Brain lesions: Can 3D FLAIR imaging replace 2D FLAIR at 3T? Shingo Kakeda1, Yasuhiro Hiai2, Norihiro Ohnari1, Toru Sato1, Yukunori Korogi1 1) Department of Radiology, University of Occupational and Environmental Health School of Medicine, Iseigaoka 1-1, Yahatanishi-ku, Kitakyushu , Japan. 2) Department of Radiology, Kumamoto University School of Medicine

A 3D FLAIR technique can reduce CSF pulsation artifacts and offer excellent SNR compared with standard 2D FLAIR (Invest Radiol 2008;43: ). Isotropic 3D FLAIR has been superior to the 2D FLAIR in the detection of MS lesions (Eur Radiol. 2002;12:559-67). However, no previous studies performed a direct comparison between 2D and 3D FLAIR to evaluate various brain lesions other than MS lesions. Introduction

Purpose Prospective study To compare the image contrast of various brain lesions on 2D and 3D FLAIR images. To determine whether 3D FLAIR can replace 2D FLAIR in routine MR examinations.

3T MR system (Signa EXCITE 3T; GE Healthcare) Three healthy volunteers We investigated the effects of varying TR and TE on the image quality and GM-WM contrasts with the 3D FLAIR sequences. Materials and Methods Healthy volunteer study Sequence parameters of 3D FLAIR TR (ms) TE (ms) TI (ms) FOV22 ST1.2 F-resol224 P-resol224 AF2.86 scan time4:155:397:048:2811:038:245:344:543:54

Optimization of TR TR=6000 TR=8000TR=10000TR= min 15 sec5min 39sec7min 4sec 8min 28sec TR of was chosen when considering acquisition time. Overall image quality and GM-WM contrast > TR=6000, TR=8000TR=10000,TR=12000

TE=83 11min 3sec TE=104 8min 24sec TE=114 7min 4sec TE=140 5min 34sec TE=15 44min 54sec TE=183 3min 54sec Optimization of TE (TR=10000) For overall image quality and GM-WM contrast, TE of 114 msec was considered the best.

2D FLAIR 3D FLAIR (Cube) TR (ms) TE (ms) TI (ms) Band width (kHz) FOV (cm)22cm Slice-thickness (mm)5mm1.2mm F-resolution P-resolution Acceleration factor12.86 Scan time (min, sec.)3:20 7:02 For 3D FLAIR, TR of and TE of 114 msec was chosen. Spatial resolution was 1.0 x 1.0 x 1.2-mm with 3D FLAIR. Sequence parameters of 2D and 3D FLAIR

Prospective study 117 patients suspected of having brain lesions underwent MR imaging both with 2D and 3D FLAIR. Materials and Methods Patient study No lesions; 35 patients Two different types of lesion in 7 of 82 patients. A total of 89 different lesions (82 patients) were evaluated.

Summary of the lesions MS lesion (n=4)Chronic trauma (n=5) Ischemic lesions or infarction (n=34)Traumatic SAH (n=1) Acute infarction (n=2)Gray matter heterotopia (n=2) Old infarction (n=22)Subdural hematoma (n=4) Moyamoya disease (n=10)Superficial siderosis (n=1) Intracranial hemorrhage (n=3)Leptomeningeal metastasis (n=1) White matter lesion (n=12)Hippocampal sclerosis (n=7) PRES (n=1) Brain tumors (n=14) Glioma (n=9) Metastatic tumor (n=3) Meningioma (n=2)

3-point grading system (Radiology 212, ) + 1: 3D FLAIR were superior to 2D FLAIR. 0: 3D and 2D FLAIR were equal. - 1: 3D FLAIR were inferior to 2D FLAIR. Qualitative analysis Three qualitatively analyses (lesion conspicuity, lesion detection, and image artifacts) Two neuroradiologists When the answers of the radiologists were scored as +1 or -1, the radiologists were asked to provide a possible reason.

Result: Qualitative analysis Lesion conspicuity; (+1) in 16 (18%) in 89 lesions, as equal (0) in 68 (76%), and as (-1) in 5 (6%). Lesion detection; (+1) in 11 (12%) in 89 lesions, equal (0) in 76 (85%), and (-1) in 2 (2%). Artifacts; (+1) in all 97 patients (100%). Radiologists rated as 3-point grading system (Radiology 212, ) + 1: 3D FLAIR were superior to 2D FLAIR. 0: 3D and 2D FLAIR were equal. - 1: 3D FLAIR were inferior to 2D FLAIR.

ConspicuityDetection MS lesion (n=4) Ischemic lesions or infarction Acute infarction (n=2) Old infarction (n=22) Moyamoya disease (n=10) Intracranial hemorrhage (n=3) White matter lesion (n=12) PRES (n=1) Chronic trauma (n=5) Gray matter heterotopia (n=2) For lesion detection, 7 lesions rated as (+1) were small and located in the brain stem, and 3 were small lesions in patient with chronic trauma. Result: Qualitative analysis-1

ConspicuityDetection Brain tumors (n=14) Glioma (n=9) Metastatic tumor (n=3) Meningioma (n=2) Traumatic SAH (n=1) Subdural hematoma (n=4) Superficial siderosis (n=1) Result: Qualitative analysis-2 For lesion conspicuity of the extraaxial tumors and the subarachnoid hemorrhage, 3D FLAIR was superior to 2D FLAIR images due to the uniform suppression of the CSF signal.

MS lesions 3D FLAIR2D FLAIR Traumatic lesion (DAI) 3D FLAIR2D FLAIR Lesions rated as (+1) 3D FLAIR2D FLAIR Cerebellopontine angle meningioma

ConspicuityDetection Leptomeningeal metastasis (n=1) Hippocampal sclerosis (n=7) Result: Qualitative analysis-3 For lesion conspicuity, 3 hippocampal sclerosis and 1 leptomeningeal metastasis were rated as (-1).

Lesions rated as (-1) 3D FLAIR2D FLAIR Left-sided hippocampal sclerosis 2D FLAIR 3D FLAIR Leptomeningeal metastasis from breast cancer

Discussion For the detection of the small lesions in the brain stem, 3D FLAIR was superior to 2D FLAIR. Possible explanations may be due to the high spatial resolution with 3D FLAIR (1.0 x 1.0 x 1.2-mm resolution). due to the suppression of CSF pulsation artifacts with 3D FLAIR. The presence of CSF pulsation artifacts on 2D FLAIR contributes to the insufficient contrast of MS lesions in the brain stem (Radiology 212, ).

Discussion In all patients, CSF pulsation artifacts on 3D FLAIR were less than those on 2D FLAIR. Uniform suppression of the CSF signal with 3D FLAIR could be useful for the detection of subarachnoid space lesions such as the extraaxial tumors or SAH.

Discussion For depiction of the hippocampal sclerosis and leptomeningeal metastasis, 3D FLAIR were inferior to 2D FLAIR. An abnormal signal intensity of the hippocampus on 3D FLAIR may have the relaxation times similar to those of adjacent brain parenchyma. The 3D FLAIR may have a lower sensitivity than 2D FLAIR for the conspicuity of the subarachnoid space or meningeal abnormalities.

A 3D FLAIR is equal or superior to the standard 2D FLAIR in the conspicuity and detection of the various brain lesions and can replace 2D FLAIR in most patients, although 3D FLAIR has some pitfalls. Conclusion