Temperature measurement of intracranial cerebrospinal fluid using second-order motion compensation diffusion tensor imaging.

To reduce the determination errors of CSF pulsation in diffusion-weighted image (DWI) thermometry, we investigated whether applying second-order motion compensation diffusion tensor imaging (2nd-MC DTI) and fractional anisotropy (FA) processing improves the measurement of intracranial cerebrospinal fluid (CSF) temperature. In a phantom study, we investigated the relationship between temperature and FA in artificial CSF (ACSF) to determine the threshold for FA processing. The calculated temperatures of ACSF were compared with those of water. In a human study, 18 healthy volunteers were scanned using conventional DTI (c-DTI) and 2nd-MC DTI on a 3.0 T magnetic resonance imaging (MRI) system. A temperature map was created using diffusion coefficients from each DWI with/without FA processing. The temperatures of intracranial CSF were compared between each DTI image using Welch's analysis of variance and Games-Howell's multiple comparisons. In the phantom study, FA did not exceed 0.1 at any temperature. Consequently, pixels exceeding the threshold of 0.1 were removed from the temperature map. Intracranial CSF temperatures significantly differed between the four methods (p < 0.0001). The lowest temperature was 2nd-MC DTI with FA processing (mean, 35.62 °C), followed in order by c-DTI with FA processing (mean, 36.16 °C), 2nd-MC DTI (mean, 37.08 °C), and c-DTI (mean, 39.08 °C;p < 0.01 for each). Because the calculated temperature of ACSF was estimated to be lower than that of water, the temperature of 2nd-DTI with FA processing was considered reasonable. The method of 2nd-MC DTI with FA processing enabled determining intracranial CSF temperature with a reduction in CSF pulsation.

Visualization of Cerebrospinal Fluid Motion in the Whole Brain Using Three-dimensional Dynamic Improved Motion-sensitized Driven-equilibrium Steady-state Free Precession.

The feasibility of the 3D dynamic improved motion-sensitized driven-equilibrium steady-state free precession (3D dynamic iMSDE SSFP) was evaluated for visualizing CSF motion and the appropriate parameters were determined. Both flow phantom and volunteer studies revealed that linear ordering and the shortest acquisition duration time were optimal. 3D dynamic iMSDE SSFP provides good quality imaging of CSF motion in the whole brain and enables visualization of flow in arbitrary planes from a single 3D volume scan.

Optimal strategy for measuring intraventricular temperature using acceleration motion compensation diffusion-weighted imaging.

DWI thermometry is affected by CSF pulsation. To achieve more accurate determination of intraventricular temperature, we compared conventional DWI (c-DWI), acceleration motion compensation DWI (aMC-DWI), and motion compensation DWI (MC-DWI) when using two different b values (commonly used b value [1000 s/mm2] and theoretically optimized b value according to the diffusion coefficient of the CSF [400 s/mm2]). Eight healthy volunteers were scanned using a 3.0-T magnetic resonance (MR) system. The temperature map was created using the diffusion coefficient from DWI with b = 1000 and 400 s/mm2, respectively. The intraventricular temperatures in the lateral ventricles (LV) with less CSF pulsation, and the third ventricle (TV), which has more CSF pulsation, were compared between three techniques using the Friedman test. We measured the body temperature in the axilla to compare it with the intraventricular temperature. With b = 1000 s/mm2, the intraventricular temperatures in TV for c-DWI were significantly higher (43.12 ± 2.86 °C) than those for the aMC-DWI (37.68 ± 1.66 °C; P < 0.05), whereas those in LV were not significantly different (P = 0.093). With b = 400 s/mm2, the intraventricular temperatures in TV for c-DWI (75.07 ± 5.48 °C) were significantly higher than those for the aMC-DWI (38.63 ± 0.92 °C; P < 0.05), whereas those in LV were not significantly different (P = 0.093). aMC-DWI provided an intraventricular temperature that was close to or slightly higher than the body temperature in either condition. However, c-DWI- and MC-DWI-measured temperatures were higher than the body temperature, particularly in the TV. Thus, aMC-DWI can accurately determine the intraventricular temperature.

Time-spatial Labeling Inversion Pulse (Time-SLIP) with Pencil Beam Pulse: A Selective Labeling Technique for Observing Cerebrospinal Fluid Flow Dynamics.

We assessed labeling region selectivity on time-spatial labeling inversion pulse (Time-SLIP) with pencil beam pulse (PB Time-SLIP) for the use of visualizing cerebrospinal fluid (CSF) flow dynamics. We compared the selectivity of labeling to the third and fourth ventricles between PB Time-SLIP and conventional Time-SLIP (cTime-SLIP) in eight volunteers and one patient using a 1.5T MRI. PB Time-SLIP provided more selective labeling in CSF than cTime-SLIP, particularly in complex anatomical regions.

Acceleration of ASL-based time-resolved MR angiography by acquisition of control and labeled images in the same shot (ACTRESS).

PURPOSE: Noncontrast 4D-MR-angiography (MRA) using arterial spin labeling (ASL) is beneficial because high spatial and temporal resolution can be achieved. However, ASL requires acquisition of labeled and control images for each phase. The purpose of this study is to present a new accelerated 4D-MRA approach that requires only a single control acquisition, achieving similar image quality in approximately half the scan time. METHODS: In a multi-phase Look-Locker sequence, the first phase was used as the control image and the labeling pulse was applied before the second phase. By acquiring the control and labeled images within a single Look-Locker cycle, 4D-MRA was generated in nearly half the scan time of conventional ASL. However, this approach potentially could be more sensitive to off-resonance and magnetization transfer (MT) effects. To counter this, careful optimizations of the labeling pulse were performed by Bloch simulations. In in-vivo studies arterial visualization was compared between the new and conventional ASL approaches. RESULTS: Optimization of the labeling pulse successfully minimized off-resonance effects. Qualitative assessment showed that residual MT effects did not degrade visualization of the peripheral arteries. CONCLUSION: This study demonstrated that the proposed approach achieved similar image quality as conventional ASL-MRA approaches in just over half the scan time. Magn Reson Med 79:224-233, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

T1ρ mapping improvement using stretched-type adiabatic locking pulses for assessment of human liver function at 3T.

PURPOSE: The purpose of this study is to investigate the performance of stretched-type adiabatic spin lock pulses for homogeneous spin locking with a flexible spin lock time (TSL) setting. METHODS: T1ρ values were obtained from 61 patients and five normal volunteers who were categorized using the Child-Pugh classification and scanned using each spin lock pulse type. The pulses used were the block and two kinds of hyperbolic secant (HS); HS8_10, and HS8_5. Visual scoring was categorized using a four point scale (1:Severe, 2:Moderate, 3:Mild and 4:None) to evaluate the homogeneity of the T1ρ map and the source images obtained by each spin lock pulse. Mean T1ρ values among the patient groups with different Child-Pugh classification were compared. RESULTS: The visual assessment scores were 1.98 ± 1.05 for block pulse locking, 3.87 ± 0.39 for HS8_10 pulse locking, and 3.83 ± 0.45 for HS8_5 pulse locking, respectively. The scores between block pulse and HS8_10 were significantly different (p < 0.001), as were those between block pulse and HS8_5 (p < 0.001). The median T1ρ values of normal liver function, Child-Pugh A, and Child-Pugh B or C were 37.00 ms, 40.77 ms, and 42.20 ms for block pulse, 46.75 ms, 50.78 ms, and 55.60 ms for HS8_10, and 48.80 ms, 55.42 ms, and 57.80 ms for HS8_5, respectively. CONCLUSION: The spin locking sequence using stretched-type adiabatic pulses provides homogeneous liver T1ρ maps with reduced artifact and is necessary for a robust evaluation of liver function using T1ρ.

Volume isotropic simultaneous interleaved black- and bright-blood imaging: a novel sequence for contrast-enhanced screening of brain metastasis.

We introduced and optimized a novel sequence of fast (about 4 min), volumetric, high resolution, simultaneous bright- and black-blood imaging with sufficient T1 contrast between enhanced metastasis and surrounding brain parenchyma for their differentiation. This proposed sequence can be used for 3-dimensional volumetric T1-weighted bright- and black-blood imaging in contrast-enhanced studies and may be promising for detecting small brain metastases by improving differentiation between blood vessels and small brain metastases.

Separate pulmonary artery and vein magnetic resonance angiography by use of an arterial spin labeling method.

A separate pulmonary vein (PV) is difficult to depict with the commonly used bright-blood magnetic resonance angiography method. Until now, no study has described the depiction of peripheral PVs without the artery. Our purpose in this study was to develop an arterial spin labeling (ASL)-based magnetic resonance angiography sequence to depict the pulmonary artery (PA) and vein separately. We developed such a sequence by using two inversion recovery pulses. The first pulse was non-selective, and the second pulse was selective and was applied to the aorta and heart. All studies were conducted on a 1.5-T clinical magnetic resonance system with six different inversion times for seven healthy volunteers. For evaluation, we categorized the inversion times by using visual scoring. Then, we used the magnitude image to evaluate the PA, and we used the real image to evaluate the PV. For the PA, an inversion time of 300 ms had the lowest score (1.43), and the score changed with increasing times; an inversion time of 1,100 ms had the highest score (3.85). For the PV, an inversion time of 300 ms had the highest score (2.68), and the score decreased with increasing times. The results indicated that the PA and vein could be depicted separately by the use of an ASL-based magnetic resonance angiography method. The optimal inversion times for the PV and artery were 300 and 1,100 ms, respectively.

[Clinical findings and macular lesions in basal laminar drusen].

PURPOSE: To investigate the clinical characteristics and accompanying macular lesions in Japanese patients with basal laminar drusen (BLD). DESIGN: Retrospective cross-sectional study. PATIENTS AND METHODS: Fifty four eyes of 27 Japanese patients with BLD were examined for the clinical characteristics of BLD and accompanying macular lesions using retro-mode imaging (Scanning Laser Ophthalmoscope F-10, Nidek) in addition to current methods such as fluorescein angiography (FA), indocyanine green angiography (IA), fundus autofluorescence (FAF) and spectral domain optical coherence tomography (SD-OCT). RESULTS: 1)BLD was more clearly identified using retro-mode imaging than any of the other current imaging methods, and was divided into two types: a crater type (relatively sparsely distributed BLD with many soft drusens) and a mesh type (uniformly distributed BLD). 2) BLD in both eyes was more common in female patients, and had the same type, distribution and similar macular lesions in both eyes. 3) Among the macular lesions, we observed macular atrophy, retinal angiomatous proliferation and vitelliform detachment in many patients, in contrast to few cases of choroidal neovascularization and no polypoidal choroidal vasculopathy. CONCLUSIONS: BLD may be regarded as a disease that is different from age-related macular degeneration (AMD).

[Problem of spectral attenuated with inversion recovery fat suppression method with respiratory-gated].

The purpose of this study was to investigate the effect of fat suppression when we use respiratory-gated spectral attenuated with inversion recovery (SPAIR) method with respiratory-gated. We experimented on phantom and in-vivo study using simulated wave of respiratory-gated SPAIR at 1.5 tesla and 3.0 tesla. As a result, the effect of fat suppression becomes wrong with longer intervals of inspiration and expiration by wave of respiratory-gated. The signal intensity also varies with each slice. This result had the same trend on phantom and in-vivo study. The longitudinal magnetization of fat becomes a stable state when SPAIR pulse is shot more than once. However, the SPAIR method with respiratory-gated collect signal before the longitudinal magnetization of fat to be stable state, and fat suppression effect becomes bad, because the inversion time does not match the null point of the fat. Therefore, when we use SPAIR method with respiratory-gated it always causes bad fat suppression.

[Detection for retinal pigment epithelial lesions in fellow eye of age-related macular degeneration by retro-mode].

PURPOSE: Using the Retro-mode (RM), to detect drusen and other minute lesions of the retinal pigment epithelium (RPE) invisible in current imaging methods in the fellow eye of Japanese patients with exudative age-related macular degeneration(AMD). DESIGN: A retrospective cross-sectional study. PATIENTS AND METHODS: The fellow eyes of nineteen Japanese patients with unilateral exudative AMD were examined using RM imaging (F-10 fundus camera, Nidek), in contrast with fluorescein angiography, indocyanine green angiography, and optic coherence tomography (3D OCT-1000, Topcon Co). We were able to identify the type of drusen and minute granular lesions (MGLs) in the RPE. RESULTS: In all patients, RM imaging gave easier to identify images of all types of drusen than other current imaging methods. Moreover, MGLs of the RPE either adjacent to drusen or without drusen, invisible in other current methods, were detected by RM imaging. CONCLUSIONS: The RM provides clearer imaging of all kind of drusen, and MGLs of the RPE invisible with current methods. These MGLs are possible precursors of drusen.

Time course of changes in metamorphopsia, visual acuity, and OCT parameters after successful epiretinal membrane surgery.

PURPOSE: To follow the changes in the metamorphopsia, visual acuity, and OCT parameters after epiretinal membrane (ERM) removal. METHODS: The study included 49 eyes of 49 patients with an ERM who underwent vitrectomy and membrane peeling. The changes in the best-corrected visual acuity (BCVA), metamorphopsia, and central foveal thickness (CFT) were evaluated at baseline and 1, 3, 6, 9, and 12 months postoperatively. M-CHARTS were used to quantify metamorphopsia. RESULTS: The mean BCVA, metamorphopsia scores for horizontal lines (MH) and vertical lines (MV), and CFT improved significantly at 12 months after surgery (P < 0.001). The baseline BCVA, MH score, and MV score were significantly correlated with the corresponding BCVA, MH score, and MV score at 12 months after surgery (P < 0.01). The MH and MV scores at 12 months was significantly correlated with the BCVA at 12 months (P < 0.01), and the baseline MV score was significantly correlated with the BCVA at 12 months (P < 0.05). The MH score but not the MV score was significantly correlated with the CFT at baseline and 12 months (P < 0.05). CONCLUSIONS: The preoperative BCVA, MH score, and MV score were prognostic factors for the corresponding postoperative BCVA, MH score, and MV score. These results suggest that surgery for ERM should be considered before severe reduction in the BCVA or the degree of metamorphopsia. In addition, the preoperative MV score was a prognostic factor for postoperative BCVA. The MH score but not the MV score was correlated with the CFT preoperatively and postoperatively.

[Improved visualization of long-axis black-blood imaging of the carotid arteries using phase sensitive inversion recovery combined with 3D IR-T1TFE].

The purpose of this study was to improve the visualization of long-axis black-blood imaging of the carotid arteries. We experimented on phantom and in-vivo study of 3 dimension (3D) inversion recovery T(1) turbo field echo combined with phase sensitive inversion recovery (PSIR-3D IR-T(1)TFE) at 3.0 Tesla. As a result, the contrast has been improved by calculated images of PSIR-3D IR-T(1)TFE set to inversion time (TI) 350 ms that is shorter than null point of blood. This displays that the contrast between blood and tissues can be improved when the longitudinal magnetization of blood is a negative. Therefore, the visualization of long-axis black-blood imaging of the carotid arteries has been improved by the calculated images of PSIR-3D IR-T(1)TFE set to TI that is shorter than null point of blood.

Diffusion-weighted magnetic resonance imaging of the liver using tracking only navigator echo: feasibility study.

PURPOSE: To introduce and assess the TRacking Only Navigator echo (TRON) technique for diffusion-weighted magnetic resonance imaging (DWI) of the liver. SUBJECTS AND METHODS: A total of 10 volunteers underwent TRON, respiratory triggered (RT), and free breathing (FB) DWI of the liver. Scan times of TRON and RT DWI were measured, and image sharpness in TRON, RT, and FB DWI was assessed and compared using nonparametric tests. Furthermore, 14 patients with liver metastasis who had undergone TRON and RT DWI of the liver were retrospectively assessed. Relative contrast ratios (RCRs) and apparent diffusion coefficients (ADCs) of the largest hepatic metastasis in TRON and RT DWI were measured. RCRs were compared using a parametric test and agreement in ADCs was assessed using the Bland-Altman method. RESULTS: In the volunteers, mean scan times of TRON and RT relative to FB DWI were 110% to 112% and 261% to 290%, respectively. On axial images, there were no significant differences in images sharpness among TRON, RT, and FB DWI, but on coronal images image sharpness in TRON was nearly always significantly better (P < 0.05) than in RT and FB DWI. In the patients, mean RCRs between TRON and RT DWI were not significantly different (P = 0.9091). Mean difference in ADC +/- limits of agreement (in 10 mm/s) between TRON and RT DWI was -0.16 +/- 0.79. CONCLUSION: TRON offers sharp diffusion-weighted images of the liver using an efficient scan time, making it an excellent alternative to RT and FB DWI. The moderate to poor agreement in ADCs of liver metastases between TRON and RT DWI requires further investigation.

Diffusion-weighted MR imaging of the liver at 3.0 Tesla using TRacking Only Navigator echo (TRON): a feasibility study.

PURPOSE: To assess the feasibility of TRacking Only Navigator echo (TRON) for diffusion-weighted magnetic resonance imaging (DWI) of the liver at 3.0T. MATERIALS AND METHODS: Ten volunteers underwent TRON, respiratory triggered, and free breathing DWI of the liver at 3.0 Tesla (T). Scan times were measured. Image sharpness, degree of stair-step and stripe artifacts for the three methods were assessed by two observers. RESULTS: Mean scan times of TRON and respiratory triggered DWI relative to free breathing DWI were 34% and 145% longer respectively. In four of eight comparisons (two observers, two b-values, two slice orientations), TRON DWI image sharpness was significantly better than free breathing DWI, but inferior to respiratory triggered DWI. In two of four comparisons (two observers, two b-values), degree of stair-step artifacts in TRON DWI was significantly lower than in respiratory triggered DWI. Degree of stripe artifacts between the three methods was not significantly different. CONCLUSION: DWI of the liver at 3.0T using TRON is feasible. Image sharpness in TRON DWI is superior to that in free breathing DWI. Although image sharpness of respiratory triggered DWI is still better, TRON DWI requires less scan time and reduces stair-step artifacts.

[Development of fat suppressed three-dimensional T1-weighted image using linear filling order for K-space].

We have developed a sequence for abdominal examination that fat suppressed 3D-T1W by a linear filling order using an adiabatic pulse for frequency selective fat suppression. We simulated the change in fat signal using a linear method and checked the starting point of data filling for the null point using a phantom of different T1 values. We then checked the contrast between the fat signal and liver. After checking by using simulation, a clinical evaluation was done. The change in fat signal was mostly the same after the fourth shot, and we were able to estimate the null point of the fat signal by the following parameters: TR, FA, TFE factor, and shot interval. Consequently, we could control the starting point of data filling in k-space for fat suppression. The contrast between fat and liver was improved because noise was reduced by the linear method. The sequence developed with the linear filling order using frequency selective fat suppression pulse proved to be useful.

[Clinical features of vitreous hemorrhage after photodynamic therapy for age-related macular degeneration].

PURPOSE: To study the clinical features of vitreous hemorrhage (VH) after photodynamic therapy (PDT) for age-related macular degeneration(AMD). MATERIALS AND METHODS: Twelve patients (12 eyes: 1.7% of the 718 eyes on which PDT was performed) who had vitrectomy due to massive VH after PDT for AMD were studied. Their medical records were reviewed and courses and characteristics were studied. RESULTS: Eight eyes (67%) were diagnosed as polypoidal choroidal vasculopathy and 7 eyes showed multiple clusters of grape-like lesions. Average greatest linear dimension (GLD) was 4533 microm, larger than common AMD. After vitrectomy, some cases retained choroidal neovascularization. Five eyes had another PDT and 3 eyes had a second vitrectomy due to recurrent vitreous hemorrhage. CONCLUSIONS: Both PCV and a large GLD are risk factors for a massive vitreous hemorrhage after PDT therapy for AMD. As many cases retain choroidal neovascularization many patients require additional treatment. Continued observation after vitrectomy is essential.

Cabergoline Effectively Induced Remission of Prolactinoma in a 9-year-old Japanese Boy.

Prolactinomas are rarely diagnosed in children under the age of 10. A 9-yr-old Japanese boy complained of severe headache and progressive visual disturbance. His growth had been retarded for approximately 3 yr, and his serum PRL level was 811.6 ng/ml. Brain magnetic resonance imaging (MRI) revealed an enlarged pituitary (2.8 × 2.6 × 2.1 cm) with heterogeneous enhancement. He was diagnosed as having a macroprolactinoma accompanied by pituitary apoplexy and growth hormone deficiency. A surgical approach was initially undertaken due to the progressive visual deficits, but a residual tumor was observed, and the level of serum PRL was still high after the surgery. Cabergoline was then started, and the dose was gradually increased to 1.5 mg/wk. The serum PRL level decreased from 138.8 ng/ml to 32.5 ng/ml and 17.7 ng/ml after 5 wk and 19 wk, respectively. At 33 wk of cabergoline treatment, brain MRI demonstrated no evidence of the residual tumor. Thereafter, the serum level of PRL decreased to less than 10 ng/ml, and remission was consistently confirmed on repeated MRI. No adverse events have been observed. The present case suggests that cabergoline can be an effective treatment for prolactinomas in prepubertal children as well as in adults.

[Trial of artifact reduction in body diffusion weighted imaging development and basic examination of "TRacking Only Navigator"(TRON method)].

In recent years, the utility of body diffusion weighted imaging as represented by diffusion weighted whole body imaging with background body signal suppression (DWIBS), the DWIBS method, is very high. However, there was a problem in the DWIBS method involving the artifact corresponding to the distance of the diaphragm. To provide a solution, the respiratory trigger (RT) method and the navigator echo method were used together. A problem was that scan time extended to the compensation and did not predict the extension rate, although both artifacts were reduced. If we used only navigator real time slice tracking (NRST) from the findings obtained by the DWIBS method, we presumed the artifacts would be ameliorable without the extension of scan time. Thus, the TRacking Only Navigator (TRON) method was developed, and a basic examination was carried out for the liver. An important feature of the TRON method is the lack of the navigator gating window (NGW) and addition of the method of linear interpolation prior to NRST. The method required the passing speed and the distance from the volunteer's diaphragm. The estimated error from the 2D-selective RF pulse (2DSRP) of the TRON method to slice excitation was calculated. The condition of 2D SRP, which did not influence the accuracy of NRST, was required by the movement phantom. The volunteer was scanned, and the evaluation and actual scan time of the image quality were compared with the RT and DWIBS methods. Diaphragm displacement speed and the quantity of displacement were determined in the head and foot directions, and the result was 9 mm/sec, and 15 mm. The estimated error was within 2.5 mm in b-factor 1000 sec/mm(2). The FA of 2DSRP was 15 degrees, and the navigator echo length was 120 mm, which was excellent. In the TRON method, the accuracy of NRST was steady because of line interpolation. The TRON method obtained image quality equal to that of the RT method with the b-factor in the volunteer scanning at short actual scan time. The TRON method can obtain image quality equal to that of the RT method in body diffusion weighted imaging within a short time. Moreover, because scan time during planning becomes actual scan time, inspection can be efficiently executed.