Can Three-Dimensional T1-weighted MR Imaging Visualize the Vascular Lumen after Carotid Artery Stenting?

PURPOSE: We aimed to evaluate the quality of various 3D T1-weighted images (T1WIs) of the stent lumen using a carotid stent phantom and determine the suitable T1WI sequence for visualization of the stent lumen after carotid artery stenting. METHODS: The carotid stent phantom consisted of polypropylene tubes that mimicked common carotid arteries with and without stenting. On 1.5T and 3.0T MRI scanners, transverse T1WIs of the carotid stent phantom were obtained using 3D turbo spin-echo (TSE), 3D fast field-echo (3D-FFE), and 3D turbo field echo volumetric interpolated breath-hold examination (VIBE) under clinical conditions. The signal intensity ratio (SIR) was determined using the mean signal intensity of the stent lumen (SIstent) divided by the lumen without a stent in each T1WI. The SNR of the stent lumen (SNRstent) was calculated from SIstent divided by the standard deviation of the uniform region near the stent lumen. RESULTS: The 3D-FFE and VIBE had higher SNRstent than other T1WIs and clearly visualized the stent lumen. The 3D-TSE had the lowest SIR and SNRstent, preventing stent lumen visualization. CONCLUSION: T1WIs obtained using 3D-FFE and VIBE allows stent lumen visualization.

Assessing the radiofrequency shielding effect of titanium mesh on diffusion-weighted imaging: a comparative study of the twice-refocused spin-echo and Stejskal-Tanner sequences.

This study compared twice-refocused spin-echo sequence (TRSE) and Stejskal-Tanner sequence (ST) to evaluate their respective effects on the image quality of magnetic resonance (MR) diffusion-weighted imaging in the presence of radiofrequency (RF) shielding effect of titanium mesh in cranioplasty. A 1.5-T MR scanner with a Head/Neck coil 20 channels and a phantom simulating the T2 and apparent diffusion coefficient (ADC) value of the human brain were used. Imaging was performed with and without titanium mesh placed on the phantom in TRSE and ST, and normalized absolute average deviation (NAAD), Dice similarity coefficient (DSC), and ADC values were calculated. The NAAD values were significantly lower for TRSE than for ST in the area below the titanium mesh, and the drop rates due to titanium mesh were 14.1% for TRSE and 9.8% for ST. The DSC values were significantly lower for TRSE than for ST. The ADC values were significantly higher for TRSE than for ST without titanium mesh. The ADC values showed no significant difference between TRSE and ST with titanium mesh. The ST had a lower RF shielding effect of titanium mesh than the TRSE.

Development of the Split-Bolus Pulmonary Arteriovenous Separating Computed Tomography Angiography Protocol Based on Time Enhancement Curve for Lung Cancer Surgery.

OBJECTIVE: We devised a split-bolus injection and imaging protocol for pulmonary artery and vein separation computed tomography (CT) angiography based on time enhancement curve characterization. Furthermore, we aimed to evaluate the contrast enhancement effect and success rate of blood vessel separation between the pulmonary artery and vein of this proposed protocol. METHODS: In this study, 102 patients (45 patients with the standard protocol and 57 patients with the proposed protocol) who underwent pulmonary arteriovenous computed tomography angiography were included. The CT values of various vessels, CT value difference between the pulmonary trunk and left atrium, and coefficient of variation in pulmonary arteries and veins were obtained from images of the standard and proposed protocols. RESULTS: The CT values in the proposed protocol for the pulmonary trunk were significantly higher than those in the standard protocol (487.3 [415.5-546.9] HU vs. 293.0 [259.0-350.0] HU, P < 0.01). The CT value difference between the pulmonary trunk and left atrium in the proposed protocol was significantly higher than that in the conventional protocol (211.3 [158.0-265.7] HU vs. 32 [-30.0-55.0] HU, P < 0.01). The coefficient of variation in the proposed protocol was 0.08 (0.06-0.10) and 0.09 (0.08-0.11) in pulmonary arteries and 0.08 (0.06-0.09) and 0.09 (0.07-0.12) in pulmonary veins, respectively. CONCLUSIONS: The proposed protocol achieved separation between the pulmonary artery and vein in many patients, making it useful for the preoperative assessment of individual thoracic anatomy.

3D phase-sensitive inversion recovery sequence for intracranial vertebrobasilar artery dissection.

BACKGROUND: T1-weighted 3D turbo spin echo (T1W-3D-TSE) sequences with variable refocusing flip angle are commonly used to diagnose intracranial vertebrobasilar artery dissection (iVAD). However, magnetic susceptibility artifacts of the cavernous sinus may cause loss of the basilar and vertebral arteries. This study investigated the effectiveness of a 3D phase-sensitive inversion recovery (3D-PSIR) sequence in reducing magnetic susceptibility artifacts in the cavernous sinus, and its imaging findings for iVAD. METHODS: Twelve volunteers and eleven patients with iVAD were included. Magnetic resonance imaging (MRI) was performed using a 3.0-T MRI system. 3D-PSIR and T1W-3D-TSE sequences were used. Vessel wall defects and contrast-to-noise ratio (CNR) were evaluated. The MRI findings were visually evaluated. RESULTS: In the 3D-PSIR images, one volunteer (8 %) had vessel wall defects, and five (42 %) had vessel wall defects (p = 0.046) in the T1W-3D-TSE images. CNR was higher in 3D-PSIR images for vessel wall-to-lumen, whereas it was higher in T1W-3D-TSE images for vessel wall-to-CSF (p < 0.001). Visual evaluation revealed similar MRI findings between the two sequences. CONCLUSIONS: The 3D-PSIR sequence may be able to improve the vessel wall defects and achieve MRI findings comparable to those of the T1W-3D-TSE sequence in iVAD. The 3D-PSIR sequence can be a useful tool for the imaging-based diagnosis of iVAD.

[Effect of Imaging Parameters for High-resolution Diffusion-weighted Imaging on Signal-to-noise Ratio and ADC in Prostate Examination].

Readout-segmented echo-planar imaging (readout segmentation of long variable echo trains [RESOLVE]) can be set to higher resolution than single-shot echo planar imaging, but there is concern that the signal-to-noise ratio (SNR) is low. The purpose was to examine the effect of imaging parameters (repetition time: TR, number of excitations: NEX) for RESOLVE on SNR and apparent diffusion coefficient (ADC) value in 1.5 T MRI, assuming a prostate examination. We imaged eight healthy male volunteers at a b value of 800 s/mm2. SNR and ADC value were calculated by setting the ROI in the transition zone (TZ) and the peripheral zone (PZ) of the prostate. Then, 3 radiologists visually evaluated the graininess. In TZ, there was no significant difference in SNR with changing TR. In PZ, SNR increased with increasing TR. In PZ, median SNR was 8.1 [6.9-9.3] at TR=11000 ms and NEX=2. On the other hand, at TR=5000 ms and NEX=3,4, median SNRs were 8.5 [7.5-9.3] and 9.8 [8.8-11.2]. Moreover, NEX=5 with median SNR of 11.1 [10.7-11.7] was significant (p<0.008). Setting more NEX was more effective in increasing SNR. In addition, visual evaluation showed similar results. The ADC value in TZ was around 1404×10-6 mm2/s, and the ADC value in PZ was around 1469×10-6 mm2/s. There were no significant differences under each condition. In conclusion, NEX is more effective than TR for improving SNR both quantitatively and visually in PZ.

[Construction of a System That Links Treatment RIS Terminals and Smartphones to Facilitate Radiation Therapy Operations].

Confirmation of patient information is required to ensure the safety of radiation therapy. The purpose of this study was to construct a system that facilitates radiation therapy operations by linking a radiation therapy information system to a smartphone. By linking a smartphone to a radiation therapy operation support system, without using a PC terminal, we were able to input information about the patient's position and fixation into images taken with a smartphone. In addition, patient information could be directly linked into the radiation therapy information system. In addition, patient information could be verified in the irradiation room by synchronizing the smartphone with the radiation therapy support system. The questionnaire was highly evaluated in terms of radio reception, usability, visibility and barcode reading. In this study, by linking a smartphone to a radiotherapy information system, it was possible to construct a system that facilitates radiotherapy operations by checking and registering patient information at hand.

Clinical value of the threshold derived from bone single-photon emission computed tomography/computed tomography in differentiating sternoclavicular arthritis.

OBJECTIVE: With the recent improvements in the quantitative accuracy of single-photon emission computed tomography (SPECT)/ computed tomography (CT), the value of using standardized uptake value (SUV) in bone SPECT/CT for quantitative assessment has been reported.We established a threshold for inflamed and normal areas of the sternoclavicular joint and examined the clinical value of bone SPECT/CT. SUBJECTS AND METHODS: The threshold between the inflamed and normal areas of the sternoclavicular joint was initially calculated. The diagnostic performance of the calculated threshold was subsequently compared with the visual assessment of the whole-body image. The clinical value of the threshold was examined in cases of ambiguous visual assessment and a sub-analysis with pustuloticarthro-osteitis (PAO) patients was done. RESULTS: The threshold between the inflamed and the normal area in the 93 sternoclavicular joints of 51 patients was 4.46. The area under the ROC curve (AUC), accuracy, sensitivity, and specificity of SUVmax for differentiating sternoclavicular arthritis were 0.92, 0.86, 0.88, and 0.85, respectively. Similarly, the AUC of visual assessment were 0.87, and the difference was not significant (P=0.11). In 25 patients with PAO, the AUC, accuracy, sensitivity, and specificity of SUVmax were 0.94, 0.90, 0.96, and 0.84, respectively with a significant higher AUC of visual assessment (0.82, P=0.032). Furthermore, for cases where there was ambiguous uptake upon visual assessment, the accuracy, sensitivity, and specificity of SUVmax were 0.84, 1.00, and 0.71, respectively, which was useful to judge regarding the initiation of treatment. CONCLUSION: Quantitative assessment using SUVmax and the threshold found using bone SPECT/CT for the presence of sternoclavicular arthritis is clinically useful and can be a useful tool for the initiation of treatment, especially in PAO patients.

Quantitative evaluation of single-photon emission computed tomography findings in lower extremity possible without computed tomography-based attenuation correction.

OBJECTIVE: For performing accurate quantitative analysis of single-photon emission computed tomography (SPECT)/computed tomography (CT) images, CT-based attenuation correction (CTAC) is considered to be necessary. However, the effect on quantitative values for an examined area close to the body surface, such as in the lower extremity, has yet to be elucidated. We performed the present investigation to determine the possibility of quantitative evaluation using a SPECT standalone device without CT. METHODS: Validation was performed using clinical data of patients who underwent a lower extremity SPECT/CT examination, with grouping based on presence or absence of CTAC, scatter correction and resolution recovery. Using a reference group in which all types of correction were applied, standardized uptake values (SUVs), including maximum (SUVmax) and peak (SUVpeak), were examined in each group and compared. RESULTS: As compared to the reference group, the difference in quantitative values became smaller in the order of the applied scatter correction and resolution recovery, applied resolution recovery, applied scatter correction, and neither scatter correction or resolution recovery applied groups, with no significant difference between the reference group and that with neither scatter correction or resolution recovery applied. A similar tendency was seen for both SUVmax and SUVpeak. CONCLUSIONS: In bone SPECT quantitative examinations of the lower extremity, quantitative evaluation without CTAC is possible without the use of scatter correction or resolution recovery. Thus, quantitative evaluation can be performed with use of a standalone SPECT device without CT.

[A Study of Patient's Dose Control at Radiography by Using a Dose Area Product Meter].

PURPOSE: The International Commission on Radiological Protection recommends adaptation of the diagnostic reference levels (DRLs). Japan DRLs 2020 apply the entrance surface dose (ESD) in radiography. However, it is difficult to measure ESD in the clinical setting. A dose area product meter has been proposed for use as a dose index in interventional radiology. We investigated the basic characteristic of a dose area product meter and the relationship of ESD and dose area product meter values in radiography. METHOD: We measured calibration factors from phantom studies and estimated ESD from the dose area product meter. Subject thickness was measured from the chest clinical images for calculation of ESD. Estimated ESD from the dose area product meter was compared with that calculated from program software (Surface Dose Evaluation Code, Sdec). RESULT: Relative dose (dose area product meter/ionization chamber) decreased when tube voltage was lower (60 kV) or higher (130 kV). A positive correlation was found between the estimated and calculated ESD. CONCLUSION: Dose area product meter can be used for patient's dose control in radiography.

[Usefulness of Combining Post-processing Scatter Correction and an Anti-scatter Grid in Chest Standing Radiography].

PURPOSE: The aim of this study was to evaluate the usefulness of combining post-processing scatter correction (IG) and an anti-scatter grid (RG) in chest radiography. METHOD: To determine the combination protocol (Hyb) that was closed to RG 12:1 (RG12), we measured the content rate of scattered radiation for each combination (RG12, IG12, RG3-12+IG3-12). Task-based modulation transfer function (MTF_Task) and SDNR were evaluated using RG12, IG12, and Hyb. Additionally, seven radiologists performed visual evaluation by using chest phantom. RESULT: The protocol of Hyb was RG8+IG3. In SDNR, Hyb (RG8+IG3) was equal to or higher than RG12, and MTF_Task was equal in all grid systems. Hyb (RG8+IG3) was significantly superior to RG12 in visual evaluation. CONCLUSION: The combining post-processing scatter correction should be useful for improving inspection throughput and reducing the risk of grid's damage.

[Examination of the Maximum Brightness of the Monitor Suitable for Radiological Technologists' Interpretation Assistance and Image Inspection].

The purpose of this study is to examine the maximum brightness of the monitor, which is suitable for radiological technologists' (hereinafter referred to as technicians) interpretation assistance and image inspection. The signal detection ability was evaluated by receiver operating characteristic (ROC) analysis using a chest X-ray image with a simulated nodule. In order to examine the ease of observation and the effect on the subjective evaluation by changing the maximum brightness, evaluation was performed by the normalized ranking method using chest X-ray images. ROC experiments were performed using images with and without simulated nodules in the chest phantom. There was no significant difference in detectability by changing the maximum brightness (p>0.05), but the average area under the curve (AUC) was higher at 350 cd/m2 than at 100 cd/m2 and 170 cd/m2. A normalized ranking method was performed focusing on simulated nodules on chest X-ray images. In the least significant difference (l.s.d.) method, there was a significant difference between the maximum luminance, and the higher the maximum luminance, the better the evaluation. From these results, the change in the maximum brightness did not significantly affect the signal detection ability of the technician's chest X-ray image, but the higher the maximum brightness, the easier it was to observe and the higher the subjective evaluation. It has been reported that the higher the maximum brightness, the shorter the signal recognition time, and a monitor with a high maximum brightness may lead to more efficient image inspection by a technician. From the results of this study, it is considered appropriate to use a medical liquid crystal display (LCD) monitor with a maximum brightness of 350 cd/m2 for the technician's interpretation assistance and image inspection.

[Influences of Tumor Volume and FWHM of the Water Peak and T2* Value of Water on the Detection Rate of the Choline Peaks in Proton MR Spectroscopy of Breast Cancer at 3.0 T-MRI].

In proton magnetic resonance (MR) spectroscopy (1H-MRS) of the breast cancer, choline peak could be detected. The purpose of this study was to evaluate the influences of the tumor volume, full width at half maximum (FWHM) of the water peak (FWHM), and T2* value of water (T2* value) on the detection rate of the choline peaks at 3.0 T-MRI. We measured FWHM and T2* value in 109 cases, and we evaluated the effect of tumor volume on the detection rate of the choline peaks and the effect of FWHM and T2* value on the detection of choline peaks. In 1H-MRS of breast cancer at 3.0 T-MRI, the detection rate of the choline peaks improved as the tumor volume was larger. As a shimming environment when acquiring 1H-MRS of breast cancer, FWHM is preferably 57.4 Hz or less and T2* value should be 11 ms or more, and T2* value has a great influence on the detection rate of the choline peaks.

[Effects of Iterative Reconstruction on Image Quality of Pediatric Body Computed Tomography Images].

This study evaluated the effects of three types of hybrid iterative reconstruction (IR) on image quality of pediatric body computed tomography images. The image quality components evaluated were noise power spectrum (NPS), task-based modulation transfer function (TTF), and system performance function (SPF). As the IR strength was increased while reducing the radiation dose, the NPS increased in a low-frequency range and the TTF decreased in low-contrast regions. In the low-contrast regions, the calculated SPF decreased over the entire frequency range. Alternatively, in the high-contrast regions, the SPF decreased in the low-frequency regions and increased in the high-frequency regions. The radiation dose reduction using the hybrid IR resulted in the deterioration of the image quality in the low-contrast regions and changes in the spatial frequency characteristics in the high-contrast regions.

Examination of cross-calibration and concentration linearity with quantitative gallium-67 single-photon emission computed tomography: phantom experiment.

We evaluated whether scattered radiation should be considered for cross-calibration and concentration linearity with quantitative gallium-67 (67Ga) single-photon emission computed tomography (SPECT). The scanned data from cylinder and spherical phantoms were used. They were reconstructed using ordered subset expectation maximization with resolution recovery, scatter, and computed tomography (CT)-based attenuation correction. The standardized uptake values (SUVs) of the cylinder phantom SPECT/CT images were calculated using system planar sensitivity with and without scatter correction, and the results were compared with the theoretical value. To determine concentration linearity, the relationship between the measured SUVs in three different spherical phantoms was evaluated. SUVs calculated by system planar sensitivity without scatter correction were closer to the theoretical values. Furthermore, the 37-mm sphere showed proper radioactive linearity. Our study suggests the utility of the SUV for 67Ga SEPCT/CT. Nevertheless, additional studies are required.

[Comparison of Detectability for the New Image Processing and Conventional Image Processing by ROC Analysis: A Phantom Study of Chest Radiography].

The purpose of this study is to compare the detectability of diseases the new image processing and the conventional image processing by receiver operating characteristic (ROC) analysis and to show the usefulness of the new image processing. Radiographs with and without nodular cancer models in the chest phantom were used for observation samples. Totally 200 radiographs were evaluated by 10 radiological technologists (each readers had over 20 years or under 4 years of experience). The mean area under the curve (AUC) calculated from the over 20 years group was 0.754 for the new processing and 0.771 for the conventional processing (p value=0.651, 95% confidence interval=-0.084/0.049 (lower bound/upper bound)). On the other hand, the average AUC calculated from under 4 years group was 0.819 for the new processing and 0.678 for the conventional processing (p value= 0.041, 95% confidence interval=0.019/0.262 (lower bound/upper bound)). New image processing provides high detectability in less than 4 years group compared to conventional processing.

[Measurement of Head and Neck Exposure in CT Guided IVR].

In April 2011, the International Radiological Protection Committee recommended that "The equivalent dose of the crystalline lens should not exceed 20 mSv/year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv". Based on this recommendation, it is predicted that the equivalent dose limit of our crystalline lens can be lowered in the near future. Therefore, it is important to grasp the current situation of radiation exposure. The purpose of this study is to measure the crystalline lens of surgeons by focusing on the CT-fluoroscopy guided interventional radiology's (IVRs). We also examined whether the exposure dose of the crystalline lens can be correctly evaluated by measuring the unequal exposure dose of the neck, which is usually used for the unequal exposure measurement. Results of the analysis of 200 CT-fluoroscopy guided IVR procedures showed that the unequal exposure dose of the neck was significantly correlated with the exposure dose of the crystalline lens which was measured near the left eye ball (R=0.83). However, the exposure dose of the crystalline was 33% lower than those of the neck. Therefore, although the individual dosimeter worn on the neck can be used as the useful index of the exposure dose of the crystalline lens, the results can be overestimated.

Influence of image noise and object size on segmentation accuracy of FDG-PET imaging: a phantom experiment.

We aimed to evaluate the influence of noise and object size on segmentation accuracy of fluorodeoxyglucose positron emission tomography (FDG-PET) imaging. The scanned data of spherical phantoms were used. For the gradient method, 40% maximum standardized uptake value (SUVmax) method, and SUV of 2.5 threshold method, we evaluated the correlation between segmentation accuracy and background variability and that between segmentation accuracy and sphere diameters. For the gradient method, background variability did not affect segmentation accuracy, but sphere diameters had a small effect. As for the 40% SUVmax threshold method, both sphere diameters and background variability affected the segmentation accuracy. In the SUV of 2.5 threshold method, segmentation accuracy was affected by sphere diameters but not by background variability. With regard to segmentation accuracy of FDG-PET imaging, the gradient method may be more accurate and reliable compared to threshold methods when applied to images with varying noise or object size.

Investigation of appropriate semi-quantitative index for assessment of esophageal and breast cancer treatment response in Japanese patients using 18F-FDG PET/CT findings.

OBJECTIVE: To examine the correlation of the quantitative indexes standardized uptake value (SUV), SUV corrected for lean body mass (SUL) and SUV corrected for Japanese lean body mass (SULj) with body weight to develop an appropriate quantitative index independent of body weight fluctuation for assessment of response to cancer treatment in Japanese patients. SUBJECTS AND METHODS: Fifty-six males with esophageal cancer and 30 females with breast cancer underwent fluorine-18-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) scans, once before and once after, receiving neoadjuvant chemotherapy prior to planned surgical resection. The maximum value, peak value, and average value of SUV, SUL and SULj were calculated by setting a spherical volume of interest (3cm diameter) in a normal area of the liver. The correlation between each index and body weight was obtained from the correlation coefficient (r) and the significance of the correlation was tested. RESULTS: Analyses were conducted with all patients (P<0.01), as well as after dividing into those with only esophageal (P<0.05) or breast (P<0.01) cancer. Regarding the correlation coefficient between each index and body weight, a significant difference was seen for SUVmax, SUVpeak and SUVmean. In contrast, there was no correlation with body weight for SULmax, SULpeak, SULmean, SULjmax, SULjpeak, or SULjmean in any of the 3 groups. CONCLUSION: Based on the correlation with body weight, we concluded that both SUL and SULj (SUL corrected for Japanese lean body mass) is useful for assessment of cancer treatment response in Japanese patients.

[Multi-facility Survey on Accuracy and Calibration Method for Dose Area Product Meter of Angiography Systems].

In many facilities, the displayed dose of dose-area product (DAP) is used for the dose management of interventional radiology. In this study, we investigated the measured dose at the patient entrance reference point (interventional reference point) and the displayed dose on each angiography systems. Also, we investigated the calibration method of each DAP. The errors of the measured dose and the displayed dose were less than 35%, but that dispersion was wide between the systems. The calibration methods varies according to a system. And even in the same manufacturer, the calibration methods were different. Therefore, to use the displayed dose of DAP for patient dose management, we need to compare that with the measured dose regularly. The differences of calibration methods induce the wide dispersion of the errors of the measured and the displayed dose. So the standardization of the calibration method in each manufacturer is expected.

Preoperative simulation by volume rendering image and intraoperative navigation by ultrasound for posterior urethroplasty: A report of initial three cases.

INTRODUCTION: In posterior urethroplasty, exposure of the proximal urethral stump is the most important step that determines surgical outcome. However, this is sometimes difficult due to deviation of the prostate or overlying scar tissue. We present a novel preoperative simulation and intraoperative navigation method for this step. CASE PRESENTATION: Three patients underwent excision and primary anastomosis for posterior urethral disruption after pelvic fracture. Preoperatively, volume-rendering image of the posterior urethra was constructed from gadolinium-enhanced magnetic resonance image, enabling simulation from the viewpoint of the operator in all three cases. Intraoperative navigation was performed in two patients by using transrectal ultrasound, visualizing the acoustic shadow of a cystoscope inserted into the prostatic urethra via the cystostomy tract. The overlying scar tissue was removed toward the urethral stumps identified by navigation. Urethroplasty was successful in all three patients. CONCLUSION: The present methods were useful for precise identification of the proximal urethral stump.