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C. DamitsC. DamitsM. Bieler M. Bieler L. Molvin L. Molvin F. AlkhadraF. AlkhadraW. Earle W. Earle
ECG-Gated Cardiovascular CT – WorkshopLucas Learning Center – Stanford Radiology
June 6, 2009
ECG-Gated Cardiovascular CT – WorkshopLucas Learning Center – Stanford Radiology
June 6, 2009
Stanford Computed Tomography
Stanford CT ScannersStanford CT Scanners
••HOSPITALHOSPITALCT1CT1 GE GE LightSpeedLightSpeed UltraUltra (GE(GE--88))CT3CT3 GEGE LightSpeedLightSpeed 1616 (GE(GE--1616))CT2CT2 GE LightSpeed VCTGE LightSpeed VCT (GE(GE--64)64)
<121 lbs (<55 kg) 60 [70] mL @ 4.0 mL/s121-143 (<65 kg) 65 [75] mL @ 4.5 mL/s143-187 (~75 kg) 75 [85] mL @ 5.0 mL/s187-209 (>85 kg) 85 [95] mL @ 5.5 mL/s>209 lbs (>95 kg) 90 [100]mL @ 6.0 mL/s> XXL 110 mL [120] @ 6.0/s
••Sequential Acquisition as fast as helical Sequential Acquisition as fast as helical ••Substantially less radiation dose (~5mSv) Substantially less radiation dose (~5mSv)
(1/3(1/3rd rd to 1/4to 1/4th th ))••ECG Triggers the scan ~ every other heat beatECG Triggers the scan ~ every other heat beat••Need a low and steady heart rate !! Need a low and steady heart rate !!
(for GE(for GE--VCT: <60; VCT: <60; 5)5)••No dynamic information (no 4D)No dynamic information (no 4D)
GE- VCT 'PADDING'
GE VCT (CT 2)Coronary CTA Image Reconstruction
PROSPECTIVE:• Default: 75% (diastolic)• additional: ~65% - 85% (in 3% intervals, depends on
33 yo man with atypical chest 33 yo man with atypical chest pain (ER)pain (ER)
CORONARY CTA RETROSPECTIVE GATINGSNAPSHOT SEGMENT
••HelicalHelical AcquisitionAcquisition••Low Pitch, redundant scanningLow Pitch, redundant scanning••ECG signal is recorded, does not trigger scanECG signal is recorded, does not trigger scan••Can Reconstruct 10 phases (0%Can Reconstruct 10 phases (0%--90%)90%)••Robust for faster Heart RatesRobust for faster Heart Rates••> 65 bpm> 65 bpm••More Radiation DoseMore Radiation Dose
What was the radiation dose in this case ?Retrospective Gating:-- 120kVp120kVp-- CTDICTDIvolvol: : 51.7 mGy (DLP 879 mGy*cm)51.7 mGy (DLP 879 mGy*cm)~ ~ 14 mSv14 mSv effective doseeffective dose
Patient Preparation
•Patient into Gown, Proper IV access•Oral Beta blocker 1-3 hours before scan •Keep Patient in Quiet environment
••Detector bank Detector bank (for coronaries)(for coronaries)32 rows 32 rows 0.6 mm0.6 mm thickness [19.2 mm]thickness [19.2 mm]but it's still a but it's still a 6464--sliceslice scanner !scanner !
ECG gating:ECG gating:••retrospective, tube current modulation retrospective, tube current modulation ••(no prospective)(no prospective)
Matrix Detector
Hybrid Detector
64 0.625 mm
GE LightSpeed VCTGE LightSpeed VCT
(Siemens Sensation 64)
z
32 0.6 mm
4 1.2 mm 4 1.2 mm
64 64 –– Channel (Slice) CT SystemsChannel (Slice) CT Systems
64 0.6 mm channels
( total detector width 40 mm )
| total detector width 28.8 mm (24x1.2mm) |
Gantry rot: 350ms, z-Resolution ~0.625
Gantry rot: 330ms, z-Resolution ~0.4
| detector width 19.2 mm |
(Siemens Sensation 64)
z32 0.6 mm
4 1.2 mm 4 1.2 mm
Dual Focal Spot: Electromagnetic field deflects electron-beam and thus allows two focal spot positions on tube anode in z-direction (4640 shifts/s)
Gantry rot: 330ms
z-resolution: 0.4 mm
New Straton Tube (580mA)
integrated scanning integrated scanning and injection and injection protocols for 64protocols for 64--channel CTchannel CT
48 y/o business48 y/o business--executive w equivocal stressexecutive w equivocal stress--echo echo (posteroinf. wall(posteroinf. wall--motion abnormality?)motion abnormality?)
100mL CM, 100mL CM, 5mL / s (20s)5mL / s (20s)Delay: Delay: ttCMTCMT+8 +8
(Care(Care--bolus)bolus)
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TroubleshootingTroubleshooting
••Use own judgement to assess patient: Use own judgement to assess patient: weight, age, general health, …. weight, age, general health, …. (general (general protocol applicable? i.e. test bolus vs. tracking?)protocol applicable? i.e. test bolus vs. tracking?)
••PostPost Processing ECG Editing and Sync Processing ECG Editing and Sync AdaptationAdaptation
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THANK YOU ..THANK YOU ..
ECG-Gated Cardiovascular CT – WorkshopLucas Learning Center – Stanford Radiology
June 6, 2009
ECG-Gated Cardiovascular CT – WorkshopLucas Learning Center – Stanford Radiology
June 6, 2009
Stanford Computed Tomography
PRACTICAL CARDIAC CT:
Siemens Definition (DualSource)
PRACTICAL CARDIAC CT:
Siemens Definition (DualSource)
Molvin, LAlkhadra, FMolvin, LMolvin, LAlkhadra, FAlkhadra, F
ECG-Gated Cardiovascular CT – WorkshopLucas Learning Center – Stanford Radiology
June 6, 2009
ECG-Gated Cardiovascular CT – WorkshopLucas Learning Center – Stanford Radiology
June 6, 2009
Stanford Computed Tomography
Siemens Definition (DualSiemens Definition (Dual-- Source)Source)(Stanford Medicine Imaging Center (Stanford Medicine Imaging Center -- SMOC)SMOC)
••Two detector banks Two detector banks (each bank same as Blake)(each bank same as Blake)2 2 32320.6mm [19.8 mm]0.6mm [19.8 mm](2 (2 64 channels)64 channels)
Siemens Definition (DualSiemens Definition (Dual-- Source)Source)(Stanford Medicine Imaging Center (Stanford Medicine Imaging Center -- SMOC)SMOC)
••Two detector banks Two detector banks (each bank same as Blake)(each bank same as Blake)2 2 32320.6mm [19.8 mm]0.6mm [19.8 mm](2 (2 64 channels)64 channels)
Siemens Definition (DualSiemens Definition (Dual-- Source)Source)(Stanford Medicine Imaging Center (Stanford Medicine Imaging Center -- SMOC)SMOC)
••(Prospective gating)(Prospective gating)detector smaller than GEdetector smaller than GE--VCT or VCT or Siemens AS+ (SMOC)Siemens AS+ (SMOC)
••Retrospective ProtocolsRetrospective Protocols-- Small (100kV)Small (100kV)-- MediumMedium-- Large (more mA for less temp.res)Large (more mA for less temp.res)
ECG tube current modulat. ECG tube current modulat. based on heart ratebased on heart rate minmin--dose, 70% of RR onlydose, 70% of RR only minmin--dose, 30dose, 30--70% of RR70% of RR
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••at low heart rate (<65 bpm) reliable still at low heart rate (<65 bpm) reliable still phase during diastolic phase of heart phase during diastolic phase of heart (diastolic: 70% or RR interval (diastolic: 70% or RR interval [65[65--75]75])) full dose only at full dose only at 7070% % of RRof RR intervalinterval
••at higher heart rates (>65 bpm) need end at higher heart rates (>65 bpm) need end systolic (30%RR) through diastolic (70%RR)systolic (30%RR) through diastolic (70%RR) full dose from full dose from 30%30%--70% RR70% RR
downdown--modulate mA to 4% during nonmodulate mA to 4% during non--diagnostic phases of cardiac cycle diagnostic phases of cardiac cycle (minDose)(minDose)
coronaries)coronaries)••need to see aortic valve open, need to see aortic valve open,
closed, and in between (throughout closed, and in between (throughout cardiac cycle)cardiac cycle)
••WHICH GATING TECHNIQUE CAN DO WHICH GATING TECHNIQUE CAN DO THIS ??THIS ??
Siemens Definition AS+Siemens Definition AS+
Setting the Pulsing RangeSetting the Pulsing Range
Points to Consider:Points to Consider:••The range from one RThe range from one R--peak to the next is peak to the next is
100%100%••Diastole usually occurs within 65 to 75%Diastole usually occurs within 65 to 75%••Systole usually occurs within 30 to 40 %Systole usually occurs within 30 to 40 %••A Range of 30 to 70% includes both Diastole A Range of 30 to 70% includes both Diastole
and Systoleand Systole
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ECG Tube Current ModulationECG Tube Current Modulation“Pulsing”“Pulsing”
Gated Chest with Gated Chest with Abd/PelAbd/Pel CTACTA
••Two Scan Ranges:Two Scan Ranges:••Both ranges have 0.3 rotation timeBoth ranges have 0.3 rotation time••Same FOV for bothSame FOV for both••Minimal time gap between rangesMinimal time gap between ranges••Single Single breathholdbreathhold
••Abd/PelAbd/Pel CTA:CTA:••Begin scan 0.7 mm below end of chest Begin scan 0.7 mm below end of chest ••6 second scan time6 second scan time
Siemens Definition AS+Siemens Definition AS+
Gated Chest with A/P CTA Injection Gated Chest with A/P CTA Injection ProtocolProtocolBIPHASIC INJECTIONBIPHASIC INJECTION
PhasePhase IIIIPhasePhase IIBodyBody WeightWeight
30 ml @ 6.030 ml @ 6.0
28 ml @ 5.528 ml @ 5.5
25 ml @ 5.025 ml @ 5.0
23 ml @ 4.523 ml @ 4.5
20 ml @ 4.020 ml @ 4.0
(scan(scan time + 5) x 4.8time + 5) x 4.8> 209 lbs> 209 lbs
(scan(scan time + 5) x 4.4time + 5) x 4.4187 187 -- 209209
(scan(scan time + 5) x 4.0time + 5) x 4.0143 143 -- 187187
(scan(scan time + 5) x 3.6time + 5) x 3.6121 121 -- 143143
(scan(scan time + 5) x 3.2time + 5) x 3.2<121 lbs<121 lbs
Gated Chest with Routine Gated Chest with Routine Abd/PelAbd/Pel
••Two Scan Ranges with the Same FOVTwo Scan Ranges with the Same FOV
••Gated Chest:Gated Chest:••0.3 rotation time0.3 rotation time
••Routine Routine Abd/PelAbd/Pel::••0.5 rotation time 0.5 rotation time ••Begin scan above dome of liverBegin scan above dome of liver••Calculate delay to begin scan 70 seconds Calculate delay to begin scan 70 seconds
following injectionfollowing injection
Siemens Definition AS+Siemens Definition AS+
Gated Chest with Routine A/P Injection ProtocolGated Chest with Routine A/P Injection Protocol