On 2014 Feb 14, Henning Voss commented:

We were aware of the possibility of artefacts in DTI at the time of publishing of [1], and therefore as noted in our study [1] we tested for increased residuals in the tensor fits, which would be a sign of the artefact described in [2] and [3]. We did not find increased residuals in the medial parietal occipital region or the cerebellar vermis. In particular for the vermis, later we also created plots corresponding to [3], Figure 2, on higher quality data of the same subject obtained with a headcoil unavailable at the time of first timepoint of study (not published) which showed the same effect. We did not find any hint for the artefact there, either. We also compared this case with 20 healthy control subjects scanned on the same equipment with the same protocol and the patient had the highest anisotropy in the medial parietal occipital region.

[1] Voss HU, Uluç AM, Dyke JP, Watts R, Kobylarz EJ, McCandliss BD, Heier LA, Beattie BJ, Hamacher KA, Vallabhajosula S, Goldsmith SJ, Ballon D, Giacino JT, Schiff ND. Possible axonal regrowth in late recovery from the minimally conscious state. J Clin Invest. 2006 Jul;116(7):2005-11. [2] Berl M, Walker L, Sarlls J, and Pierpaoli, C. Investigation of vibration induced artifacts in clinical diffusion weighted imaging of the brain. Proc. Intl. Soc. Mag. Reson. Med. 20, 3740 (2012). [3] Gallichan D, Scholz J, Bartsch A, Behrens TE, Robson MD, Miller KL. Addressing a systematic vibration artifact in diffusion-weighted MRI. Hum Brain Mapp. 2010 Feb;31(2):193-202.

H.U. Voss and N.D. Schiff

On 2013 Nov 04, Jamie Horder commented:

In a conference abstract, Berl and colleagues suggested that the striking results presented in this paper may have been the result of an artifact, observed in some MRI DTI sequences.

They argued that although the vibration signal-loss artifact in question is best known as an issue on Siemens MRI scanners, GE scanners, such as the one used in the Voss study, are not immune.

Berl et al wrote:

"The artifact may be the basis for a clinical misinterpretation that has been cited as evidence to change policy and practice [i.e the Voss study]. The speed that this article was propagated was assisted by the inherent interest of the case details; however, it also illustrates the danger of premature clinical interpretation of DTI data.

We suggest that repositioning the patient by adjusting the roll would be a simple and practical method to determine if such findings were indeed axonal regrowth or artifact."

On 2013 Nov 04, Jamie Horder commented:

In a conference abstract, Berl and colleagues suggested that the striking results presented in this paper may have been the result of an artifact, observed in some MRI DTI sequences.

They argued that although the vibration signal-loss artifact in question is best known as an issue on Siemens MRI scanners, GE scanners, such as the one used in the Voss study, are not immune.

Berl et al wrote:

"The artifact may be the basis for a clinical misinterpretation that has been cited as evidence to change policy and practice [i.e the Voss study]. The speed that this article was propagated was assisted by the inherent interest of the case details; however, it also illustrates the danger of premature clinical interpretation of DTI data.

We suggest that repositioning the patient by adjusting the roll would be a simple and practical method to determine if such findings were indeed axonal regrowth or artifact."

On 2014 Feb 14, Henning Voss commented:

We were aware of the possibility of artefacts in DTI at the time of publishing of [1], and therefore as noted in our study [1] we tested for increased residuals in the tensor fits, which would be a sign of the artefact described in [2] and [3]. We did not find increased residuals in the medial parietal occipital region or the cerebellar vermis. In particular for the vermis, later we also created plots corresponding to [3], Figure 2, on higher quality data of the same subject obtained with a headcoil unavailable at the time of first timepoint of study (not published) which showed the same effect. We did not find any hint for the artefact there, either. We also compared this case with 20 healthy control subjects scanned on the same equipment with the same protocol and the patient had the highest anisotropy in the medial parietal occipital region.

[1] Voss HU, Uluç AM, Dyke JP, Watts R, Kobylarz EJ, McCandliss BD, Heier LA, Beattie BJ, Hamacher KA, Vallabhajosula S, Goldsmith SJ, Ballon D, Giacino JT, Schiff ND. Possible axonal regrowth in late recovery from the minimally conscious state. J Clin Invest. 2006 Jul;116(7):2005-11. [2] Berl M, Walker L, Sarlls J, and Pierpaoli, C. Investigation of vibration induced artifacts in clinical diffusion weighted imaging of the brain. Proc. Intl. Soc. Mag. Reson. Med. 20, 3740 (2012). [3] Gallichan D, Scholz J, Bartsch A, Behrens TE, Robson MD, Miller KL. Addressing a systematic vibration artifact in diffusion-weighted MRI. Hum Brain Mapp. 2010 Feb;31(2):193-202.

H.U. Voss and N.D. Schiff