Coronary CT angiography: Diagnostic value and clinical challenges

Coronary computed tomography (CT) angiography has been increasingly used in the diagnosis of coronary artery disease due to improved spatial and temporal resolution with high diagnostic value being reported when compared to invasive coronary angiography. Diagnostic performance of coronary CT angiography has been significantly improved with the technological developments in multislice CT scanners from the early generation of 4-slice CT to the latest 320- slice CT scanners. Despite the promising diagnostic value, coronary CT angiography is still limited in some areas, such as inferior temporal resolution, motion-related artifacts and high false positive results due to severe calcification. The aim of this review is to present an overview of the technical developments of multislice CT and diagnostic value of coronary CT angiography in coronary artery disease based on different generations of multislice CT scanners. Prognostic value of coronary CT angiography in coronary artery disease is also discussed, while limitations and challenges of coronary CT angiography are highlighted

Radiation dose measurements in coronary CT angiography

Coronary computed tomography (CT) angiography is associated with high radiation dose and this has raised serious concerns in the literature. Awareness of various parameters for dose estimates and measurements of coronary CT angiography plays an important role in increasing our understanding of the radiation exposure to patients, thus, contributing to the implementation of dose-saving strategies. This article provides an overview of the radiation dose quantity and its measurement during coronary CT angiography procedures

Beta-blocker administration protocol for prospectively ECG-triggered coronary CT angiography

The aim of this article is to discuss the protocol of beta-blockers that is commonly used for prospectively ECG-triggered coronary computed tomography angiography (CCTA). It is essential to ensure a low and regular heart rate in patients undergoing prospectively ECG-triggered CCTA for optimal visualization of coronary arteries. Although early generations of computed tomographyscanners are not applicable to be tailored according to patients’ heart rate, a low and regular heart rate is possible to be achieved by the administration of medications according to the beta-blocker protocol. Beta-blocker can be safely administered to reduce patients’ heart rate for CCTA examination if patients are screened for certain contraindications

Coronary CT angiography: State of the art

Coronary computed tomography (CT) angiography has been recognized as the most rapidly developed imaging technique in the diagnosis of coronary artery disease due to the emergence and technological advances in multislice CT scanners. Coronary CT angiography has been confirmed to demonstrate high diagnostic and predictive value in coronary artery disease when compared to invasive coronary angiography. However, it suffers from high radiation dose which raises concerns in the medical field. Various dose-reduction strategies have been proposed with effective outcomes having been achieved to reduce radiation exposure to patients. This article provides an introduction and overview of the series of articles that will focus on each particular topic related to coronary CT angiography

Coronary CT angiography: Dose reduction strategies

With the introduction of 64- and post-64 slice computed tomography (CT) technology, coronary CT angiography has been increasingly used as a less invasive modality for the diagnosis of coronary artery disease. Despite its high diagnostic value and promising results compared to invasive coronary angiography, coronary CT angiography is associated with high radiation dose, leading to potential risk of radiation-induced cancer. A variety of dose-reduction strategies have been reported recently to reduce radiation dose with effective outcomes having been achieved. This article presents an overview of the various methods currently used for radiation dose reduction

Coronary CT angiography : radiation dose measurements and image quality assessments

Prospective ECG-triggering is regarded as one of the most effective approaches for reduction of radiation dose to patients during coronary CT angiography (CCTA). This study was conducted to investigate the diagnostic performance of prospective ECG-triggered CCTA with regard to the image quality and dose reduction, based on a multi-centre research. The research was performed in four stages, with stage 1 investigating the different CT scanning protocols and conventional angiography procedures with corresponding radiation dose measurements; stage 2 focused on the analysis of radiation dose in patients undergoing different generations of multislice CT scanners; stage 3 conducted a survey among medical specialists and radiographers with the aim of obtaining opinions regarding the benefits and difficulties in performing prospective ECG-triggered CCTA; stage 4 analysed image quality and radiation dose in patients undergoing single-source and dual-source 64-slice CT coronary angiography with use of prospective ECG-triggering.Stage 1 is a pilot study conducted on an anthropomorphic phantom. In this experiment, the radiation dose was compared between the invasive coronary angiography (ICA) and CCTA. These imaging protocols for ICA included the standard angular projection views with different magnifications. These ICA protocols were compared with several CT protocols including prospective and retrospective ECG gating. In addition, tube current modulation was applied in retrospective gating protocol. The radiation dose was also measured at the selected radiosensitive organs including breast and thyroid gland. Although ICA produced lower radiation dose than CCTA, application of modified techniques in both CCTA and ICA is recommended in clinical practice for further radiation dose reduction.Stage 2 involved a retrospective analysis of radiation dose in patients undergoing prospective ECG-triggered CCTA with different CT generations including single-source 64-slice CT (SSCT), dual-source 64-slice CT (DSCT), dual-source 128-slice CT and 320-slice CT based on several hospitals in Perth, Western Australia and Kuala Lumpur, Malaysia. A total of 164 patients undergoing prospective ECG-triggered CCTA with different types of CT scanners were studied. The analysis showed that the mean effective dose was estimated at 6.8 mSv, 4.2 mSv, 4.1 mSv, and 3.8 mSv, corresponding to 128-slice DSCT, 64-slice DSCT, 64-slice SSCT and 320-slice CT scanners, respectively. A positive relationship was found between effective dose and body mass index (BMI) in this study. Low radiation dose was achieved in prospective ECG-triggered CCTA, regardless of any CT scanner generation. BMI is identified as the major factor that has a direct impact on the effective dose associated with prospective ECG-triggered CCTA.A well-designed survey was performed in stage 3 among specialists and radiographers from 6 national health institutions in Malaysia in order to explore the opinion concerning the benefits and difficulties in performing prospective ECG triggered CCTA. In total, 53 responses were received (85%), comprising specialists (21%) and radiographers (79%). Across all the respondents, the main benefits of prospective triggering were agreed as: radiation dose reduction, image quality improvement and patients’ output increases. On the other hand, the issue of heart rate was agreed by all respondents as a main challenge when performing prospective triggered CCTA. The remaining challenges such as difficulty in obtaining cardiac functional assessments, diagnostic accuracy concerns and data processing management issue have been seen to vary according to the groups of respondents and the scanner type. Radiation dose reduction seems to be the main benefit, which is most agreed upon, while the issue of the heart rate is seen as the main challenge in prospective ECG-triggered CCTA.Finally, stage 4 is a comparative study consisting of quantitative and qualitative analysis, and it was conducted to investigate the image quality and radiation dose performance between retrospective gated and prospective ECG triggered CCTA with use of 64-slice SSCT and DSCT. The SSCT component was performed in the Royal Perth Hospital, Western Australia, while the DSCT component was conducted in the National heart Institute, Kuala Lumpur, Malaysia. A total of 209 patients who underwent CCTA with suspected coronary artery disease (CAD) scanned with SSCT (n=95) and DSCT (n=114) scanners using prospective ECG-triggering and retrospective ECG-gating protocols. The image was qualitatively assessed by two experienced observers, while quantitative assessment was performed by measuring the image noise, the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR).A total of 2,087 coronary artery segments were evaluated. Both DSCT and SSCT resulted in good image quality, regardless of prospective or retrospective gating protocols. Although radiation dose calculated between DSCT (6.5 mSv) and SSCT (6.2 mSv) showed no significant difference, the effective dose in prospective triggering was significantly lower than that in retrospective gating protocol. The results indicated that in the retrospective gating protocol, the effective dose with DSCT (18.2 mSv) was also significantly lower than that in SSCT (28.3 mSv). This study confirmed that prospective ECG triggered CCTA reduces radiation dose significantly compared to retrospective ECG-gating CCTA, while maintaining good image quality.In summary, the results of this project show that coronary CT angiography with prospective ECG-triggering is a reliable diagnostic technique with resultant very low radiation dose, but still maintaining diagnostic images. With widespread use of coronary CT angiography in the diagnosis of coronary artery disease, increased awareness of radiation dose associated with coronary CT angiography is of paramount importance, and application of dose-reduction strategies is highly recommended for routine clinical practice

Perbandingan Dos Sinaran antara Prosedur Urografi Intravena (IVU) dan Tomografi Berkomputer Helikal Tanpa Kontras (UHCT) Urografi

Urografi intravena (IVU) dan tomografi berkomputer helikal tanpa kontras (UHCT) urografi adalah dua prosedur utama yang akan dijalankan semasa penyiasatan radiologi bagi pengesanan urolitiasis (batu karang) pada sistem genitourinari. Dedahan terhadap sinaran radiasi merupakan faktor kebimbangan utama dalam kedua-dua prosedur. Oleh itu, satu kajian perbandingan dos sinaran telah dijalankan antara prosedur IVU dan UHCT urografi di samping menentukan faktor dedahan optimum bagi kedua-dua prosedur tersebut. Kajian ini telah dijalankan ke atas fantom antropomorfi k seluruh tubuh mengikut protokol sebenar bagi prosedur UHCT urografi dan penghasilan radiografi bersiri berserta dengan pemberian media berkontras bagi prosedur IVU. Sebanyak tiga parameter dedahan voltan tiub digunakan iaitu 75 kVp, 80 kVp dan 85 kVp bagi prosedur IVU dan 100 kVp, 120 kVp dan 140 kVp bagi prosedur UHCT urografi . Hasil dos sinaran bagi prosedur IVU yang diperolehi adalah 1.40 mSv, 2.10 mSv dan 2.79 mSv bagi 75 kVp, 80 kVp dan 85 kVp. Manakala bagi prosedur UHCT urografi , sebanyak 0.76 mSv, 1.32 mSv dan 1.82 mSv dos sinaran direkodkan bagi 100 kVp, 120 kVp dan 140 kVp. Hasil kualiti imej optimum adalah menggunakan dedahan sebanyak 85 kVp bagi prosedur IVU dan 120 kVp bagi prosedur UHCT urografi . Kesimpulannya, walaupun tidak terdapat perbezaan signifi kan, dos sinaran yang terhasil daripada prosedur IVU adalah kekal lebih tinggi daripada prosedur UHCT urografi

Perbandingan dos sinaran antara prosedur urografi intravena (IVU) dan tomografi berkomputer helikal tanpa kontras (UHCT) Urografi

Urografi intravena (IVU) dan tomografi berkomputer helikal tanpa kontras (UHCT) urografi adalah dua prosedur utama yang akan dijalankan semasa kajian radiologi bagi pengesanan urolitiasis (batu karang) pada sistem genitourinari. Dedahan terhadap sinaran radiasi merupakan faktor kebimbangan utama dalam kedua-dua prosedur. Oleh itu, satu kajian perbandingan dos sinaran telah dijalankan antara prosedur IVU dan UHCT urografi di samping menentukan faktor dedahan optimum bagi kedua-dua prosedur tersebut. Kajian ini telah dijalankan ke atas fantom antropomorfi seluruh tubuh mengikut protokol sebenar bagi prosedur UHCT urografi dan penghasilan radiografi bersiri beserta dengan pemberian media berkontras bagi prosedur IVU. Sebanyak tiga parameter dedahan voltan tiub digunakan iaitu 75, 80 dan 85 kVp bagi prosedur IVU dan 100, 120 dan 140 kVp bagi prosedur UHCT urografi. Hasil dos sinaran bagi prosedur IVU yang diperoleh adalah 1.40, 2.10 dan 2.79 mSv bagi 75, 80 dan 85 kVp. Manakala bagi prosedur UHCT urografi, sebanyak 0.76, 1.32 dan 1.82 mSv dos sinaran direkodkan bagi 100, 120 dan 140 kVp. Hasil kualiti imej optimum adalah menggunakan dedahan sebanyak 85 kVp bagi prosedur IVU dan 120 kVp bagi prosedur UHCT urografi. Kesimpulannya, walaupun tidak terdapat perbezaan signifikan, dos sinaran yang terhasil daripada prosedur IVU adalah tekal lebih tinggi daripada prosedur UHCT urografi

Image quality of coronary CT angiography (CCTA) using 640-slice scanner: qualitative and quantitative assessments of coronary arteries visibility

The purpose of this study was to evaluate the image quality and diagnostic accuracy of coronary computed tomography angiography (CCTA) using 640-slice scanner. Advancement of multidetector computed tomography (MDCT) technology with higher spatial, temporal resolution, and increasing detector array have improved the image quality and diagnostic accuracy of CCTA. A total of 25 patients (12 men and 13 women) underwent CCTA was chosen and data was acquired by 640-slice scanner. All 16 segments of coronary arteries were evaluated by two reviewers using a 4-likert scale for qualitative assessment. In quantitative assessment, the evaluation of 4 main coronary arteries were analysed in terms of signal intensity (SI), image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). All 25 patients with a mean age of 52.88 ± 14.75 years old and body mass index (BMI) of 24.24 ± 3.28 kg/m2 were analysed. In qualitative assessment, from the total of 400 segments, 379 segments (95 %) have diagnostic value while 21 segments do not have diagnostic value, which means 5 % artefact was detected. In quantitative assessment, there was no statistical differences in gender, race, and BMI (p>0.05). Overall evaluation showed that higher SI at the left main artery (LM) at 393.7 ± 47.19. Image noise was higher at right coronary artery (RCA) at 39.01 ± 13.97. SNR and CNR showed higher at left anterior descending (LAD) with 12.73 ± 5.17 and LM 9.14 ± 4.2, respectively. In conclusion, this study indicates that 640-slice MDCT has higher diagnostic value in CCTA examination with 95 % vessel visibility with 5 % artefact detection

Radiation dose comparison in CT thorax, CT abdomen and CT thorax-abdomen-pelvis (TAP) using 640-and 160-slice computed tomography (CT) scanners

This study was carried out to compare the effective dose, size specific dose estimation (SSDE) and scan length between genders and between CT scanner with different slice number. A total of 245 set data of radiation dose and scan length for CT scanning procedure involving thorax, abdomen and pelvis regions were obtained retrospectively for comparisons. 111 patients (60 males and 51 females) were scanned using 160-slices CT scanner while 134 patients (71 males and 63 females) were scanned using 640-slices CT scanner. Generally, there were no significant differences in the radiation dose and scan length among genders. However, differences for SSDE in CT thorax and CT thorax-abdomen-pelvis (TAP) protocols exist whereby in CT thorax protocol, 640-slices CT scanner had a significantly higher value of SSDE (9.06±2.67 mGy) than that in 160-slices CT scanner (7.82±1.33 mGy). Similarly to the CT TAP protocol, whereby 640-slices CT scanner had a significantly lower value in SSDE (9.17±1.59 mGy) than that in 160-slices CT scanner (10.76±3.72 mGy). In conclusion, there was no significant difference in the radiation dose and scan length between genders but significant difference was only observed in SSDE due to the presence of body size variation among the study population especially in different CT scanners