Wide-Detector CT for TAVR Planning:

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1 Wide-Detector CT for TAVR Planning: Impact on Iodine Dose, Radiation Dose, and Image Quality SCBTMR 2015 Annual Course Thursday, October 8 William P. Shuman MD FSCBTMR Department of Radiology University of Washington, Seattle

2 Disclosures WPS administers research grants from GE Healthcare which support clinical CT research

3 Wide Detector Technology 16 cm detector with focally aligned detector modules Post patient collimator

4 Detector Technology 16 cm Wide-Detector

5 Mitigating Wide Coverage Issues cone beam Focally aligned detector modules designed for cone beam geometry VHD reconstruction reduces Hounsfield unit uniformity variation across 160 mm z-axis coverage

6 Post-Patient Collimator

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8 Wide Detector Technology Axial step-and-shoot technique with 16 cm slabs No helical artifacts Stitching reconstruction of anatomical structures to control or eliminate step-off artifacts

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10 Wide Detector Technology Faster rotation time (0.28 sec) Better ACTM and auto-kvp Partial model-based iterative reconstruction (ASIR-V)

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13 TAVR Transcutaneous Aortic Valve Replacement Patients with severe calcific AS and AI who are not operative candidates due to co-morbidities Femoral, transapical,or trans axillary approaches Implanted ring/valve overlies native valve, displacing leaflets

14 TAVR Transcutaneous Aortic Valve Replacement Patients with severe calcific AS and AI who are not operative candidates due to co-morbidities Femoral, transapical, or trans axillary approaches Implanted ring/valve overlies native valve, displacing leaflets

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25 Background Wide-detector CT is faster, enabling scanning of chestabdomen-pelvis as a single acquisition with one bolus of contrast Wide Detector CT also has new radiation dose reduction features

26 Purpose To compare an older clinical standard TAVR planning protocl on a 4 cm detector CT with a new clinical standard protocol on a 16 cm wide-detector CT for: Iodine dose utilized Radiation dose Subjective and objective image quality

27 Methods IRB approved retrospective study December 2014 January 2015 Large urban academic medical center

28 Methods Patients Reviewed 36 consecutive patients scanned for TAVR planning on wide-detector Carefully match for gender, age, and BMI to 36 patients previously scanned for TAVR planning on 4 cm detector

29 Methods Wide-detector Protocol 1 Continuous scanning of ECG gate chest and non-gated abdomen-pelvis cm slabs in the chest, cm slabs in the abdomen-pelvis Scan duration: seconds

30 Methods Wide-detector Protocol 1 NI = 30 for chest, 18 for abd/pel, kvp = rotation 0.28 or 0.35 sec Contrast: cc at 3-5 cc/sec base on Z axis Injection duration 5 sec longer than scan duration Reconstructed with ASIR-V 70%

31 Methods Standard 4cm Detector Protocol 2 Separate acquisitions of the chest (helical ECG gated) and of the abdomen/pelvis (helical non-gated) 30 second pause between the two acquisitions Scan duration: 47 seconds

32 Methods Standard 4 cm detector Protocol 2 NI = 50 for chest, 30 for abd/pel, kvp = rotation time = 0.35 or 0.5 sec Contrast: cc at 4 cc/sec Reconstructed with 70% ASIR

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34 Methods Images reconstructed: Axial 2.5 mm of the chest, abdomen, and pelvis mm double oblique of aortic valve mm magnified - with measurements of annulus, leaflet length, and coronary ostia distances.

35 Protocol 1 Protocol 2 A B C D

36 Methods Image Evaluation by 2 independent Reviewers (subjective 4 point Likert scales): aortic enhancement overall image quality for non-vascular structures image quality of aortic annulus

37 Methods Objective Measurements: HU vascular attenuation at 8 locations in aorta and iliofemorals Psoas HU and Image Noise in air Calculated SNR, CNR

38 Results Demographics No difference in age, gender, or BMI

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40 Results Wide detector scanner acquisition time averaged 32 seconds less than 4 cm detector scanner

41 Results Wide detector scanner iodine dose averaged 33% less than standard 4 cm detector scanner

42 Results Wide detector scanner radiation dose in SSDE was 28 45% lower than standard 4cm detector scanner 53% reduction in total exam DLP with no statistical difference in scan range (mm)

43 Results Wide detector scanner mean vascular HU attenuation was statistically greater overall and was greater at each of the 8 measurement levels than standard 4cm detector scanner

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45 Results Image noise, SNR, and CNR were the same for both scanners

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47 Results Subjective scores for vascular enhancement and overall image quality were the same Subjective image quality scores for the magnified aortic root measurement images were statistically better for the wide detector scanner

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49 Discussion Wide detector scanner features: Axial step-and-shoot technique No helical artifacts Whole heart in one beat Effective Stitching = no step-off artifacts

50 Discussion Wide detector scanner features: Focally aligned detector modules Less cone beam artifact Better dose efficiency

51 Discussion Wide detector scanner features: Three dimensional post-patient collimator Eliminates scatter radiation Less image noise

52 Discussion Wide detector scanner features: Faster rotation time 0.28 sec Better temporal resolution

53 Discussion Wide detector scanner features: Faster overall scan acquisition time Transition from ECG gated to ungated shortened from 30 secs. down to 5 secs. Enables single contrast bolus technique

54 Discussion Wide detector scanner features: ASIR-V reconstruction Partial model based iterative recon. 30% lower noise than statistical iterative recon Supports reduced radiation technique Similar reconstruction time

55 Conclusion Wide detector axial step-and-shoot TAVR planning CT resulted in: Greater vascular attenuation Similar subjective and objective image noise Lower radiation dose Less iodine dose

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