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.

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.

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.