Voxel-based Investigations of Phase Mask Effects on Susceptibility Weighted Images

Eo Jin Hwang; Min Ji Kim; Hyug Gi Kim; Chang Woo Ryu; Geon Ho Jahng

doi:10.14316/pmp.2013.24.1.25

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Hwang, Kim, Kim, Ryu, and Jahng: Voxel-based Investigations of Phase Mask Effects on Susceptibility Weighted Images

Original Article

Progress in Medical Physics 2013;24(1):25-34.

Published online: 20 March 2013

DOI: https://doi.org/10.14316/pmp.2013.24.1.25

Voxel-based Investigations of Phase Mask Effects on Susceptibility Weighted Images

Eo Jin Hwang^∗, Min Ji Kim^∗, Hyug Gi Kim^†, Chang Woo Ryu^∗, Geon Ho Jahng^∗,

^∗Department of Radiology, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University, Seoul, Korea

^†Department of Biomedical Engineering, College of Electronic Information Engineering, Kyung Hee University, Yongin, Korea

Corresponding Author: Geon-Ho Jahng, Department of Radiology, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University, 149, Sangil-dong, Gangdong-gu, Seoul 134-727, Korea Tel: 02)440-6187, Fax: 02)440-6932 E-mail: ghjahng@gmail.com

This study was supported by a grant of the Korean Health TechnologyR&D Project, Ministry of Health & Welfare, Republic of Korea (A111282).

Received 8 November 2012 Accepted 5 March 2013

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

To investigate effects of phase mask on susceptibility-weighted images (SWI) using voxel-based analyses in normal elderly subjects. A three-dimensional (3D) gradient echo sequence ran to obtain SWIs in 20 healthy elderly subjects. SWIs with two (SWI2) and four (SWI4) phase multiplications were achieved with positive (PSWI) and negative (NSWI) phase masks to investigate phase mask effects. The voxel-based comparisons were performed using paired t-tests between PSWI and NSWI and between SWI2 and SWI4. Differences of signal intensities between magnitude images and SWI4 were larger than those between magnitude images and SWI2s. Differences of signal intensities between magnitude images and PSWIs were larger than those between magnitude images and NSWIs. Moreover, the signal intensities from NSWI2s and NSWI4s were greater than those from PSWI2s and PSWI4s, respectively. More differences of signal intensities between NSWI4 and PSWI4s were found than those between NSWI2s and PSWI2s in the whole brain images. The voxel-based analyses of SWI could be beneficial to investigate susceptibility differences on the entire brain areas. The phase masking method could be chosen to enhance brain tissue contrast rather than to enhance venous blood vessels. Therefore, it is recommended to apply voxel-based analyses of SWI to investigate clinical applications.

Keywords: Susceptibility Weighted Imaging (SWI), Phase mask, Voxel-wise investigation

References

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Fig. 1.

The representative whole brain images obtained from a healthy human subject. Magnitude (a), phase (b), positively phase-masked susceptibility-weighted image (SWI) with 2 phase mask multiplications (PSWI2, c), negatively phase-masked SWI with 2 phase mask multiplications (NSWI2, d), positively phase-masked SWI with 4 phase mask multiplications (PSWI4, e), negatively phase-masked SWI with 4 phase mask multiplications (NSWI4, f).

Fig. 2.

Results of voxel-wise comparisons between magnitude images and positively (P) phase-masked susceptibility weighted images (SWIs) with two different phase mask multiplications. Comparison between magnitude images and positively phase-masked SWI with 2 phase mask multiplications (magnitude＞ PSWI2, a) and between magnitude images and positively phase-masked SWI with 4 phase mask multiplications (magnitude＞PSWI4, b). No significant differences were found between P_SWI2 and P_SWI4.

Fig. 3.

Results of voxel-wise comparisons between magnitude images and negatively (N) phase- masked susceptibility weighted image (SWI) with two different phase mask multiplications. Comparisons between magnitude images and negatively phase-masked SWI with 2 phase mask multiplications (magnitude＞NSWI2, (a), between magnitude images and negatively phase-masked SWI with 4 phase mask multiplications (magnitude＞NSWI4, (b), and between NSWI2 and NSWI4 (NSWI2＞NSWI4, c).

Fig. 4.

Results of voxel-wise comparisons between susceptibility-weighted imaging (SWI) with the positive (P) phase mask and that with the negative (N) phase mask with the whole brain with the threshold of family-wise error rate (FWE) p=0.005. (a) Comparison between the whole brain negatively phase-masked SWI with 2 phase mask multiplications and positively phase-masked SWI with 2 phase mask multiplications (NSWI2＞ PSWI2). (b) Comparison between the whole brain negatively phase-masked SWI with 4 phase mask multiplications and positively phase-masked SWI with 4 phase mask multiplications (NSWI4＞PSWI4).

Table 1.

Anatomical regions showing significant differences between magnitude and positively (P) phase-masked susceptibility-weighted imaging (SWI).

Anatomy	Magnitude＞PSWI2				Magnitude＞PSWI4
	Talairach coordinate			T－score	Talairach coordinate			T－score
	x	y	z	T	x	y	z	T
R. Culmen	6.35	－47.78	－6.45	41.98	6.35	－47.78	－6.45	40.56
					5.29	－69.72	－3.14	40.31
					8.15	－51.77	－4.09	39.86
L. Culmen	－8.46	－59.55	－10.52	39.06	－8.45	－44.9	－6.43	42.17
	－16.8	－61.46	－9.94	39.57
R. Dendate					14.86	－56.5	－23.35	52.37
R. Superior Frontal Gyrus					4.91	17.89	52.9	50.22
					3.84	9.57	61.1	37.45
R. Medial Frontal Gyrus					3.78	－7.37	61.3	37.92
L. Medial Frontal Gyrus					3.03	－16.13	45.14	37.15
R. Precentral Gyrus					49.37	－11.28	41.88	45.31
					34.33	－27.5	54.5	38.28
R. Paracentral Lobule					3.03	－16.13	45.14	37.15
L. Paracentral Lobule					－3.57	－24.25	51.47	46.32
					－3.68	－32.4	57.9	41.31
R. Parahippocampal Gyrus	16.77	－16.8	－15.95	44.35
L. Sub-Gyral	－23.16	－18.48	－6.87	38.76
R. Anterior Cingulate					1.88	32.95	4.73	37.79
L. Anterior Cingulate	－24.05	33.84	6.18	38.25
R. Uncus					28	－5.82	－22.83	40.38
R. Lingual Gyrus	8	－78.47	－0.32	39.77	8.91	－78.56	0.59	46.72
					1.5	－70.4	3.94	38.04
R. Red Nucleus					6.49	－19.3	－9.15	45.95
R. Postcentral Gyrus					38.93	－34.13	54.85	46.11
					19.44	－38.11	57.75	43.89
					34.52	－21.54	41.56	37.22
L. Postcentral Gyrus					－31.4	－31.06	54.85	39.07
R. Inferior Parietal Lobule					37.11	－45.8	49.21	37.46
R. Cerebellar Tonsil					26.06	－65	－32.97	41.27
L. Cerebellar Tonsil	－12.73	－49.63	－34.87	37.82
R. Declive					38.84	－59.94	－17.86	41.57
R. Medial Globus Pallidus	12.01	－4.02	－2.21	48.89
R. Claustrum	26.75	15.53	8.9	39.53	37.02	－2.11	－3.4	38.1
L. Claustrum	－33.29	－11.65	－9.1	39.21	－35.19	－18.42	－7.07	40.26
L. Putamen	－20.57	－2.54	12.7	41.85
L. Medial Globus Pallidus					－10.14	－0.76	－5.88	49.49
L. Thalamus	0.79	0.67	7.96	39
	－15.01	－13.48	9.05	38.23
L. Inferior Temporal Gyrus					－44.63	－53.54	－3.35	48.49
L. Superior Temporal Gyrus					－35.52	－31.86	15.07	43.63
L. Sub-Gyral					－42.53	－4.23	－7.65	39.91
					－33.36	－25.88	－7.75	37.38

After the threshold with family-wise error rate (FWE) p=0.0000000001 as the cluster level, only the Talairach coordinates with T-score greater than 37 are indicated on the list.

R: Right, L: Left, SWI2: SWI with 2 phase mask multiplications, SWI4: SWI with 4 phase mask multiplications.

Table 2.

Anatomical regions showing significant differences between magnitude and negatively (N) phase-masked susceptibility-weighted imaging (SWI).

Anatomy	Magnitude＞NSWI2				Magnitude＞NSWI4
	Talairach coordinate			T-score	Talairach coordinate			T-score
	x	y	z	T	x	y	z	T
R. Culmen	7.21	－53.72	－3.39	43.17	17.67	－27.89	－17.89	45.43
					9.1	－47.03	－4.53	40.29
					8.48	－35.62	－25.08	39.03
R. Nodule	3.85	－56.68	－30.76	37.20	3.84	－57.61	－30.84	37.88
L. Nodule	－4.5	－57.65	－30.09	38.21
R. Precentral Gyrus	49.53	－2.78	31.88	38.67
L. Precentral Gyrus	－49.48	－2.18	29.36	37.6	－49.48	－1.25	29.45	38.93
	－17.46	－23.33	52.22	40.46	－17.44	－23.24	51.33	37.74
R. Paracentral Lobule	18.53	－40.72	55.68	37.12
L. Paracentral Lobule	－17.58	－38.85	57.05	37.17	－9.17	－33.71	52.28	39.28
L. Medial Frontal Gyrus	－10.18	－25.41	53.95	56.24	－9	－26.25	52.95	47.73
	－15.45	9.79	49.99	38.07
L. Cingulate Gyrus	7.88	－16.28	27.19	39.93
R.Parahippocampal Gyrus					19.68	－13.06	－25.45	37.22
L. Parahippocampal Gyrus	－25.91	－21.93	－9.95	39.48
R. Anterior Cingulate					8.98	12.36	22.72	38.85
L. Red Nucleus	－2.88	－21.9	－1.45	39.59	－2.88	－21.9	－1.45	43.41
R. Lingual Gyrus	7.07	－81.26	－0.6	38.96	7.07	－81.26	－0.6	45.67
L. Lingual Gyrus	－6.83	－88.64	－1.53	37.50
	－7.65	－85.99	－9.4	37.38
R. Cerebellar Tonsil					8.56	－50.59	－35.5	38.15
L. Uvula					－13.81	－62.61	－27.11	38.88
R. Lateral Globus Pallidus					20.4	0.01	－5.29	48.58
					21.19	－15.59	0.46	43.29
L. Lateral Globus Pallidus					－24.09	－10.27	－4.31	40.91
R. Putamen					25	－2.89	－4.58	44.78

After the threshold with family-wise error rate (FWE) p=0.0000000001 as the cluster level, only the Talairach coordinates with T-score greater than 37 are indicated on the list.

R: Right, L: Left, SWI2: SWI with 2 phase mask multiplications, SWI4: SWI with 4 phase mask multiplications.

Table 3.

Anatomical regions showing significant differences between the whole brain susceptibility-weighted imaging (SWI) with the positive (P) phase mask and that with the negative (N) phase mask.

Anatomy	NSWI2＞PSWI2				NSWI4＞PSWI4
	Talairach coordinate			T-score	Talairach coordinate			T-score
	x	y	z	T	x	y	z	T
L. Anterior Cingulate	－9.15	26.25	－3.3	14.04
	－8.18	34.8	－4.27	16.73	－2.69	10.55	－6.48	17.13
R. Anterior Cingulate	2.86	16.87	－3.99	14.58	4.72	17.88	－4.76	15.96
R. Red Nucleus	5.55	－19.39	－8.28	14.92	5.55	－18.46	－8.19	17.93
L. Lateral Globus Pallidus	－25.06	－14.25	－2	15.64	－25.96	－14.07	－3.8	22.56
					－26.08	－14.94	5.12	19.96
					－24.19	7.23	9.06	15.51
R. Lateral Globus Pallidus	23.99	－13.57	－1.11	16.7	24.92	－14.51	－1.18	19.11
					24.81	－14.36	6.94	16.51
L. Caudate	－12.18	7.93	11.13	17.6	－12.18	7	11.04	16.01
					9.29	－0.86	－5.56	14.61
	－2.77	13.58	1.01	15.62	－4.61	16.48	0.36	18.76
R. Caudate	10.06	6.21	8.64	16.1	10.93	7.63	13.29	18.47
	15.53	17.23	10.68	14.49	16.53	16.16	12.39	17.65
Thalamus					5.45	－18.31	－0.07	15.5
					－11.17	－13.39	－1.68	15.46
					10.1	－12.66	－0.35	14.19
Cerebellar Tonsil					0.22	－51.56	－34.84	14.78

After the threshold with family-wise error rate (FWE) p=0.005 as the cluster level, only the Talairach coordinates with T-score greater than 14 are indicated on the list.

R: Right, L: Left, SWI2: SWI with 2 phase mask multiplications, SWI4: SWI with 4 phase mask multiplications.

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