Fig 3 - uploaded by Faisal Khosa
Content may be subject to copyright.
Source publication
The purpose of this study was to evaluate the relation between radiation dose reduction and volume scan length for prospectively ECG-gated 320-MDCT angiography in the diagnosis of coronary artery disease.
MDCT with prospective ECG gating was performed at one of the three volume scan lengths depending on heart length. Of 175 patients, 95 (55%; body...
Similar publications
The purpose of this study was to compare radiation dose and image quality of 320- and 64-MDCT angiography using prospective gating.
One hundred seventy-four patients underwent 320-MDCT, and 95 patients underwent 64-MDCT. The scan parameters for 320-MDCT were 120 kVp, 400 mA, and gantry rotation of 350 milliseconds; the parameters for 64-MDCT were 1...
Citations
... This can be achieved in two ways, depending on the scanner. In scanners that allow a detector coverage of >=16 cm, a complete dataset can be acquired without moving the patient and during a single heartbeat, depending on the heart rate [35,36]. Conversely, with dual-source scanners, an ECG-triggered high pitch "helical" or "spiral" acquisition (a pitch value of ≈3) or so-called "Flash" mode allows for the entire dataset to be sampled in one heartbeat [37,38]. ...
Recent technological advances, together with an increasing body of evidence from randomized trials, have placed coronary computer tomography angiography (CCTA) in the center of the diagnostic workup of patients with coronary artery disease. The method was proven reliable in the diagnosis of relevant coronary artery stenosis. Furthermore, it can identify different stages of the atherosclerotic process, including early atherosclerotic changes of the coronary vessel wall, a quality not met by other non-invasive tests. In addition, newer computational software can measure the hemodynamic relevance (fractional flow reserve) of a certain stenosis. In addition, if required, information related to cardiac and valvular function can be provided with specific protocols. Importantly, recent trials have highlighted the prognostic relevance of CCTA in patients with coronary artery disease, which helped establishing CCTA as the first-line method for the diagnostic work-up of such patients in current guidelines. All this can be gathered in one relatively fast examination with minimal discomfort for the patient and, with newer machines, with very low radiation exposure. Herein, we provide an overview of the current technical aspects, indications, pitfalls, and new horizons with CCTA, providing examples from our own clinical practice.
... The radiation dose reduction obtained with the WV mode compared to the helical mode can be explained by several physical phenomena. The automatic tube current modulation is in clinical practice the most efficient approach because the radiation dose is adjusted according to patient attenuation value in three dimensions, to maintain a satisfactory image [12][13][14]. In helical mode, there is a very precise modulation, performed at every rotation, which reduces the dose by 43% to 66% when compared to acquisitions without modulation on abdominopelvic scans [13]. ...
Purpose:
To evaluate the best collimation used in wide volume (WV) mode to cover the abdomen in computed tomography (CT) urography in terms of radiation dose and image quality.
Materials and methods:
This study was performed on a 320×0.5mm detector row CT unit. The first part identified the lowest volume CT dose index (CTDIvol) by using the topograms data of 25 medium size patients (13 men and 12 women; mean age: 52±9 [SD] years; age range: 46-68 years) using different collimations on WV from 6cm to 16cm and the one of the helical mode for the same coverage length. The second part consisted of a clinical evaluation of this result including 45 medium size patients (32 men and 13 women; mean age: 68±14 [SD] years; age range: 45-72 years). The qualitative evaluation included several items based on a 5-point Likert scale.
Results:
The first part of the study indicated that a collimation of 10cm (200×0.5mm) in WV mode with 5 volumes had the lowest CTDIvol (2.78±0.35mGy; range: 2.35-3.21mGy) compared to helical mode (4.38±0.48mGy, range: 3.75-4.95mGy). In the second part, the mean radiation dose reduction by comparison with helical mode was 44.03%±0.36% (P<0.001) and 51.16%±1.22% (P<0.005) for CTDIvol and DLP, respectively.
Conclusion:
Wide volume mode of the abdomen can be performed with a significant radiation dose reduction with a collimation of 10cm (200×0.5mm) and five volumes.
... It combines sequential single rotations with table motion in-between. Our study is the first, to the best of our knowledge, to investigate the technical aspect and the clinical use of this mode with more than two acquisitions to cover a broader distance [9]. ...
... Therefore, the scan range should be limited to the extent that is necessary for addressing the clinical question and will enable radiation dose savings. 71 In the case of most coronary CTA scans of the native coronary arteries, the range should only include the heart. Obtaining a low dose scan to determine the smallest required scan field in order to minimize radiation dose is not recommended, because it does add radiation and utilization of anatomic landmarks is generally sufficient. ...
In response to recent technological advancements in acquisition techniques as well as a growing body of evidence regarding the optimal performance of coronary computed tomography angiography (coronary CTA), the Society of Cardiovascular Computed Tomography Guidelines Committee has produced this update to its previously established 2009 “Guidelines for the Performance of Coronary CTA” (1). The purpose of this document is to provide standards meant to ensure reliable practice methods and quality outcomes based on the best available data in order to improve the diagnostic care of patients. Society of Cardiovascular Computed Tomography Guidelines for the Interpretation is published separately (2). The Society of Cardiovascular Computed Tomography Guidelines Committee ensures compliance with all existing standards for the declaration of conflict of interest by all authors and reviewers for the purpose ofclarity and transparency.
... We therefore conducted the present study to investigate whether the diagnostic accuracy for the evaluation of in-stent restenosis can be improved by applying the same method. To minimize motion-related effects and an increase in the radiation dose, only those patients who were capable of holding their breath for 25 s and exhibited an HR of B61 bpm were selected [25][26][27]. ...
In conventional coronary computed tomography angiography (CCTA), metal artifacts are frequently observed where stents are located, making it difficult to evaluate in-stent restenosis. This study was conducted to investigate whether subtraction CCTA can improve diagnostic accuracy in the evaluation of in-stent restenosis. Subtraction CCTA was performed using 320-row CT in 398 patients with previously placed stents who were able to hold their breath for 25 s and in whom mid-diastolic prospective one-beat scanning was possible. Among these patients, 126 patients (94 men and 32 women, age 74 ± 8 years) with 370 stents who also underwent invasive coronary angiography (ICA) were selected as the subjects of this study. With ICA findings considered the gold standard, conventional CCTA was compared against subtraction CCTA to determine whether subtraction can improve diagnostic accuracy in the evaluation of in-stent restenosis. When non-assessable stents were considered to be stenotic, the diagnostic accuracy in the evaluation of in-stent restenosis was 62.7 % for conventional CCTA and 89.5 % for subtraction CCTA. When the non-assessable stents were considered to be non-stenotic the diagnostic accuracy was 90.3 % for conventional CCTA and 94.31 % for subtraction CCTA. When subtraction CCTA was used to evaluate only the 138 stents that were judged to be non-assessable by conventional CCTA, 116 of these stents were judged to be assessable, and the findings for 109 of them agreed with those obtained by ICA. Even for stents with an internal diameter of 2.5-3 mm, the lumen can be evaluated in more than 80 % of patients. Subtraction CCTA provides significantly higher diagnostic accuracy than conventional CCTA in the evaluation of in-stent restenosis.
... The volume scan mode in a 320-detector row CT scanner has been implemented into clinical practices, such as brain perfusion Siebert et al., 2010), thoracic scan (Johnston et al., 2013;Kroft et al., 2010), coronary artery CT angiography (Einstein et al., 2010;Khan et al., 2011), lumbar spine (Gervaise et al., 2012), and extremities scan (Barfett et al., 2010). The volume scan mode during CT scanning was recommended to reduce the effects of overbeaming and overranging because the unnecessary radiation doses of overbeaming and overranging can be reduced when compared with those in helical scan modes. ...
The purpose of this study was to evaluate the performance of volume scan tube current modulation (VS-ATCM) with adaptive iterative dose reduction 3D (AIDR3D) technique in abdomen CT examinations. We scanned an elliptical cone-shaped phantom utilizing AIDR3D technique combined with VS-ATCM mode in a 320-detector row CT scanner. The image noise distributions with conventional filtered back-projction (FBP) technique and those with AIDR3D technique were compared. The radiation dose profile and tube current time product (mAs) in three noise levels of VS-ATCM modes were compared. The radiation beam profiles of five preset scan lengths were measured using Gafchromic film strips to assess the effects of overbeaming and everlapping. The results indicated that the image noises with AIDR3D technique was 13-74% lower than those in FBP technique. The mAs distributions can be a prediction for various abdominal sizes when undergoing a VS-ATCM mode scan. Patients can receive the radiation dose of overbeaming and overlapping during the VS-ATCM mode scans.
... As MDCT is considered a major source of ionizing radiation in medicine, further in depth study of radiation exposure with these new scanners is therefore paramount [8,9]. Amongst the various parameters which affect and account for the amount of radiation required during MDCTA examination are maximum body mass index (BMI), tube voltage (kVp), retrospective versus prospective image acquisition, volume scan length, heart rate (HR), and tube current time product (mAs) [10][11][12][13][14][15][16][17]. In addition, the effect of kVp variation on radiation dose depends on the type of CT scanner due to individualized internal scanner filtration and geometry. ...
Aim. To determine absorbed radiation dose (ARD) in radiosensitive organs during prospective and full phase dose modulation using ECG-gated MDCTA scanner under 64- and 320-row detector modes. Methods. Female phantom was used to measure organ radiation dose. Five DP-3 radiation detectors were used to measure ARD to lungs, breast, and thyroid using the Aquilion ONE scanner in 64- and 320-row modes using both prospective and dose modulation in full phase acquisition. Five measurements were made using three tube voltages: 100, 120, and 135 kVp at 400 mA at heart rate (HR) of 60 and 75 bpm for each protocol. Mean acquisition was recorded in milligrays (mGy). Results. Mean ARD was less for 320-row versus 64-row mode for each imaging protocol. Prospective EKG-gated imaging protocol resulted in a statistically lower ARD using 320-row versus 64-row modes for midbreast (6.728 versus 19.687 mGy, P < 0.001), lung (6.102 versus 21.841 mGy, P < 0.001), and thyroid gland (0.208 versus 0.913 mGy; P < 0.001). Retrospective imaging using 320- versus 64-row modes showed lower ARD for midbreast (10.839 versus 43.169 mGy, P < 0.001), lung (8.848 versus 47.877 mGy, P < 0.001), and thyroid gland (0.057 versus 2.091 mGy; P < 0.001). ARD reduction was observed at lower kVp and heart rate. Conclusions. Dose reduction to radiosensitive organs is achieved using 320-row compared to 64-row modes for both prospective and retrospective gating, whereas 64-row mode is equivalent to the same model 64-row MDCT scanner.
... [6][7][8] Scanning protocols such as prospective versus retrospective gating, heart rate (HR) control with beta blockers, tube current modulation, selection of appropriate tube current (mA) based on body mass index (BMI), lower tube voltage (kVp) and restriction of volume scan length based on heart length are known to reduce radiation exposure and improve image quality in MDCTA. [9][10][11][12][13][14][15][16][17][18] Tube voltage (kVp) is a scan parameter with exponential relationship to radiation exposure, which determines image quality. [12] Lowering tube voltage decreases photon energy causing greater absorption by iodinated contrast media, thus increasing contrast between the artery lumen and surrounding tissue. ...
The objective of the following study is to evaluate the effect of reducing tube voltage from 120 to 100 kVp using prospective gating 320 row multi-detector computed tomography angiography on image quality and reduction in radiation dose.
A total of 78 sequential patients were scanned with prospective electrocardiogram gating. A total of 45 patients (Group 1) with mean body mass index (BMI) 29 ± 2 and heart rate (HR) 57 ± 7 beats per minute (BPM) were scanned at 120 kVp. 33 patients (Group 2) with mean BMI 23 ± 3 and HR 58 ± 6 bpm were scanned at 100 kVp. Effective dose was calculated using dose length product and factor (k = 0.014). Quantitative assessment of image quality was calculated by measuring signal to noise ratio (SNR) and contrast to noise ratio (CNR) in the left ventricle and left main coronary artery. Two experienced cardiac radiologists using a three-point ordinal scale assessed subjectively image quality.
In Group 1, the median radiation dose was 5.31 mSv (95% confidence interval [CI]: 4.86-6.09) and for Group 2 (P = 0.009) the mean radiation dose was 3.71 mSv (95% CI: 2.76-4.87), representing 30% decrease in radiation dose. In multivariate analyses, adjusting for age, gender, HR, BMI, tube current and scan length, an absolute median reduction of 2.21 mSv (1.13-3.29 mSv) was noted in patients scanned with 100 kVp (P < 0.0001). The quantitative image quality (SNR and CNR) was not statistically significant between the groups. Subjective image quality was rated as good or excellent in 99% of coronary segments for both groups (P value was considered as non-significant).
Our study suggests that radiation dose may be lowered from 120 to 100 kVp with preservation of image quality in patient's whose BMI is ≤27.
... dynamic CTA was achieved with the injection of 40-mL contrast media (Iopamidol 370 mgI/mL) followed by 35-mL saline flush at the rate of 4 mL/sec from right antecubital vein. To reduce the radiation dose, we used 100-kV tube voltage and the scan length was limited to 100 mm (Khan et al. 2011) (200-rows mode with 0.5-mm slice thickness) for the inclusion of the PAVF and parent vessels. Other scan parameters were shown on Table 1. ...
Pulmonary arteriovenous fistula is a congenital and rarely acquired anomalous direct communications between pulmonary arteries and veins. Transcatheter embolization using metallic coil or detachable balloon is one of the common treatment procedure. However, recanalization after the embolization is one of the concern and its differentiation from the retrograde filling via pulmonary vein is difficult except using invasive angiography. We report a case with recanalized pulmonary arteriovenous fistula non-invasively detected by dynamic CT angiography with 320-rows multi detector CT.
A 45-year-old women who had underwent coil embolization for pulmonary arteriovenous fistula was examined with dynamic CT angiography and antegrade contrast enhancement of the fistula was noted. The recanalization through the embolized artery was confirmed by digital subtraction angiography, and the second coil embolization was performed. The follow-up dynamic CT angiography at three months after the second procedure found the retrograde enhancement of aneurysmal sac and no antegrade shunt. The dynamic CT angiography was useful for the detect the recanalization of pulmonary arteriovenous fistula.
Delayed pulmonary artery recanalization was reported to be observed in 5- 10% of cases as a complication after the successful occlusion of segmental pulmonary artery. Lack of change in aneurysmal diameter of pulmonary arteriovenous fistula demonstrated by CT was reported as the result of persistent aneurysmal perfusion or aneurysmal thrombosis. However, the retrograde filling of aneurysmal sac via pulmonary vein or remnant collateral pathway to the pulmonary arteriovenous fistula were also considered. Therefore, before the invasive procedure, we performed dynamic CT angiography to detect the flow direction and pathway to the pulmonary arteriovenous fistula. Using dynamic CT angiography, we could obtain hemodynamic information through the aneurysmal sac of pulmonary arteriovenous fistula and decide to proceed to the invasive embolotherapy. Prospective perfusion CT scan could be an alternative to invasive angiography in the initial follow-up after the embolotherapy or in the cases with the recanalization of pulmonary arteriovenous fistula.
Electronic supplementary material
The online version of this article (doi:10.1186/2193-1801-2-169) contains supplementary material, which is available to authorized users.
... All scans were of diagnostic quality despite a wide range of patient sizes (66.4% of patients were overweight, obese, or morbidly obese) and a wide range of heart rates (34-95 beats per minute). The median estimated radiation exposure was 0.93 mSv, and this represents at least a 75% reduction compared with previous reports from the first-generation 320-detector row CT scanner (11,12,23,24). This level of dose exposure was achieved by means of a combination of judicious use of bblockers to help slow the resting heart rate and carefully controlling cranialcaudal scan range. ...
... In addition, tailoring the field of view of the examination to the clinical indication conforms to the "as low as reasonably achievable," or ALARA, principal. Radiation dose is directly related to the craniocaudal scan range (24,27), a factor that the physician and technologist must control. Most of the scans were obtained with prospective ECG gating, which not only reduces radiation exposure by approximately 69%-83% over retrospective gating but also preserves image quality (29,30). ...
