Flash CT Research Articles

Evaluation of non-breath-hold, ultra-fast, low-dose high-pitch (flash) CT scan as a practical alternative to standard spiral scan for pre-TAVI patients: a real-world single-center experience

Abstract Introduction and aim Aortic annulus dimensions change during the cardiac cycle. A retrospective ECG-gated (Spiral) scan is the default technique for pre TAVR evaluation since it includes systolic phases considered optimal for aortic annulus assessment. Ultra-fast, Low-Dose High-Pitch (FLASH) offers faster, potentially low radiation and low contrast dose scans. However, it lacks the ability to time data acquisition to the systole. Therefore, measurements derived from FLASH scan are considered suboptimal for reporting. The effect of this potential annular measurement difference on procedural success and safety was not evaluated. Therefore, we aimed to assess the feasibility and safety of FLASH vs. Spiral scan before TAVI. Methods We conducted a retrospective, single-center study. 409 patients underwent CT-TAVI scan with either FLASH or SPIRAL acquisition. Baseline characteristics, CT study, procedural and f/u data were acquired from the EMR. Outcomes defined by Valve Academic Research Consortium3 (VARC-2) endpoint definitions included in-hospital mortality, bleeding, vascular complications, acute kidney injury (AKI), conduction disorders, mechanical complications, and prosthetic aortic valve regurgitation. Composite endpoints such as device success were also examined. Results Of the 409 patients, 55.7% underwent FLASH scans. The median age was 80 years, and males accounted for 55%. The FLASH-protocol patients had higher rate of chronic kidney disease, their CT-measured aortic annulus area and diameter were smaller, and they were exposed to a smaller amount of contrast agent and radiation than the SPIRAL group. There was no statistically significant difference in primary clinical and safety endpoints between the two groups, including mechanical complications (such as annular rupture and valve malposition) and conduction disorders. Conclusions FLASH CT scan is a pragmatic and safe approach that potentially may replace spiral scan for the evaluation before TAVI procedure in the appropriate patients. Funding Acknowledgement Type of funding sources: None.

ROLE OF DUAL ENERGY COMPUTED TOMOGRAPHY IMAGING IN GOUT

Context: Gout is a crystal induced inammatory arthritis triggered by crystallization of uric acid in joints. The detection of urate crystals is done using polarization light microscopy after synovial uid aspiration which is approach is invasive. Dual energy CT (DECT) is a new imaging modality that is able to identify tophi based on their chemical composition. To evaluate the rol Aims: e of Dual Energy Computed Tomography imaging in gout. A cross sectional observational study, comprising of 30 clinically suspected pati Settings And Design: ents of gout underwent DECT of all peripheral joints (including hand, wrist, elbow, ankle, foot and knee). This Methods And Material: study was conducted on 128 slice SIEMENS Somatom Denition Flash CT scan. A dual energy gout colour coded protocol assessed the chemical composition of the material and an automated volume assessment software, measured the monosodium urate crystal deposition volume. Analysis was Statistical Analysis Used: done using SPSS version 21.0. In lower limb the MTP joint (73.33%) was commonest foll Results: owed by ankle (33%) and knee (26%) with mean crystal volume of 3.51 cm3. In upper limb, MCP and PIP joints (20%) of hand are most commonly affected with mean volume of 0.24cm3. High serum uric acid (>6.4mg/dl) levels showed a positive correlation with MSU crystal deposition in all peripheral joints on DECT. Conclusions: DECT is useful for the diagnosis of gout in symptomatic patients. It can detect MSU crystals volume and urate burden non-invasively.

Comparison of Turbo Flash and dual-energy modes of third-generation dual-source CT in pre-transplant renal angiography: a prospective observational study

BackgroundThe purpose of this study was to compare the Image Quality, Contrast Medium Volume, and Radiation dose in renal angiography performed using Turbo Flash mode and dual-energy (DE) mode in the third-generation dual-source dual-energy CT.This prospective observational study was performed on renal donors who underwent CTA imaging as a pre-transplant workup. The study population was divided into two groups. Group A underwent DECT renal angiography. Group B underwent Turbo Flash Mode CT renal angiography. For group A, a contrast volume of 1 ml/kg and for group B at 0.5 ml/kg was administered. Image Quality was evaluated objectively by calculating CNR and SNR and subjectively by a 5-point scale. Radiation Dose analysis was done by noting CTDIvol and DLP on the scanner system and calculating effective radiation dose (ED).ResultsThe subjective image quality scores for the Turbo Flash group were comparable with the DE group in qualitative image analysis. Additionally, in the Turbo Flash group, there was a reduction in contrast media and effective radiation dose by 47.5% and 32.7%, respectively. Nevertheless, mean attenuation of the abdominal arteries, CNR, SNR, and Noise (S.D) showed statistical significance between the two groups (p value < 0.01).ConclusionsTo our knowledge, no previous study compared Turboflash mode with DE protocol in CT renal angiography in a donor group of patients. Turbo Flash CT is an excellent modality that is faster and has an added advantage of decreased radiation dose and contrast media volume reduction, which can be recommended for screening of voluntary kidney donors but needs further clinical studies, validation, and standardization with tailored protocols.

Contrast medium administration with a body surface area protocol in step-and-shoot coronary computed tomography angiography with dual-source scanners

We evaluated the feasibility and image quality of prospective electrocardiography (ECG)-triggered coronary computed tomography angiography (CCTA) using a body surface area (BSA) protocol for contrast-medium (CM) administration on both second- and third-generation scanners (Flash and Force CT), without using heart rate control. One-hundred-and-eighty patients with suspected coronary heart disease undergoing CCTA were divided into groups A (BSA protocol for CM on Flash CT), B (body mass index (BMI)-matched patients; BMI protocol for CM on Flash CT), and C (BMI-matched patients; BSA protocol for CM on Force CT). Patient characteristics, quantitative and qualitative measures, and radiation dose were compared between groups A and B, and A and C. Of the 180 patients, 99 were male (median age, 62 years). Average BSA in groups A, B, and C was 1.80 ± 0.17 m2, 1.74 ± 0.16 m2, and 1.64 ± 0.17 m2, respectively, with groups A and C differing significantly (P < 0.001). Contrast volume (50.50 ± 8.57 mL vs. 45.00 ± 6.18 mL) and injection rate (3.90 ± 0.44 mL/s vs. 3.63 ± 0.22 mL/s) differed significantly between groups A and C (P < 0.001). Groups A and C (both: all CT values > 250 HU, average scores > 4) achieved slightly lower diagnostic image quality than group B. The BSA protocol for CM administration was feasible in both Flash and Force CT, and therefore may be valuable in clinical practice.

Value of Ultrasonic Cardiogram Combined with Flash CT in Diagnosis of Conotruncal Defects

The paper aims at exploring the value of ultrasonic cardiogram (UCG) combined with Flash CT in the diagnosis of conotruncal defects (CTD). This complex cyanotic congenital heart disease is divided into several types by using UCG and Flash dual source CT imaging. The results show that the detection method of UCG is simple and fast, but it has some deficiencies in the display of extracardiac vessels. Flash CT technology has a strong image post-processing function, which makes up for the shortcomings of UCG and is an important supplementary means for patients after echocardiographic examination. Therefore, UCG combined with Flash CT technology can detect the patient's disease more accurately and quickly, avoid the traumatic detection of angiography, and is more convenient. It is hopeful to replace angiography as the gold standard for the diagnosis of congenital heart disease.

Accuracy and reliability of measurements performed using two different software programs on digital models generated using laser and computed tomography plaster model scanners.

ObjectiveThe aim of this study was to compare the accuracy and reliability of measurements performed using two different software programs on digital models generated using two types of plaster model scanners (a laser scanner and a computed tomography [CT] scanner).MethodsThirty plaster models were scanned with a 3Shape laser scanner and with a Flash CT scanner. Two examiners performed measurements on plaster models by using digital calipers and on digital models by using Ortho Analyzer (3Shape) and Digimodel® (OrthoProof) software programs. Forty-two measurements, including tooth diameter, crown height, overjet, overbite, intercanine and intermolar distances, and sagittal relationship, were obtained.ResultsStatistically significant differences were not found between the plaster and digital model measurements (ANOVA); however, some discrepancies were clinically relevant. Plaster and digital model measurements made using the two scanning methods showed high intraclass coefficient correlation values and acceptable 95% limits of agreement in the Bland-Altman analysis. The software used did not influence the accuracy of measurements.ConclusionsDigital models generated from plaster casts by using laser and CT scanning and measured using two different software programs are accurate, and the measurements are reliable. Therefore, both fabrication methods and software could be used interchangeably.

Impact of advanced detector technology and iterative reconstruction on low-dose quantitative assessment of lung computed tomography density in a biological lung model.

Quantitative computed tomography (QCT)-derived measures of lung density are valued methods for objectively characterizing lung parenchymal and peripheral airways disease and are being used in a growing number of lung disease focused trials. Detector and reconstruction improvements in CT technology have allowed for significant radiation dose reduction in image acquisition with comparable qualitative image quality. We report the impact of detector type and reconstruction type on QCT lung density measures in relation to decreasing dose indices. Two sets of studies were completed in an in vivo pig model with a SOMATOM Definition Flash CT system: (a) prior to system upgrade with conventional detectors (UFC) and filtered back projection (FBP), and (b) post system upgrade with integrated electronic detectors (STELLAR) and iterative reconstruction (SAFIRE). CT data were acquired across estimated CT volume dose indices (CTDIvol ) ranging from 0.75 to 15 mGy at both inspiratory and expiratory breath holds. Semiautomated lung segmentations allowed calculation of histogram median, kurtosis, and 15th percentile. Percentage of voxels below -910 HU and -950 HU (inspiratory), and -856 HU (expiratory) were also examined. The changes in these QCT metrics from dose reduction (15 mGy down to 0.75 mGy) were calculated relative to paired reference values (15 mGy). Results were compared based on detector and reconstruction type. In this study, STELLAR detectors improved concordance with 15 mGy values down to 3 mGy for inspiratory scans and 6 mGy for expiratory scans. The addition of SAFIRE reconstruction in all acquired measurements resulted in minimal deviation from reference values at 0.75 mGy. The use of STELLAR integrated electronic detectors and SAFIRE iterative reconstruction may allow for comparable lung density measures with CT dose indices down to 0.75 mGy.

Applicability of a clinical cardiac CT protocol in post mortem studies

Abstract Objective Confirmation whether an optimized clinical cardiac CT scan protocol is also optimal for post mortem cardiac CT scans without iodine contrast or the reconstruction parameters should be changed. Materials and methods 27 CT volumes (three cases for three recon- struction kernel with three different iterative reconstruction settings) were graded by six readers in order to find the optimal reconstruction parame- ters. The scans were performed on a Siemens Definition Flash CT scanner using 120 kV tube potentials. Results The study has shown that from the investigated options the softest cardiac kernel with the strongest iterative reconstruction were pre- ferred by the readers (I26 Safire 3). Conclusion The results indicate that the scan protocol which was adopted from clinical practice is applicable in forensic radiology too even though iodine contrast agent was not administered.

Application value of CT spectrum curve and iodine measurement in the early diagnosis of gastric cancer

To explore the value of dual-source CT spectrum curve and iodine measurement in the early diagnosis of gastric cancer. Imaging materials of 21 cases with early gastric cancer confirmed by gastroscope and pathology, and 38 cases with normal stomach in our department from November 2011 to June 2013 were retrospectively analyzed. All the cases underwent dual-energy scanning with SOMATOM Definition Flash CT. The iodine concentration of the lesion in arterial phase and venous phase was measured respectively. The iodine concentration of small curvature side and aorta of same level was also measured for the cases with normal stomach. Normalized iodine concentration (NIC) difference was studied between early gastric cancer lesions and normal gastric wall. Spectrum curve characteristics of gastric cancer lesions and normal gastric lesser curvature were analyzed. There were significant differences in NIC between early gastric cancer lesions and normal gastric wall (arterial phase, 0.21 vs. 0.09, P=0.000; venous phase, 0.72 vs. 0.26, P=0.000). Spectrum curves of normal gastric wall and early gastric cancer, both in arterial and venous phase, showed descending tendency. Spectrum curve of early gastric cancer located above that of normal gastric wall, and was more steep. Difference between these two curves became greater during 40 to 70 keV, and became smaller during 80 to 140 keV. NIC and spectrum curve tendency are helpful to identify the early gastric cancer and the normal gastric wall through the dual-energy model scan.

Quantum noise properties of CT images with anatomical textured backgrounds across reconstruction algorithms: FBP and SAFIRE.

Quantum noise properties of CT images are generally assessed using simple geometric phantoms with uniform backgrounds. Such phantoms may be inadequate when assessing nonlinear reconstruction or postprocessing algorithms. The purpose of this study was to design anatomically informed textured phantoms and use the phantoms to assess quantum noise properties across two clinically available reconstruction algorithms, filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE). Two phantoms were designed to represent lung and soft-tissue textures. The lung phantom included intricate vessel-like structures along with embedded nodules (spherical, lobulated, and spiculated). The soft tissue phantom was designed based on a three-dimensional clustered lumpy background with included low-contrast lesions (spherical and anthropomorphic). The phantoms were built using rapid prototyping (3D printing) technology and, along with a uniform phantom of similar size, were imaged on a Siemens SOMATOM Definition Flash CT scanner and reconstructed with FBP and SAFIRE. Fifty repeated acquisitions were acquired for each background type and noise was assessed by estimating pixel-value statistics, such as standard deviation (i.e., noise magnitude), autocorrelation, and noise power spectrum. Noise stationarity was also assessed by examining the spatial distribution of noise magnitude. The noise properties were compared across background types and between the two reconstruction algorithms. In FBP and SAFIRE images, noise was globally nonstationary for all phantoms. In FBP images of all phantoms, and in SAFIRE images of the uniform phantom, noise appeared to be locally stationary (within a reasonably small region of interest). Noise was locally nonstationary in SAFIRE images of the textured phantoms with edge pixels showing higher noise magnitude compared to pixels in more homogenous regions. For pixels in uniform regions, noise magnitude was reduced by an average of 60% in SAFIRE images compared to FBP. However, for edge pixels, noise magnitude ranged from 20% higher to 40% lower in SAFIRE images compared to FBP. SAFIRE images of the lung phantom exhibited distinct regions with varying noise texture (i.e., noise autocorrelation/power spectra). Quantum noise properties observed in uniform phantoms may not be representative of those in actual patients for nonlinear reconstruction algorithms. Anatomical texture should be considered when evaluating the performance of CT systems that use such nonlinear algorithms.

Compact Robotically Steerable Image-Guided Instrument for Multi-Adjacent-Point (MAP) Targeting

Accurately targeting multi-adjacent points (MAPs) during image-guided percutaneous procedures is challenging due to needle deflection and misalignment. The associated errors can result in inadequate treatment of cancer in the case of prostate brachytherapy, or inaccurate diagnosis during biopsy, while repeated insertions increase procedure time, radiation dose, and complications. To address these challenges, we present an image-guided robotic system capable of MAP targeting of irregularly shaped volumes after a single insertion of a percutaneous instrument. The design of the compact CT-compatible drive mechanism is based on a nested screw and screw-spline combination that actuates a straight outer cannula and a curved inner stylet that can be repeatedly straightened when retracted inside the cannula. The stylet translation and cannula rotation/translation enable a 3-D workspace to be reached with the stylet's tip. A closed-form inverse kinematics and image-to-robot registration are implemented in an image-guided system including a point-and-click user interface. The complete system is successfully evaluated with a phantom under a Siemens Definition Flash CT scanner. We demonstrate that the system is capable of MAP targeting for a 2-D shape of the letter “H” and a 3-D helical pattern with an average targeting error of 2.41 mm. These results highlight the benefit and efficacy of the proposed robotic system in seed placement during image-guided brachytherapy.

SU-C-12A-07: Effect of Vertical Position On Dose Reduction Using X-Care

Purpose: Reduction of absorbed dose to radiosensitive tissues is an important goal in diagnostic radiology. Siemens Medical has introduced a technique (X-CARE) to lower CT dose to anterior anatomy by reducing the tube current during 80° of rotation over radiosensitive tissues. Phantom studies have shown 30-40% dose reduction when phantoms are positioned at isocenter. However, for CT face and sinus exams, the center of the head is commonly positioned below isocenter. This work investigated the effects of vertical patient positioning on dose reduction using X-CARE. Methods: A 16cm Computed Tomography Dose Index phantom was scanned on a Siemens Definition Flash CT scanner using a routine head protocol, with the phantom positioned at scanner isocenter. Optically stimulated luminescent dosimeters were placed on the anterior and posterior sides of the phantom. The phantom was lowered in increments of 2cm and rescanned, up to 8cm below isocenter. The experiment was then repeated using the same scan parameters but adding the X-CARE technique. The mean dosimeter counts were determined for each phantom position, and the difference between XCARE and routine scans was plotted as a function of distance from isocenter. Results: With the phantom positioned at isocenter, using XCARE reduced dose to the anteriormore » side of the phantom by 40%, compared to dose when X-CARE was not used. Positioned below isocenter, anterior dose was reduced by only 20-27%. Additionally, using X-CARE at isocenter reduced dose to the anterior portion of the phantom by 45.6% compared to scans performed without X-CARE 8cm below isocenter. Conclusion: While using X-CARE substantially reduced dose to the anterior side of the phantom, this effect was diminished when the phantom was positioned below isocenter, simulating common practice for face and sinus scans. This indicates that centering the head in the gantry will maximize the effect of X-CARE.« less

Electrocardiographically triggered CT angiography of the whole aorta and coronary arteries with highpitch dual-source CT

Objective To investigate the feasibility of comprehensive assessment of the whole aorta and coronary arteries (CA) simultaneously with high-pitch 128-slice dual-source CT ECG-gated FLASH protocol. Methods A total of 48 consecutive patients with suspected aortic diseases underwent CTA examination of the whole aorta and CA using a ECG-gated FLASH CT protocol (pitch=3.2) without heart rate (HR) control.Aorta,aortic valves and CA were shown with different post-processing modalities.The image quality of the aorta,aortic valves and CA was evaluated and compared according to HR (low HR group≤65 bpm,high HR group>65 bpm).The scan time,effective dose and contrast medium volume were recorded.Inter-observer differences were calculated by Kappa test.Differences between groups were analyzed by Mann-Whitney test with count data and variance test with measurement data. Results All examinations were completed successfully.The image quality was acceptable in the aorta,aortic valve (100%,48/48) and CA (94.0%,551/586).Percentage of diagnostic quality images was slightly higher in low HR group (94.7%,232/245,93.5%,319/341,Z=-2.504,P<0.05).Inter-reader reproducibility was 95.8% (46/48) in the aorta and aortic valve,96.6% (566/586) in CA,yielded good agreement (Kappa=0.81 and 0.89).The mean attenuation of aorta and CA were higher than 300 HU,especially in low HR group (357.0—446.0) HU.Except proximal segment of right CA,the CNR of whole aorta and coronary arteries were significantly higher in the low HR group (24.5—29.0) than that in the high HR group (20.0—23.1,P<0.05).SNR of the whole aorta was higher in the low HR group (13.7—17.9) than the high HR group (11.5—13.9,P<0.05).The mean scan time was (1.56±0.08) s,effective dose was (4.12±1.23) mSv (2.77—6.77 mSv),and contrast medium volume was (72.8±2.1) ml. Conclusions CT angiography of whole aorta and coronary arteries could be performed simultaneously within 2 seconds with CT ECG-gated FLASH protocol.The images were of diagnostic quality for aortic and CA disease with low dose of radiation and contrast media.However,high HR could decrease the image quality of CA. Key words: Aorta; Coronary vessels; Angiography; Tomography,spiral computed

Bronchial Carcinoid Imaged With Cardiac Gated, 128-Slice, Dual-Source, Flash CT Scanner to Direct Operative Management

Carcinoid is a rare lung cancer that typically presents with a relatively indolent clinical behavior. We present the case of a 32-year-old male with progressive respiratory symptoms, which resulted in the diagnosis of typical bronchial carcinoid. This case shows a novel imaging technique for staging a bronchial carcinoid for determination of optimal management. This case also shows the multidisciplinary approach required for management of patients with carcinoid tumors.

Determination of Ureter Stent Appearance on Dual-energy Computed Tomography Scan

To examine the dual-energy computed tomography (DECT) properties of 7 commonly used ureteral stents to optimize stent selection for calculi monitored using DECT. The use of DECT to evaluate renal and ureteral calculi has recently increased. Seven stents were individually placed in a fish bowl phantom and imaged using a Siemens Somatom Definition Flash CT scanner. DECT peak tube potentials of 80 and 140 kVp and 100 and 140 kVp were used, reflecting our current dual-energy protocols. These were compared to 31 in vivo stents of known composition. The data were reconstructed on a multimodality WorkPlace (Siemens) using CT syngo Post-Processing Suite software. The average patient age was 64 years (range 27-90). The average body mass index was 31.9 kg/m(2) (range 24-51.6). Of the 27 patients, 4 had uric acid stones and 22 had calcium-based stones; 1 patient had undergone renal transplantation. No difference was seen in the dual-energy characterization of stents from the same manufacturer. All imaged Cook and Bard stents had a dual-energy characterization that approached that of calcium stones (blue). All Boston Scientific and Gyrus ACMI stents had a dual-energy characterization resembling that of uric acid stones (red). The present study evaluated the stent appearance on DECT for various stent manufacturers. This information will aid in the optimal stent selection for patients undergoing treatment of renal calculi and followed up with DECT.

SU‐E‐I‐10: Skin Dose in Routine CT Brain Perfusion Studies Using Siemens 64 Slice, Definition Dual Source, and Flash CT Scanners

Purpose: To determine and compare the entrance skin doses from the routine CT brain perfusion protocols on various Siemens CT scanners. Methods: Four Siemens CT scanners were surveyed using their brain perfusion protocol (see supporting document): two Sensation 64‐slice scanners (EC‐CT‐2 and IP‐CT‐2), one Definition Dual Source (64‐slice), and one Definition Flash (128‐slice). The skin dose was measured using a RANDO® anthropomorphic phantom and Landauer optically stimulated luminescent (OSL) nanoDot dosimeters. We performed the scan three times on each scanner with the OSL nanoDots on the surface of the head at the 0, 90, 180, and 270 degree positions. We then averaged the skin doses from the three scans at each of the four positions to calculate an average skin dose for each CT scanner and an average skin dose per scan, independent of position. Results: The mean skin doses obtained were 341.7 mGy ± 44.5 for the Definition Dual Source, 326.7 mGy ± 37.3 for EC‐CT‐2 (64 slice), 326.6 mGy ± 55.6 for IP‐CT‐2 (64 slice), and 435.6 mGy ± 29.7 mGy for the Flash CT. The skin doses of the two 64‐slice scanners and the Definition dual source CT were similar, as expected, since they employed the same beam width. The skin dose of the Flash CT was 32.8% higher, which as expected, since its beam width is ∼33% larger (38.4 mm for the Flash vs. 28.8 mm for the others). Conclusions: Based on the phantom study, the skin doses for routine CT brain perfusion protocols on the mentioned scanners are 325–435 mGy, which is far below the dose threshold for possible radiation induced skin damage (2000 mGy)

Charge cross talk in sub-lithographically shrinked 32 nm Twin Flash™ memory cells

The extended scalability of Twin Flash memory cells down to 32 nm half pitch is demonstrated in a conventional planar cell layout. Starting with 63 nm line space array and doubling the number of word lines, a cell size of 0.0112 μm 2 can be achieved. By dividing available space into 43 nm cell width and 20 nm space between adjacent cells the electrical cell characteristics could be maintained the same as in the previous 63 nm generation. It was found that the proposed aggressive shrinking of the cell spacing in word line direction results in a cross talk of 300 mV when both neighboring cells are programmed to the highest MLC level. The charge cross talk in charge trapping memory (CT) cells is reported for the first time and becomes an issue when cell spacing between Twin Flash and other CT cells as e.g. TANOS approaches the 20 nm mark.