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arXiv 2406.16074eess.IVcs.CV

CAVM:用于对比增强脑肿瘤MRI合成的条件自回归视觉模型

CAVM: Conditional Autoregressive Vision Model for Contrast-Enhanced Brain Tumor MRI Synthesis

School of Medical Technology, Beijing Institute of Technology(北京理工大学医学技术学院);School of Integrated Circuits and Electronics, Beijing Institute of Technology(北京理工大学集成电路与电子学院)

Lujun Gui, Chuyang Ye, Tianyi Yan

AI总结:

针对钆基对比剂成本高、有副作用且现有深度学习合成对比增强脑肿瘤MRI质量不足的问题,提出CAVM模型,通过逐步提升剂量的自回归策略结合分解分词与掩码注意力,实现高质量虚拟对比增强MRI合成。

摘要:

对比增强磁共振成像(MRI)在脑肿瘤分割与分析流程中至关重要。钆基对比剂作为最常用的对比剂,价格昂贵且可能存在潜在副作用,因此无需实际使用对比剂即可获取对比增强脑肿瘤MRI扫描图像的需求十分迫切。现有深度学习方法已被用于从非增强图像合成虚拟对比增强MRI扫描,但由于该合成问题本质上是不适定的,这些方法难以生成高质量结果。本研究提出条件自回归视觉模型(Conditional Autoregressive Vision Model, CAVM),以改进脑肿瘤对比增强MRI的合成效果。由于图像强度的增强程度随对比剂剂量升高而增加,我们假设合成低剂量虚拟图像的难度更低,此时对比增强图像与非增强图像之间的差异更小。因此,CAVM逐步提升对比剂剂量,基于先前的低剂量图像生成更高剂量的图像,直至达到最终所需剂量。受剂量逐步提升过程与自然语言处理中思维链(Chain-of-Thought)方法相似性的启发,CAVM采用结合分解分词器与解码器的自回归策略。具体而言,分词器用于获取更紧凑的图像表示以提升计算效率,并将图像分解为剂量相关token与剂量无关token。随后,研究设计了掩码自注意力机制用于自回归过程,基于剂量相关token逐步提升虚拟图像的剂量。最后,将对应所需剂量的更新后剂量相关token与剂量无关token共同解码,生成最终的对比增强MRI。

英文摘要:

Contrast-enhanced magnetic resonance imaging (MRI) is pivotal in the pipeline of brain tumor segmentation and analysis. Gadolinium-based contrast agents, as the most commonly used contrast agents, are expensive and may have potential side effects, and it is desired to obtain contrast-enhanced brain tumor MRI scans without the actual use of contrast agents. Deep learning methods have been applied to synthesize virtual contrast-enhanced MRI scans from non-contrast images. However, as this synthesis problem is inherently ill-posed, these methods fall short in producing high-quality results. In this work, we propose Conditional Autoregressive Vision Model (CAVM) for improving the synthesis of contrast-enhanced brain tumor MRI. As the enhancement of image intensity grows with a higher dose of contrast agents, we assume that it is less challenging to synthesize a virtual image with a lower dose, where the difference between the contrast-enhanced and non-contrast images is smaller. Thus, CAVM gradually increases the contrast agent dosage and produces higher-dose images based on previous lower-dose ones until the final desired dose is achieved. Inspired by the resemblance between the gradual dose increase and the Chain-of-Thought approach in natural language processing, CAVM uses an autoregressive strategy with a decomposition tokenizer and a decoder. Specifically, the tokenizer is applied to obtain a more compact image representation for computational efficiency, and it decomposes the image into dose-variant and dose-invariant tokens. Then, a masked self-attention mechanism is developed for autoregression that gradually increases the dose of the virtual image based on the dose-variant tokens. Finally, the updated dose-variant tokens corresponding to the desired dose are decoded together with dose-invariant tokens to produce the final contrast-enhanced MRI.

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