Adaptive Sampling of k-Space in Magnetic Resonance for Rapid Pathology Prediction

TL;DR

This paper introduces ASMR, an adaptive k-space sampling method that significantly reduces MRI scan time while maintaining high accuracy in disease detection, outperforming existing sampling techniques.

Contribution

The work presents a novel adaptive sampling policy for MRI that directly optimizes for pathology detection, reducing scan time without sacrificing diagnostic performance.

Findings

ASMR achieves within 2% of full-sample classifier performance using only 8% of k-space.

Outperforms prior methods like EMRT, LOUPE, and DPS in pathology classification tasks.

Effective across multiple organs including Knee, Brain, and Prostate.

Abstract

Magnetic Resonance (MR) imaging, despite its proven diagnostic utility, remains an inaccessible imaging modality for disease surveillance at the population level. A major factor rendering MR inaccessible is lengthy scan times. An MR scanner collects measurements associated with the underlying anatomy in the Fourier space, also known as the k-space. Creating a high-fidelity image requires collecting large quantities of such measurements, increasing the scan time. Traditionally to accelerate an MR scan, image reconstruction from under-sampled k-space data is the method of choice. However, recent works show the feasibility of bypassing image reconstruction and directly learning to detect disease directly from a sparser learned subset of the k-space measurements. In this work, we propose Adaptive Sampling for MR (ASMR), a sampling method that learns an adaptive policy to sequentially select k-space samples to optimize for target disease detection. On 6 out of 8 pathology classification tasks spanning the Knee, Brain, and Prostate MR scans, ASMR reaches within 2% of the performance of a fully sampled classifier while using only 8% of the k-space, as well as outperforming prior state-of-the-art work in k-space sampling such as EMRT, LOUPE, and DPS.