagnosis. The author should at least address this point. If yes, whether this comorbidity could have an impact on the results. 2, The authors reported the results of both nonparametric and parametric tests. I think nonparametric results are good enough to illustrate the main findings of this study and more strict to identify the abnormal regions in OCD in this paper. So, I would suggest to remove the results of parametric results. 3, In the introduction, the author mentioned higher signal-to-noise ratio in the pCASL, which could be helpful to sensitively detect the brain abnormalities in OCD. Moreover, they found lower rCBF in the regions of the temporal pole and frontal operculum, which is in or very close to the regions with lower signal-to-noise ratio in the neuroimaging correction. Could the authors test the effect of SNR among these regions showing between-group differences? 4, In the discussion, the authors could add more discussion about the relationship between decreased rCBF and its associated disrupted pathophysiology of OCD. In other words, why does OCD show decreases of rCBF, rather than increased rCBF? What does lower rCBF imply in the links with the symptomatology of OCD? Minor comments: 1, In the abstract, the authors said the alterations of cerebral perfusion may precede structrual changes in OCD, which does not make sense and is not rigorous. The authors did not have longitudinal results to support this point. It's very difficult to make a conclusion of the order of functional and structural changes for the current results. The authors could just say there is no structural changes in OCD while physiological disruption occurs in OCD patients. Thus, I would suggest to remove this kind of description in the manuscript. 2, In the Methods, the authors did not mention the resample of neuroimaging. Resample to 333? 3, Even though the authors regressed out total brain volume in the between-group comparisons of rCBF, they should report the results of between-group comparison of total brain volume before they do the VBM analysis. Because sometimes structural changes did not meet the multiple testing in voxel-level analysis, while it could have subtle changes in the global or regional level. 4, In the Methods, the authors run the nonparametric analysis with 5000-time permutation. Why not choose 10000 permutations, which is more commonly used. Reviewer #2: This paper proposes to identify abnormalities of regional cerebral blood flow (rCBF) in obsessive compulsive disorder (OCD) patients by means of a voxel-based analysis of pseudo continuous arterial spin labeling (pCASL) perfusion images. A study of 23 OCD patients and 64 health controls is conducted by performing a patient recruitment, MRI data acquisition, data preprocessing, Voxel-based morphometry and statistical analysis. The results and discussion are included to show that the rCBF reductions in these regions observed in OCD patients could be associated with the pathophysiology of OCD. Overall this is an interesting paper that studies an important topic in rCBF analysis of OCD patients. The author novelly proposed to use the entire brain analysis instead of ROI-based methods. Essential research protocols and experiments are set up to study the subjects. The pseudo-continuous ASL (pCASL) perfusion imaging technique is used for MRI to capture and examine the difference in rCBF between patients and healthy controls. In the statistical analysis and discussion, a concrete observation and precise conclusion is summarized with enough discussion about limitation. From the application and study perspective, this paper proposes a good method in medical field with sufficient experiment details. However, there are several points that can be further improved: * The data is not clearly explained and published, which may violate the PLOS Data policy. It's suggested to give a location of the data used and made it public available. Specifically, the statistic analysis part doesn't give a detail about data points, there is only limited summary and overview. * The experiment is a little bit weak to support the effectiveness of proposed approach. It's suggested to compare the results with other baseline approaches (for example, ROI-based approach). Such comparison will make it more clear to readers and highlights the improvement over other existing methods. Overall this is an interesting paper, I recommend the author to further improve this paper and address above issues to make it better. ******** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: No Reviewer #2: No [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". 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Revision 1
13 Jun 2020 Author Response Reviewer #1: Major comments: 1, In the inclusion criteria of OCD patients, the authors did not mention whether the patients have the comorbidity of depression and anxiety symptoms, as comorbidity issue is very common in the clinically psychiatric diagnosis. The author should at least address this point. If yes, whether this comorbidity could have an impact on the results. Response: In this study, we excluded OCD patients with a comorbid axis I diagnosis (including mood and anxiety disorders) by using the structured clinical interview for the DSM-IV axis I disorders, patient edition (p.8, lines 99-102). Thus, none of the OCD patients in this study had any comorbid axis I disorders. 2, The authors reported the results of both nonparametric and parametric tests. I think nonparametric results are good enough to illustrate the main findings of this study and more strict to identify the abnormal regions in OCD in this paper. So, I would suggest to remove the results of parametric results. Response: We have removed the results for the parametric analyses as suggested. All analyses including the comparison of rCBF and gray matter volume between the OCD patients and healthy controls and the regression analysis within the OCD patients used the nonparametric test. The results obtained with the nonparametric test were the same as those obtained with the parametric test. 3, In the introduction, the author mentioned higher signal-to-noise ratio in the pCASL, which could be helpful to sensitively detect the brain abnormalities in OCD. Moreover, they found lower rCBF in the regions of the temporal pole and frontal operculum, which is in or very close to the regions with lower signal-to-noise ratio in the neuroimaging correction. Could the authors test the effect of SNR among these regions showing between-group differences? Response: In general, ASL using EPI inevitably suffers from susceptibility artifacts in mesial temporal regions due to the proximity of the skull base and air-containing structures (Petcharunpaisan et al., World J Radiol 2010;2). Distortions of raw pCASL images in regions of high magnetic field susceptibility may lead to a low signal-to-noise ratio (SNR) to some extent; we have therefore measured SNRs within the circular region-of-interest (ROI) placed on the right temporal pole and the right frontal operculum on the label images of the pCASL in all subjects. The SNR was also measured in the right cerebellar hemisphere as a reference. We calculated the SNRs by using the following formula (Yu et al., BMC Medical Imaging 2018;18): SNR=0.655 × μ_tissue⁄σ_air where μ_tissue is the mean signal intensity within the ROI positioned on each area of the brain, and σ_air is the standard deviation of the signal intensity within the ROI placed on the air. As a result, the SNR in the right temporal pole was high enough, and there was no major difference in mean SNR between the right temporal pole and the right cerebellar hemisphere (175.8 ± 104.3 vs. 214.0 ± 124.5). In addition, as we did not directly analyze raw pCASL images but rather focused on the between-group differences in quantitative rCBF maps, we think that the SNR of the raw pCASL image doesn’t critically affect the final results. However, since the SNR of the right temporal lobe was a little lower in fact, we have added this issue to the limitation section of the Discussion (p. 23-24, line 348-354). The SNR of the right frontal operculum was also high enough and not lower than that of the right cerebellar hemisphere (358.8 ± 260.0 vs. 214.0 ± 124.5). 4, In the discussion, the authors could add more discussion about the relationship between decreased rCBF and its associated disrupted pathophysiology of OCD. In other words, why does OCD show decreases of rCBF, rather than increased rCBF? What does lower rCBF imply in the links with the symptomatology of OCD? Response: Considering the neurovascular coupling theory, the reduction in rCBF shown in the present study might reflect functional decline of the corresponding areas. We have clarified this point throughout the Discussion section and more thoroughly discussed the relationships between the functional decline of the areas detected in the present study and the symptomatology of OCD, referencing previous functional MRI studies (p.17-20, 252-299). Minor comments: 1, In the abstract, the authors said the alterations of cerebral perfusion may precede structrual changes in OCD, which does not make sense and is not rigorous. The authors did not have longitudinal results to support this point. It's very difficult to make a conclusion of the order of functional and structural changes for the current results. The authors could just say there is no structural changes in OCD while physiological disruption occurs in OCD patients. Thus, I would suggest to remove this kind of description in the manuscript. Response: We have removed the description about the order of functional and structural changes. Instead, we concluded as follows: it was possible that the ASL could sensitively detect physiologically impaired areas without structural abnormalities even in the small sample size (p.21, line 315-317). 2, In the Methods, the authors did not mention the resample of neuroimaging. Resample to 333? Response: Thank you for pointing this out. In the present study, the rCBF maps were first resampled to 1�1�1 mm. Specifically, the M0 images are co-registered and resampled to the 3D T1WIs with 1�1�1 mm resolution; then, the same transformations were applied to the raw rCBF maps. After the normalization to the brain template and smoothing, the resolution was finally changed to 2�2�2 mm. We have added a new Fig 2 which illustrates the details of the preprocessing steps applied to the pCASL maps. 3, Even though the authors regressed out total brain volume in the between-group comparisons of rCBF, they should report the results of between-group comparison of total brain volume before they do the VBM analysis. Because sometimes structural changes did not meet the multiple testing in voxel-level analysis, while it could have subtle changes in the global or regional level. Response: Thank you for this suggestion. We have compared the total brain volume between the OCD patients and healthy controls and confirmed that there was no significant difference. We have added this result to Table 1. In addition, detailed subjects’ information including total brain volume has been added as supplemental data (S1 and S2 Appendices). 4, In the Methods, the authors run the nonparametric analysis with 5000-time permutation. Why not choose 10000 permutations, which is more commonly used. Response: We have re-calculated all nonparametric analyses with 10,000-time permutations. The main findings are identical. We have replaced the previous 5,000-permuations results with the new results with 10,000-time permutations. Reviewer #2: The data is not clearly explained and published, which may violate the PLOS Data policy. It's suggested to give a location of the data used and made it public available. Specifically, the statistic analysis part doesn't give a detail about data points, there is only limited summary and overview. Response: We have added the subjects' detailed information including individual age, gender, education years, total brain volume, illness duration, and Y-BOCS score as supplemental data (S1 and S2 Appendices). The raw results of the rCBF comparison between the OCD patients and healthy controls acquired by using SnPM13 were also added as S3 Appendix. Regarding the statistical analysis section, we have added descriptions of the analytical methods, tools and parameters in as much detail as possible (p.13-14, line 179-198). The experiment is a little bit weak to support the effectiveness of proposed approach. It's suggested to compare the results with other baseline approaches (for example, ROI-based approach). Such comparison will make it more clear to readers and highlights the improvement over other existing methods. Response: We have performed an ROI-based analysis in addition to the main voxel-based analysis in order to compare the analytical methods. The ROI-based analysis was performed focusing on the areas corresponding to the right putamen, the right frontal operculum, the left midcingulate cortex, and the right temporal pole, which demonstrated significant rCBF reductions in the OCD patients compared to the healthy controls in the voxel-based analysis. The detailed information of the additional ROI-based analysis is provided as Appendix S4. The ROI-based analysis detected a reduction of the rCBF in the areas corresponding to the right putamen and right temporal pole; however, it failed to detect an rCBF reduction in the right frontal operculum or the left midcingulate cortex (p.16, line 231-237). This might be because the ROIs gathered together large heterogeneous subregions with separate functional roles, resulting in the missing of small foci of decreased rCBF. Thus, it seems that the voxel-based approach has an advantage over the ROI-based approach in detecting smaller areas with rCBF abnormalities. We have added this description to the Discussion (p.22-23, line 327-335). Attachments Attachment Submitted filename: Response to Reviewers.docx https://doi.org/10.1371/journal.pone.0236512.r002
9 Jul 2020 Decision Letter - Xi Chen, Editor A voxel-based analysis of cerebral blood flow abnormalities in obsessive-compulsive disorder using pseudo-continuous arterial spin labeling MRI PONE-D-20-05758R1 Dear Dr. Momosaka, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Xi Chen Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation. Reviewer #1: All comments have been addressed Reviewer #2: All comments have been addressed ******** 2. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 4. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 6. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: All the points that I mentioned have been well addressed. A good paper to identify some interesting regions associated with OCD in ASL. Reviewer #2: The revised version addressed the major and minor issues in the comments. Specifically, more descriptions about dataset are included in the article with supplement materials. In additional, a ROI-based analysis is added with sufficient details in the statistical analysis and discussion. Some of the key points and questions are also answered and reflected in the corresponding section to be more concise and convincing. I would suggest to accept this paper for publishing. ****** 7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: No Reviewer #2: No https://doi.org/10.1371/journal.pone.0236512.r003
Formally Accepted
14 Jul 2020 Acceptance Letter - Xi Chen, Editor PONE-D-20-05758R1 A voxel-based analysis of cerebral blood flow abnormalities in obsessive-compulsive disorder using pseudo-continuous arterial spin labeling MRI Dear Dr. Momosaka: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Xi Chen Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0236512.r004

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