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Purpose The aim of this study was to investigate the diagnostic accuracy of computed tomography (CT) for the prediction of ablation zones from microwave ablation (MWA) and cryoablation (CA) in an ex vivo porcine liver model. Methods Sequential (30 seconds) CT scans were acquired during and after MWA and CA in an ex vivo porcine liver model. We generated 120-kVp equivalent reconstructions of generic dual-energy CT data sets, and comprehensive region-of-interest measurements were statistically correlated with invasive temperature monitoring using Pearson correlation coefficient. Binary logistic regression was performed for prediction of successful ablation. Results With the use of pooled data from 6 lesions in 2 separate experiments, correlation analysis of attenuation in Hounsfield units (HU) and temperature yielded r = -0.79 [confidence interval (CI), -0.85 to -0.71] for MWA and r = 0.62 (CI, 0.55 to 0.67) for CA.For MWA, there was a linear association between attenuation and temperature up to 75°C; thus, linear regression yielded a slope of -2.00 HU/°C (95% CI, -1.58 to -2.41). For CA, a linear association between attenuation and temperature was observed in the cooling phase with a slope of 2.11 HU/°C (95% CI, 1.79 to 2.58). In MWA treatment, binary logistic regression separated less than 70°C and greater than 70°C with 89.2% accuracy. Within the ice ball, temperatures above and below -20°C were distinguished with 65.3% accuracy. Conclusions Our experiments reveal several difficulties in predicting ablation zone temperature from CT attenuation. Microwave ablation leads to gas production in the tissue, which degrades the accuracy of noninvasive temperature measurement, especially at higher temperatures. In CA, CT thermometry is limited by ice ball formation, which leads to homogeneous attenuation, nearly independent of temperature. Further research is needed to define the role of CT thermography in ablation zone monitoring in liver malignancies.

To evaluate the diagnostic accuracy of single-source dual-energy computed tomography (DECT) for the detection of bone marrow oedema (BME) in patients with vertebral compression fractures. Patients over 50 years of age with radiographically suspected vertebral compression fracture of the thoracic or lumbar spine were prospectively enrolled. All patients underwent DECT with sequential acquisition of 80 and 135 kVp datasets on a 320-row detector CT scanner and 1.5-Tesla magnetic resonance imaging (MRI) including T1-weighted and short-tau inversion recovery (STIR) sequences. Virtual non-calcium (VNCa) images were reconstructed using a three-material decomposition algorithm. Vertebrae with height loss in CT were scored for the presence of BME in both MRI and DECT and used to determine signal- and contrast-to-noise ratios (SNR and CNR). Contingency analysis using MRI as standard of reference and Fleiss’s kappa were calculated. IRB approval was obtained. In total 192 vertebral compression fractures in 70 patients (23 men, 47 women; mean age 70.7 years (SD 9.8)) were included in our analysis. DECT showed a reader-dependent sensitivity of 72% and specificity of 70% for BME. Fleiss’s kappa was .40 for DECT and .58 for MRI. T1-weighted images had significantly better SNR and CNR compared to STIR, CT, and VNCa (p < .0001); however, there was no difference between STIR and VNCa. VNCa images depict BME with adequate sensitivity and specificity and can be acquired on a single-source system. Image quality is adequate but trained readers are needed for image interpretation. • Dual-energy CT in a single-source technique can help to detect bone marrow oedema in patients with vertebral compression fractures. • However, given the inferior inter-rater reliability and limited specificity compared to MRI, experienced readers are needed for image interpretation. • Dual-energy CT of the spine has limited sensitivity for the detection of bone marrow oedema in vertebra with previous surgical intervention.

Dual-energy computed tomography detects tophi in patients with chronic gout. However, other information that can be obtained from the same scan is not the focus of the current research, e.g., the detection of bone marrow edema (BME) using virtual bone marrow imaging (VBMI). The aim of this study was to evaluate if BME in patients with acute arthritis can be detected with VBMI using magnetic resonance imaging (MRI) as the standard of reference.This retrospective study included 11 patients who underwent both MRI and dual-energy computed tomography (mean interval of 40 days). BME in MRI (standard of reference) and VBMI was judged independently by two different blinded readers. φ-correlation coefficient and Cohen's κ were performed for statistical analysis. Approval was waived by the IRB.Two patients with a final diagnosis of RA and one with septic arthritis showed osteitis on MRI and VBMI. However, in each case, there were individual bones identified with osteitis on MRI but not VBMI. Three additional patients with the final diagnosis of RA were identified correctly as negative for BME. There was a good correlation between both modalities (φ = 0.8; κ = 0.8). Inter-rater reliability was excellent for both modalities (κ = 0.9).We have shown that detecting osteitis using VBMI is feasible in patients with inflammatory arthritis. Further studies are needed on larger, more-targeted populations to better define the indications, accuracy, and added value of this technique.

OBJECTIVE: To assess the accuracy of an iterative reconstruction (IR) technique for coronary artery calcium scoring with reduced radiation dose. METHODS: 163 consecutive patients underwent twofold scanning by 320-row detector CT at 120 kVp. A low-dose scan at 25% tube current but with standard scan length (14 cm) was followed by a standard dose scan with routine tube current but reduced scan length (10 cm). Reduced dose images were constructed using filtered back-projection (FBP) and IR (adaptive iterative dose reduction in three dimensions). The standard dose scan reconstructed with FBP served as the gold standard for comparisons. Image noise and Agatston coronary calcium scores were determined and compared between the groups. RESULTS: Compared with FBP at standard dose, noise at reduced dose increased markedly with FBP but remained low with IR. Mean Agatston score with FBP at reduced dose showed a significant increase as compared with FBP at standard dose. No significant difference was observed when applying IR at reduced dose. At reduced dose, 38 (23.3%) patients were reassigned to a different cardiovascular risk category with FBP but only 8 (4.9%) with IR. Out of 47 patients with a zero Agatston score, 15 patients (31.9%) were false-positive with FBP at reduced dose, but no false positives were found with IR. CONCLUSION: IR allows accurate coronary artery calcium scoring with a radiation dose reduced by 75%. ADVANCES IN KNOWLEDGE: The application of adaptive iterative dose reduction in three dimensions allows the maintenance of accurate Agatston scores and risk stratification at significantly reduced tube current, thus reducing the patient’s exposure to ionizing radiation.

Objectives We hypothesize that, compared with filtered back projection (FBP), iterative reconstruction (IR) increases the detected volume of uric acid, which serves as a measure of the sensitivity of the method, and therefore allows examinations with lower radiation exposure. Thus, the aim of our study was to evaluate the role of IR in dual-energy computed tomography (DECT) for gout assessment and volumetry in an ex vivo gout model using an epoxy phantom and a biophantom. Materials and methods We prepared specimens with different concentrations of monosodium uric acid in ultrasound gel (30%-50%) and inserted them into an epoxy-based phantom and a porcine foreleg. Computed tomography scanning was performed on a 320-row single-source DECT scanner in volume mode with an ascending order of tube currents. Image data sets were reconstructed using FBP and IR with 2 iteration levels (IR1 and IR2). Measurements in regions of interest (ROIs) and volumetric measurements were performed using either fixed parameters for the analysis software (epoxy phantom) or parameters specifically adapted for each data set (porcine phantom). Seven retrospectively identified clinical data sets were used for validation in patients. Rm-ANOVA was used for statistical analysis. No institutional review board approval was required. Results We found no differences in Hounsfield units between the different reconstruction algorithms (P = 0.09 and 0.05 for 80 and 135 kVp, respectively) and the calculated dual-energy gradient (P = 0.27). Filtered back projection detected less uric acid compared with IR (with fixed parameters: 6.0 ± 0.3 cm for FBP and 6.1 ± 0.2 for IR1 and IR2; with adapted thresholds: 1.2 ± 0.3 cm for FBP and 1.8 ± 0.1 and 2.0 ± 0.1 for IR1 and IR2, respectively). The differences were significant for all measurements (P = 0.0003). Also in the test cases, FBP detected significantly fewer tophi (mean volume, 1.38 ± 2.1 cm) compared with IR1 (1.86 ± 2.9) and IR2 (2.07 ± 3.1) (P = 0.04). Conclusions Iterative reconstruction has the potential to improve the sensitivity of a DECT scan for gouty tophi, to decrease radiation exposure, or to combine both options.

To investigate the diagnostic value of single-source dual-energy computed tomography (SDECT) in gouty arthritis and to compare its capability to detect urate depositions with digital radiography (DR) and conventional computed tomography (CT).Forty-four patients who underwent SDECT volume scans of the feet for suspected gouty arthritis were retrospectively analyzed. SDECT, CT (both n=44) and DR (n=36) were scored by three blinded readers for presence of osteoarthritis, erosions, and tophi. A diagnosis was made for each imaging modality. Results were compared to the clinical diagnosis using the American College of Rheumatology (ACR) classification criteria.The patient population was divided into a gout (n=21) and control (n=23) group based on final clinical diagnosis. Osteoarthritis was evident in 15 joints using CT and 30 joints using DR (p=0.165). There were 134 erosions detected by CT compared to 38 erosions detected by DR (p0.001). In total 119 tophi were detected by SDECT, compared to 85 tophi by CT (p=0.182) and 25 tophi by DR (p0.001). SDECT had best diagnostic value for diagnosis of gout compared to DR and conventional CT (sensitivity and specificity for SDECT: 71.4% and 95.7%, CT: 71.4% and 91.3% and DR: 44.4% and 83.3%, respectively). For all three readers, Cohen's kappa for DR and conventional CT were substantial for all scoring items and ranged from 0.75 to 0.77 and 0.72-0.76, respectively. For SDECT Cohen's kappa was good to almost perfect with 0.77-0.84.SDECT is capable to detect uric acid depositions with good sensitivity and high specificity in feet, therefore diagnostic confidence is improved. Using SDECT, inter-reader variance can be markedly reduced for the detection of gouty tophi.

We sought to evaluate and validate a low-dose protocol for respiratory-gated multislice computed tomography (CT) for volume calculations in small ventilated neonatal animals as a model for the ventilated human neonatal lung.Five mechanically ventilated newborn piglets were imaged in a multislice CT scanner (0.5-mm slice thickness, 4:16 pitch, 0.5 seconds rotation time, 120 kV) using a normal (100 mAs) and a reduced (10 mAs) dose protocol. All animals were scanned twice (at 100 and 10 mAs) at each of 3 different ventilator settings. Complete volume datasets were reconstructed throughout the respiratory cycle in increments of 10% using retrospective half-scan reconstruction. End-inspiratory volumes and volumes during maximal expiration (functional residual capacity) were calculated by a customized software and values for normal and reduced dose protocols were compared using Kolmogorov-Smirnov test and Bland-Altman plots.Two volume datasets (one normal and one reduced dose protocol) showed artifacts on the axial images, which could not be analyzed by the software. Those values were determined after manual segmentation and excluded from final analysis. The mean (+/-SD) end-inspiratory volumes and functional residual capacity were 34.3 +/- 10.1 mL and 25.3 +/- 8.0 mL for the normal-dose protocol versus 33.1 +/- 10.0 mL and 24.7 +/- 8.1 mL for the reduced-dose protocol, respectively. There was no statistically significant difference between normal and reduced dose protocol (KS-Test: D = 0.14Dmax).Lung volume calculation in ventilated newborn piglets (end-inspiratory volumes and functional residual capacity) can be performed using respiratory-gated multislice CT even at a substantially reduced dose (eg, to 10 mAs). This makes the technique a candidate for future pediatric use.

Dual-energy computed tomography (DECT) is an emerging imaging technique for examining patients with suspected gout. Single-source dual-energy CT (S-DECT) is a new way of obtaining DECT information on conventional CT scanners rather than using special dual-source CT systems. We tested the feasibility of S-DECT (320-row CT; Aquilion ONE, Toshiba Medical Systems, Otawara, Japan) in 6 patients (5 men, 1 woman; mean age 61.3, range 48 to 69 years) with acute arthralgia and suspected gout, and compared the S-DECT findings with the results of joint aspiration. Three patients had a diagnosis of gouty arthritis with negatively birefringent crystals in synovial fluid, in addition to gouty tophi in S-DECT. Three patients had no detectable crystals by polarization microscopy and no tophi on DECT. Their final diagnoses were rheumatoid arthritis, activated osteoarthritis, and septic arthritis in one case each. This initial experience suggests that S-DECT might be a valuable alternative to dual-source CT. Hence, more patients may benefit from its additional diagnostic abilities in the future.

Purpose: To evaluate multi-slice spiral computed tomography (MSCT) for measurements of left ventricular volumes, ejection fraction (EF), and myocardial mass in comparison with electron beam CT (EBCT) as a reference method. Material and Methods: Six minipigs underwent both standardized contrast-enhanced MSCT (effective acquisition time per cardiac cycle 125.7±30.1 ms, reconstructed slice thickness 8 mm) and EBCT (acquisition time 50 ms, collimated slice thickness 8 mm). The contrast-to-noise ratio of the left ventricle was measured in each animal, and the contour sharpness of the myocardium was analyzed. Volumes (EDV, ESV, SV) ejection fraction (EF), and muscle mass were calculated by MSCT and by EBCT using the slice summation method. Results: MSCT had a higher contrast-to-noise ratio and delineated the myocardial contours more sharply than EBCT. There was a close linear correlation between both modalities for all parameters (EDV: rP=0.88, ESV: rP=0.91, SV: rP=0.85, EF: rP=0.93; mass: rP=0.90; P Conclusions: Image quality in MSCT is superior to that of EBCT. Functional parameters correlate well between both modalities, but the accuracy of MSCT is limited by its lower temporal resolution.

The use of the CT scanner for cardiac imaging is mainly influenced by the spatial and temporal resolution that can be achieved with the applied technologies and procedures. The data acquisition with 16 x 0.5 mm scan slice thickness and a special multisegment image reconstruction procedure are a new combination for accurate imaging of the cardiac morphology. A 0.5 mm slice thickness and an overlapping pitch < 0.35 generate an isotropic image voxel of 0.35 x 0.35 x 0.35 mm. The object size of a coronary artery with a diameter of 2.5 mm amounts to a relative spatial blurring factor K (d) of approximately 15 %. The segment reconstruction with 4 segments from 4 consecutive cardiac cycles requires the optimum acquisition time of 50 ms for one frame. The relative exposure factor K (t) with reference to the R-R interval is an appropriate measure to validate the influence of coronary artery movement on the image quality at different heart rates. This relative exposure varies between 10 % and 20 % for a heart rate of 40 to 140 beats per minutes (bpm) and its mean is approximated by a linear trend function with K (t) = 14 %. A constant value in this linear trend function means a constant "blurring" of the imaged coronary arteries, independent of the actual heart rate. Thus, computed tomographic examinations can be carried out for heart rates between 40 and 140 bpm without using beta-blocking medication. Case studies of the 3D reconstruction and curved reformatting of coronary arteries with stents and calcifications show the achievable image quality at different heart rates.

PURPOSE To evaluate the potential of multisegmental reconstruction and variable gantry rotation time for reducing motion-induced artifacts in coronary artery imaging by multislice helical CT. MATERIALS AND METHODS The data sets of 20 patients (8 with HR 60 bpm) were analyzed. The patients underwent multislice helical CT (Aquilion 8, Toshiba, Otawara, Japan) using the following parameters: 0.5 mm slice thickness, 250 mA, 120 kV, pitch of 0.25 and variable gantry rotation times of 400, 500, or 600 msec. Images were generated by halfscan and multisegmental reconstruction. In 9 coronary segments of each patient, the presence and severity of motion artifacts were assessed and graded on a scale between 5 (no artifacts) and 1 (heaviest artifacts). RESULTS Diagnostically relevant motion artifacts were rare at low heart rates ( 60 bpm) were associated with an increase in motion artifacts on halfscan reconstructions (33% of all segments, p 0.05), whereas at higher heart rates image quality was better for multisegmental reconstruction than for halfscan reconstruction (4.23 +/- 0.47 vs. 3.11 +/- 0.63; p < 0.05). CONCLUSION Multisegmental reconstruction with variable gantry rotation times suppresses motion artifacts and thus improves assessment of the coronary arteries in patients with higher heart rates.

The aim of this study was to perform phantom measurements to prove the feasibility of single-source dual-energy computed tomography (DECT) of the extremities using a volume scan mode. In addition, we, for the first time, wanted to determine which concentrations of monosodium urate (MSU) in gout and calcium pyrophosphate (CP) in pseudogout are needed to detect or distinguish these soft tissue depositions with DECT.We created a hand-shaped plastic phantom assembled with a descending order of concentrations of MSU (6.25%-50%) and CP (1.56%-50%) with similar attenuation in conventional computed tomographic (CT) images. Dual-energy imaging was done on a standard 320-row CT scanner with acquisition of 2 volumes: one at 80 and the other at 135 kV. Using linear regression analysis, dual-energy gradients were calculated for MSU and CP. Thereafter, we selected a specific region of interest on the dual-energy graph to color-code MSU and CP on the images. Three blinded readers scored 10 scans of the randomly equipped phantom, corresponding to 60 samples, to determine the sensitivity and specificity of this technique. Receiver operating characteristics analysis was done to determine the diagnostic power.We found a dual-energy gradient for MSU of 1.020 ± 0.006 and for CP of 0.673 ± 0.001. Assessment of the randomized phantom scans indicates reliable detection of MSU at concentrations of 12.5 % or higher and that of CP at 6.25 % or higher, corresponding to deposits with mean Hounsfield unit values of 59.8 for MSU and 101.1 for CP. The sensitivity for MSU ranged from 83.3% to 97.3% at 15/90 mA (135/80 kV) and from 86.7% to 97.3% at 100/570 mA. Specificity was 96.7% to 100% in 15/90 mA and 100% in 100/570 mA of scans. However, there was inferior sensitivity for CP owing to lower concentrations. In the receiver operating characteristics analysis, the area under the curve for MSU ranged from 0.867 to 0.947 at 15/90 mA and from 0.867 to 0.919 at 100/570 mA and that for CP from 0.659 to 0.745 and from 0.718 to 0.750, respectively.This phantom study shows that single-source DECT allows detection and characterization of crystal deposits when present in soft tissue at relatively low concentrations. Further studies in patients have to prove its benefits in diagnostic imaging and treatment monitoring as well as its significance compared with dual-source CT systems.

To compare tube current adaptation based on 3 body mass index (BMI) categories versus anterior-posterior chest diameter (APD) for radiation dose optimisation in patients undergoing dynamic volume cardiac CT. Two cardiac imaging centres participated in the study. 20 patients underwent a prospectively triggered 320-slice single beat cardiac CT using the X-ray tube current [mA] manually adjusted to the patient’s BMI (group I). In 20 subsequent patients, the tube current was adapted according to the patient’s APD (group II). All other parameters were kept constant. Image noise was defined as the standard deviation of attenuation values and measured using a ROI in the descending aorta. Variation in image noise was statistically compared between both patient groups. Average and standard deviation of pixel noise were 29.1 HU and 14.8 HU in group I and 28.0 HU and 4.2 HU in group II. Inter-individual variation of pixel noise was significantly lower in group II compared to group I (p < 0.0001). Tube current adaptation based on APD is superior to stepwise adaptation based on BMI for optimising radiation dose in dynamic volume cardiac CT and therefore limits unnecessary radiation dose while ensuring diagnostic image quality in patients with diverse body habitus.

Purpose: The purpose of this study was to evaluate and validate dynamic volume calculation by respiratory-gated multislice computed tomography (CT) in small neonatal animals. Materials and Methods: Six mechanically ventilated newborn piglets were imaged in a multislice CT with 0.5-mm slice thickness (4:16 pitch, 0.5-second rotation time, 120 kV). The respirator was connected to the CT unit for recording the respiratory signal. Simultaneously, tidal volume was measured by the respirator and functional residual capacity (FRC) using a multiple-breath washin -washout technique (MBW) with heptafluoropropane (HFP) as tracer gas. Complete volume datasets were reconstructed throughout the respiratory cycle in increments of 10% using retrospective half-scan gating. All animals were scanned in 3 different ventilator settings. Dynamic lung volumes (tidal volumes) were calculated by means of segmentation of the lung parenchyma during the respiratory cycle using work-in-progress software. Results: The mean (′standard deviation) FRC determined by CT was 24.7 ′ 8.6 mL versus 24.8 ′ 7.3 mL for the MBW technique. There was no statistically significant difference (P = 0.555). Pearson's correlation coefficient showed a strong correlation between the data obtained with CT and that obtained with the MBW technique (r = 0.886). After exclusion of one outlier, tidal volumes showed a similar correlation (r = 0.837) without significant differences in the mean values (CT: 8.9 ′ 2.4 mL and respirator: 8.7 ′ 2.4 mL. P = 0.566). Conclusion: Dynamic multislice CT with respiratory gating allows for calculation of lung volumes and may be useful for future CT applications in human neonatal lung imaging.

A 54-year-old man had global aphasia and hemiparesis after an acute cerebral embolism. He had undergone unspecified cardiac surgery as a child. An ECG-gated multislice CT study demonstrated dilated aneurysm of the ascending aorta (Figure 1), large internal thoracic arteries (Figures 1, 2⇓A), and a synthetic patch sutured over a kinked luminal narrowing of the aortic isthmus (Figure 2 …

Currently, radiography is the only imaging technique used to diagnose bone pathology in wild animals situated under ‘‘field conditions’’. Nevertheless, while chronic foot disease in captive mega-herbivores is widely reported, foot radiographic imaging is confronted with scarcity of studies. Numerous hindrances lead to such limited numbers and it became very clear that the traditional perspective on bone imaging in domestic animals based on extensive studies and elaborated statistical evaluations cannot be extrapolated to their non-domestic relatives. For these reasons, the authors initiated a multi-modality imaging study and established a pioneering approach of synchronized computed tomography (CT) and digital radiography (DR), based on X-ray projections derived from three-dimensional CT reconstructed images. Whereas this approach can be applied in any clinical field, as a case of outstanding importance and great concern for zoological institutions, we selected foot bone pathologies in captive rhinoceroses to demonstrate the manifold applications of the method. Several advances were achieved, endowing the wildlife clinician with all-important tools: prototype DR exposure protocols and a modus operandi for foot positioning, advancing both traditional projections and, for the first-time, species-related radiographic views; assessment of radiographic diagnostic value for the whole foot and, in premiere, for each autopodial bone; together with additional insights into radiographic appearance of bone anatomy and pathology with a unique, simultaneous CT-DR correlation. Based on its main advantages in availing a wide range of keystone data in wildlife imaging from a limited number of examined subjects and combining advantages of CT as the golden standard method for bone diseases’ diagnostic with DR’s clinical feasibility under field conditions, synchronized CT-DR presents a new perspective on wildlife’s health management. With this we hope to provide veterinary clinicians with concrete imaging techniques and substantial diagnostic tools, which facilitate straightforward attainment and interpretation of field radiography images taken worldwide.