A Novel Imaging Technique for Analyzing Condylar Movement During Mastication in Patients With Jaw Deformities: Four-Dimensional Computed Tomography.

OBJECTIVE: This study aimed to reveal characteristic condylar movements in patients with jaw deformities. STUDY DESIGN: Thirty patients with jaw deformities before surgery were enrolled and instructed to chew a cookie during 4-dimensional computed tomography (4DCT). The distance between the most anterior and posterior positions of the bilateral condyles on 4DCT images was measured and compared among patients with different skeletal classes. Correlations between the condylar protrusion and cephalometric values were also determined. RESULTS: The distances of condylar protrusion during mastication were significantly greater in the skeletal class II group than in the skeletal class III group ( P =0.0002). Significant correlations were found between the distances of condylar protrusion during mastication and the sella-nasion-B point angle ( r =-0.442, P =0.015), A point-nasion-B point angle ( r =0.516, P =0.004), sella-nasion plane to ramus plane angle ( r =0.464, P =0.01), sella-nasion plane to occlusal plane angle ( r =0.367, P =0.047), and condylion-gonion length ( r =-0.366, P =0.048). CONCLUSION: Motion analysis with 4DCT images revealed that condylar movement in patients with retrognathism was larger than in patients with mandibular prognathism. Skeletal structure was therefore correlated with condylar movement during mastication.

The impact of the procedural parameters on the lesion characteristics associated with AF recurrence: Late-gadolinium enhancement magnetic resonance imaging (LGE-MRI) analysis.

BACKGROUND: Lesion gaps assessed by late-gadolinium enhancement magnetic resonance imaging (LGE-MRI) are associated with the atrial fibrillation (AF) recurrence after pulmonary vein isolation. Animal studies have demonstrated that the catheter-contact force (CF), stability, and orientation are strongly associated with lesion formation. However, the impact of those procedural factors on the lesion characteristics associated with AF recurrence has not been well discussed. METHODS: A total of 30 patients with paroxysmal AF who underwent catheter ablation were retrospectively enrolled. Radiofrequency (RF) applications were performed with 35 W for 30 s in a point-by-point fashion under esophageal temperature monitoring. The inter-lesion distance was 4 mm. The lesions were visualized by LGE-MRI 3 months postprocedure and assessed by the LGE volume (ml), gap number (GN), and average gap length (AGL [mm]). The gaps were defined as nonenhancement sites of >4 mm. The procedural factors including the catheter-CF, stability, and orientation were calculated on the NavX system. RESULTS: Six (20%) of 30 patients had AF recurrences 12 months postablation. A univariate analysis demonstrated that the AGL was associated with AF recurrence (hazard ratio [HR]: 1.20, confidence interval [CI]: 1.03-1.42, p = .02). All AF recurrence were found in patients with an AGL of >7 mm. The catheter-CF and stability were associated with an AGL of >7 mm, but not the orientation (CF-HR: 0.62, CI: 0.39-0.97, p = .038; stability-HR: 0.8, CI: 0.66-0.98, p = .027). CONCLUSIONS: RF ablation with a low CF and poor catheter stability has a potential risk of creating large lesion gaps associated with AF recurrence.

Deep learning image reconstruction to improve accuracy of iodine quantification and image quality in dual-energy CT of the abdomen: a phantom and clinical study.

OBJECTIVES: To investigate the effect of deep learning image reconstruction (DLIR) on the accuracy of iodine quantification and image quality of dual-energy CT (DECT) compared to that of other reconstruction algorithms in a phantom experiment and an abdominal clinical study. METHODS: An elliptical phantom with five different iodine concentrations (1-12 mgI/mL) was imaged five times with fast-kilovoltage-switching DECT for three target volume CT dose indexes. All images were reconstructed using filtered back-projection, iterative reconstruction (two levels), and DLIR algorithms. Measured and nominal iodine concentrations were compared among the algorithms. Contrast-enhanced CT of the abdomen with the same scanner was acquired in clinical patients. In arterial and portal venous phase images, iodine concentration, image noise, and coefficients of variation for four locations were retrospectively compared among the algorithms. One-way repeated-measures analyses of variance were used to evaluate differences in the iodine concentrations, standard deviations, coefficients of variation, and percentages of error among the algorithms. RESULTS: In the phantom study, the measured iodine concentrations were equivalent among the algorithms: within ± 8% of the nominal values, with root-mean-square deviations of 0.08-0.36 mgI/mL, regardless of radiation dose. In the clinical study (50 patients; 35 men; mean age, 68 ± 11 years), iodine concentrations were equivalent among the algorithms for each location (all p > .99). Image noise and coefficients of variation were lower with DLIR than with the other algorithms (all p < .01). CONCLUSIONS: The DLIR algorithm reduced image noise and variability of iodine concentration values compared with other reconstruction algorithms in the fast-kilovoltage-switching dual-energy CT. KEY POINTS: • In the phantom study, standard deviations and coefficients of variation in iodine quantification were lower on images with the deep learning image reconstruction algorithm than on those with other algorithms. • In the clinical study, iodine concentrations of measurement location in the upper abdomen were consistent across four reconstruction algorithms, while image noise and variability of iodine concentrations were lower on images with the deep learning image reconstruction algorithm.

The impact of the atrial wall thickness in normal/mild late-gadolinium enhancement areas on atrial fibrillation rotors in persistent atrial fibrillation patients.

Background: Some of atrial fibrillation (AF) drivers are found in normal/mild late-gadolinium enhancement (LGE) areas, as well as moderate ones. The atrial wall thickness (AWT) has been reported to be important as a possible AF substrate. However, the AWT and degree of LGEs as an AF substrate has not been fully validated in humans. Objective: The purpose of this study was to evaluate the impact of the AWT in normal/mild LGE areas on AF drivers. Methods: A total of 287 segments in 15 persistent AF patients were assessed. AF drivers were defined as non-passively activated areas (NPAs), where rotational activation was frequently observed, and were detected by the novel real-time phase mapping (ExTRa Mapping), mild LGE areas were defined as areas with a volume ratio of the enhancement voxel of 0% to <10%. The AWT was defined as the minimum distance from the manually determined endocardium to the epicardial border on the LGE-MRI. Results: NPAs were found in 20 (18.0%) of 131 normal/mild LGE areas where AWT was significantly thicker than that in the passively activated areas (PAs) (2.5 ± 0.3 vs. 2.2 ± 0.3 mm, p < .001). However, NPAs were found in 41 (26.3%) of 156 moderate LGE areas where AWT was thinner than that of PAs (2.1 ± 0.2 mm vs. 2.23 ± 0.3 mm, p = .02). An ROC curve analysis yielded an optimal cutoff value of 2.2 mm for predicting the presence of an NPA in normal/mild LGE areas. Conclusion: The location of AF drivers in normal/mild LGE areas might be more accurately identified by evaluating AWT.

Visualization of intensive atrial inflammation and fibrosis after cryoballoon ablation: PET/MRI and LGE-MRI analysis.

BACKGROUND: Atrial inflammation plays an important role in initiating atrial fibrosis, which could perpetuate atrial fibrillation (AF). However, the method of visualization of atrial inflammation has not been established. We sought to investigate whether the intensive atrial inflammation caused by cryoballoon ablation (CBA) could be detected by positron emission tomography/ magnetic resonance imaging (PET/MRI) and whether the atrial inflammation could be associated with consequent fibrosis. METHODS: A total of 10 paroxysmal atrial fibrillation patients after CBA were enrolled. To detect and quantify intensive atrial inflammation, PET/MRI was performed to assess regional 18F-fluorodeoxyglucose (18F-FDG) uptake one day after the CBA, and the standardized uptake values (SUV) max were compared between the pulmonary vein (PV) antrum where CBA could be applied and the healthy left atrial (LA) wall where CBA could not be applied. Furthermore, the atrial inflammation one day after the procedure and atrial fibrosis areas one month after the procedure were three-dimensionally quantified by PET/MRI and late-gadolinium enhancement magnetic resonance imaging (LGE-MRI), respectively. RESULTS: The mean SUV max at the PV antrum was significantly higher than that on the healthy LA wall (2.12 ± 0.35 vs 1.73 ± 0.30, P = .00021). The volume of the atrial inflammation strongly correlated with that of the atrial fibrosis (r = .94 [.76-.99], P = .00006). CONCLUSIONS: The atrial inflammation after CBA could be detected by PET/MRI. CBA-induced atrial inflammation was strongly associated with consequent lesion maturation.

Feasibility of catheter ablation in patients with persistent atrial fibrillation guided by fragmented late-gadolinium enhancement areas.

BACKGROUND: A computer simulation model has demonstrated that atrial fibrillation (AF) driver can be attached to heterogeneous fibrosis assessed by late gadolinium enhancement magnetic resonance imaging (LGE-MRI). However, it has not been well elucidated in patients with persistent AF. The aim of this study was to investigate whether radiofrequency (RF) applications in the fragmented LGE area (FLA) could terminate AF or convert it to atrial tachycardia (AT) and improve the rhythm outcome. METHODS: A total of 31 consecutive persistent AF patients with FLAs were enrolled (FLA ablation group, mean age: 69 ± 8 years, mean left atrial diameter: 42 ± 6 mm). A favorable response was defined as direct AF termination or AT conversion during RF applications at the FLA. The rhythm outcome was compared between the FLA ablation group and FLA burden-matched pulmonary vein isolation (PVI) group. RESULTS: Favorable responses were found in 15 (48%) of 31 patients in the FLA group (AF termination in seven, AT conversion in eight patients), but not in the PVI group. AF recurrence at 12 months follow-up was significantly less in the FLA ablation group than in the PVI group (4 [13%] vs. 12 [39%] of 31 patients, log-rank p = .023). In patients with a favorable response, AT recurred in 1 (7%) of 15 patients, but AF did not. CONCLUSIONS: FLA ablation could terminate AF or convert it to AT in half of the patients. No AF recurrence was documented in patients with a favorable response.

Late-gadolinium enhancement properties associated with atrial fibrillation rotors in patients with persistent atrial fibrillation.

BACKGROUND: A computational model demonstrated that atrial fibrillation (AF) rotors could be distributed in patchy late-gadolinium enhancement (LGE) areas and play an important role in AF drivers. However, this was not validated in humans. OBJECTIVE: The purpose of this study was to evaluate the LGE properties of AF rotors in patients with persistent AF. METHODS: A total of 287 segments in 15 patients with persistent AF (long-standing persistent AF in 9 patients) that underwent AF ablation were assessed. Non-passively activated areas (NPAs), where rotational activation (AF rotor) was frequently observed, were detected by the novel real-time phase mapping (ExTRa Mapping). The properties of the LGE areas were assessed using the LGE heterogeneity and the density which was evaluated by the entropy (LGE-entropy) and the volume ratio of the enhancement voxel (LGE-volume ratio), respectively. RESULTS: NPAs were found in 61 (21%) of 287 segments and were mostly found around the pulmonary vein antrum. A receiver operating characteristic curve analysis yielded an optimal cutoff value of 5.7% and 10% for the LGE-entropy and LGE-volume ratio, respectively. The incidence of NPAs was significantly higher at segments with an LGE-entropy of >5.7 and LGE-volume ratio of >10% than at the other segments (38 [30%] of 126 vs. 23 [14%] of 161 segments; p = .001). No NPAs were found at segments with an LGE-volume ratio of >50% regardless of the LGE-entropy. Of five patients with AF recurrence, NPAs outside the PV antrum were not ablated in three patients and the remaining NPAs were ablated, but their LGE-entropy and LGE-volume ratio were low. CONCLUSION: AF rotors are mostly distributed in relatively weak and much more heterogenous LGE areas.

Lesion characteristics between cryoballoon ablation and radiofrequency ablation with a contact force-sensing catheter: Late-gadolinium enhancement magnetic resonance imaging assessment.

BACKGROUND: Pulmonary vein isolation (PVI) lesions after cryoballoon ablation (CBA) are characterized as a wider and more continuous than that after conventional radiofrequency catheter ablation (RFCA) without the contact force (CF)-sensing technology. However, the impact on the lesion characteristics of ablation with a CF-sensing catheter has not been well discussed. We sought to assess the lesions using late-gadolinium enhancement magnetic resonance imaging (LGE-MRI) and to compare the differences between the two groups (CB group vs. RF group). METHODS: A total of 30 consecutive patients who underwent PVI were enrolled (CB group, 18; RF group, 12). The RF applications were delivered with a target lesion size index (LSI) of 5. The PVI lesions were assessed by LGE-MRI 3 months after the PVI. The region around the PV was divided into eight segments: roof, anterior-superior, anterior carina, anterior inferior, bottom, posterior inferior, posterior carina, and posterior superior segment. The lesion width and visual gap of each segment were compared between the two groups. The visual gaps were defined as no-enhancement site of >4 mm. RESULTS: The mean LSI was 4.7 ± 0.7. The lesion width was significantly wider but the visual gaps were more frequently documented at the bottom segment of right PV in the CBA group (lesion width: 8.1 ± 2.2 vs. 6.3 ± 2.2 mm; p = .032; visual gap at the bottom segment or right PV: 39% vs. 0%; p = .016). CONCLUSIONS: The PVI lesion was wider after CBA, while the visual gaps were fewer after RFCA with a CF-sensing catheter.

Can four-dimensional computed tomography support diagnosis and treatment planning?: a case report before and after coronoidectomy.

INTRODUCTION: Elongated mandibular coronoid process is a rare condition defined as enlargement of the coronoid process. The only useful way to treat the mouth-opening limitation is resection of the elongated coronoid process. Four-dimensional CT (4DCT; three spatial dimensions plus time axis) is a novel imaging technique. Its usefulness of for evaluation of dynamic movements such as joint motion has been reported. Here, we show the potential usefulness of 4DCT evaluation in a patient with elongated mandibular coronoid process. CASE PRESENTATION: A 59-year-old female who suffered from mouth-opening difficulty and pressure during mouth opening was referred to our department. Elongation of the right coronoid process was evident in a panoramic X-ray image. The mandibular movement and temporal muscle motility before and after coronoidectomy in this patient on 4DCT could be evaluated. CONCLUSIONS: 4DCT is useful in the diagnosis and surgical outcome of elongated coronoid process.

Visualization of Inflammation After Cryoballoon Ablation in Atrial Fibrillation Patients　- Protocol for Proof-of-Concept Feasibility Trial.

Background: Atrial fibrosis and inflammation play important roles in perpetuating and initiating atrial fibrillation (AF). Although the fibrotic area can be visualized as a delayed enhancement area on late gadolinium enhancement magnetic resonance imaging (LGE-MRI), atrial inflammation has not yet been visualized on any imaging modality. We describe the protocol for a feasibility study to visualize atrial inflammation on positron emission tomography/MRI (PET/MRI). Methods and Results: This is a single-arm, prospective, open-label proof-of concept trial, involving AF patients after cryoballoon ablation (CBA). A total of 30 paroxysmal AF patients will be enrolled and undergo simultaneous PET/MRI for the assessment of regional 18F-fluorodeoxyglucose (18F-FDG) uptake 1 day after the CBA. Furthermore, LGE-MRI will be performed before CBA, and at 1 and 4 weeks after assessing the regional LGE area. The main outcome measures will be (1) the feasibility of imaging inflammation in the left atrium on PET/MRI; and (2) the safety of the intervention. Conclusions: There are few data on the visualization of atrial inflammation using PET/MRI. Establishing the visualization methodology will contribute to elucidating the fundamental histopathologic findings of the progress to fibrosis, and to the planning and execution of a larger definitive trial to test the usefulness of PET/MRI.

Lesion distribution after cryoballoon ablation and hotballoon ablation: Late-gadolinium enhancement magnetic resonance imaging analysis.

INTRODUCTION: Pulmonary vein isolation (PVI) lesions after cryoballoon ablation (CBA) are wide and continuous, however, the distribution can depend on the pulmonary vein (PV) size. We sought to assess the relationship between the lesion distribution and PV size after CBA and hotballoon ablation (HBA). METHODS AND RESULTS: A total of 80 consecutive patients who underwent PVI were enrolled (40 with CBA). The lesions were visualized by late-gadolinium enhancement magnetic resonance imaging. The lesion width, lesion gaps, and distance from the PV ostium (PVos) to distal lesion edge (DLE) were assessed. If the DLE extended inside the PV, the value was expressed as a negative value. Although the lesion width was significantly wider in the CB group (7.8 ± 2.0 vs 4.9 ± 1.0 mm, P < .001), the number of lesion gaps was significantly less in the HB group (2.9 ± 2.4 vs 1.3 ± 1.4 gaps, P = .001). The distance from the PVos to DLE was a negative value in both groups, but the impact was significantly greater (-1.5 ± 1.8 vs -0.2 ± 1.2 mm, P < .001) and negatively correlated with PV size in the CB group, but not in HB group (r = -0.27, P = .007). The AF recurrence 12 months after the procedure did not differ (5 [12.5%] of 40 in the CB group vs 4 [10%] of 40 in the HB group, P = .695). CONCLUSIONS: The PVI lesions after HBA were characterized by (a) narrower, but (b) more continuous, (c) smaller lesion inside the PV, and (d) irrespective of PV size as compared to that after CBA.

Quantification of Cisplatin Using a Modified 3-Material Decomposition Algorithm at Third-Generation Dual-Source Dual-Energy Computed Tomography: An Experimental Study.

OBJECTIVE: The aim of this study was to assess the ability of third-generation dual-source dual-energy computed tomography to quantify cisplatin concentration using a 3-material decomposition algorithm in an experimental phantom. MATERIALS AND METHODS: Fifteen agarose-based phantoms containing various concentrations of iodine (0, 1.0, 2.0 mg I/mL) and cisplatin (0, 0.5, 1.0, 2.0, 3.0 mg Pt/mL) were scanned using third-generation dual-source dual-energy computed tomography at 80 kV and 150 kV with tin prefiltration. A cisplatin map was generated using the cisplatin-specific 3-material decomposition algorithm to differentiate cisplatin from iodine and agar. The computed tomography (CT) values at 80 kV, 150 kV, mixed 120 kV, and the cisplatin map were measured. Interobserver variabilities for the CT measurements on the cisplatin map were assessed using interclass correlation coefficients. Correlation between the CT values and titrated cisplatin concentrations was correlated using Spearman rank correlation analysis. To assess the influence of iodine, linear regression lines for the CT values on the cisplatin map and titrated cisplatin concentrations were compared using an analysis of covariance. RESULTS: Interobserver agreement revealed almost perfect agreements (interclass correlation coefficients = 0.941-0.995). Significant and excellent positive correlations were observed between the CT values on the cisplatin map and titrated cisplatin concentrations (ρ = 0.980, P < 0.001 for all). The cisplatin map could identify the lowest cisplatin concentration of 0.5 mg Pt/mL in the presence of iodine. The iodine concentration had no significant effect on the CT measurements on the cisplatin map (P = 0.297, adjusted R = 0.993). CONCLUSIONS: The cisplatin map generated from the 3-material decomposition algorithm allows quantification of a cisplatin concentration in an experimental phantom, independent of co-present iodine.

The lesion characteristics assessed by LGE-MRI after the cryoballoon ablation and conventional radiofrequency ablation.

Background: Rhythm outcomes after the pulmonary vein isolation (PVI) using the cryoballoon (CB) are reported to be excellent. However, the lesions after CB ablation have not been well discussed. We sought to characterize and compare the lesion formation after CB ablation with that after radiofrequency (RF) ablation. Methods: A total of 42 consecutive patients who underwent PVI were enrolled (29 in the CB group and 13 in the RF group). The PVI lesions were assessed by late gadolinium enhancement magnetic resonance imaging 1-3 months after the PVI. The region around the PVs was divided into eight segments: roof, anterior-superior, anterior-carina, anterior-inferior, bottom, posterior-inferior, posterior-carina, and posterior-superior segment. The lesion width and lesion gap in each segment were compared between the two groups. Lesion gaps were defined as no-enhancement sites of >4 mm. Results: As compared to the RF group, the overall lesion width was significantly wider and lesion gaps significantly fewer at the anterior-superior segment of the left PV (LAS) and anterior-inferior segment of the right PV (RAI) in the CB group (lesion width: 8.2 ± 2.2 mm vs 5.6 ± 2.0 mm, P = .001; lesion gap at LAS: 7% vs 38%, P = .02; lesion gap at RAI: 7% vs 46%, P = .006). Conclusions: The PVI lesions after CB ablation were characterized by extremely wider and more continuous lesions than those after RF ablation.

Axial four-dimensional computed tomographic images to analyze crosswise differences in protrusive condylar movement in patients who underwent mandibulectomy and free flap reconstruction.

OBJECTIVE: Few studies evaluate condylar movement following mandibular reconstruction. The main objective of this study was to show that axial four-dimensional computed tomography (4DCT) could visualize bilateral protrusive condylar movement directly. We used axial 4DCT images to assess condylar protrusion in patients who underwent mandibular reconstruction. METHODS: We enrolled seven healthy volunteers (median age 30 years, range 27-38 years) and seven patients (median age 65 years, range 52-80 years), who underwent mandibulectomy (segmental in five, hemi in one, marginal in one) and free flap reconstruction (using the fibula in six and the radial forearm in one). Six study subjects were instructed to masticate a cookie during the 4DCT scan (the seventh made chewing motions). The distance between the most anterior and posterior positions of the bilateral condyles on 4DCT (axial view) images was then measured and compared between controls and patients using the Mann-Whitney U-test. RESULTS: The crosswise difference in the distances of condylar protrusion was significantly greater in patients than in the controls. CONCLUSION: Axial 4DCT images can visualize a bilateral condylar protrusive path. Axial 4DCT images for patients who have undergone mandibulectomy and reconstruction may be useful for evaluation of functional movement of condyles.

Application of dual-energy CT to suppression of metal artefact caused by pedicle screw fixation in radiotherapy: a feasibility study using original phantom.

The objective of the present study was the determination of the potential dosimetric benefits of using metal-artefact-suppressed dual-energy computed tomography (DECT) images for cases involving pedicle screw implants in spinal sites. A heterogeneous spinal phantom was designed for the investigation of the dosimetric effect of the pedicle-screw-related artefacts. The dosimetric comparisons were first performed using a conventional two-directional opposed (AP-PA) plan, and then a volumetric modulated arc therapy (VMAT) plan, which are both used for the treatment of spinal metastases in our institution. The results of Acuros® XB dose-to-medium (Dm) and dose-to-water (Dw) calculations using different imaging options were compared with experimental measurements including the chamber and film dosimetries in the spinal phantom. A dual-energy composition image with a weight factor of -0.2 and a dual-energy monochromatic image (DEMI) with an energy level of 180 keV were found to have superior abilities for artefact suppression. The Dm calculations revealed greater dosimetric effects of the pedicle screw-related artefacts compared to the Dw calculations. The results of conventional single-energy computed tomography showed that, although the pedicle screws were made from low-Z titanium alloy, the metal artefacts still have dosimetric effects, namely, an average (maximum) Dm error of 4.4% (5.6%) inside the spinal cord for a complex VMAT treatment plan. Our findings indicate that metal-artefact suppression using the proposed DECT (DEMI) approach is promising for improving the dosimetric accuracy near the implants and inside the spinal cord (average (maximum) Dm error of 1.1% (2.0%)).

Improved image quality in abdominal CT in patients who underwent treatment for hepatocellular carcinoma with small metal implants using a raw data-based metal artifact reduction algorithm.

OBJECTIVES: To determine the value of a raw data-based metal artifact reduction (SEMAR) algorithm for image quality improvement in abdominal CT for patients with small metal implants. METHODS: Fifty-eight patients with small metal implants (3-15 mm in size) who underwent treatment for hepatocellular carcinoma were imaged with CT. CT data were reconstructed by filtered back projection with and without SEMAR algorithm in axial and coronal planes. To evaluate metal artefact reduction, mean CT number (HU and SD) and artefact index (AI) values within the liver were calculated. Two readers independently evaluated image quality of the liver and pancreas and visualization of vasculature using a 5-point visual score. HU and AI values and image quality on images with and without SEMAR were compared using the paired Student's t-test and Wilcoxon signed rank test. Interobserver agreement was evaluated using linear-weighted κ test. RESULTS: Mean HU and AI on images with SEMAR was significantly lower than those without SEMAR (P < 0.0001). Liver and pancreas image qualities and visualizations of vasculature were significantly improved on CT with SEMAR (P < 0.0001) with substantial or almost perfect agreement (0.62 ≤ κ ≤ 0.83). CONCLUSIONS: SEMAR can improve image quality in abdominal CT in patients with small metal implants by reducing metallic artefacts. KEY POINTS: • SEMAR algorithm significantly reduces metallic artefacts from small implants in abdominal CT. • SEMAR can improve image quality of the liver in dynamic CECT. • Confidence visualization of hepatic vascular anatomies can also be improved by SEMAR.

Emphysema Quantification Using Ultralow-Dose CT With Iterative Reconstruction and Filtered Back Projection.

OBJECTIVE: The purpose of this study was to evaluate agreement between standard-dose CT (SDCT) and ultralow-dose CT (ULDCT) findings with respect to emphysema quantification. ULDCT images were reconstructed with and without iterative reconstruction (IR). Adaptive iterative dose reduction with 3D processing was used for IR. MATERIALS AND METHODS: Fifty patients who underwent SDCT and ULDCT were included. The tube current for SDCT was 250 mA, and that for ULDCT was 10 mA. SDCT, ULDCT without IR, and ULDCT with IR were used for emphysema quantification. The low-attenuation volume percentage (LAV%) in the lungs at four thresholds (-970, -950, -930, and -910 HU), mean lung attenuation, and total lung volume were computed. Concordance correlation coefficients (CCC) were used to assess the agreement of emphysema quantification between SDCT and ULDCT. RESULTS: The LAV% CCC values were 0.310-0.789 between SDCT and ULDCT without IR and 0.934-0.966 between SDCT and ULDCT with IR. The agreement of LAV% improved when IR was used for ULDCT. The mean lung attenuation CCC value between SDCT and ULDCT without IR was substantial (0.957), whereas that between SDCT and ULDCT with IR was poor (0.890). The total lung volume CCC values were substantial (0.982 with IR, 0.983 without IR). CONCLUSION: ULDCT with and without IR can substitute for SDCT in emphysema quantification.

Four-dimensional computed tomography evaluation of jaw movement following mandibular reconstruction: A pilot study.

PURPOSE: The purpose of this study was to analyze jaw movement during mastication in patients who underwent mandibular reconstruction following segmental mandibulectomy, including mouth opening and mastication time, based on four-dimensional computed tomography (4D CT) images. MATERIAL AND METHODS: This study included six surgical patients, who underwent segmental mandibulectomy and simultaneous reconstruction with a free fibula osteocutaneous flap, and four controls. 4D CT was performed during mastication of a cookie to evaluate the movement of the jaw during natural function. The maximum mouth opening, mastication time, and movement of the mandibular angle during mastication were evaluated from the 4D CT images. RESULTS: 4D CT images enabled visualization of jaw movement during mastication. When compared with the controls, the maximum mouth opening during mastication and excursion of the mandibular angle, especially on the diseased side, tended to decrease in surgical patients; however, this did not occur with mastication time. The numerical differences between the diseased and nondiseased side in surgical patients tended to be higher than the crosswise differences in controls. CONCLUSION: 4D CT images revealed differences in jaw function between patients who underwent mandibular reconstruction and controls. 4D CT could be used to evaluate postoperative outcomes following mandibular reconstruction.

Four-dimensional noise reduction using the time series of medical computed tomography datasets with short interval times: a static-phantom study.

Backgrounds. This study examines the hypothesis that four-dimensional noise reduction (4DNR) with short interval times reduces noise in cardiac computed tomography (CCT) using "padding" phases. Furthermore, the capability of reducing the reduction dose in CCT using this post-processing technique was assessed. Methods. Using base and quarter radiation doses for CCT (456 and 114 mAs/rot with 120 kVp), a static phantom was scanned ten times with retrospective electrocardiogram gating, and 4DNR with short interval times (50 ms) was performed using a post-processing technique. Differences in the computed tomography (CT) attenuation, contrast-to-noise ratio (CNR) and spatial resolution with modulation transfer function in each dose image obtained with and without 4DNR were assessed by conducting a Tukey-Kramer's test and non-inferiority test. Results. For the base dose, by using 4DNR, the CNR was improved from 1.18 ± 0.15 to 2.08 ± 0.20 (P = 0.001), while the CT attenuation and spatial resolution of the image of 4DNR did not were significantly inferior to those of reference image (P < 0.001). CNRs of the quarter-dose image in 4DNR also improved to 1.28 ± 0.11, and were not inferior to those of the non-4DNR images of the base dose (P < 0.001). Conclusions. 4DNR with short interval times significantly reduced noise. Furthermore, applying this method to CCT would have the potential of reducing the radiation dose by 75%, while maintaining a similar image noise level.

3D lung motion assessments on inspiratory/expiratory thin-section CT: Capability for pulmonary functional loss of smoking-related COPD in comparison with lung destruction and air trapping.

PURPOSE: To evaluate the utility of three-dimensional (3D) lung motion on inspiratory and expiratory CT for pulmonary functional loss in smoking-related COPD in comparison with lung destruction and air trapping assessments. METHOD AND MATERIALS: Forty-four consecutive smokers and COPD patients prospectively underwent inspiratory and expiratory CT. A 3D motion vector map was generated from these CTs, and regional motion magnitudes were measured at the horizontal axis (X-axis), the ventrodorsal axis (Y-axis), and the craniocaudal axis (Z-axis). All mean magnitudes within the entire lung (MMLX, MMLY, and MMLZ) were normalized by expiratory CT lung volume. Moreover, CT-based functional lung volume (FLV) on inspiratory CT and air trapping lung volume (ATLV) on expiratory CT were assessed quantitatively. To evaluate the capability for pulmonary function loss assessment, all MMLs were correlated with pulmonary function tests. Then, discrimination analysis was performed to determine the concordance capability for clinical stage, and correct classification capabilities were compared by means of McNemar's test. RESULTS: Multiple regression analysis showed MMLY (ß=0.657, p<0.001) and FLV (ß=0.375, p=0.019) were correlated with percentage of predicted forced expiratory volume in 1 second. Correct classification capabilities using patient characteristics and MMLs (68.2 (30/44)%) were significantly higher than those obtained by patient characteristics, FLV, and ATLV (54.5 (24/44)%), p=0.031). CONCLUSION: 3D lung motion parameter assessment is useful for smoking-related COPD assessment as well as lung parenchymal destruction and/or air trapping evaluations.