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PPT

  1. 1. Cardiac CT in Pediatric Patients Marilyn J. Siegel, M.D. Mallinckrodt Institute of Radiology Washington University School of Medicine St. Louis, MO. USA
  2. 2. FDA Questions: Contrast-enhanced Pediatric Cardiac CT <ul><li>Indications for CT </li></ul><ul><li>Impact of CT on diagnosis & treatment </li></ul><ul><li>Contrast-specific questions: </li></ul><ul><ul><li>Methods of determining dosing </li></ul></ul><ul><ul><li>Limitations of contrast-enhanced CT </li></ul></ul><ul><ul><li>Methods of safety monitoring </li></ul></ul><ul><li>Efficacy data (adults & children) </li></ul><ul><li>Direction of future drug development or utilization for contrast agents in children </li></ul>
  3. 3. Cardiac CT: Basic Facts <ul><li>Need multidetector CT </li></ul><ul><li>Faster imaging times </li></ul><ul><ul><li>fewer motion artifacts </li></ul></ul><ul><li>Higher spatial resolution </li></ul><ul><ul><li>0.5 to 1.25 mm </li></ul></ul><ul><ul><li>superb 3D images </li></ul></ul><ul><li>Better contrast enhancement </li></ul><ul><li>THE USE OF CT IS INCREASING </li></ul>
  4. 4. Frequency of Contrast Usage <ul><li>Contrast mandatory </li></ul><ul><ul><li>100% of cases </li></ul></ul><ul><li>Inherent problems in children </li></ul><ul><ul><li>Small patient size </li></ul></ul><ul><ul><li>Lack of perivisceral fat </li></ul></ul><ul><li>Poor differentiation of soft tissue structures on non-enhanced CT scans </li></ul><ul><li>Solution: IV contrast </li></ul>
  5. 5. FDA Questions: Contrast-enhanced Pediatric Cardiac CT <ul><li>Indications for CT </li></ul><ul><li>Impact of CT on diagnosis & treatment </li></ul><ul><li>Contrast-specific questions: </li></ul><ul><ul><li>Methods of determining dosing </li></ul></ul><ul><ul><li>Limitations of contrast-enhanced CT </li></ul></ul><ul><ul><li>Methods of safety monitoring </li></ul></ul><ul><li>Efficacy data (adults & children) </li></ul><ul><li>Direction of future drug development or utilization for contrast agents in children </li></ul>
  6. 6. Indications: Pediatric Cardiac CT <ul><li>Detection of disease or pathology </li></ul><ul><ul><li>i.e., diagnosis </li></ul></ul><ul><li>Improve clinical decision making </li></ul><ul><ul><li>Need for other diagnostic testing </li></ul></ul><ul><ul><li>Use of specific intervention </li></ul></ul><ul><li>No role in defining normal anatomy </li></ul><ul><li>No role in assessing function </li></ul><ul><li>Not a screening tool </li></ul>
  7. 7. Specific Disease States or Pathology <ul><li>Extracardiac great vessel anomalies </li></ul><ul><li>Intracardiac shunt lesions </li></ul><ul><li>Post-operative anatomy </li></ul><ul><li>In children, CT is performed most often for congenital diseases </li></ul>
  8. 8. Pediatric Heart Diseases <ul><li>Common extracardiac lesions </li></ul><ul><ul><li>Aortic arch anomalies </li></ul></ul><ul><ul><li>Aortic coarctation </li></ul></ul><ul><ul><li>Interrupted arch </li></ul></ul><ul><ul><li>Patent ductus arteriosus </li></ul></ul><ul><ul><li>Pulmonary artery sling </li></ul></ul>
  9. 9. Arch Anomalies Neonate Adolescent Right arch Double Arch
  10. 10. Pulmonary Sling: Left pulmonary artery arises from right pulmonary artery Case from J. Schoepf Neonate
  11. 11. Aortic Coarctation 10-day old girl with CHF; 8 cc contrast, 3D CT CT
  12. 12. Patent Ductus Arteriosus CT MR
  13. 13. Other Indications for Pediatric Cardiac CT <ul><li>Diagnosis of cardiac shunts </li></ul><ul><ul><li>atrial septal defects </li></ul></ul><ul><ul><li>ventricular septal defects </li></ul></ul><ul><li>Evaluate post-operative anatomy </li></ul><ul><ul><li>usually complex cyanotic heart disease </li></ul></ul>
  14. 14. Shunt Lesion: Septal Defects Post ASD repair ASD/VSD ASD
  15. 15. Post-operative Evaluation: Graft right atrium to pulmonary artery Grafts subclavian arteries to pulmonary arteries
  16. 16. FDA Questions: Contrast-enhanced Pediatric Cardiac CT <ul><li>Indications for CT </li></ul><ul><li>Impact of CT on diagnosis & treatment </li></ul><ul><li>Contrast-specific questions: </li></ul><ul><ul><li>Methods of determining dosing </li></ul></ul><ul><ul><li>Limitations of contrast-enhanced CT </li></ul></ul><ul><ul><li>Methods of safety monitoring </li></ul></ul><ul><li>Efficacy data (adults & children) </li></ul><ul><li>Direction of future drug development or utilization for contrast agents in children </li></ul>
  17. 17. Impact on Management <ul><li>Predict whether patient should undergo further invasive diagnostic testing (angiography) </li></ul><ul><li>Clarify equivocal angiographic findings </li></ul><ul><li>Predict whether patient needs surgery </li></ul>
  18. 18. Therapeutic Intervention: Indications for Re-operation Leaking Baffle CT prompted angiography Pseudoaneurysm Prompted surgery
  19. 19. FDA Questions: Contrast-enhanced Pediatric Cardiac CT <ul><li>Indications for CT </li></ul><ul><li>Impact of CT on diagnosis & treatment </li></ul><ul><li>Contrast-specific questions: </li></ul><ul><ul><li>Methods of determining dosing </li></ul></ul><ul><ul><li>Limitations of contrast-enhanced CT </li></ul></ul><ul><ul><li>Methods of safety monitoring </li></ul></ul><ul><li>Efficacy data (adults & children) </li></ul><ul><li>Direction of future drug development or utilization for contrast agents in children </li></ul>
  20. 20. Contrast Dosing <ul><li>Contrast volume is determined empirically based on patient weight </li></ul><ul><li>Nonionic contrast medium </li></ul><ul><ul><li>280 to 320 mg I </li></ul></ul><ul><li>Dose </li></ul><ul><ul><li>2 mL/kg (max 4 mL/kg or 125 mL) </li></ul></ul>
  21. 21. Contrast Injection <ul><li>Power Injection </li></ul><ul><ul><li>Antecubital catheter </li></ul></ul><ul><ul><li>Flow rate: variable </li></ul></ul><ul><ul><ul><li>22g 1.5 -2.0 mL/sec </li></ul></ul></ul><ul><ul><ul><li>20 g 2.0 -3.0 mL/sec </li></ul></ul></ul><ul><ul><ul><li>24g or central line 1.0 mL/sec </li></ul></ul></ul><ul><li>Hand Injection: </li></ul><ul><ul><li>Peripherally positioned catheter </li></ul></ul>
  22. 22. FDA Questions: Contrast-enhanced Pediatric Cardiac CT <ul><li>Indications for CT </li></ul><ul><li>Impact of CT on diagnosis & treatment </li></ul><ul><li>Contrast-specific questions: </li></ul><ul><ul><li>Methods of determining dosing </li></ul></ul><ul><ul><li>Limitations of contrast-enhanced CT </li></ul></ul><ul><ul><li>Methods of safety monitoring </li></ul></ul><ul><li>Efficacy data (adults & children) </li></ul><ul><li>Direction of future drug development or utilization for contrast agents in children </li></ul>
  23. 23. Limitations of Contrast-Enhanced CT <ul><li>Contrast-related: </li></ul><ul><ul><li>Extravasation at injection site </li></ul></ul><ul><ul><li>Adverse contrast reactions </li></ul></ul><ul><li>Device-related: </li></ul><ul><ul><li>Radiation exposure </li></ul></ul>
  24. 24. Contrast-Related Risks <ul><li>Extravasation at injection site </li></ul><ul><ul><li>Power injector: 0.4% </li></ul></ul><ul><ul><li>Manual injection: 0.3% </li></ul></ul>Kaste Pediatr Radiol 1995; 26:449
  25. 25. Incidence Contrast Reactions: Meta-analysis <ul><li>LOCM(NICM) </li></ul><ul><ul><li>All 1-3% </li></ul></ul><ul><ul><li>Minor near 1% </li></ul></ul><ul><ul><li>Major (severe) .04% (1:10,000) </li></ul></ul><ul><ul><li>Late 5-8% </li></ul></ul><ul><li>Mortality rate - LOCM since 1980 1:100,000 </li></ul>
  26. 26. Adverse Contrast Reactions: Pediatric Population <ul><li>321 children </li></ul><ul><li>Questionnaire (73% return rate) </li></ul><ul><li>Omnipaque 300/450 (Iohexol) </li></ul><ul><li>Acute reactions 1.9% </li></ul><ul><ul><li>Minor (mild) </li></ul></ul><ul><ul><li>Older patients (> 24 kg) </li></ul></ul><ul><li>Late reactions 6.2% </li></ul><ul><ul><li>Mild or intermediate </li></ul></ul><ul><ul><li>Younger (< 24 kg) </li></ul></ul>Mikkonen, Pediatr Radiol 1995; 25:350
  27. 27. Adverse Contrast Reactions <ul><li>Nonionic n=168,363 (1986-1988) </li></ul><ul><li>Overall prevalence of ADRS: 3.13% </li></ul><ul><ul><li>Severe 0.04%, deaths 0.004% </li></ul></ul><ul><li>70% within 5 minutes, remainder later </li></ul><ul><li>Prevalence by age: </li></ul><ul><ul><li>< 10 yrs: 0.4% </li></ul></ul><ul><ul><li>10-19 yrs: 2.52% </li></ul></ul><ul><ul><li>20-49 yrs: 4.1-4.6% </li></ul></ul><ul><ul><li>> 50 yrs: 1.5-2.6% </li></ul></ul>Katayama H. Radiology 1990; 175:621
  28. 28. Radiation Exposure
  29. 29. Radiation Risks <ul><li>CT </li></ul><ul><ul><li>10% of all radiological procedures </li></ul></ul><ul><ul><li>65% effective dose of all medical x-rays </li></ul></ul><ul><li>Chest X-ray 0.10 mSv </li></ul><ul><li>Pediatric chest CT 1-10 mSv </li></ul><ul><li>Adult chest CT 7-15 mSv </li></ul><ul><li>Cardiac Cath 20-30 mSv </li></ul><ul><ul><li>(3.5 min fluoro/75 sec cine) </li></ul></ul>
  30. 30. Relative Risks <ul><li>To individual: </li></ul><ul><ul><li>Lifetime risk of cancer: 20-25% (1 in 4 or 5) </li></ul></ul><ul><ul><li>Added risk: 0.05% (negligible, 1 in 2000) </li></ul></ul><ul><li>To population: </li></ul><ul><ul><li>600,000 pediatric CT’s in the US / year </li></ul></ul><ul><ul><li>Without CT: 135,000 will die of cancer </li></ul></ul><ul><ul><li>With CT: 135,300 will die of cancer </li></ul></ul>Courtesy Jim Brink, M.D.
  31. 31. FDA Questions: Contrast-enhanced Pediatric Cardiac CT <ul><li>Indications for CT </li></ul><ul><li>Impact of CT on diagnosis & treatment </li></ul><ul><li>Contrast-specific questions: </li></ul><ul><ul><li>Methods of determining dosing </li></ul></ul><ul><ul><li>Limitations of contrast-enhanced CT </li></ul></ul><ul><ul><li>Methods of safety monitoring </li></ul></ul><ul><li>Efficacy data (adults & children) </li></ul><ul><li>Direction of future drug development or utilization for contrast agents in children </li></ul>
  32. 32. Safety Monitoring <ul><li>Dosing </li></ul><ul><ul><li>IV contrast drawn up by technologist </li></ul></ul><ul><ul><li>Dose verified by radiologist prior to injection </li></ul></ul><ul><ul><li>Contrast administered by radiologist </li></ul></ul><ul><li>Procedural </li></ul><ul><ul><li>Catheter site monitored for extravasation </li></ul></ul>
  33. 33. Mitigating & Preventing Adverse Contrast Reactions <ul><li>Identify patients at risk: </li></ul><ul><ul><li>Prior moderate contrast reaction </li></ul></ul><ul><ul><li>Medically treated asthma </li></ul></ul><ul><li>Premedication with corticosteroids </li></ul>
  34. 34. Safety Monitoring Radiation Dose <ul><li>Directly proportional to: </li></ul><ul><ul><li>Tube current </li></ul></ul><ul><ul><li>Kilovoltage </li></ul></ul><ul><ul><li>Scan time </li></ul></ul><ul><ul><li>Slice thickness </li></ul></ul><ul><ul><li>Total number of slices </li></ul></ul>
  35. 35. Radiation Risks: Recommendations <ul><li>Optimize CT settings </li></ul><ul><ul><li>Reduce tube current and voltage </li></ul></ul><ul><ul><li>Increase table speed (mm/sec) </li></ul></ul><ul><ul><li>Limit number of scans </li></ul></ul><ul><ul><li>Use automated dose reduction technology </li></ul></ul><ul><li>Eliminate inappropriate referrals for CT </li></ul>
  36. 36. FDA Questions: Contrast-enhanced Pediatric Cardiac CT <ul><li>Indications for CT </li></ul><ul><li>Impact of CT on diagnosis & treatment </li></ul><ul><li>Contrast-specific questions: </li></ul><ul><ul><li>Methods of determining dosing </li></ul></ul><ul><ul><li>Limitations of contrast-enhanced CT </li></ul></ul><ul><ul><li>Methods of safety monitoring </li></ul></ul><ul><li>Efficacy data (adults & children) </li></ul><ul><li>Direction of future drug development or utilization for contrast agents in children </li></ul>
  37. 37. Efficacy Data <ul><li>In adults, large amount of data related to CT angiography of the coronary arteries and acute aortic events </li></ul><ul><li>In children, overall paucity of data </li></ul><ul><ul><li>Minimal data on aortic imaging </li></ul></ul><ul><li>Several review articles on CT angiography of congenital heart disease </li></ul>
  38. 38. Coronary Artery Stenosis <ul><li>Several studies have shown that CT allows reliable detection of coronary artery disease </li></ul><ul><li>95% sensitivity, 86% specificity </li></ul><ul><ul><ul><li>detecting > 50% stenosis </li></ul></ul></ul><ul><ul><ul><li>vessels 2-4 mm in diameter </li></ul></ul></ul>Nieman: Circulation 2002; 106:2051 Fayad: Circulation 2002; 106:2026
  39. 39. Pediatric Aortic Arch Anomalies <ul><li>22 pediatric patients </li></ul><ul><li>Confirmatory studies: </li></ul><ul><ul><li>Echocardiography (n=7) </li></ul></ul><ul><ul><li>Angiography (n=7) </li></ul></ul><ul><ul><li>Surgery (n=8) </li></ul></ul><ul><li>Accuracy CT: 96% </li></ul><ul><ul><li>Stenotic vessels: 2 to 5 mm in diameter </li></ul></ul>Lee E, Siegel MJ. AJR, In Press
  40. 40. FDA Questions: Contrast-enhanced Pediatric Cardiac CT <ul><li>Indications for CT </li></ul><ul><li>Impact of CT on diagnosis & treatment </li></ul><ul><li>Contrast-specific questions: </li></ul><ul><ul><li>Methods of determining dosing </li></ul></ul><ul><ul><li>Limitations of contrast-enhanced CT </li></ul></ul><ul><ul><li>Methods of safety monitoring </li></ul></ul><ul><li>Efficacy data (adults & children) </li></ul><ul><li>Direction of future drug development or utilization for contrast agents in children </li></ul>
  41. 41. Future Directions in Contrast-Enhanced CT <ul><li>Goal: To get the highest contrast enhancement with the least amount of contrast agent </li></ul><ul><li>2 main factors affect contrast enhancement: </li></ul><ul><ul><li>Flow rate or injection duration </li></ul></ul><ul><ul><li>Iodine concentration </li></ul></ul>
  42. 42. Injection Rate vs. Arterial Enhancement <ul><ul><ul><li> injection rate increases contrast enhancement </li></ul></ul></ul>Bae 2002 0 50 100 150 200 250 300 350 Contrast Enhancement (HU) 0 25 50 75 100 125 150 175 200 Time (sec) 1 mL/s 3 mL/s 5 mL/s
  43. 43.  Injection rate <ul><li>Higher levels of enhancement may result in smaller volumes of contrast </li></ul><ul><li>But in children there is a limit how fast we can inject, because small gauge catheters and catheters in hand and foot need slower injection rate </li></ul>
  44. 44. Concentration vs. Enhancement Varying iodine concentrations Total iodine mass and flow rate constant (5mL/s)  iodine concentration =  contrast enhancement Bae 2002 0 50 100 150 200 250 300 350 0 10 20 30 40 50 Time (sec) Aortic CE (HU) 400 mgI/mL 350 mgI/mL 300 mgI/mL
  45. 45. Concentration vs. Flow Rate <ul><li>Left ventricular density (200-300 HU) </li></ul><ul><ul><li>300 mgI/mL at 3.5 mL/sec </li></ul></ul><ul><ul><li>400 mgI/mL at 2.5 mL/sec </li></ul></ul><ul><li>Injecting low-concentration contrast at high flow rate or higher-concentration at lower flow rate produces similar enhancement density </li></ul>Becker Appl Radiol 2003; S50
  46. 46. Effect of Iodine Concentration <ul><li>Implication in children </li></ul><ul><li>Use of higher concentration contrast material at may result in smaller contrast volumes </li></ul><ul><li>Disadvantage </li></ul><ul><ul><li> Viscosity (not usable > 400 mgI/mL) </li></ul></ul><ul><li>Challenge for future research </li></ul>
  47. 47. CT: Future Clinical Utilization <ul><li>Ventricular function studies based on images in systole and diastole </li></ul><ul><li>Pulmonary perfusion studies </li></ul><ul><ul><li>Peak attenuation & time to peak attenuation measured </li></ul></ul>
  48. 48. Pulmo CT: Color Coded Display Potential for studying perfusion abnormalities associated with heart/lung disease
  49. 49. Summary <ul><li>Role of CT will increase </li></ul><ul><li>Challenges: </li></ul><ul><ul><li>Optimize contrast enhancement </li></ul></ul><ul><ul><li>Lower radiation dose </li></ul></ul>

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