Low Tube Voltage Research Articles

Effect Of Low Tube Voltage On The Radiation Dosage And Image Quality Using Coronary Computed Tomography Angiography

Introduction: Lowering the tube voltage in coronary CT angiography lowers the radiation dose but may compromise the image quality. We compared image quality and radiation dose of 80-kilovolt peak (kVp) with the standard 100 kVp and 120 kVp scan protocol using a 256-detector wide coverage CT scanner.

Optimisation of CT scan parameters to increase the accuracy of gross tumour volume identification in brain radiotherapy

AbstractAim:This study aimed to optimise computed tomography (CT) simulation scan parameters to increase the accuracy for gross tumour volume identification in brain radiotherapy. For this purpose, high-contrast scan protocols were assessed.Materials and methods:A CT accreditation phantom (ACR Gammex 464) was used to optimise brain CT scan parameters on a Toshiba Alexion 16-row multislice CT scanner. Dose, tube voltage, tube current–time and CT dose index (CTDI) were varied to create five image quality enhancement (IQE) protocols. They were assessed in terms of contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and noise level and compared with a standard clinical protocol. Finally, the ability of the selected protocols to identify low-contrast objects was examined based on a subjective method.Results:Among the five IQE protocols, the one with the highest tube current–time product (250 mA) and lowest tube voltage (100 kVp) showed higher CNR, while another with a tube current–time product of 150 mA and a tube voltage of 135 kVp had improved SNR and lower noise level compared to the standard protocol. In contouring low-contrast objects, the protocol with the highest milliampere and lowest peak kilovoltage exhibited the lowest error rate (1%) compared to the standard protocol (25%).Findings:CT image quality should be optimised using the high-dose parameters created in this study to provide better soft tissue contrast. This could lead to an accurate identification of gross tumour volume recognition in the planning of radiotherapy treatment.

Clinical application of four-dimensional noise reduction filtering with a similarity algorithm in dynamic myocardial computed tomography perfusion imaging

We aimed to evaluate the effects of four-dimensional noise reduction filtering using a similarity algorithm (4D-SF) on the image quality and hemodynamic parameter of dynamic myocardial computed tomography perfusion (CTP). Sixty-eight patients who underwent dynamic myocardial CTP for the assessment of coronary artery disease were enrolled. Dynamic CTP was performed using a 320-row CT with low tube voltage scan (80kVp). Two different datasets of dynamic CTP were reconstructed using iterative reconstruction (IR) alone and a combination of IR and 4D-SF. Qualitative (5-grade scale) and quantitative image quality scores were assessed, and the CT-derived myocardial blood flow (CT-MBF) was quantified. These results were compared between the two different CTP images. The qualitative image quality in CTP images reconstructed with IR and 4D-SF was significantly higher than that with IR alone (noise score: 4.7 vs. 3.4, p < 0.05). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in CTP images reconstructed with IR and 4D-SF were significantly higher than those with IR alone (SNR: 20.6 vs. 9.7; CNR: 7.9 vs. 3.9, respectively; p < 0.05). There was no significant difference in mean CT-MBF between the two sets of CTP images (3.01 vs. 3.03mL/g/min, p = 0.1081). 4D-SF showed incremental value in improving image quality in combination with IR without altering CT-MBF quantification in dynamic myocardial CTP imaging with a low tube potential.

Image quality in dual-source multiphasic dynamic computed tomography of the abdomen: evaluating the effects of a low tube voltage (70 kVp) in combination with contrast dose reduction

To compare the image quality of multiphasic (arterial, portal, and equilibrium phases) dynamic computed tomography (CT) of the abdomen obtained by a low tube voltage (70kVp) in combination with a half-dose iodine load using low-concentration contrast agent in high tube output dual-source CT with a standard tube voltage (120kVp) and full-dose iodine load using the same group of adult patients. Fifty-five patients who underwent both low-tube-voltage (70kVp) abdominal CT with a half-dose iodine load and standard-tube-voltage (120kVp) CT with a full-dose iodine load were analyzed. The mean CT values and signal-to-noise ratio (SNR) of the liver, aorta and portal veins were quantitatively assessed. In addition, the contrast enhancement of the abdominal organs and overall image quality were qualitatively evaluated. The mean CT values and SNR of the liver parenchyma were significantly higher in 70-kVp protocol than in 120-kVp protocol in all 3 phases (p = 0.018 ~ < 0.001). Regarding the qualitative analysis, the overall image quality in the 70-kVp protocol was significantly better than in the 120-kVp protocol in all 3 phases (p < 0.001). In addition, the contrast enhancement scores of the liver parenchyma and hepatic vein in the equilibrium phase were also significantly higher in the 70-kVp protocol than in the 120-kVp protocol (p < 0.001). A low tube voltage (70kVp) in combination with a half-dose iodine load using a low-concentration contrast agent and an iterative reconstruction algorithm in high tube output dual-source CT may improve the contrast enhancement and image quality in multiphasic dynamic CT of the abdomen in patients under 71kg of body weight.

Visualizing the internal structure of polyethylene glycol-impregnated wood by digital breast tomosynthesis

This study proposes digital breast tomosynthesis (DBT) as a low-tube-voltage method for imaging wood artifacts treated with polyethylene glycol (PEG). In case of general clinical X-ray Computed Tomography (X-CT), PEG-impregnated wood images typically suffer from low contrast between the PEG and the tree-ring. Because X-CT uses high-tube-voltage X-rays that have high energy, they are transmitted regardless of the X-ray absorption difference of the substance, and therefore, it is not suitable for imaging PEG-impregnated wood. Mammography uses low-tube-voltage X-rays, and therefore, it is suitable for delineating substances with small X-ray absorption differences. However, although mammography can produce high-contrast images of wood, it cannot distinguish three-dimensional (3D) structures such as tree rings, because those are projection images. DBT is a type of mammography used to enhance contrast using low-tube voltage, and it enables imaging 3D structures by exposure X-rays to objects several times changing the exposure angle, and it can obtain quasi-computed tomography. Therefore, we believe that by applying DBT to dendroarchaeology, it would be possible to obtain high-contrast, high-resolution images in the visualization of the internal structure of wood.In this study, we used clinical X-CT, mammography, and DBT to obtain images of wood after PEG impregnation, and we evaluated the internal structure of the wood and the visibility of annual rings. We obtained DBT images as a tomogram with a thickness of 1 mm, which eliminated the distortion of tree rings in the sagittal direction and duplication of the PEG and the tree-ring. Further, tree-rings were easily visualized without a noticeable blur, and the DBT contrast was improved compared to clinical X-CT contrast because DBT was performed at low voltage. Important wooden artifacts excavated from ruins were preserved by PEG. Therefore, this method can be expected to become a very useful tool for dendroarchaeology when used as a complementary tool for microfocus X-CT.

Protocol analysis of dual-energy CT for optimization of kidney stone detection in virtual non-contrast reconstructions.

Previous studies have shown that split-bolus protocols in virtual non-contrast (VNC) reconstructions of dual-energy computed tomography (DE-CT) significantly decrease radiation dose in patients with urinary stone disease. To evaluate the impact on kidney stone detection rate of stone composition, size, tube voltage, and iodine concentration for VNC reconstructions of DE-CT. In this prospective study, 16 kidney stones of different sizes (1.2-4.5mm) and compositions (struvite, cystine, whewellite, brushite) were placed within a kidney phantom. Seventy-two scans with nine different iodine contrast agents/saline solutions with increasing attenuation (0-1400HU) and different kilovoltage settings (70kV/150kV; 80kV/150kV; 90kV/150kV; 100kV/150kV) were performed. Two experienced radiologists independently rated the images for the presence and absence of stones. Multivariate classification tree analysis and descriptive statistics were used to evaluate the diagnostic performance. Classification tree analysis revealed a higher detection rate of renal calculi > 2mm in size compared with that of renal calculi < 2mm (84.7%; 12.7%; p < 0.001). For stones with a diameter > 2mm, the best results were found at 70kV/Sn 150kV and 80kV/Sn 150kV in scans with contrast media attenuation of 600HU or less, with sensitivity of 99.6% and 96.0%, respectively. A higher luminal attenuation (> 600HU) resulted in a significantly decreased detection rate (91.8%, 0-600HU; 70.7%, 900-1400HU; p < 0.001). In our study setup, the detection rates were best for cystine stones. Scan protocols in DE-CT with lower tube current and lower contrast medium attenuation show excellent results in VNC for stones larger than 2mm but have limitations for small stones. • The detection rate of virtual non-contrast reconstructions is highly dependent on the surrounding contrast medium attenuation at the renal pelvis and should be kept as low as possible, as at an attenuation higher than 600HU the VNC reconstructions are susceptible to masking ureteral stones. • Protocols with lower tube voltages (70kV/Sn 150kV and 80kV/Sn 150kV) improve the detection rate of kidney stones in VNC reconstructions. • The visibility of renal stones in virtual non-contrast of dual-energy CT is highly associated with the size, and results in a significantly lower detection rate in stones below 2mm.

Japanese Survey of Radiation Dose Associated With Coronary Computed Tomography Angiography - 2013 Data From a Multicenter Registry in Daily Practice.

Although coronary computed tomography angiography (CTA) is frequently used for identifying coronary artery disease, no studies have investigated the radiation dose in detail in Japan. The aim of this study was to estimate the radiation dose of coronary CTA in Japanese clinical practice and to identify the independent predictors associated with radiation dose.Methods and Results:A multicenter, retrospective, observational study (54 institutions) was conducted for estimating the radiation dose of coronary CTA in 2,469 patients between January and December 2013. Independent predictors associated with radiation dose were investigated on linear regression analysis. Median dose-length product (DLP) was 809.0 mGy·cm (IQR, 350.0-1,368.8 mGy·cm), corresponding to an estimated radiation dose of 11 mSv. The DLP per site significantly differed between institutions (median DLP per site, 92-2,131 mGy·cm; P<0.05). Independent predictors associated with radiation dose on multivariable linear regression were body weight, heart rate, non-stable sinus rhythm, scan length, tube voltage setting, electrocardiogram (ECG)-gated scanning protocol, and the image reconstruction technique (P<0.05 each). The coronary CTA radiation dose was relatively high in 2013, and it varied significantly between institutions. Effective strategies for radiation dose reduction were low tube voltage ≤100 kVp, retrospective ECG-gated scanning with dose modulation technique, prospective ECG-gated scanning, and the iterative reconstruction technique.

Computed Tomography Dose Reduction in Children: Review Paper

Increasing the needs of Computed Tomography (CT) for children is quietly augmented over the last decades, although it’s one of the most important modalities in diagnostic finalization. However, it carries a higher risk for the patient in term of radiation dose and cancer risk due to higher sensitivity to radiation than the adult. This study was conducted to review the multiple methods of dose reduction technique as presented by different authors where the different scanning protocols, machine and types of the studies were presented Here, more studies and books were selected, where they are carefully summarized and outlined into different categories for which the result stated that; the most frequent examination done in the CT department is head, neck, and sinuses in which where taken as an example of dose reduction methods. The use of the most modern technical advances was recommended in order to optimize the dose level, comfortable, constants (anesthesia if required) position and using low number of phases as possible according to the pathology of interest (low phases with better visualizations), scanning with thin collimation and view thicker as possible, increasing pitch, automatic exposure control, only the area of interest should be examined, with low tube voltage and using of tube current modulation system can give better result of dose reduction and there were multiple methods presented here. Where is most important for radiologist, technicians, and the person who conduct such studies to increase their knowledge in radiation protection, technical advances and how to interpret the different CT protocols.

A Comparison of Density and Patient Doses According to kVp and mAs Changes in General Radiography

Low energy x-rays that occur in the low tube voltage radiography of general radiography are absorbed strongly in the body and do not aid image quality enhancement. This study maintains titer in general radiography while using tube current that are proportional to density and the tube voltage 15% principle according to density to reduce patient exposure doses, and area doses and entrance surface doses were measured to compare patient exposure doses. In hand, knee, abdomen, and skull radiography, kVp was increased to 115% and mAs was decreased to 50% and kVp was decreased to 85% while mAs was increased to 200% and area doses and entrance surface doses were measured to compare relative doses. Also, 5 places in each image were set, density was measured, and Kruskal wallis H test was conducted to observe significance probabilities between groups. To fix density, kVp was increased to 115% and mAs was decreased to 50% and after measurements of mean area doses and entrance surface doses were made by each part, each decreased to 58.68% and 59.85% when standard doses were set to 100%, and each increased to 147.28% and 159.9% when kVp was decreased to 85% and mAs was increased to 200%. Comparisons of density changes showed that hand, knee, abdomen, and skull radiography all displayed significance probabilities>0.05, showing no changes in concentration. Radiography that increases kVp and lowers mAs through reasonable calculations within ranges that don’t affect resolution and contrast seems to be a simple way to decrease patient exposure doses.

Application of Dual Tree Complex Wavelet for Performance Improvement of CT Images

Computed tomography (CT) has been increasing in frequency and indications for use in clinical diagnosis and treatment decisions. Multidetector CT has the advantage of shortening the inspection time and obtaining a high resolution image compared to a single detector CT, but has been pointed out the disadvantage of increasing the radiation exposure. In addition, when the low tube voltage is used to reduce the exposure dose in the CT, noise increases relatively. In the existing method, the method of finding the optimal image quality using the method of adjusting the parameters of the image reconstruction method is not a fundamental measure. In this study, we applied a double-tree complex wavelet algorithm and analyzed the results to maintain the normal signal and remove only noise. Experimental results show that the noise is reduced from 8.53 to 4.51 when using a complex oriented 2D method with 100kVp and 0.5sec rotation time. Through this study, it was possible to remove the noise and reduce the patient dose by using the optimal noise reduction algorithm. The results of this study can be used to reduce the exposure of patients due to the low dose of CT.

The application of 320-slice CT " double-low" MIP imaging technique in obstructive sleep apnea syndrome with coronary heart disease

Objective To evaluate the value of 320-slice computed tomography (CT) maximum density projection (MIP) imaging protocol (low tube voltage and contrast agent concentration) in obstructive sleep apnea syndrome (OSAS) with coronary heart disease. Methods 40 cases of OSAS with coronary heart disease in our hospital were selected. All patients underwent 320-slice MIP imaging and received conventional coronary angiography (CAG) within 1 month. With reference to CAG examination results, the accuracy of 320-slice double low MIP-imaging technique in diagnosing the Obstructive sleep apnea syndrome with coronary heart disease can be evaluated. Results The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of 320-slice CT double-low MIP imaging in the diagnosis of obstructive respiratory sleep disorder with coronary disease were 95.14%, 94.43%, 95.33%, 83.62%, 98.20%. respectively. The heart rate of testers was (65.20±4.79)bpm/min, the dose length product (DLP) was (98.22±32.54)mGy·cm, and the effective radiation dose (ED) was (1.35±0.42)mSv. Conclusions Compared with CAG, the 320-slice MIP imaging technique reduced doses of radiation while maintained the good quality of image. Therefore, this technique has high application value as a clinical diagnosis method to diagnose patients with obstructive respiratory sleep disorder and coronary heart disease. Key words: Sleep apnea, obstructive; Coronary disease; Tomography, X-ray computed

Simultaneous Assessment of Left Ventricular Function and Coronary Artery Anatomy by Third-generation Dual-source Computed Tomography Using a Low Radiation Dose.

BACKGROUNDTo assess left ventricular function and coronary artery simultaneously by third-generation dual-source computed tomography (CT) using a low radiation dose.METHODSA total of 48 patients (36 men, 12 women; mean age 57.0 ± 9.5 years) who underwent both electrocardiography-gated cardiac CT angiography (CCTA) using 70–90 kVp and echocardiography were included in this retrospective study. The correlation between left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), and left ventricular ejection fraction (LVEF) measured using CCTA and echocardiography was determined. The quality of coronary artery images was analyzed using a 4-point scale (1, excellent; 4, poor). The effective radiation dose of CCTA was calculated.RESULTSMean heart rate during the CT examination was 59.9 ± 9.9 bpm (range 38–79) and the body mass index of 48 patients was 24.5 ± 2.6 kg/m2 (range 17.0–29.4). LVEDV, LVESV, and LVEF measured using CCTA and echocardiography demonstrated a fair to moderate correlation (Pearson correlation coefficient: r = 0.395, p = 0.005 for LVEDV; r = 0.509. p < 0.001 for LVESV; r = 0.551, p < 0.001 for LVEF). Average image quality score of coronary arteries was 1.0 ± 0.1 (range 1–2). A total of 99.0% (783 of 791) of segments had an excellent image quality score, and 1.0% (8 of 791) of segments had a good score. Mean effective radiation dose was 2.2 ± 0.7 mSv.CONCLUSIONSThird-generation dual-source CT using a low tube voltage simultaneously provides information regarding LV function and coronary artery disease at a low radiation dose. It can serve as an alternative option for functional assessment, particularly when other imaging modalities are inadequate.

Application of Artificial Intelligence-based Image Optimization for Computed Tomography Angiography of the Aorta With Low Tube Voltage and Reduced Contrast Medium Volume.

The purpose of this study was to evaluate the impact of artificial intelligence (AI)-based noise reduction algorithm on aorta computed tomography angiography (CTA) image quality (IQ) at 80 kVp tube voltage and 40 mL contrast medium (CM). After obtaining institutional review board approval and 8 written informed consents, 60 patients (35 men, 25 women; age range: 18 to 85 y) referred for aorta CTA examination were assigned to 2 groups at random. Group A underwent an 80 kVp protocol with 40 mL CM (320 mg I/mL). Group A reconstructed with iterative reconstruction was named as group A1 and further AI-based noise reduction was named as group A2. Group B was scanned with standard 120 kVp, 80 mL CM, and iterative reconstruction algorithm. The quantitative assessment of IQ included aorta CT attenuation, noise, signal-to-noise ratio, and contrast-to-noise ratio. A 5-point scale (5-excellent, 1-poor) was used by 2 radiologists independently for qualitative IQ analysis. The image noise significantly decreased while signal-to-noise ratio and contrast-to-noise ratio significantly increased in the order of group A1, B, and A2 (all P<0.05). Compared with group B, the subjective IQ score of group A1 was significantly lower (P<0.05), while that of group A2 had no significant difference (P>0.05). The effective dose and CM volume of group A were reduced by 79.18% and 50%, respectively, than that of group B. The AI-based noise reduction could improve the IQ of aorta CTA with low kV and reduced CM, which achieved the potential of radiation dose and contrast media reduction compared with conventional aorta CTA protocol.

Use of a computer simulator to investigate optimized tube voltage for chest imaging of average patients with a digital radiography (DR) imaging system.

The aim of this study was to investigate via computer simulation a proposed improvement to clinical practice by deriving an optimized tube voltage (kVp) range for digital radiography (DR) chest imaging. A digitally reconstructed radiograph algorithm was used which was capable of simulating DR chest radiographs containing clinically relevant anatomy. Five experienced image evaluators graded clinical image criteria, i.e. overall quality, rib, lung, hilar, spine, diaphragm and lung nodule in images of 20 patients at tube voltages across the diagnostic energy range. These criteria were scored against corresponding images of the same patient reconstructed at a specific reference kVp. Evaluators were blinded to kVp. Evaluator score for each criterion was modelled with a linear mixed effects algorithm and compared with the score for the reference image. Score was dependent on tube voltage and image criteria in a statistically significant manner for both. Overall quality, hilar, diaphragm and spine criteria performed poorly at low and high tube voltages, peaking at 80-100 kVp. Lung and lung nodule demonstrated little variation. Rib demonstrated superiority at low kVp. A virtual clinical trial has been performed with simulated chest DR images. Results indicate mid-range tube voltages of 80-100 kVp are optimum for average adults. There are currently no specific recommendations for optimized tube voltage parameters for DR chest imaging. This study, validated with images containing realistic anatomical noise, has investigated and recommended an optimal tube voltage range.

Coronary CT Angiography Using Low Iodine Delivery Rate and Tube Voltage Determined by Body Mass Index: Superiority in Clinical Practice.

To explore the feasibility and superiority of iodine delivery rate (IDR) and tube voltage determined by patients' body mass index (BMI) in coronary CT angiography (CCTA), a total of 1567 patients undertaking CCTA during Feb. and Dec. 2016 were enrolled and divided into two groups. In the control group, the IDR and tube voltage were fixed, while in the experimental group, the IDR and tube voltage were determined by patients' BMI. The volume of iodinated contrast media (ICM), extravasation rate, extravasation volume, extravasation recovery interval, incidence rate of adverse reactions, effective dose (ED) and image quality of the two groups were compared. The experiments demonstrated that the ICM volume, extravasation rate, extravasation volume, extravasation recovery interval, incidence of adverse reactions and ED were lower or shorter in the experimental group than in the control group, and the differences were statistically significant (all P<0.05). However, there were no significant differences in the mean CT value, image noise, signal to noise ratio and contrast to noise ratio between the two groups (all P<0.05), which were consistent with the diagnosticians' subjective evaluation outcomes. Our findings suggested that in CCTA, it is feasible to determine the IDR and tube voltage based on patients' BMI; low tube voltage and IDR are superior to the fixed tube voltage and IDR and are worthy of clinical promotion.

False-Negative Low Tube Voltage Coronary CT Angiography: High Intravascular Attenuation at Coronary CT Angiography Can Mask Calcified Plaques.

To determine the impact of low tube voltage coronary CT angiography on detection of subclinical atherosclerosis. Retrospective sampling of an emergency department coronary CT angiography registry was performed. All patients in the registry underwent a noncontrast coronary artery calcium (CAC) scoring scan at 120 kV before coronary CT angiography. The study sample (n = 264) constituted patients with subclinical atherosclerosis (Coronary Artery Disease Reporting and Data System™ [CAD-RADS] 1 or 2) randomly mixed one-to-one with patients without atherosclerosis (CAD-RADS 0). The patients with coronary CT angiography performed at 70-90 kV were considered the low tube voltage group (n = 159) and patients with coronary CT angiography performed at 100-120 kV were considered the standard tube voltage group (n = 105). The number of coronary plaques and overall CAD-RADS classification (per patient) were evaluated twice: initially, by reading coronary CT angiography alone, and then, by coronary CT angiography in combination with a CAC scan. Considering the combined reading (CT angiography plus CAC scan) as the reference standard, the performance of coronary CT angiography alone was assessed for plaque detection and appropriate CAD-RADS (per patient) classification. The comparisons were made between the low tube voltage and standard tube voltage groups by using a Fisher exact test and χ2 test for proportions and a Mann-Whitney test and Kruskal-Wallis test for means. In total, 455 plaques were identified in 118 patients (70 of 159 patients in the low tube voltage group; 48 of 105 in the standard tube voltage group). When reading coronary CT angiographic images alone, 97 of 455 (21%) plaques were missed that led to an incorrect CAD-RADS classification in 16 of 264 (6%) studies (interpreted as CAD-RADS 0 instead of CAD-RADS 1 or 2). Missed plaques were significantly more frequent in the low tube voltage group versus the standard tube voltage group (41% [85 of 206] vs 5% [12 of 249], respectively; P < .001). Incorrect CAD-RADS classification was also seen more commonly in the low tube voltage group (8.8% [14 of 159] vs 2% [two of 105]; P = .01), typically at low plaque burden (median CAC score, 1; range, 1-4). Calcified plaques that appeared isodense to luminal contrast material attenuation were seen more frequently in the low tube voltage group compared with the standard tube voltage group (20% [32 of 159] vs 7.6% [eight of 105], respectively; P = .005). Coronary artery plaques may be missed at low tube voltage coronary CT angiographic examination performed without a concomitant CAC scan.© RSNA, 2019Supplemental material is available for this article.See also the commentary by Truong in this issue.

P6182Combination of a new iterative reconstruction technique with low tube voltage and high tube current has important role of detection of late enhancement on 320 slice CT

Abstract Background New iterative reconstruction tecniques, including Adaptive Iterative Dose Reduction 3D (AIDR 3D) and Forward Projected Model-based Iterative Reconstruction SoluTion (FIRST), have been recently available on new generation 320 slice CT, and they can provide high-quality CT images. Purpose The aim of this study was to evaluate the diagnostic performance of detection of abnormal late enhancement (LE) in left ventricular (LV) myocardium (LVM) using 320-slice CT with new iterative reconstruction techiniques, AIDR 3D (Figure A) and FIRST (Figure B). Methods A total of 100 patients who were suspected of having various myocardial diseases and underwent late phase acquisition both on cardiac CT and CMR within 3 months were analyzed. The first 50 consecutive patients (Group 1) underwent 320-slice CT with AIDR 3D, 120 Kv tube voltage, 519±71 mA tube current. The next 50 consecutive patients (Group 2) underwent 320-slice CT with FIRST, 80 or 100Kv tube voltage, 803±20 mA tube current. We compared diagnostic accuracy of CT for detection of LE in LVM against that of CMR (the gold standard) in between the 2 groups. Results On patient-by-patient analysis, sensitivity, specificity, positive (PPV) and negative predictive values (NPV), and overall accuracy for detection of LE on CT vs CMR were 87, 95, 96, 82, and 90% in Group 1, and 97, 83, 91, 88, and 90% in Group 2. There were no significant difference of diagnostic accuracy on patient-by-patient analysis in between the 2 groups (Figure C). However, on a segment-by-segment analysis (using 17 American Heart Association LV segment model), these values for detection of LE on CT vs CMR were 60, 95, 73, 91, and 88% in Group 1, and 85, 95, 86, 95, and 93% in Group 2. Sensitivity, PPV, NPV and overall accuracy were significantly higher in Group 2 than in Group 1 (all P&lt;0.01) (Figure D). Conclusions Diagnostic accuracy of detection of LE in LVM on CT combining low tube voltage and high tube current acquisition on a new generation 320-slice CT with FIRST was superior to 320-slice CT with AIDR 3D. Acknowledgement/Funding TSUCHIYA MEMORIAL MEDICAL FOUNDATION

Bismuth shield affecting CT image quality and radiation dose in adjacent and distant zones relative to shielding surface: A phantom study

BackgroundTo quantify image quality and radiation doses in regions adjacent to and distant from bismuth shields in computed tomography (CT). MethodsAn American College of Radiology accreditation phantom with four solid rods embedded in a water-like background was scanned to verify CT number (CTN) accuracy when using bismuth shields. CTNs, image noise, and contrast-to-noise ratios (CNRs) were determined in the phantom at 80–140 kVp. Image quality was investigated on image portions in the zones adjacent (A zone) to and distant (D zone) from a bismuth shield. Surface radiation doses were measured using thermoluminescent dosimeters. Streak artefacts were graded on a 3-point-scale. ResultsChanges in CTN caused by a bismuth shield resulted in changes in X-ray spectra. CTN changes were more apparent in the A zone than in the D zone, particularly for a low tube voltage. The degrees of CTN changes and image noise were proportional to the thickness of the bismuth shields. A 1-ply bismuth shield reduced surface radiation doses by 7.2%–15.5%. The overall CNRs were slightly degraded, and streak artefacts were acceptable. ConclusionsUsing a bismuth shield could result in significant CTN changes and perceivable artefacts, particularly for a superficial organ close to the shield, and is not recommended for quantification CT examinations or follow-up CT examinations.

Utilization of sinogram affirmed iterative reconstruction on 128 multi slice computed tomography scan to reduce radiation dose and improve image quality on thorax multi slice computed tomography scan: chest phantom study

Background: Thorax MSCT examination is a diagnostic imaging that is capable of displaying both normal and pathological lung and respiratory organs. MSCT examination also has a better level of sensitivity and specificity compared to other modalities, but the radiation exposure given is very high, so the radiation dose given to patients is high. The reduction in radiation dose is very important because of the direct exposure to sensitive tissue. One method of reducing radiation dose is by reducing the tube voltage. However, the decrease in tube voltage causes a decrease in image quality as indicated by increased noise and decreased CNR. To maintain the quality of the image at low tube voltage setting, an IR reconstruction of SAFIRE was used. The purpose of this research is to know the impact of using SAFIRE on dose radiation and image quality of thorax MSCT.Methods: This study was an experimental study with a quasi-experimental study design. The object used was the N-1 Lungman chest phantom in which an artificial tumor was attached. Radiation dose assessment used CTDI value, while image quality assessment used noise and CNR. Data processing was conducted using linear regression test.Results: There was an effect of tube voltage setting and SAFIRE setting on radiation dose and image quality.Conclusions: Tube voltage ssetting and SAFIRE setting had an effect on radiation dose and image quality. Tube voltage setting and SAFIRE strength level setting that were able to provide optimal radiation dose and image quality were tube voltage of 80 kVp and SAFIRE strength levels 3 and 4 (S3 and S4).

Evaluation of image quality and radiation dose in low tube voltage coronary computed tomography angiography.

BACKGROUNDCoronary computed tomography angiography (CCTA) is an important modality in diagnosis of coronary artery disease (CAD). Owing to the fact that computed tomography (CT) examinations are performed using ionizing radiation; applying radiation dose-reduction strategies seems to be necessary. Lowering tube voltage (in kV) according to the patient’s body mass index (BMI) or weight is an approach that is investigated by many researchers. The goal of this study was to evaluate the impact of low tube voltage CCTA on radiation dose and image quality in order to decrease radiation dose in selected patients who meet inclusion criteria of the introduced protocol.METHODSPatients with clinical indications of CCTA who met inclusion criteria were classified in two groups randomly. Imaging of two groups was performed using 120 kV and 100 kV, respectively. Subjective and objective parameters of image quality and radiation dose of two groups were measured. Afterward, data were analyzed by appropriate statistical tests using SPSS software.RESULTSWhile differences in image quality between two groups were not significant, radiation dose of patients who underwent 100 kV CCTA was significantly lower than the other group. Effective doses (EDs) of first and second groups were 22.30 ± 5.48 mSv and 13.82 ± 2.00 mSv, respectively (P < 0.001).CONCLUSIONLowering tube voltage in non-obese patients is an effective and practical approach to radiation dose reduction without missing image quality that should be considered especially for female patients.