====== Readout segmentation ======

Readout [[segmentation]] (RS-EPI) has been suggested as a promising variant to [[echo-planar imaging]] (EPI) for high-resolution [[imaging]].

[[Diffusion tensor imaging tractography]] is commonly used in neurosurgical practice but is largely limited to the [[preoperative]] setting. This is due primarily to image degradation caused by [[susceptibility artifact]] when conventional single-shot (SS) [[echo-planar imaging]] (EPI) DTI (SS-DTI) is acquired for open cranial, surgical position intraoperative DTI (iDTI). Readout-segmented (RS) EPI DTI (RS-DTI) has been reported to reduce such artifact but has not yet been evaluated in the [[intraoperative magnetic resonance imaging]] (iMRI) environment. 
Elliott et al. evaluated the performance of RS versus SS EPI for DTI of the human brain in the iMRI setting.

Pre- and intraoperative 3-T 3D T1-weighted and 2D multislice RS-iDTI (called RESOLVE [readout segmentation of long variable echo-trains] on the Siemens platform) and SS-iDTI images were acquired in 22 adult patients undergoing intraaxial iMRI resections for suspected [[low-grade glioma]] (14; 64%), high-grade glioma (7; 32%), or focal cortical dysplasia. Regional susceptibility artifact, anatomical deviation relative to T1-weighted imaging, and tractographic output for surgically relevant tracts were compared between iDTI sequences as well as the intraoperative tract shifts from preoperative DTI.

RS-iDTI resulted in qualitatively less regional susceptibility artifact (resection cavity, orbitofrontal and anterior temporal cortices) and mean anatomical deviation in regions most prone to susceptibility artifact (RS-iDTI 2.7 ± 0.2 vs SS-iDTI 7.5 ± 0.4 mm) compared to SS-iDTI. Although tract reconstruction success did not significantly differ by DTI method, susceptibility artifact-related tractography failure (of at least 1 surgically relevant tract) occurred for SS-iDTI in 8/22 (36%) patients, and in 5 of these 8 patients RS-iDTI permitted successful reconstruction. Among cases with successful tractography for both sequences, maximal intersequence differences were substantial (mean 9.5 ± 5.7 mm, range -27.1 to 18.7 mm).

[[Readout segmentation]] EPI enables higher quality and more accurate [[DTI]] for surgically relevant [[tractography]] of major [[white matter tract]]s in intraoperative, open cranium neurosurgical applications at [[3 Tesla]]
((Elliott CA, Danyluk H, Aronyk KE, Au K, Wheatley BM, Gross DW, Sankar T,
Beaulieu C. Intraoperative acquisition of DTI in cranial neurosurgery:
readout-segmented DTI versus standard single-shot DTI. J Neurosurg. 2019 Aug
16:1-10. doi: 10.3171/2019.5.JNS19890. [Epub ahead of print] PubMed PMID:
31419798.
)).