MRDT-GAN: generative adversarial network with multi-scale residual dense transformer generator for low-dose CT denoising

Abstract Objective. Low-dose computed tomography (LDCT) reduces radiation exposure but introduces noise and artifacts that degrade diagnostic quality. Existing deep learning–based denoising methods still face challenges such as over-smoothing, loss of fine structures, and uneven contrast. This study aims to develop an LDCT denoising framework that enhances noise suppression while preserving anatomical details and structural fidelity. Approach. We propose a Multi-Scale Residual Dense Transformer Generative Adversarial Network (MRDT-GAN). In the generator, we adopt the Multi-Scale Residual Dense Transformer Block (MRDTB) as the core unit, which introduces multi-scale strategy into residual dense network to reduce over-smoothing and preserve fine details, and also Patching Transformer Block (PTB) to capture long-range dependencies, mitigating distortions caused by localized receptive fields in CNN-based approaches. A Hybrid Attention Module (HAM) is also introduced in the generator to process spatial, frequency, and contrast information, enabling the network to focus on critical regions for noise suppression, improve contrast uniformity, and maintain texture consistency. In the discriminator, we adversarially explore differences on global, pixel, and also sub-scale between denoised LDCT and normal dose CT to better capture structural variations, reduce local noise and distortions, and ensure more realistic texture reconstruction while minimizing artifacts. Main results. We validate MRDT-GAN on both the NIH-AAPM-Mayo Clinic LDCT dataset and a real-world dataset. Experimental results indicate that MRDT-GAN achieves superior denoising performance compared with existing methods, effectively preserves details, enhances visual quality, and achieves a better balance between noise suppression and structural integrity. Significance. MRDT-GAN provides an effective and generalizable LDCT denoising solution that balances noise reduction with fine-detail preservation. By integrating multi-scale residual dense Transformer modeling, hybrid attention mechanisms, and multi-difference adversarial learning, the framework offers improved clinical applicability and supports high-quality image reconstruction for downstream diagnostic tasks.