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A Projection Quality-Driven Tube Current Modulation Method in Cone-Beam CT

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K Men

K Men, J Dai* , National Cancer Center / Cancer Hospital, Chinese Academy of Medical Scien and Peking Union Medical College, Beijing,China


SU-F-201-5 (Sunday, July 30, 2017) 2:05 PM - 3:00 PM Room: 201

Purpose: To develop a projection quality-driven tube current modulation (P-TCM) method in cone-beam CT (CBCT) based on the prior attenuation information obtained by the planning CT, and then evaluate its effect in imaging dose reduction.

Methods: With a serial of tube current-exposure time product (mAs) setting and different attenuation (μ), a set of CBCT projections were acquired using the X-ray volumetric imaging (XVI) system on a Versa HD (Elekta, Stockholm, Sweden) system. The two-dimensional contrast-to-noise ratio (CNR2D) was analyzed for each projection to create a look-up table related mAs vs. (CNR2D,μ). Before patient underwent CBCT scan, the max attenuation (μ_max) of different projection angles (θ) was estimated according to the planning CT images. Then a desired CNR2D value was selected and the mAs setting at θ was calculated with the look-up table mAs vs. (CNR2D,μ_max). The 3D CBCT images were reconstructed using the projections acquired with the selected mAs. Performance of the proposed method was analyzed using a Catphan 503 phantom with an oval body annulus and a pelvis phantom.

Results: CBCT images of Catphan 503 reconstructed using the P-TCM method have a similar image quality with the conventional CBCT, however, the P-TCM method could reduce the imaging dose by ≈ 16%-33% to achieve an equivalent CNR value. For the pelvis phantom, the structural similarity (SSIM) index is 0.992 with a dose reduction of ≈ 39.7% for the P-TCM method.

Conclusion: CBCT with the P-TCM method could reduce the additional dose to the patient while not degrading the image quality. It is benefit to apply the proposed method to the frequently used CBCT in radiotherapy.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by the National Natural Science Foundation of China [grant numbers 11605291, 11475261] and the National Key Projects of Research and Development of China [grant number 2016YFC0904600]. The authors report no conflicts of interest with this study.

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