CT Scan Site TrainingYear 20 Exam J. Jeffrey Carr, MD, MSCE April 2005 Wake Forest University School of Medicine Departments of Radiology & Public Health Sciences
Objectives • Learn about the study. • Learn and understand the CT scanning protocol. • Opportunity ask/submit questions to the CTRC at Wake Forest!!!! • This presentation is designed to provide the needed information and supplement the detailed CT manual of operation which is located in the 3-ring binder provided to each CT scan site.
What is CARDIA? • CARDIA is studying how heart disease starts in young adults to develop prevention strategies for heart attacks and strokes. • Calcified Atherosclerotic Coronary Plaque (CACp) indicates: • Subclinical disease • Higher risk of heart attacks and CVD deaths • We are doing the Cardiac CT exams so we can determine how calcified plaque has changed since the year 15 exam.
How is the study organized? • 4 field centers across the country • Birmingham, Chicago, Minnesota, San Francisco • CT Reading Center • Wake Forest U. Health SciencesWinston-Salem, NC • Data Coordinating Center • Univ. of Alabama-Birmingham • Other components: laboratory, ultrasound, genetics, etc… across the country
CT exams will be sent to WFU using a DICOM send from the CT site Chicago CT CT Reading Center will send the results to the data coordinating center CARDIA Coordinating Center UAB WFUCT Reading Center UAB CT UMN CT CT exams will be performed at the 4 Field Centers ~ 3,200 participants San Francisco CT
Let’s Learn the CT Protocol! • Phantom Quality Control (QC) procedures • Phantom placement for scanning • ECG stuff • CT scanning stuff • Sending the images to us at Wake Forest
Scales Require Calibration - So do CT Scanners! • We all know that you can “adjust” the zero value of a scale to weight “heavy” or preferably “light” • CT Scanners can have the CT number value of water (0 H.U.) adjusted to be “brighter” or “darker”
Centertorso plug Torso phantom (oval) QCT Calibration phantom (rectangle) 4 tubes containing:0, 50, 100 & 200 mg/cc Calcium CT Phantom – PartsSetup for Quality Control scans Other parts • Blue cushion with insert for QCT phantom • Gel bag (goes b/t patient and phantom) • Made by Image Analysis
Why are we scanning the Torso & QCT phantoms? • To make sure your CT scanner’s ability to measure CT numbers (HU) is correct & not changing over time • Participant scanning • Allow adjustment so that scores will be as similar as possible across sites using different CT scanners • Objective measure of “noise” in scan
QC Scan Procedure – 1st & 15th of each month • Place calibration phantom on CT couch • Mark position with tape (optional) • Place torso phantom in middle of calibration phantom • Mark position with tape • Align torso phantom so “center plug” is at isocenter • Record table height • Mark positioning with tape so you can quickly set it up each time in the same position.
QA Scanner Setup This should be at isocenter using your laser alignment system
QA procedure – twice a month1st & 15th of each month • Perform scan of Torso & QCT phantom twice every month • Use the CARDIA protocol saved in the CT scanner • Scouts • Axial scans (cardiac series- ECG gating off or simulated) • Send images to WFU Reading Center just like a participants scan • Measure regions-of-interest (roi’s) on scanner • 4 along bottom + 1 center plug • Record on QA sheet in your CARDIA CT notebook • Fax to Reading Center (fax 336.716.4340)
Example CT System data entry for QCT Torso Phantom: Name: QC UAB ID number: UABYYMMDD
When the phantom is scanned on April 1st 2005 at UAB: Name: QC UAB ID number: UAB050401 (or UI050401, UMN050401, WC050401)
When the phantom is scanned on April 15th 2005 at UAB: Name: QC UAB ID number: UAB050415
Preparing for Participants • Scan feet or head first - but be consistent at your site • Place QCT phantom in blue holder (optional) • Place gel bag over plastic QCT phantom(optional) • Position participant so that phantom is underneath the heart
CT Scan of heart with QCT phantom QCT phantom with 4 tubes
Entering Participant Information Into the CT Scanner • We are entrusted to maintain the confidentiality of the participant for now and in the future. • For the results to be meaningful we have to positively identify each person. • We will identify participants by codes assigned by the coordinating center – two codes are used: • Study ID number (a.k.a. SID) • Pseudonym (alpha code)
Example CT System data entry demographic fields: Name: ABCDE160 ID number: 12345 Date of Birth: 03 MAR 1947 Weight: 160 lbs Technologist: 51 Referring Physician: Marcus Welby Indication: CARDIA y20
How do you know what to type in to the CT scanner? • Each participant is consented & screened by the clinic prior to the CT exam • Consent form is sign • Women are check for potential pregnancy • The participant is scheduled for the CT exam • You will be sent a Cover Sheet & “CT scan completion Form 76” (A copy of this form is in the appendix of the MOO)
CT scan completion Form 76 Acrostic to replace real name Study ID DOB &Gender Weight
CT scan completion Form 76 CT Tech ID Let us know any problems!
CT Scanning overview • Scouts - Thoracic • Frontal • Lateral (optional) • Heart 1 w/ ECG gating • Heart 2 w/ ECG gating
Participant Preparation • Instruction prior to scan (tell clinic staff) • No caffeine products before scan • Will have to change into gown • Have clinic fax / deliver participant CT scheduling and CT completion forms prior to study. • Immediate pre-scan • Change into hospital gown or loose clothing • Easier if opens in front (placing ECG leads) • Safety checks which are routine at your institution (i.e. LMP, pregnancy etc..)
Breathholding • Script = • “Take a deep breath in <pause> • blow it all the way out <pause> • Take a deep breath in <pause> • blow it all the way out <pause> • Take a deep breath in and hold it. • ******Scan 20-40 seconds***** • Breath and relax”
Cardiac CT scan is during Inspiration • Greeting participant • Make sure they are the right person and they are there for the “CARDIA CT Scan” • Prepare participant by indicating there will be several times they are asked to hold their breath – some short (the scouts) and some longer • Instruction & observation during scout images • Watch how they do – provide further instructions • Heart scan 1 • Rest period (2 minutes) check 1st study • Heart scan 2
Breathholding – why so long? • End inspiration. • Pushes liver down. • Valsalva lowers heart rate. • Easier to do than end expiration. • Blowing off C02 (hyperventilation) makes it easier! • Must do same breathing instructions for scout and heart scans. • Consider pre-recorded voice if available. • Have them do the best they can – breath out slowly if they cannot hold the entire time.
ECG – Lead placement • Arms overhead • Reposition leads if necessary • Make sure amplitude (i.e. size) is OK per your CT scanner instructions
ECG positioning • Manufacturer or local recommendations • “White is Right – Smoke (black) over Fire (red) (left side) • Must have identifiable R-wave for gating • Reposition leads, check connections • Prospective triggering/gating mode-late diastole phase • EBCT @ 80% (636-736) • Siemens at 50%-TBD, (428, 755) • GE at 70% ( 437-763)
Check Thorax Scouts for: • Participant centered? • Phantom centered and behind spine? • Prescribe cardiac scan • Carina thru inferior aspect of the heart • Lateral scout may be useful to prescribe AP centering of reconstructions – be sure to include the entire QCT phantom in the 35 cm FOV !!!!!!!!
End Start Start End QCT Phantomunderneath participant QCT Phantomunderneath participant Scouts – QCT Position & Landmarks for Prescribing Scans
CT Technique – Siemens Sensation 16 • Axial mode “CaScSeq” • Kernel B30F • cardiac gating/triggering per CT system specific protocol (50%) • KVp 120, 6 slices by 3 mm • 0.4 sec gantry rotation, partial scan reconstruction - “Quick Scan”
CT Technique – MDCT Weight determines the mAs for the cardiac scans !!!!! The participant is weighed at the clinic and the weight is printed on CT completion form 76
Weight and mAs If the weight is less than 220 lbsSet mAs = Standard If the weight is 220 lbs or greaterSet mAs = Standard*1.25%
Cardiac Scan 1 • Check coverage • Check centering • Check ECG • Confirm correct technique (KV, mAs, slice thickness 3 mm or 2.5 mm) • Fix anything that is sub optimal • Go to cardiac scan 2
Why Two Scans of the Heart? • Best estimate is the average of the both • If there is a problem with 1 scan - we will use the information from the other • If there is a problem with – note in the comment field on the scan completion form 76 • Don’t do a third scan!!! This will result in increase radiation exposure to the participant!!!
Reconstruct Thin slices • GE MDCT - Retrorecon • 1.25 mm slice thickness at 26 cm dfov • 5 mm slice thickness at 50 cm dfov • Siemens - Recon between • 1-1.5 mm at 26 cm dfov • 5 mm slice thickness at 50 cm dfov • GE Imatron - • no thin slice recons • 5 mm slice at a 50 cm dfov
Internet Transfer of CT scans • Scans will be transferred to the CT reading center over the Internet • DICOM send from a computer workstation or the scanner depending upon your networks configurations • CT center will coordinate with your site • Contact Josh Tan or Chris O’Rourke • email@example.com • firstname.lastname@example.org 336 716 8909 • Main: 336.716.7234 • Send Entire Exam • Heart 1 • Heart 2 • Additional reconstructions
DICOM Networking to WFU • Your CT scanner or workstation should already be configured to send to our Reading Center • It is recommended that you configure in the protocol to automatically send to WFU and anywhere else you want the exam to go. • Alternatively send it to us as soon as possible • Fax the Scan Completion form to the CT Reading Center (fax no. 336-716-4340) and to your local clinic • Store in Notebook (3 ring binder)
We are here to help you and answer any questions • Call us at: • Let the Reading Center know your concerns!!! • We will try very hard to make adjustment which will make your life easier and listen to your suggestions
“Homework” • Copy of CT system’s last full calibration by field engineer of physicist and send to us • Verify reconstruction thickness • Program “CARDIA Y20” protocol into CT scanner