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Pediatric Cardiac CTA: Applications and Strategies for Dose Reduction

This course consists of a previously recorded webcast for radiologists and technologists.  The presentation covers the main applications of Cardiac CTA for pediatric cardiology patients. This session includes a discussion of the risks and benefits for advanced imaging techniques and  radiation dose reduction strategies. The presenter is Dr. B. Kelly Gleason Han, Pediatric Cardiologist, Children’s Heart Clinic, Minneapolis.

Pediatric Cardiac CTA:  Applications & Strategies for Dose Reduction Dr. Kelly Han, MD The statements by Siemens’ customers described herein are based on results that were achieved in the customer's unique setting. Since there is no "typical" hospital and many variables exist (e.g., hospital size, case mix, level of IT adoption) there can be no guarantee that other customers will achieve the same results. Identify key factors related to Congenital Heart Disease (CHD) including mortaility rates, symptoms, and available interventions. This course reviews the following topics: Recognize applications of Flash scanner for pediatric cardiac population including complex congenital imaging, coronary artery imaging, and function analysis in patients with pacemakers. • The number of adults with palliated congenital heart disease is growing exponentially • Since 2000, there are more adults with palliated congenital heart disease than patients in the pediatric age range • Catheterization is becoming primarily interventional • There is a recent dramatic shift toward non-invasive diagnostics • The dual source scanner is changing the way we care for our patients • Since the risk to benefit ratio of Cath/MRI/CT is being redefined by new technology • CTA is becoming the preferred method of imaging for certain applications due to:   – Rapid image acquisition   – Low radiation dose   – Excellent spatial & temporal resolution Echocardiography is the mainstay for diagnosis of congenital cardiac disease A small subset of patients will need additional imaging to evaluate cardiac or extracardiac anatomy CHC 2009 –  >10,000 echoes –  286 MRI/CT 2/3 MRI 1/3 CTA (rapidly increasing) Cardiac Catheterization • Invasive, interventional radiation exposure MRI/MRA • • Noninvasive, lengthy scan times Angiogram requires suspended respiration MDCTA with high pitch Dual Source Scanner • • Noninvasive, fast image acquisition, minimal radiation exposure for Flash scans Angiogram can be performed free breathing MR Advantages • No radiation • Functional information • Flow analysis and shunt quantification • No heart rate limitations   CT Advantages • Better for airway/vascular definition • Minimal artifact from stainless steel stents/coils • Compatible with pacemaker/defibrillator • Fast image acquisition • Superior coronary artery definition MR Disadvantages • Longer scan time • < 8 y.o. needs anesthesia • Contraindicated in patients with pacemakers • In small children, signal to noise is technically challenging (small voxels with little signal) • Stainless steel stents/coils cause artifact   CTA Disadvantages • Radiation dose • Heart rate limitations   • The lifetime risk of cancer is proportional to total accumulated radiation dose • Younger patients have higher dose for the same scan • Growing/dividing cells are more susceptible to radiation damage • DLP - dose X length product   - Minimize scan range   - Minimize kVp and mAs   - Use EKG pulsed radiation • CTA radiation dose between 4-11 mSv historically, estimated as high as 25 mSv for EKG gated studies • CXR     - AP - AP/LAT 0.02 mSv 0.04 mSv • CT of head/pelvis/abdomen 10 mSv • Catheter cardiac angiogram 4.6 - 15.8 mSv   - With PTCA up to 57 mSv • Cardiac CTA Scan (64 sl) 9-40 mSv - With aortic arch 29 mSv • Nuclear Cardiac Stress Scan - Thallium - Sestamibi 17 mSv 9 mSv • PET scans (various) 14 mSv Pediatric Cardiac CT Referral Diagnosis • Definition of complex neonatal anatomy • Coronary Artery Imaging (50%) • Complex heart disease, pacemaker dependent (40%)  - Ventricular function  - Regurgitant fraction (stroke volume differences)  - Prosthetic valve function • Vascular Ring with airway compromise • Critically ill patient in ICU where long imaging time for MRI is contraindicated (10%) Radiation Risk from Pediatric Cardiac Catheterization: Friendly Fire on Children with Congenital Heart Disease Andreassi, Circulation 2009;120:1847-1849 H2AX Foci as a Biomarker for Patient X-Ray Exposure in Pediatric Cardiac Catheterization: Are we underestimating the risks? Circulation 2009:120:1903-1909, Beels, et a • Median effective dose from cath 6.4 mSv (0.5 - 53 mSv) • Age adjusted mSv 13 for neonate, 8 for 1 year old • Lifetime exposure of a contemporary young adolescent with CHD is 20 mSv • Increased (LAR) cancer risk 1/248 per procedure • Exposed Dose - What did the scanner deliver? • Effective Dose - What did the patient receive? • CT dose measured in three ways:    - Calculations based on phantoms  - CTDI or DLP from scanner with tissue weighting and age adjustment  - Monte Carlo simulations - directly measures scanner output   DLP ICRP (International Commission on Radiological Protection) - 103 (2007)  IEC 2002   IAEC International Atomic Energy Agency   BEIR VII Health risk of low levels of ionization radiation   AAPM Diagnostic Imaging Council CT Committee 2008 mSv DLP 100 Head .0031   Chest 0.014   Abdomen 0.015   .31 mSv 1.4 mSv 1.5 mSv SCAN DLP 100   Age Adjusted 0 year old 0.039 1 year old 0.026   5 year old 0.018   10 year old 0.013   Adult 0.014   3.9 mSv 2.6 mSv 1.8 mSv 1.3 mSv 1.4 mSv The Measurement, Reporting, and Management of Radiation dose in CT Task Group 23 of the Diagnostic Imaging Council CT Committee, January 2008 High Pitch MDCTA May Potentially Reduce Radiation and Anesthesia Risks in Young Children: Comparison with Standard 64 Slice MDCTA in Complex Congenital Heart Disease IRB exemption obtained for retrospective review of a clinical quality improvement database* All patients referred to Cardiac CT over a two year period were reviewed (62 scans) Clinical indication for scan was arterial/venous or cardiac anatomy Separated into two group: Group 1 - 64 slice single pitch CT scanner at CHCMN (Toshiba Acquilon (pitch 0.8) Group 2 - 2nd generation dual source CT scanner at MHI (Siemens FLASH scanner (variable pitch 2.25 - 3.4) *This was an IRB-approved internal study conducted by Dr. Kelly B. Han, et. al., at the Minneapolis Heart Institute.  Results were presented at the 6th Annual SCCT meeting in Denver, Colorado, July 14-16, 2011. Source Study Citation: Han, B. K., Rigsby, C. K., Hlavacek, A., Leipsic, J., Nicol, E. D., Siegel, M. J., … Crean, A. M. (2015). Computed tomography imaging in patients with congenital heart disease part I: Rationale and utility. An expert consensus document of the Society of Cardiovascular Computer Tomography (SCCT). Journal of Cardiovascular Computed Tomography,9(6), 475-492. doi:10.1016/j.jcct.2015.07.004. Also Referenced Here: Barnes, E., & AuntMinnie.com. (2011, July 19). Pediatric CT techniques scan hearts in a fraction of the dose. Retrieved from ttp://www.auntminnie.com/index.aspx?sec=ser&sub=def&pag=dis&ItemID=95899. Patient & scan characteristics Image quality: Quantitative - Qualitative - Diagnostic Accuracy Anesthesia needs Radiation dose 64 Slice MDCTA 28 Scans BSA 0.27 m2 Scan length 17 +/- 3 cm Image acquisition = 5-15 seconds All breath hold sequences Anesthesia   Dual Source MDCTA 32 Scans (18 High Pitch) BSA 0.28 m2 Scan length 16 +/- 3 cm Image acquisition = .25-0.5 seconds All free breathing IV Sedation High Image Noise 44 Moderate Image Noise 32 Low Image Noise 15   Noise Contrast/Noise 64 Slice MDCTA 21 17.2 Dual Source MDCTA - Variable Pitch 42 9.7 Dual Source MDCTA - Fixed 3.4 Pitch 57 8.5          Noise 33, C/N 11                                                                 Noise 23, C/N 18 • Flash scans had increased noise and lower contrast to noise • 3.4 fixed pitch scans had incrementally increased noise and lower contrast to noise • The change in noise and contrast/noise did not affect diagnostic quality of scans   Sharpness Noise Texture Diagnostic Confidence 64 Slice MDCTA 1 1.1 0.2 1 Dual Source MDCTA (Variable Pitch 2.2-3.4) 1.1 1.75 0.95 1.05 Dual Source MDCTA (Fixed 3.4 Pitch) 1.3 1.9 1 1.1 *European guidelines for image quality analysis     #pts DLP 0.014 Age Adj mSv Length 64 Slice MDCTA 29 79 +/- 54 1.1 +/- 0.8 2.6 +/- 1.8 15.2 cm Dual Source MDCTA (Variable Pitch 2.2-3.4) 28 18.4 +/- 19.4 0.69 +/- 0.27 0.69 +/- 0.75 16.1 cm Dual Source MDCTA (Fixed 3.4 Pitch) 14 5.4 +/- 2.5 0.07 +/- 0.04 0.2 +/- 0.07 15.8 cm   #pts DLP 0.014 Age Adj mSv Length 64 Slice MDCTA 29 66 (29-272) 1.1 (0.4-3.8) 2.6 (1.1-10.6) 15.2 cm Dual Source MDCTA Variable Pitch (2.25-3.0) 14 28 (8-50) 0.39 (0.1-0.6) 1.05 (0.3-1.9) 16.2 cm Dual Source MDCTA High Pitch (3.4) 18 5.4 (3-12) 0.07 (.04-.11) 0.2 (0.12-0.17) 15.8 cm 5 fold DLP reduction with 3.4 pitch vs. variable high pitch scan mode     Breath hold sequences •  64 MDCTA - 6-15 seconds of apnea •  DS MDCTA - 0.3-0.5 seconds free breathing All patients requiring a breath hold sequence were under general anesthesia No patient was intubated for the dual source scan, one was intubated for respiratory failure All dual source patients received sedation All patients were sedated for exam Prior study evaluated non-sedated FLASH scans •  20% of flash scans had motion artifact Our patients were undergoing evaluation prior to surgery (3-4 mm shunts) and were cyanotic Sedation may not be needed for some exam indications Arterial Phase DLP 66 Venous Phase DLP 66 Venous + arterial in the same image acquisition Separate venous acquisition CATH DAP 50 (10-19 mSv) Femoral Arterial/Venous access Contrast 33 cc Angiograms x 6 80 minutes of anesthesia 57 minutes of fluoroscopy CTA < 1 mSv PIV Contrast 8 cc Angiogram x 1 One dose of IV sedation CATH Four hours anesthesia 107 minutes of fluoro 19 biplane angiograms 5.7 cc/kg contrast 36 mSv, >50 age adj    - DAP 180 Dual Source CTA Spiral function + flash 2.5 mSv Cath MRI High Pitch Dual Source CT Anesthesia +++ +++  (Avg 55 minutes) +  (Sedation only) Vascular Access Central Venous PIV only PIV only Radiation Exposure +++  (Avg 5 mSv) None ++  (Avg 0.3 mSv) Diagnostic Accuracy +++ +++ +++ Airway Definition - + +++ Hemodynamics + Intervention +++ ++ - Cost +++ ++ + Metal Artifact - +++ - Contrast + (iodinated) - Gadolinium NSF + (iodinated)       EKG Gated, no modulation •  Full radiation entire cardiac cycle Spiral – retrospective •  Full radiation 5-30% R-R interval •  Minimal systolic radiation for entire cardiac cycle – function imaging Sequential – prospective •  Full radiation 5-30% R-R interval •  Minimal systolic radiation for 90% of cardiac cycle – function imaging •  Coronary imaging fast HR EKG gated, 3.4 pitch •  FLASH Anomalous coronary artery Reimplanted coronary artery •  Arterial switch, Ross procedure Kawasaki disease   Sequential (Prospective) •  Heart rate > 60 bpm FLASH •  Heart rate < 60 bpm kVp DLP mSv Helical/Spiral 80 (n=17) 108 +/- 57 1.5 +/- 0.8 100 (n=5) 325 +/- 46 4.55 +/- 0.6 Sequential 80 (n=24) 61 +/- 29 0.85 +/- 0.4 100 (n=5) 142 +/- 50 2.0 +/-0.7 120 (n=1) 471 6.5 FLASH 80 (n=11) 12 +/- 5 0.17 +/- .07 100 (n=5) 69 +/- 17 0.97 +/- 0.24 120 (n=1) 141 2.11 5 Year old female Coronary Baffle, s/p Arterial Switch 1.2 mSv 4 Year old male Single Coronary Artery Orifice • 17 year old male • d-TGA, s/p atrial baffle • Pacemaker placed for sinus pause of 3 seconds on routine holter • V-fib arrest from which he was resuscitated • CTA showed anomalous left coronary artery with intra-arterial course • 13 year old male, s/- arterial switch operation • Chest pain while downhill skiing • Stress echo and nuclear perfusion scan inconclusive • CTA showed left main stenosis at site of reimplantation • 5 year old male - Atypical Kawasaki Disease • 3 months later - chest pain   - Seen by cardiologist, echo normal, CP noncardiac • Continued symptoms   - Took himself out of t-ball, playground games • CTA with beta blockade, anesthesia   - Left main coronary artery subtotal occlusion   - Scan DLP 33     Functional Imaging in Congenital Heart Disease Tetralogy of Fallot (PI and RVEDV) Complex Single Ventricle Anatomy Pacemaker dependent patients Dose reduction   - 1.2 collimator   - Narrow padding   - Minimize scan range (spiral + FLASH)   Spiral Minimal Dose Protocol   - Retrospective, entire cardiac cycle Sequential Step and Shoot   - Prospective, 80% of cardiac cycle Click the Play ► button below for audio & video.   Click the Play ► button below for audio & video.     • Improved visualization of vessel/airway anatomy • Improved visualization in calcified conduits • Improved visualization with stents • Excellent definition of prosthetic AV valve CTA better for airway/vascular definition Relationship of MAPCA/RPA to bronchus Congenital heart disease is the most common congenital anomaly* The past generation has seen a dramatic reduction in mortality for complex CHD The next generation needs to focus on reduced morbidity *Centers for Disease Control and Prevention, December 22, 2015. Congenital Heart Defects (CHDs): Data & Statistics. Retrieved from: http://www.cdc.gov/ncbddd/heartdefects/data.html. Weight range - 1.3 - 175 kg Age range - Infant to 51 year old 1.3 kg, 32 week premature baby Non EKG gated for vascular and airway anatomy   Complex CHD in the US (Single Ventricle/TGA/Truncus/Heterotaxy) Year of Birth Birth Rate/Years Prevalence (1.5/1,000) Survival Rate  (First Year) Survival Rate   (to Yr 2000) 1940-1959 3 million x  20 years 4,500 90,000 20% 18,000 10% 9,000 1960-1979 4 million x  20 years 6,000 120,000 65% 78,000 50% 60,000 1980-1989 4 million x  10 years 6,000 60,000 85% 51,000 80% 48,000 Totals     147,000 117,000 32nd Bethesda Conference: "Care of the Adult with Congential Heart Disease" JACC Vol 37, No5, 2001: 1161-98 Moderate CHD in the US (AV canal/TOF/PAPVR/AS/PS/COA) Year of Birth Birth Rate/Years Prevalence (2.5/1,000) Survival Rate  (First Year) Survival Rate   (to Yr 2000) 1940-1959 3 million x  20 years 7,500 150,000 60% 90,000 55% 82,500 1960-1979 4 million x  20 years 10,000 200,000 70% 140,000 65% 130,000 1980-1989 4 million x  10 years 10,000 100,000 90% 90,000 90% 90,000 Totals     320,000 302,500 32nd Bethesda Conference: "Care of the Adult with Congential Heart Disease" JACC Vol 37, No5, 2001: 1161-98 Summary CTA is becoming the imaging modality of choice for certain applications because of rapid image acquisition and excellent spatial resolution The main obstacle has been radiation exposure, minimized by dual source Flash CT The decrease in image quality from low dose scanning techniques does not affect image quality – which is EXCELLENT   Revenue Implications Today Fee for service - providers and hospital  benefit from expensive procedures (cath brings in 90% more revenue than CTA) Patient Protection and Affordable Care Act 2010 Accountable care organizations Health plans will be given a  set reimbursement to manage a patient population or disease process This will likely decrease the use of subspecialty service providers and testing Section 2706 “pediatric Accountable Care organization Demonstration project” commences Jan 2012, pediatric ACO may be eligible to receive a bonus payment for savings achieved.  Clinical and cost outcomes may be used to compete for patients/contracts. Episode of care compensation Health systems will get a set amount for a set diagnosis/procedure Contrast timing is critical Difficult to predict with shunting lesions Pre injection of contrast can define venous/arterial anatomy in the same scan acquisition 3.4 fixed pitch scan mode is the lowest radiation exposure Reduced image quality but with excellent diagnostic quality To reduce patient dose, each scan must be tailored to the clinical question For certain patients  (pulmonary atresia, neonatal coronary arteries) increased dose may be needed to improve diagnostic accuracy     • 9 month old male • s/p ASO for d-TGA • Heart block post-op • Poor ventricular function • ? Coronary arteries • Referred for transplant evaluation Atrial Baffle for d-TGA

  • CHD
  • coronary heart disease
  • pediatric
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  • definition
  • flash
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