Corrigendum to “Intracranial vascular feature changes in time of flight MR angiography in patients undergoing carotid revascularization surgery” [Magn. Reson. Imaging, 75, Jan 2021, 45–50] (Magnetic Resonance Imaging (2021) 75 (45–50), (S0730725X20306093), (10.1016/j.mri.2020.10.004))

The authors regret that in our original paper, an incorrect intensity scaling factor was used during calculation of the quantitative cerebral blood flow (CBF) map from the arterial spin labeling (ASL) perfusion-weighted image (i.e. Control - Label) and proton density (PD) image. Specifically, to calculate CBF from PWI and PD images that are acquired with the GE Discovery MR750 scanner and saved in Dicom format, the following equation, which is adapted from the recommended model by Alsop D et al. [1], should be used: [Formula presented] where λ is the blood–brain partition coefficient and assumed to be 0.9 mL/g, PLD is the post labeling delay, T_{1, blood} is the T1 relaxation time of blood and assumed to be 1.65 s at 3 T, α is the labeling efficiency and assumed to be 0.8, τ is the labeling duration, TR is the repetition time, T_{1, gm} is the T1 relaxation time of gray matter and assumed to be 1.2 s at 3 T, the term [Formula presented] is used to compensate the incomplete recovery of longitudinal magnetization in the PD image, SI_PWI and SI_PD are the signal intensities in the Dicom images of PWI and PD, respectively, 32 is a constant scaling factor used for GE MR scanner, and NEX is the number of averages and has a value of 3 or 4 in this study. In our original paper, we incorrectly used a scaling factor of 100 instead of 32 ∙ NEX. After updating the ASL CBF values with the correct equation, the behavior of ASL CBF across the three time points remained similar to that in the original paper, i.e. the CBF value increased dramatically from TP1 to TP2 and then decreased to a level slightly larger than TP1 at TP3. However, the difference between TP1 and TP3 became statistically insignificant (i.e. the P value changed from 0.027 to 0.159). Additionally, the correlation of ASL CBF between TP2 and TP3 became statistically significant. These updates do not change the main message of this study, which is focused on the vascular features on TOF MRA, but do necessitate revisions to the article. Below are details of the needed revisions: 1. In the Abstract, the sentence “Similar to ASL CBF, TOF vascular features (i.e. total vessel length, total vessel volume and number of branches) increased dramatically from baseline to post-surgery, then returned to a level slightly higher than the baseline in long-term follow-up (All P < 0.05). Correlation between time points was observed for all three TOF vascular features but not for ASL CBF” should read as “Similar to ASL CBF, TOF vascular features (i.e. total vessel length, total vessel volume and number of branches) increased dramatically from baseline to post-surgery, then returned to a level slightly higher than the baseline in long-term follow-up (all P < 0.05 except difference between baseline and long-term follow-up ASL CBF). Correlation between the three time points was observed for nearly all three TOF vascular features, while only correlation between post-surgery and long-term follow-up was observed for ASL CBF.”2. The ASL CBF maps in Fig. 1 should be updated. The updated Fig. 1 is as follows:[Formula presented]3. The ASL CBF maps in Fig. 2 should be updated. The updated Fig. 2 is as follows: [Formula presented] 4. The ASL CBF maps in Fig. 3 should be updated. The updated Fig. 3 is as follows:[Formula presented]5. In legend of Fig. 3, the sentence “then decreased to a level slightly larger than TP1 at TP3” should read as “then decreased to a level similar to or slightly larger than TP1 at TP3”.6. The ASL CBF values in Table 2 should be updated. The updated Table 2 is as follows: [Table presented] 7. The statistical results related to ASL CBF in Table 3 should be updated. The updated Table 3 is as follows: [Table presented] 8. On page 47, the last paragraph of Results section, the sentences “For ASL CBF and the TOF vascular features, values increased greatly from TP1 to TP2 and then decreased to a level slightly larger than TP1 at TP3 (all P < 0.05). Representative images on 3 subjects are shown in Fig. 3. The ASL CBF showed no correlation between time points, while most of the TOF vascular features did.” should read as “For ASL CBF and the TOF vascular features, values increased greatly from TP1 to TP2 and then decreased to a level slightly larger than TP1 at TP3 (all P < 0.05 except difference between TP1 and TP3 ASL CBF). Representative images on 3 subjects are shown in Fig. 3. The ASL CBF showed correlation only between TP2 and TP3, while most of the TOF vascular features showed correlation for all pairs of time points.”.9. On Page 47, the second paragraph of Discussion section, the sentences “Several studies also examined long-term (more than one month after surgery) perfusion measurements and reported findings similar to this study, that long-term perfusion is smaller than that acquired early post-operatively [18,20]. However, unlike findings of the present study that TP3 perfusion is slightly larger than TP1 (see Tables 2–3), these previous studies did not observe a significant difference between preoperative and long-term perfusion [18,20] except one study indicating a long-term increase of the ipsilateral ASL CBF in the MCA borderzone region [21]. This inconsistency may be due to multiple factors, such as the small sample size in most of these studies, unattended potential labeling failures in previous studies using ASL imaging [20], different study populations, and different time interval from surgery.” should be changed to “Several studies also examined long-term (more than one month after surgery) perfusion measurements and reported findings similar to this study, that long-term perfusion is smaller than that acquired early post-operatively and similar to that acquired pre-operatively [18,20].”, given that the difference between TP1 and TP3 ASL CBF was not statistically significant after updating the data.10. On Page 47–48, the third paragraph of Discussion section, the sentence “In particular, the observation that the TOF vascular features had slightly larger values at TP3 than TP1 seems to strengthen the same observation on ASL CBF, which was seldomly reported by previous studies.” should read as “The observation that the TOF vascular features had slightly larger values at TP3 than TP1 seems to be in line with the similar trend on ASL CBF, although this trend on ASL CBF was not statistically significant.”.11. On Page 48, the fourth paragraph of Discussion section, the sentence “On the other hand, unlike ASL CBF, there are correlations between time points for TOF vascular features (Table 3).” should read as “On the other hand, unlike ASL CBF that showed correlation only between post-surgery and long-term follow-up, there are correlations for almost all pairs of time points for TOF vascular features (Table 3).”.The authors sincerely apologize to readers for these errors.