A dual-domain cone beam computed tomography reconstruction framework with improved differentiable domain transform for cone-angle artifact correction

doi:10.12122/j.issn.1673-4254.2024.06.21

Abstract

Abstract:

Objective We propose a dual-domain cone beam computed tomography (CBCT) reconstruction framework DualCBR-Net based on improved differentiable domain transform for cone-angle artifact correction. Methods The proposed CBCT dual-domain reconstruction framework DualCBR-Net consists of 3 individual modules: projection preprocessing, differentiable domain transform, and image post-processing. The projection preprocessing module first extends the original projection data in the row direction to ensure full coverage of the scanned object by X-ray. The differentiable domain transform introduces the FDK reconstruction and forward projection operators to complete the forward and gradient backpropagation processes, where the geometric parameters correspond to the extended data dimension to provide crucial prior information in the forward pass of the network and ensure the accuracy in the gradient backpropagation, thus enabling precise learning of cone-beam region data. The image post-processing module further fine-tunes the domain-transformed image to remove residual artifacts and noises. Results The results of validation experiments conducted on Mayo's public chest dataset showed that the proposed DualCBR-Net framework was superior to other comparison methods in terms of artifact removal and structural detail preservation. Compared with the latest methods, the DualCBR-Net framework improved the PSNR and SSIM by 0.6479 and 0.0074, respectively. Conclusion The proposed DualCBR-Net framework for cone-angle artifact correction allows effective joint training of the CBCT dual-domain network and is especially effective for large cone-angle region.

Key words: cone beam computed tomography, cone-angle artifact, differentiable domain transform

Shengwang PENG, Yongbo WANG, Zhaoying BIAN, Jianhua MA, Jing HUANG. A dual-domain cone beam computed tomography reconstruction framework with improved differentiable domain transform for cone-angle artifact correction[J]. Journal of Southern Medical University, 2024, 44(6): 1188-1197.

Figures/Tables 11

Fig.1 Initial and extended geometry of CBCT. A: Initial geometry of CBCT. φ: cone-angle. Pink and green zones represent the effective volume and missing volume, respectively. B: Extended geometry of CBCT. M: Number of detector rows; m: Extended number of detector rows in each ends; Z: Number of reconstructed slices; z: Number of extended reconstructed slices in both ends.

Fig.2 Overall architecture of the proposed DualCBR-Net. IDT represents the improved differentiable domain transform module.

Fig.3 Results of expanded projection data using different methods at two different views. The blue dashed lines at the top and bottom represent the 2 m rows of the projected data. The contrast regions are indicated by red arrows.

Tab.1 Quantitative comparison results of expanded projection data for different methods (Mean±SD)

Methods	PSNR	SSIM	RMSE
WCF	28.8022±2.5542	0.9650±0.0045	9.6567±2.7958
WCF-PRNet	40.1381±0.7931	0.9818±0.0023	2.5204±0.2356
PE-PRNet	45.9624±0.3935	0.9870±0.0013	1.2849±0.0582

Fig.4 Ground truth image and reconstruction results with different methods in the axial plane. The dashed blue boxes highlight the enlarged region of interest. The display range is (-1150, 350) Hu. The contrast regions are indicated by red arrows and the artifact regions by yellow arrows.

Fig.5 Ground truth image and reconstruction results with different methods in the coronal plane. The white curves at the top and bottom of the image indicate the regions affected by cone-angle artifacts. The display range is (-1150, 350) Hu. The contrast regions are indicated by red arrows and the artifact regions by yellow arrows.

Fig.6 Ground truth image and reconstruction results with different methods in the sagittal plane. The white curves at the top and bottom of the image indicatethe regions affected by cone-angle artifacts. The display range is (-1150, 350) Hu. The contrast regions are indicated by red arrows and the artifact regions by yellow arrows.

Fig.7 Profile comparison between the ground truth image and different methods. The horizontal profile is indicated by green line in Fig.5.

Tab.2 Quantitative comparison results of cone-angle artifact removal performance for different methods (Mean±SD)

Methods	PSNR	SSIM	RMSE
FDK	31.7062±7.1703	0.8049±0.1469	10.6439±14.0262
CWFDK	33.7062±1.8418	0.8417±0.0323	5.3882±1.2773
WCF	34.7489±1.7365	0.8675±0.0284	4.7616±0.9647
FDK-Net	35.4597±2.0657	0.8769±0.0286	4.4279±1.1314
DBP-Net	30.7556±1.6946	0.8471±0.0236	7.5277±1.3869
GADR-Net	36.3036±1.6391	0.8871±0.0254	3.9708±0.7276
DualCBR-Net	36.9515±1.6658	0.8945±0.0280	3.6882±0.6994

Fig.8 Validation results of the projection expansion strategy. The upper and lower rows are coronal plane and sagittal plane reconstruction images, respectively. The white curves at the top and bottom of the image indicated the regions affected by cone-angle artifacts. Projection extension strategy is not used for images in the "w/o PE" column. The display range was (-1150, 350) Hu. The contrast areas are indicated by red arrows.

Tab.3 Quantitative comparison results in ablation studies (Mean±SD)

Methods	PSNR	SSIM	RMSE
PENet	35.0010±1.2653	0.8523±0.0284	4.6987±0.6780
DualCBR-Net (w/o IRNet)	35.2349±1.1689	0.8695±0.0281	4.3842±0.6548
DualCBR-Net (w/o AM)	36.4023±1.5633	0.8825±0.0356	3.9054±0.5966
DualCBR-Net (4 slices)	36.5393±1.5784	0.8890±0.0325	3.8529±0.6498
DualCBR-Net (6 slices)	36.6722±1.6950	0.8901±0.0278	3.7021±0.6447
DualCBR-Net (10 slices)	36.2839±1.7725	0.8760±0.0252	4.0133±0.6561
DualCBR-Net (w/o $L s s i m$ )	36.4529±1.5612	0.8796±0.0265	3.9255±0.6846
DualCBR-Net	36.9515±1.6658	0.8945±0.0280	3.6882±0.6994

Tab.3 Quantitative comparison results in ablation studies (Mean±SD)

Methods	PSNR	SSIM	RMSE
PENet	35.0010±1.2653	0.8523±0.0284	4.6987±0.6780
DualCBR-Net (w/o IRNet)	35.2349±1.1689	0.8695±0.0281	4.3842±0.6548
DualCBR-Net (w/o AM)	36.4023±1.5633	0.8825±0.0356	3.9054±0.5966
DualCBR-Net (4 slices)	36.5393±1.5784	0.8890±0.0325	3.8529±0.6498
DualCBR-Net (6 slices)	36.6722±1.6950	0.8901±0.0278	3.7021±0.6447
DualCBR-Net (10 slices)	36.2839±1.7725	0.8760±0.0252	4.0133±0.6561
DualCBR-Net (w/o $L s s i m$ )	36.4529±1.5612	0.8796±0.0265	3.9255±0.6846
DualCBR-Net	36.9515±1.6658	0.8945±0.0280	3.6882±0.6994

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