• “ In the context of possibility of achieving submillisievert doses on cCTA, the relative dose shift in proportion with CAC scanning becomes significant and hence requires careful attention.”
  Radiation Dose Shift in Relative Proportion: The Case of Coronary Artery Calcium Scores
  Mahesh M, Zimmerman SL, Fishman EK
  JACR 2014 Feb; 634-635
• “ It is equally important to recognize that CAC scores may not be warranted for patients with known coronary artery diseases or for younger patients (<30 years of age).”
  Radiation Dose Shift in Relative Proportion: The Case of Coronary Artery Calcium Scores
  Mahesh M, Zimmerman SL, Fishman EK
  JACR 2014 Feb; 634-635
• Dose Reduction for Coronary Artery Calcium Studies
  - Iterative reconstruction techniques
  - Lower tube voltage from 120 to 100 kV
  - Minimize scan length on topogram
  - Obtain calcium score from contrast enhanced CTA (WIP)
  - Calcium scoring may not be needed in patients under age 30
  - Radiation Dose Shift in Relative Proportion: The Case of Coronary Artery Calcium Scores
  Mahesh M, Zimmerman SL, Fishman EK
  JACR 2014 Feb; 634-635

• “ The combination of a gantry rotation time of 275 msec, wide volume coverage, iterative reconstruction, automated exposure control, and larger x-ray power generator of the second-generation CT scanner provides excellent image quality over a wide range of body sizes and heart rates at low radiation doses.”
  Submillisievert Median Radiation Dose for Coronary Angiography with a Second Generation 320-Detector Row CT Scanner in 107 Consecutive Patients
  Chen MY et al.
  Radiology 2013; 267:76-86
• “ Overall, these technical advances combined with individually optimized scan ranges resulted in a median radiation dose of 0.93 mSv; the radiation dose was less than 1 mSv in 54.2% of the CT angiography examinations (58 of 107 patients) and less than 4 mSv in 96.3% (103 of 107 patients).”
  Submillisievert Median Radiation Dose for Coronary Angiography with a Second Generation 320-Detector Row CT Scanner in 107 Consecutive Patients
  Chen MY et al.
  Radiology 2013; 267:76-86
• “ The area of the thoracic solid tissue at the level of the aortic root predicts image noise and may hence be used for the decision to reduce tube voltage from 120 to 100 kV.”
  Patient-specific predictors of image noise in Coronary CT angiography
  Schuhbaeck A et al.
  J Cardiovasc Comput Tomogr 7(2013) 39-45
• “ Breast shields for woman undergoing coronary CT angiography slightly increased noise but did not negatively affect signal, signal to noise ratio, quality, or interpretability. Breast shields use warrants further study.”
  Comparison of Coronary CT Angiography Image Quality With and Without Breast Shields
  Hulten E et al.
  AJR 2013; 200:529-536
• “ In such dosimetry studies measuring radiation precisely at the breast tissue, dose reduction to the breast achieved by breast shields has been reported to be as much as a statistically significant 37.1%.”
  Comparison of Coronary CT Angiography Image Quality With and Without Breast Shields
  Hulten E et al.
  AJR 2013; 200:529-536
• “ Heart rate frequency and absence of motion artifacts on preceding high-pitch CAC are significant independent predictors of image quality of high pitch coronary CTA. At a HR frequency of - 63 bpm, 91% of high pitch coronary CTA will be of diagnostic image quality. If preceding high-pitch CAC shows no motion artifacts, high-pitch coronary will allow the diagnostic visualization of 96% of the studies regardless of HR frequency or variability.”
  Predictors of Image Quality in High Pitch Coronary CT Angiography
  Stolzmann P et al.
  AJR 2011; 197:851-858
• “ Wide area-detector coronary CT angiography protocols have reduced radiation dose, with image quality maintained at the same level, compared with 64-MDCT technologies.”
  Image Quality and Radiation Dose Stratified by Patient heart Rate for Coronary 64- and 320-MDCT Angiography
  Fujimoto S et al.
  AJR 2012; 765-770
• “ In conclusion, patients undergoing coronary imaging with 320-MDCT have a range of estimated radiation doses corresponding to heart rate. The beam pitch and phase window width can be adjusted with respect to heart rate to produce consistent high quality images.”
  Image Quality and Radiation Dose Stratified by Patient heart Rate for Coronary 64- and 320-MDCT Angiography
  Fujimoto S et al.
  AJR 2012; 765-770

• “ A patient centered approach to imaging as a component of patient centered care individualizes the decision to use imaging with ionizing radiation for every patient, avoids unnecessary repeat exposure to ionizing radiation, leads to performance of imaging studies in a manner that minimizes radiation while maintaining image quality sufficient for confident and accurate interpretation.”
  Radiation Dose in Cardiac Imaging: How Should It Affect Clinical Decisions
  Shapiro BP et al.
  AJR 2013; 200:508-514

• “ Retrospective ECG-gated helical techniques may be used in patients who do not qualify for prospective ECG-triggered scanning because of irregular heart rhythm or high heart rates (specific value depends on specific scanner characteristics and cardiovascular indication) or both.”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• “ Prospective ECG-triggered axial techniques should be used in patients who have stable sinus rhythm and low heart rates (typically <60-65 beats/min but specific values depend on specific scanner characteristics and cardiovascular indication). For prospective ECG triggered axial techniques, the width of the data acquiaition window should be kept at a minimum.”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• “ Prospective ECG-triggered axial techniques should be used in patients who have stable sinus rhythm and low heart rates (typically <60-65 beats/min but specific values depend on specific scanner characteristics and cardiovascular indication).”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• “For prospective ECG triggered axial techniques, the width of the data acquisition window should be kept at a minimum.”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• “ A tube potential of 100 kV could be considered for patients weighing ≤ 90 kg or with a BMI ≤ 30 kg/m2; a tube potential of 120 kV is usually indicated for patients weighing >90 kg and with a BMI > 30 kg/m2.”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• “ Use of breast shields is not recommended for cardiovascular CT.”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224

• “ Retrospective ECG-gated helical techniques may be used in patients who do not qualify for prospective ECG-triggered scanning because of irregular heart rhythm or high heart rates (specific value depends on specific scanner characteristics and cardiovascular indication) or both.”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• “ Prospective ECG-triggered axial techniques should be used in patients who have stable sinus rhythm and low heart rates (typically <60-65 beats/min but specific values depend on specific scanner characteristics and cardiovascular indication). For prospective ECG triggered axial techniques, the width of the data acquiaition window should be kept at a minimum.”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• “ Prospective ECG-triggered axial techniques should be used in patients who have stable sinus rhythm and low heart rates (typically <60-65 beats/min but specific values depend on specific scanner characteristics and cardiovascular indication).”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• “For prospective ECG triggered axial techniques, the width of the data acquisition window should be kept at a minimum.”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• “ A tube potential of 100 kV could be considered for patients weighing ≤ 90 kg or with a BMI ≤ 30 kg/m2; a tube potential of 120 kV is usually indicated for patients weighing >90 kg and with a BMI > 30 kg/m2.”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• “ Use of breast shields is not recommended for cardiovascular CT.”
  SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT
  Halliburton SS et al.
  J Cardiovasc Computed Tomogr (2011)5, 198-224
• Radiation Dose Reduction Strategies 2011
  - 80 kVp versus 100 kVp or 120 kVp
  - Iterative reconstruction
  - High pitch (3.4) on a dual source scanner
• “ Coronary CTA using 80 kVp instead of 100 kVp was associated with a nearly 50% reduction in radiation dose with no significant difference in interpretability and noninferior image quality despite lower signal-to-noise and contrast to noise ratios.”
  Coronary CT Angiography of Patients With a Normal Body Mass Index Using 80 kVp Versus 100 kVp: A Prospective, Multicenter, Multivendor Randomized Trial
  LaBounty TM et al.
  DOI;10:2214/AJR 11.6787
• “ Coronary CTA using 80 kVp instead of 100 kVp was associated with a nearly 50% reduction in radiation dose with no significant difference in interpretability and noninferior image quality despite lower signal-to-noise and contrast to noise ratios. The use of 80 kVp tube voltage should be considered in dose reduction strategies for coronary CTA of individuals with a normal BMI.”
  Coronary CT Angiography of Patients With a Normal Body Mass Index Using 80 kVp Versus 100 kVp: A Prospective, Multicenter, Multivendor Randomized Trial
  LaBounty TM et al.
  DOI;10:2214/AJR 11.6787
• “ The use of 80 kVp tube voltage should be considered in dose reduction strategies for coronary CTA of individuals with a normal BMI.”
  Coronary CT Angiography of Patients With a Normal Body Mass Index Using 80 kVp Versus 100 kVp: A Prospective, Multicenter, Multivendor Randomized Trial
  LaBounty TM et al.
  DOI;10:2214/AJR 11.6787
• “ Automated scan-specific threshold level-based quantification of plaque components from coronary CT angiography allows rapid, accurate measurement of noncalcified plaques volumes, compared with intravascular US, and requires a fraction of the time needed for manual analysis.”
  Automated Three-dimensional Quantification of Noncalcified Coronary Plaque from Coronary CT Angiography: Comparison with Intravascular US
  Dey D et al.
  Radiology 2010; 257:516-522
• “ Because tube current reduction is related to the square of the noise reduction, our measured 17% noise reduction with 40% ASIR reconstruction would theoretically permit a tube current reduction of 30-40%, resulting in a proportional decrease in the effective radiation dose without altering image noise.”
  Adaptive Statistical Iterative Reconstruction: Assessment of Image Noise and Image Quality in Coronary CT Angiography
  Leipsic J et al.
  AJR 2010; 195:649-654
• “ ASIR resulted in noise reduction and significantly impacted image quality. When using a low tube current technique, cardiac CTA reconstruction using 40% or 60% ASIR significantly improved image quality and the proportion of interpretable segments compared with FBP reconstruction.”
  Adaptive Statistical Iterative Reconstruction: Assessment of Image Noise and Image Quality in Coronary CT Angiography
  Leipsic J et al.
  AJR 2010; 195:649-654
• “ Compared with QCA (quantitative coronary angiogram) the automated detection algorithm evaluated had relatively high accuracy for diagnosing significant coronary artery stenosis at cCta. If used as a second reader the high negative predictive value may futher enhance the confidence of excluding significant stenosis based on a normal or near normal cCTA study.”
  Automated computer-aided stenosis detection at coronary CT angiography: initial experience
  Arnoldi E et al.
  Eur Radiol 20(5):1160-7, May 2010
  

   

• "Artifacts and sub-optimal image quality usually lead to false positive findings in coronary CT angiography-false positive interpretation is much more frequent than false negative studies."

  Limiting radiation exposure in coronary CT angiography: much can be achieved with little extra effort
  Achenbach S Int
  J Cardiovasc Imaging (2009) 25:421-423

   

• "Significantly lower doses occur with a PE protocol on a Siemens Healthcare 64-MDCT scanner than on the GE Healthcare counterpart, largely owing to differences in automated tube current modulation method."

  Radiation Dose for Body CT Protocols: Variability of Scanners at One Institution
  Jaffe TA et al.
  AJR 2009; 193;1141-1147

• "The mean effective doses for the pulmonary embolism protocol ranged from 9.9 to 18.5 mSv and for the chest, abdomen, and pelvis protocol from 6.7 to 18.5 mSv."

  Radiation Dose for Body CT Protocols: Variability of Scanners at One Institution
  Jaffe TA et al.
  AJR 2009; 193;1141-1147

• "According to phantom data, patients are subject to different radiation exposures for similar body CT protocols depending on scanner assignment. In general doses are lowest with use of 64-MDCT scanners."

  Radiation Dose for Body CT Protocols: Variability of Scanners at One Institution
  Jaffe TA et al.
  AJR 2009; 193;1141-1147

• Ten Steps to Lower CT Radiation Dose for Patients While Maintaining Image Quality
  - 1. increase awareness and understanding of CT radiation dose issues among radiologic technologist
  - 2. enlist the services of a qualified medical physicist
  - 3. obtain accredidation from the American College of Radiology for your CT program
  - 4. when appropriate use an alternative imaging strategy that does not involve radiation
  - 5. determine if the ordered CT is justified by the clinical indication
  - 6. establish baseline radiation dose for adult sized patients
  - 7. establish radiation doses for pediatric patients by “child-sizing” CT scanning parameters
  - 8. optimize pediatric examination parameters
  - 9. scan only the indicated area: scan once
  - 10. prepare a child-friendly and expeditious CT environment

Image Gently: Ten Steps You Can Take to Optimize Image Quality and Lower CT Dose for Pediatric Patients
Strauss KJ et al.
AJR 2010; 194:868-873

• Ten Steps to Lower CT Radiation Dose for Patients While Maintaining Image Quality
  - 1. increase awareness and understanding of CT radiation dose issues among radiologic technologist
  - 2. enlist the services of a qualified medical physicist
  - 3. obtain accredidation from the American College of Radiology for your CT program
  - 4. when appropriate use an alternative imaging strategy that does not involve radiation

• "This article suggests 10 steps that radiologists and radiologic technologists, with the assistance of their medical physicist, can take to obtain good quality CT images while properly managing radiation dose for children undergoing CT."

  Image Gently: Ten Steps You Can Take to Optimize Image Quality and Lower CT Dose for Pediatric Patients
  Strauss KJ et al.
  AJR 2010; 194:868-873

• Typical Effective Dose Values (CT)
  
  

  Examination	mSv
  Head CT	1-2
  Chest CT	5-8
  Abdomen CT	5-8
  Pelvis CT	3-6
  Abdomen and Pelvis CT	8-14
  Coronary Artery Calcium CT	0.1-3
  Coronary CT Angiogram	1-18

• "Effective dose is not the risk for any one individual. Due to the inherent uncertainties and oversimplifications involved, effective dose should not be used for epidemiologic studies or for estimating population risks."

  How Effective is Radiation Dose as a Predictor of Radiation Risk?
  McCollough CH et al
  AJR 2010; 194:890-896

• How to reduce dose of a cardiac CT scan: Options
  - ECG controled tube current modulation
  - Adaptive pitch
  - Reduced tube voltage of 100 kV
  - Sequential scanning (step and shoot)
  - Large detector coverage
  - High pitch mode (Flash mode)

• " A combination of several dose saving algorithmns is often feasible and leads to an efficient reduction in the overall radiation dose for a cardiac CT study."

  Trends in radiation protection in CT: Present and future status
  Bischoff B et al.
  J Cardiovasc Comput Tomogr (2009) 3, Supplement 2, S65-S73

• "In summary, it is important and necessary to individually adapt the scan protocol, with the use of every possible strategy for dose reduction."

  Trends in radiation protection in CT: Present and future status
  Bischoff B et al.
  J Cardiovasc Comput Tomogr (2009) 3, Supplement 2, S65-S73

• "The scout view derived scan length (mean ± SD, 139 ± 13 mm) was significantly greater than the calcium scoring derived scan length (117 ± 9mm)."

  Scan Length Adjustment of CT Coronary Angiography Using the Calcium Scoring Scan: Effect on Radiation Dose
  Leschka S et al.
  AJR;194: March 2010 DOI:10.2214/AJR.09.2970

• "Adjustment of the scan length of CT coronary angiography using the images from calcium scoring instead of the scout view is feasible and is associated with a 16% reduction in radiation dose of dual source CT coronary angiography."

  Scan Length Adjustment of CT Coronary Angiography Using the Calcium Scoring Scan: Effect on Radiation Dose
  Leschka S et al.
  AJR;194: March 2010 DOI:10.2214/AJR.09.2970

   

• "The mean effective dose was 5.7 ± 1.7 mSv (range, 1.6-11.1 mSv) for 151(75%) patients scanned with one heart beat acquisition. For patients scanned with 2 or 3 heart beat acquisition, radiation dose was higher with mean exposure of 13.0± 3.3 mSv and 19.5 mSv, respectively."

  First experience with 320-row multidetector CT coronary angiography scanning with prospective electrocardiogram gating to reduce radiation dose
  Hoe J, Toh KH
  J Cardiovasc Comput Tomogr (2009) 3, 257-261

   

• Radiation Dose
  - 64 MDCT with retrospective gating (8-18 mSv)
  - 64 MDCT with prospective gating (1-5 mSv)
  - 320 MDCT (<5 mSv)
  - DSCT with FLASH (128 detectors x 2) (<1-3 mSv)

• Radiation Dose
  - 64 MDCT with retrospective gating
  - 64 MDCT with prospective gating
  - 320 MDCT
  - DSCT with FLASH (128 detectors x 2)

• "Radiation dose increase with the square of tube voltage and small changes in tube voltage result in a relatively large change in radiation dose (120 to 100 kV is a dose reduction of 40%, 120 to 80 kV is a reduction of 80%)."
  
  Image Quality in a Low Radiation Exposure Protocol for Retrospectively ECG-Gated Coronary CT Angiography
  Pflederer T, Achenbach S et al.
  AJR 2009; 192:1045-1050

• "We found a significant decrease in radiation exposure--almost 39%-- by using a tube voltage of 100 kV instead of the most frequently recommended value of 120kV."
  
  Image Quality in a Low Radiation Exposure Protocol for Retrospectively ECG-Gated Coronary CT Angiography
  Pflederer T et al.
  AJR 2009; 192:1045-1050

• "The purpose of our study was to systematically compare the image quality of dual source CT coronary angiography using 100kV instead of 120 kV."
  
  Image Quality in a Low Radiation Exposure Protocol for Retrospectively ECG-Gated Coronary CT Angiography
  Pflederer T et al.
  AJR 2009; 192:1045-1050

• "Mean intraluminal attenuation,contrast enhancement, and image noise were significantly higher for 100 kV, whereas signal to noise and contrast to noise ratios were not different between the two scanning protocols."
  
  Image Quality in a Low Radiation Exposure Protocol for Retrospectively ECG-Gated Coronary CT Angiography
  Pflederer T et al.
  AJR 2009; 192:1045-1050

   

• "Advances in CT technology have resulted in a significant increase in cardiac CT applications. It is imperative that the radiologist understand the resulting dose implication to the patient and actively engage in optimal protocol design to achieve adequate image quality with patient dose reduction in mind."

  Radiation Dose in Cardiac CT
  Mayo JR, Leipsic JA
  AJR 2009;192:646-653

• Reducing Radiation Dose in Cardiac CTA: Strategies
  
  " In summary a variety of algorithms for reducing dose in CCT are available for use in daily practice. Most of the described dose saving strategies can be combined, resulting in an efficacious reduction of overall radiation exposure."
  
  Tips to minimize radiation exposure
  Hausleiter J, Meyer T
  J Cardiovasc Comput Tomogr (2008) 2. 325-327

• In this article, we summarize several strategies and new scanning techniques for dose reduction in cardiac CT, including the following:
  1. "Coronary CT angiography should not be performed in patients with extensive coronary calcifications because the probability to rule out obstructive disease coronary artery disease diminishes with increasing coronary artery calcium scores"
  2. The scan length in CT angiography should be individually adjusted to the minimum needed length
  3. Electrocardiogram-correlated modulation of the tube current should be applied in all patients with stable sinus rhythm.
  4. The tube voltage should be reduced to 100 kV in non-obese patients (patient weight <85-90 kg="")
  5. A sequential scan mode with prospective electrocardiogram triggering should be considered in patients with a stable heart rate ≤63 beats/min."
  With the appropriate use of these strategies for dose reduction, the diagnostic image quality is maintained."
  
  Tips to minimize radiation exposure
  Hausleiter J, Meyer T
  J Cardiovasc Comput Tomogr (2008) 2. 325-327

• "Using a low radiation dose and nongated MDCT we can detect coronary artery calcium and obtain results comparable to those obtained with dedicated calcium scoring CT that uses a higher dose and ECG gating."
  
  Coronary Calcium Screening Using Low Dose Lung Cancer Screening:Effectiveness of MDCT with Retrospective Reconstruction
  Kim SM et al.
  AJR 2008;190:917-922

• Computed tomography--an increasing source of radiation exposure
  
  Brenner DJ,Hall EJ
  N Engl J Med 2007 Nov 29.357(22):2277-2284

• There is major interest by ABC News programs in the article in NEJM today (release 5P) on CT scans being an increasing source of radiation risk. Below is our internal summary. CT SCANS AN INCREASING SOURCE OF RADIATION & CANCER RISK Americans are getting more CT scans than ever, an estimated 62 million per year, up from around 3 million in 1980. In a new review, doctors discuss what the possible consequences of this increase could be.

• Right now there are no definitive studies to tell us whether CT scans increase the risk of cancer, but doctors estimate that the radiation from 2-3 CT scans is enough to measurably increase cancer risk. In fact, researchers estimate that up to 2% of cancers could be attributed to CT scans today. The risk to any one individual is small, and likely is outweighed by the need for the scan, especially when it is being used to DIAGNOSE an illness. But CT screening may NOT prove beneficial to the population as a whole.

• ECG Controlled Dose Modulation
  
  - Dose reduction in 50% range
  - Minimal tube output during systole
  - Need a regular rythmn and rate to succeed

• "This study showed the combined effect of lowering the kilovoltage setting (80 kV) and using an automatic modulation technique (ECG-pulsed tube current modulation) for coronary CT. Radiation dose exposure can be reduced by up to 88% for slim patients without impairing image quality."
  
  MDCT of the Coronary Arteries: Feasibility of Low-Dose CT with ECG-Pulsed Tube Current Modulation to Reduce Radiation Dose
  Abada HT
  AJR 2006; 186: S387-S390.

• "Fact: Slim patients were defined as < 60 kg, mean age 40 years (range 13-77).
  
  MDCT of the Coronary Arteries: Feasibility of Low-Dose CT with ECG-Pulsed Tube Current Modulation to Reduce Radiation Dose
  Abada HT
  AJR 2006; 186: S387-S390.