Richard A P Takx

Publications of Richard A P Takx

• Quantification of left and right ventricular function and myocardial mass: Comparison of low-radiation dose 2nd generation dual-source CT and cardiac MRI.

  Authors: Richard A P Takx, Antonio Moscariello, U Joseph Schoepf, J Michael Barraza, John W Nance, Gorka Bastarrika, Marco Das, Mathias Meyer, Joachim E Wildberger, Stefan O Schoenberg, Christian Fink, Thomas Henzler

  European journal of radiology. 08/2011;

  OBJECTIVE: To prospectively evaluate the accuracy of left and right ventricular function and myocardial mass measurements based on a dual-step, low radiation dose protocol with prospectivelyOBJECTIVE: To prospectively evaluate the accuracy of left and right ventricular function and myocardial mass measurements based on a dual-step, low radiation dose protocol with prospectively ECG-triggered 2nd generation dual-source CT (DSCT), using cardiac MRI (cMRI) as the reference standard. MATERIALS AND METHODS: Twenty patients underwent 1.5T cMRI and prospectively ECG-triggered dual-step pulsing cardiac DSCT. This image acquisition mode performs low-radiation (20% tube current) imaging over the majority of the cardiac cycle and applies full radiation only during a single adjustable phase. Full-radiation-phase images were used to assess cardiac morphology, while low-radiation-phase images were used to measure left and right ventricular function and mass. Quantitative CT measurements based on contiguous multiphase short-axis reconstructions from the axial CT data were compared with short-axis SSFP cardiac cine MRI. Contours were manually traced around the ventricular borders for calculation of left and right ventricular end-diastolic volume, end-systolic volume, stroke volume, ejection fraction and myocardial mass for both modalities. Statistical methods included independent t-tests, the Mann-Whitney U test, Pearson correlation statistics, and Bland-Altman analysis. RESULTS: All CT measurements of left and right ventricular function and mass correlated well with those from cMRI: for left/right end-diastolic volume r=0.885/0.801, left/right end-systolic volume r=0.947/0.879, left/right stroke volume r=0.620/0.697, left/right ejection fraction r=0.869/0.751, and left/right myocardial mass r=0.959/0.702. Mean radiation dose was 6.2±1.8mSv. CONCLUSIONS: Prospectively ECG-triggered, dual-step pulsing cardiac DSCT accurately quantifies left and right ventricular function and myocardial mass in comparison with cMRI with substantially lower radiation exposure than reported for traditional retrospective ECG-gating.

• Coronary CT angiography: image quality, diagnostic accuracy, and potential for radiation dose reduction using a novel iterative image reconstruction technique-comparison with traditional filtered back projection.

  Authors: Antonio Moscariello, Richard A P Takx, U Joseph Schoepf, Matthias Renker, Peter L Zwerner, Terrence X O'Brien, Thomas Allmendinger, Sebastian Vogt, Bernhard Schmidt, Giancarlo Savino, Christian Fink, Lorenzo Bonomo, Thomas Henzler

  European radiology. 05/2011; 21(10):2130-8.

  To compare image noise, image quality and diagnostic accuracy of coronary CT angiography (cCTA) using a novel iterative reconstruction algorithm versus traditional filtered back projection (FBP) andTo compare image noise, image quality and diagnostic accuracy of coronary CT angiography (cCTA) using a novel iterative reconstruction algorithm versus traditional filtered back projection (FBP) and to estimate the potential for radiation dose savings. Sixty five consecutive patients (48 men; 59.3 ± 7.7 years) prospectively underwent cCTA and coronary catheter angiography (CCA). Full radiation dose data, using all projections, were reconstructed with FBP. To simulate image acquisition at half the radiation dose, 50% of the projections were discarded from the raw data. The resulting half-dose data were reconstructed with sinogram-affirmed iterative reconstruction (SAFIRE). Full-dose FBP and half-dose iterative reconstructions were compared with regard to image noise and image quality, and their respective accuracy for stenosis detection was compared against CCA. Compared with full-dose FBP, half-dose iterative reconstructions showed significantly (p = 0.001 - p = 0.025) lower image noise and slightly higher image quality. Iterative reconstruction improved the accuracy of stenosis detection compared with FBP (per-patient: accuracy 96.9% vs. 93.8%, sensitivity 100% vs. 100%, specificity 94.6% vs. 89.2%, NPV 100% vs. 100%, PPV 93.3% vs. 87.5%). Iterative reconstruction significantly reduces image noise without loss of diagnostic information and holds the potential for substantial radiation dose reduction from cCTA.

• Radiation dose at coronary CT angiography: second-generation dual-source CT versus single-source 64-MDCT and first-generation dual-source CT.

  Authors: Christian Fink, Radko Krissak, Thomas Henzler, Ursula Lechel, Gunnar Brix, Richard A P Takx, John W Nance, Joseph A Abro, Stefan O Schoenberg, U Joseph Schoepf

  AJR. American journal of roentgenology. 05/2011; 196(5):W550-7.

  The purpose of this study was to assess the radiation doses of different coronary CTA (CTA) protocols: second-generation dual-source 128-MDCT, first-generation dual-source 64-MDCT, and single-sourceThe purpose of this study was to assess the radiation doses of different coronary CTA (CTA) protocols: second-generation dual-source 128-MDCT, first-generation dual-source 64-MDCT, and single-source 64-MDCT. Thermoluminescent dosimetry was used to determine scanner-specific dose coefficients for standard coronary CTA of an anthropomorphic phantom. These coefficients were used to estimate the effective doses (EDs) of retrospectively gated, prospectively triggered, and prospectively triggered high pitch coronary CTA performed at 100 and 120 kV. The coronary CTA protocols used in imaging of 43 patients undergoing dual-source 128-MDCT were analyzed for ED, image quality, and signal-to-noise ratio. Regardless of coronary CTA protocol and CT system, imaging at 100 kV lowered the ED 40-50%. In retrospectively gated 120-kV coronary CTA, the ED ranged from 5.7 to 10.7 mSv and was approximately 50% lower with single-source 64-MDCT than with either DSCT protocol. In prospectively triggered 120-kV coronary CTA, the ED ranged from 3.8 to 4.0 mSv. The lowest ED of all protocols (1.3 mSv) was observed in prospectively triggered high-pitch 100-kV coronary CTA performed with dual-source 128-MDCT. Patient measurements showed similar dose reductions for prospective triggering and low voltage settings without an influence on signal-to-noise ratio or image quality. A combination of prospective triggering with low voltage settings is an effective measure for reducing the ED of coronary CTA to values of 2-4 mSv independent of scanner system. Further dose reduction to nearly 1 mSv can be achieved with high-pitch prospectively triggered coronary CTA.