Abstract
PurposeIn radiation treatment planning for thoracic and abdominal tumors, 4D‐MRI has shown promise in respiratory motion characterization with improved soft‐tissue contrast compared to clinical standard, 4D computed tomography (4D‐CT). This study aimed to further improve vessel–tissue contrast and overall image quality in 3D radial sampling‐based 4D‐MRI using a slab‐selective (SS) excitation approach.MethodsThe technique was implemented in a 3D radial sampling with self‐gating‐based k‐space sorting sequence. The SS excitation approach was compared to a non‐selective (NS) approach in six cancer patients and two healthy volunteers at 3T. Improvements in vessel–tissue contrast ratio (CR) and vessel signal‐to‐noise ratio (SNR) were analyzed in five of the eight subjects. Image quality was visually assessed in all subjects on a 4‐point scale (0: poor; 3: excellent). Tumor (patients) and pancreas (healthy) motion trajectories were compared between the two imaging approaches.ResultsCompared with NS‐4D‐MRI, SS‐4D‐MRI significantly improved the overall vessel–tissue CR (2.60 ± 3.97 vs. 1.03 ± 1.44, P < 0.05), SNR (63.33 ± 38.45 vs. 35.74 ± 28.59, P < 0.05), and image quality score (2.6 ± 0.5 vs. 1.4 ± 0.5, P = 0.02). Motion trajectories from the two approaches exhibited strong correlation in the superior–inferior (0.96 ± 0.06), but weaker in the anterior–posterior (0.78 ± 0.24) and medial–lateral directions (0.46 ± 0.44).ConclusionsThe proposed 4D‐MRI with slab‐selectively excited 3D radial sampling allows for improved blood SNR, vessel–tissue CR, and image quality.
Highlights
We aimed to develop an improved vessel-enhanced method at 3.0 T using a slab-selective 3D radial sampling-based gradient recalled echo (GRE) acquisition approach
Large and small (SMA) blood vessels are well delineated in the SS-4DMRI approach compared to the NS-4D-magnetic resonance imaging (MRI) approach
Significantly (P < 0.05) higher signal-to-noise ratio (SNR) was observed in the SS-4D-MRI (63.33 Æ 38.45) method compared to NS-4D-MRI (35.74 Æ 28.59)
Summary
Radiation therapy is one of the most common treatments for cancer.[1,2,3,4,5,6,7] Patient specific treatment planning based on imaging is required for precise calculation and delivery of radiation dose to tumors while reducing dose to normal tissues.[5,6,7,8,9] In the thoracic and abdominal regions, this is, complicated by respirationinduced tumor and organ motion.[2,10,11,12,13,14] Four-dimensional computed tomography (4D-CT) is currently the clinical standard to quantify tumor and organ geometry and motion trajectories.[8,15,16,17]. This makes it challenging to target radiation dose to the area of tumor that’s in contact with the blood vessels, which is needed in, for example, pancreatic cancer patients to downstage unresectable tumors and obtain margin negative resections for significantly prolonged survival.[2,9]
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