Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Takashi Abe, Maki Ohtomo, Taniguchi Yo, Ono Masaharu and Bito Yoshitaka : Calculation of molar relaxivity and concentration map of Gd-DTPA map using quantitative parameter map before and after injection for brain metastasis, Proceedings of the 27th Annual Meeting of ISMRM, No.4983, 2019.
Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Takashi Abe, Maki Ohtomo and Miyoshi Mitsuharu : Chemical exchange saturation transfer imaging depending on several neurodegenerative diseases at 3T, Proceedings of the 27th Annual Meeting of ISMRM, No.2795, 2019.
Yuki Kanazawa, Yuki Matsumoto, Masafumi Harada, Hiroaki Hayashi, Tsuyoshi Matsuda and Hideki Otsuka : Appropriate echo time selection for quantitative susceptibility mapping., Radiological Physics and Technology, No.in press, 2019.
(Summary)
The purpose of our study was to clarify the dependence of quantitative susceptibility mapping (QSM) on echo time (TE). We constructed a phantom consisting of six tubes; three tubes were filled with different concentrations (0.5, 1.0, and 2.5 mM) of gadopentetate dimeglumine (Gd-DTPA), and three were filled with different concentrations (100, 200, and 350 mg/mL) of calcium hydroxyapatite. Real and imaginary images from multi-echo spoiled gradient-echo data (12 echoes) were acquired. We then used four datasets with three serial echoes. The QSM procedure consists of four steps: field map estimation, phase unwrapping, background removal, and dipole inversion. For each sample, we compared the measured mean susceptibility value with the theoretical susceptibility value and conducted a linear regression analysis. Accordingly, the relationship between the measured susceptibility and concentration of Gd-DTPA was shown to agree well with the theoretical values (TEs = 16.4, 20.8, and 25.2 ms; slope = 0.24, R = 1.00). Furthermore, the relationship between the measured susceptibility and concentration of hydroxyapatite also showed good linearity (TEs = 16.4, 20.8, and 25.2 ms; slope = - 0.00121, R = 1.00). In conclusion, the optimization of the TE in QSM makes it possible to obtain more detailed information regarding the susceptibility of biomaterials.
Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Maki Ohtomo, Amgalan Enkh Dolgorsuren, Ariumbold Gankhuyag, Takamatsu Shin and Yamashita Yuichi : Which number of b-value is better for accurate calculation of virtual MR elastography?, European Congress of Radiology (EPOS), C-1761, 2019.
Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Maki Ohtomo, Ariunbold Gankhuyag, Amgalan Enkh Dolgorsuren, Takamatsu Shin and Yamashita Yuichi : Why are shear stiffness and estimated intravoxel incoherent motion map correlated in the liver?, European Congress of Radiology (EPOS), C-1789, 2019.
Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Maki Ohtomo and Mitsuharu Miyoshi : Chemical exchange saturation transfer imaging for neurodegenerative diseases, Proceedings of the 26th Annual Meeting of ISMRM, No.2096, 2018.
Yuki Kanazawa, Kotaro Baba, Tosiaki Miyati, Masafumi Harada, Hiroaki Hayashi, Ikuho Kosaka, Mitsuharu Miyoshi, Michael Carl and Yuki Matsumoto : Does the amount of signal change depend on calcium concentration in lipid-rich core plaque?, Proceedings of the 26th Annual Meeting of ISMRM, No.3473, 2018.
Yuki Kanazawa, Toshiaki Sasaki, Hiroaki Hayashi, Kotaro Baba, Ikuho Kosaka, Yuki Matsumoto, Mitsuharu Miyoshi and Masafumi Harada : T1 dependency of magnetization transfer effect in human brain, Proceedings of the 26th Annual Meeting of ISMRM, No.3179, 2018.
Yuki Kanazawa, Masafumi Harada, Mitsuharu Miyoshi, Ikuho Kosaka, Kotaro Baba, Hiroaki Hayashi and Yuki Matsumoto : Nuclear Overhauser enhancement effect of low B1 power CEST RF in human brain at 3.0 T, Proceedings of the 26th Annual Meeting of ISMRM, No.5117, 2018.
Natsuki Ikemitsu, Yuki Kanazawa, Yuki Matsumoto, Hiroaki Hayashi, Toshiaki Sasaki, Mitsuharu Miyoshi and Masafumi Harada : Development of correction for signal-to-noise ratio using a T2* with improved Phase method, Journal of Computer Assisted Tomography, Vol.42, No.1, 117-123, 2018.
(Summary)
This study aims to improve the signal-to-noise ratio (SNR) of the phase image focusing T2 and to develop an improved phase (iPhase) image acquired high SNR. The iPhase images of phantom and brain were acquired with multi-echo spoiled gradient-echo. The phantom component was a gadopentetate dimeglumine (Gd-DTPA) solution made of different concentrations (0.1, 0.5, and 1 wt%) and Gd-DTPA (0.1, 0.5, and 1 wt%) with agar (1.0 wt%). We applied the iPhase image to susceptibility weighed image (SWI) and evaluated SNR of SWI. In phantom study, SNRs of conventional SWI at each sample were 19.8, 15.7, 7.4, 20.0, 17.4, and 27.3, respectively. Signal-to-noise ratios of SWI derived from iPhase method were 29.5, 33.7, 21.7, 28.5, 24.3, and 14.7, respectively. Then, the SNR showed an improvement of 196% at maximum (for the Gd-DTPA 1 wt% sample). In healthy volunteer study, SWI derived from iPhase method had the good contrast between white matter and gray matter. The iPhase image was able to improve the phase SNR. Moreover, iPhase method makes it possible to obtain a high SNR image when applying to SWI.
Yuki Kanazawa, Masafumi Harada, Mitsuharu Miyoshi, Yuki Matsumoto, Hiroaki Hayashi, Toshiaki Sasaki and Natsuki Ikemitsu : Baseline of Chemical Exchange Saturation Transfer Imaging for Brain, Proceedings of the 25th Annual Meeting of ISMRM, 4646, 2017.
Yuki Kanazawa, Masafumi Harada, Mitsuharu Miyoshi, Yuki Matsumoto, Hiroaki Hayashi, Toshiaki Sasaki, Natsuki Ikemitsu and Michael Carl : Dura Mater imaging with UTE T2* Mapping, Proceedings of the 25th Annual Meeting of ISMRM, 4682, 2017.
Natsuki Ikemitsu, Yuki Kanazawa, Yuki Matsumoto, Hiroaki Hayashi, Takatoshi Usuda, Toshiaki Sasaki, Mitsuharu Miyoshi and Masafumi Harada : An improvement of signal-to-noise ratio for phase image, European Congress of Radiology (EPOS), C-0803, 2017.
Toshiaki Sasaki, Yuki Kanazawa, Yuki Matsumoto, Hiroaki Hayashi, Natsuki Ikemitsu, Takatoshi Usuda, Mitsuharu Miyoshi and Masafumi Harada : T1 dependence of magnetization transfer effect for macromolecules, European Congress of Radiology (EPOS), C-0827, 2017.
(Summary)
Purpose: To assess the relationship between T1 and magnetization transfer (MT) effect on macromolecules, we determined T1 map derived from variable flip angle (VFA) method with MT pulse. Materials and Methods: On a 3.0 T magnetic resonance (MR) system, we performed a phantom study using spoiled gradient-echo sequences; TR, 600 ms; TE, 5.8 ms; FA, 5, 20, 40, 60, and 90 degrees; without and with MT pulse (offset frequency, 800 ,1200 , and 1600 Hz). The phantom components were six samples; water and polyethylene glycol (PEG) solutions at different concentrations (10, 20, 30, 40, and 50 wt%). We calculated T1 maps from image datasets without and with MT pulse. Then, the MT ratio (MTR) maps were calculated from each FA image. Results: The mean T1 range without MT pulse for each sample was from 1200 to 2039 ms. The mean T1 ranges with MT pulse of each sample were from 1322 to 1886 at 800 Hz; from 1310 to 1926 ms at 1200 Hz; from 1300 to 1909 ms at 1600 Hz. The MTR of each sample showed the highest value at FA 5 degrees and offset 800 Hz. The mean MTR values of each sample were 6.54 ± 2.78, 3.94 ± 1.92, 2.50 ± 1.67, 1.96 ± 1.33, 1.44 ± 1.15, and 1.78 ± 1.53%. Conclusion: Determination of T1 with MT pulse makes it possible to obtain more detailed information of macromolecules.
Our purpose in this study was to reduce the noise in order to improve the SNR of Dw images with high b-value by using two correction schemes. This study was performed with use of phantoms made from water and sucrose at different concentrations, which were 10, 30, and 50 weight percent (wt%). In noise reduction for Dw imaging of the phantoms, we compared two correction schemes that are based on the Rician distribution and the Gaussian distribution. The highest error values for each concentration with use of the Rician distribution scheme were 7.3 % for 10 wt%, 2.4 % for 30 wt%, and 0.1 % for 50 wt%. The highest error values for each concentration with use of the Gaussian distribution scheme were 20.3 % for 10 wt%, 11.6 % for 30 wt%, and 3.4 % for 50 wt%. In Dw imaging, the noise reduction makes it possible to apply the correction scheme of Rician distribution.
Yuki Kanazawa, Yuki Matsumoto, Hiroaki Hayashi, Tsuyoshi Matsuda, Munguu Ganbold and Masafumi Harada : Simple improvement method of uniformity of MR elastography on liver, Proceedings of the 24th Annual Meeting of ISMRM, 2972, 2016.
Yuto Konishi, Yuki Kanazawa, Takatoshi Usuda, Yuki Matsumoto, Hiroaki Hayashi, Tsuyoshi Matsuda and Masafumi Harada : Comparison with statistical analysis of signal correction in diffusion weighted MR image, European Congress of Radiology (EPOS), C-0291, 2016.
Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Takashi Abe, Maki Ohtomo, Taniguchi Yo, Ono Masaharu and Bito Yoshitaka : Calculation of molar relaxivity and concentration map of Gd-DTPA map using quantitative parameter map before and after injection for brain metastasis, ISMRM 27th Annual Meeting, Montreal, May 2019.
Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Takashi Abe, Maki Ohtomo and Miyoshi Mitsuharu : Chemical exchange saturation transfer imaging depending on several neurodegenerative diseases at 3T, ISMRM 27th Annual Meeting, Montreal, May 2019.
Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Maki Ohtomo, Ariunbold Gankhuyag, Amgalan Enkh Dolgorsuren, Takamatsu Shin and Yamashita Yuichi : Why are shear stiffness and estimated intravoxel incoherent motion map correlated in the liver?, European Congress of Radiology, Wien, Mar. 2019.
Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Maki Ohtomo, Amgalan Enkh Dolgorsuren, Ariumbold Gankhuyag, Takamatsu Shin and Yamashita Yuichi : Which number of b-value is better for accurate calculation of virtual MR elastography?, European Congress of Radiology, Wien, Mar. 2019.
Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Maki Ohtomo and Miyoshi Mitsuharu : Chemical exchange saturation transfer imaging for brain tumors, RSNA2018 (Radiological Society of North America), Chicago, Nov. 2018.
Yuki Kanazawa, Kotaro Baba, Tosiaki Miyati, Masafumi Harada, Hiroaki Hayashi, Ikuho Kosaka, Mitsuharu Miyoshi, Michael Carl and Yuki Matsumoto : Does the amount of signal change depend on calcium concentration in lipid-rich core plaque?, ISMRM 26th Annual Meeting, Paris, Jun. 2018.
Yuki Matsumoto, Yuki Kanazawa, Toshiaki Sasaki, Natsuki Ikemitsu, Hiroaki Hayashi, Mitsuharu Miyoshi, Masafumi Harada and Hideki Otsuka : Which is More Important for Quantitative Susceptibility Mapping? SNR of Phase vs Spin Dephasing., Radiological Society of North America (RSNA), Chicago, Nov. 2017.
Yuki Matsumoto, Yuki Kanazawa, Toshiaki Sasaki, Natsuki Ikemitsu, Hiroaki Hayashi, Mitsuharu Miyoshi, Masafumi Harada and Hideki Otsuka : Phase Correction for Quantitative Susceptibility Mapping (QSM) using T2* Mapping, The 5th International Congress on Magnetic Resonance Imaging, Vol.2017, No.FA, 111, Seoul, Mar. 2017.
(Summary)
Objectives : The purpose of this study is to develop a phase correction method focusing on the SNR of phase and to improve the quantitative measurement of QSM. Methods : On a 3.0 T MRI system (Discovery MR750; GE Healthcare), using three-dimensional spoiled gradient-echo (3D-SPGR) sequence with multiple TEs were used in this study. The imaging parameters were TE, 12 echoes from 3.1 to 51.7 ms (ΔTE = 4.4 ms); repetition time, 55.5 ms; spatial resolution, 1.0 × 1.0 × 1.0 mm; and pixel bandwidth, 244.1 Hz. We conducted a phantom experiment in this study. Five tubes were filled with different concentrations (100, 150, 200, 250, and 300 mg/mL) of calcium hydroxyapatite samples. In this study, we focused on the computation of off-set frequency of each voxel (i.e., field map estimation). At first, we calculate the TE having the maximum for our setting number of echo from the measured T2* map. Second, the ``appropriate TE dataset'' was defined as the maximum SNR dataset with appropriate TE and two datasets with neighboring TE. Third, after estimating the field map using the appropriate TE dataset, a corrected phase angle at each phase angle of the appropriate TE dataset was calculated from a mean resultant length which is the length of the average vectors calculated from all phase angles. Then, the corrected phase angle was defined from mean resultant length. Finally, all phase angles in FOV were corrected for each appropriate TE dataset. Results : The linearity of the relationship between the measured susceptibility and the concentration of hydroxyapatite in the corrected phase dataset was significantly higher than other methods (R = 0.30 VS 0.97). Conclusions : The correction method in QSM using phase correction method makes it possible to more accurately obtain susceptibility information of tissue having a short T2*.
(Keyword)
QSM / echo time / T2* / SNR of phase / susceptibility
Toshiaki Sasaki, Yuki Kanazawa, Yuki Matsumoto, Hiroaki Hayashi, Natsuki Ikemitsu, Takatoshi Usuda, Mitsuharu Miyoshi and Masafumi Harada : T1 dependence of magnetization transfer effect for macromolecules, European Congress of Radiology, Wien, Mar. 2017.
(Summary)
Purpose: To assess the relationship between T1 and magnetization transfer (MT) effect on macromolecules, we determined T1 map derived from variable flip angle (VFA) method with MT pulse. Materials and Methods: On a 3.0 T magnetic resonance (MR) system, we performed a phantom study using spoiled gradient-echo sequences; TR, 600 ms; TE, 5.8 ms; FA, 5, 20, 40, 60, and 90 degrees; without and with MT pulse (offset frequency, 800 ,1200 , and 1600 Hz). The phantom components were six samples; water and polyethylene glycol (PEG) solutions at different concentrations (10, 20, 30, 40, and 50 wt%). We calculated T1 maps from image datasets without and with MT pulse. Then, the MT ratio (MTR) maps were calculated from each FA image. Results: The mean T1 range without MT pulse for each sample was from 1200 to 2039 ms. The mean T1 ranges with MT pulse of each sample were from 1322 to 1886 at 800 Hz; from 1310 to 1926 ms at 1200 Hz; from 1300 to 1909 ms at 1600 Hz. The MTR of each sample showed the highest value at FA 5 degrees and offset 800 Hz. The mean MTR values of each sample were 6.54 ± 2.78, 3.94 ± 1.92, 2.50 ± 1.67, 1.96 ± 1.33, 1.44 ± 1.15, and 1.78 ± 1.53%. Conclusion: Determination of T1 with MT pulse makes it possible to obtain more detailed information of macromolecules.
Natsuki Ikemitsu, Yuki Kanazawa, Yuki Matsumoto, Hiroaki Hayashi, Takatoshi Usuda, Toshiaki Sasaki, Mitsuharu Miyoshi and Masafumi Harada : An improvement of signal-to-noise ratio for phase image, European Congress of Radiology, Wien, Mar. 2017.
Yuki Matsumoto, Yuki Kanazawa, Nattsuki Ikemitsu, Toshiaki Sasaki, Hiroaki Hayashi, Mitsuharu Miyosh, Masafumi Harada and Hideki Otsuka : Proposal of an appropriate echo time-input function for quantitative susceptibility mapping., International Conference On Medical Physics (ICMP) 2016, Bangkok, Dec. 2016.
(Summary)
Purpose To improve the quantitative assessment for both diamagnetic and paramagnetic materials, we developed a quantitative susceptibility mapping (QSM) method using an appropriate echo time (TE)-input function. Methods On 3.0 T MR system, we performed a phantom experiment using a multi-echo spoiled gradient-echo (12 echos; delta TE = 4.4 ms). The phantom consisted of gadopentetate dimeglumine (Gd-DTPA) and hydroxyapatite samples, which were made using three different concentrations of each material. After a multiple TE dataset was acquired, T2* values were calculated from the dataset. When a field map estimation was computed, the appropriate T2* value was used as TE-input function. Next, phase unwrapping and background removal were performed. Finally, the reconstruction of QSM was performed. Moreover, we compared susceptibility values derived from TE-input function and conventional methods. Results The mean T2* values of each Gd-DTPA and hydroxyapatite sample were 365 ± 74, 194 ± 9, 86 ± 3, 24 ± 2, 14 ± 1, and 11 ± 1 ms, respectively. Compared with the conventional method, the proposed TE-input function method indicated good positive linearity for the relationship between the Gd-DTPA concentration and susceptibility (slope = 0.26 ppm/mmol/L, R2 = 0.97, P = 0.11). Additionally, the proposed TE-input function method indicated good negative linearity for the relationship between the concentration and hydroxyapatite susceptibility (slope = -0.0019 ppm/mg/mL, R2 = 1.00, P = 0.02). Conclusions QSM with the TE-input function makes it possible to evaluate simultaneously diamagnetic and paramagnetic materials. e.g. Gd-DTPA and hydroxyapatite.
Yuki Matsumoto, Yuki Kanazawa, Hiroaki Hayashi, Kazuki Takegami, Tsuyoshi Matsuda, Masafumi Harada and Hideki Otsuka : How do you Determine the Echo Time When Calculation of Quantitative Susceptibility Mapping (QSM)?, Radiological Society of North America (RSNA) 2016, Chicago, Dec. 2016.
(Summary)
TEACHING POINTS The purpose of this exhibit is to learn that 1. It is important to know dependence of signal loss due to T2* decay, corresponding to echo time (TE) and susceptibility of biomaterial. 2. Magnetic susceptibility have paramagnetic and diamagnetic characterization, i.e., these indicate positive and negative values, respectively. TABLE OF CONTENTS/OUTLINE -Aims The aim of our study is to investigate the difference in magnetic susceptibility for various TEs. -Method On a 3.0 T MR system, we performed a phantom experiment. The phantom consisted of Gd-DTPA and hydroxyapatite samples which were made using three different concentrations of each. In order to investigate the difference in the magnetic susceptibility of each TE, multiple TEs were acquired and several TE datasets were made. Then, we analyzed with each dataset. -Results The TEs = 3.1, 7.5 and 11.9 ms datasets indicated highest positive linearity for the Gd-DTPA samples (slope = 0.244, R2 = 0.998, P = 0.021). Moreover, the TEs = 3.1, 7.5 and 11.9 ms datasets indicated highest negative linearity for the hydroxyapatite samples (slope = -0.001, R2 = 0.997, P = 0.035). -Conclusion QSM makes it possible to accurately calculation of magnetic susceptibility by using the appropriate TE.
Yuki Kanazawa, Yuki Matsumoto, Nattsuki Ikemitsu, Toshiaki Sasaki, Hiroaki Hayashi, Kazuki Takegami, Tsuyoshi Matsuda and Masafumi Harada : Hybrid assessment of gadopentetic acid and bone structure with ultrashort echo time imaging, International Conference On Medical Physics (ICMP) 2016, Bangkok, Dec. 2016.
(Summary)
Purpose To clarify the phase cycles of Gd-DTPA and calcium carbonate (CaCO3), we evaluated the quantitative susceptibility map (QSM) for dual-ultrashort echo time (UTE) imaging in a phantom experiment. Materials and Methods On a 3.0 T MR system, we performed a phantom study using a three-dimensional dual UTE sequence (TE, 32 µs and 3.2 ms). The phantom components were made from different concentrations of a Gd-DTPA solution (0.1, 0.5, and 1 wt%) and CaCO3 sections. The QSM algorithm was applied to the dual (32 µs and 3.2 ms) and single (32 µs) UTE datasets. We then set the region-of-interest for each material section on QSM images, and measured susceptibility values. Furthermore, linear regression analyses were used to determine the significance between Gd-DTPA concentration and susceptibility for each TE dataset. Results The mean susceptibility value of CaCO3 calculated from the dual UTE showed 1.09 ± 0.35 ppm. Additioally, the mean susceptibility values of 0.1, 0.5, and 1.0 wt% Gd-DTPA calculated from the dual UTE were -0.14 ± 0.03, -0.61 ± 0.02, and -1.24 ± 0.03 ppm. Moreover, there was a negative correlation between Gd-DTPA concentration and susceptibility derived from dual UTE (R2 = 0.9995, P = 0.0141). In contrast, there was no correlation between these values derived from single UTE (R2 = 0.00157, P = 0.9747). Conclusion QSM using dual UTE imaging makes it possible to simultaneously evaluate Gd-DTPA and CaCO3, i.e., bone tumor imaging with contrast-enhanced MRI.
(Keyword)
magnetic resonance image (MRI); ultrashort echo time (UTE); susceptibility; bone tumor
Yuto Konishi, Yuki Kanazawa, Takatoshi Usuda, Yuki Matsumoto, Hiroaki Hayashi, Tsuyoshi Matsuda and Masafumi Harada : Comparison with statistical analysis of signal correction in diffusion weighted MR image, European Congress of Radiology (EPOS), Wien, Mar. 2016.
Yuki Matsumoto, Masafumi Harada, Yuki Kanazawa, Takashi Abe, Maki Ohtomo, Taniguchi Yo, Ono Masaharu and Bito Yoshitaka : Calculation of molar relaxivity and concentration map of Gd-DTPA map using quantitative parameter map before and after injection for brain metastasis, ISMRM Japanese Chapter, Dec. 2018.
Maki Ohtomo, Takashi Abe, Yuki Matsumoto, Yuki Kanazawa and Masafumi Harada : Evaluating reproducibility and gender differences of cerebral perfusion in healthy volunteers observed by multi-delay post labeling delay time ASL Multi-PLD, 第46回日本磁気共鳴学会大会, Sep. 2018.
Yuki Kanazawa, Yuki Kinjoh, Masafumi Harada, Hiroaki Hayashi, Yo Taniguchi, Yoshitaka Bito, Yuki Matsumoto and Masaharu Ono : Construction of voxel-based morphometry of R1 and R2* derived from quantitative parameter mapping, Sep. 2018.
(Summary)
The aim of our study is to construct of VBM using relaxation rate derived from QPM magnetic resonance imaging, i.e., novel Synthetic MRI. VBM of relaxation rates derived from QPM enable to made high quality and accuracy region matching for quantitative analysis of hemodynamic in brain.
Yuki Matsumoto, Yuki Kanazawa, Toshiaki Sasaki, Hiroaki Hayashi, Natsuki Ikemitsu, Masafumi Harada and Hideki Otsuka : Evaluation of Mechanical Waves of MR Elastography, JSRT, Apr. 2017.
(Summary)
[Purpose] The purpose of our study is to assess the mechanical waves that occur during MR elastography using circular statistical analysis. [Methods] On a 1.5 T MR system, we performed a phantom experiment. The phantom was composed of two blocks of agar at a concentration of 0.75 and 1.0 wt%. All imaging data were acquired using gradient echo (GRE) specialized for MRE. The imaging parameters were TE, 19.4 ms; repetition time, 50 ms; field of view, 420 × 420 mm; slice thickness, 80 mm; bandwidth 32.3 kHz; motion-encoding gradient frequency, 60 Hz; driver amplitude, 70. After acquiring the dataset, MRE images were calculated from a multi scale direct inversion algorithm. Additionally, we measured mean wavelength values of offset phase images obtained during MRE using circular statistical analysis. [Results] Mean shear stiffness values at 0.75 wt% and 1.0 wt% agar concentrations were 1.95 ± 0.35 and 6.45 ± 0.97 kPa, respectively. Mean wavelength values for each agar concentration at three column line profile settings (from left to right side) were 1000 and 1920 mm for the 20th column, 760 and 1880 mm for the 90th column, and 160 and 1960 mm for the 160th column, respectively. [Conclusion] Circular statistical analysis makes it possible to obtain and evaluate more detailed information during MRE.
Yuki Matsumoto, Yuki Kanazawa, Nattsuki Ikemitsu, Toshiaki Sasaki, Hiroaki Hayashi, Mitsuharu Miyosh, Masafumi Harada and Hideki Otsuka : Noise estimation of phantom phase image in ultra-short echo time imaging, JSMRM2016, Sep. 2016.
(Summary)
Purpose: To estimate accurately noise of phase rotation, we evaluated a signal phase of ultra-short echo time (UTE) imaging. Materials and Methods: On 3.0T MR system, we performed a phantom experiment using a dual-echo UTE imaging. The imaging parameters were TE, 0.032 ms (first-echo) and 3.3 ms (second-echo); matrix sizes, 256 ×256; slice, 16. The phantom consisted of Gd-DTPA and hydroxyapatite samples, which were made using three different concentrations of each material; Gd-DTPA, 0.5, 1.0, and 2.5 mmol/L; hydroxyapatite, 100, 200, and 350 mg/mL. Then, region of interest analysis was performed on two phase images, e.g., first-echo, and second-echo phase images. Results: The mean first-echo phase values on each Gd-DTPA (0.5, 1.0, and 2.5 mmol/L) and hydroxyapatite (100, 200, and 350 mg/mL) sample were 32.4 ± 0.04, 32.2 ± 0.04, 32.0 ±0.01, 32.4 ± 0.02, 43.6 ± 0.03, and 60.0 ± 0.01 degree, respectively. The mean second-echo phase values on each Gd-DTPA (0.5, 1.0, and 2.5 mmol/L) and hydroxyapatite (100, 200, and 350 mg/mL) sample were 39.1 ± 0.04, 36.0 ± 0.04, 35.5 ± 0.05, 137.9 ± 0.06, 83.4 ± 0.06, and 88.02 ± 0.06 degree, respectively. The mean background phase value first-echo, and second-echo were 33.5 ± 0.11 and 87.1 ± 0.12 degree, respectively. Discussion & Conclusion: The phase rotation of hydroxyapatite occurred difference of phase value in each sample, i.e., this leads good contrast in UTE image. In contrast, the phase rotation of Gd-DTPA at TE 0.032 ms is small enough to estimate noise because the Gd-DTPA phase values were almost equal. Thus, UTE imaging may lead to noise derived from a phase rotation. Noise estimation using UTE imaging may render it possible to obtain more detailed information of paramagnetic materials, e.g., Gd-DTPA.