Trial results evaluating the effect of 2D antiscatter grids on Cone Beam Computed Tomography (CBCT) image quality for conditions including Prostate Cancer were posted on 2026-05-06. The study found that in proton therapy participants, the median shift in Hounsfield Unit (HU) error between standard and research CBCT was -128.8, indicating improved image quality.
Background
Cone Beam Computed Tomography (CBCT) is a crucial imaging modality used in radiation therapy for patient positioning and treatment verification. However, image quality can be degraded by scatter radiation, leading to artifacts and inaccuracies in tissue delineation. For patients undergoing radiation therapy for cancers such as prostate, head and neck, and upper abdomen, precise image guidance is essential for accurate tumor targeting and sparing of healthy tissues. Technologies like 2D antiscatter grids aim to improve CBCT image quality by reducing scatter, potentially enhancing the accuracy of treatment delivery and patient outcomes.
Trial design
This completed pilot study (NCT04565457) enrolled 43 participants to investigate the improvement in CBCT image quality provided by 2D antiscatter grid technology. The study compared "Research CBCT" (presumably with 2D antiscatter grids) to "Standard CBCT" (without grids). Participants had various conditions, including Prostate Cancer, Head and Neck Cancers, and Upper Abdomen Cancers. The primary objective was to assess the improvement in tissue visualization in a blinded observer study.
Key results
The study reported several key measurements and analyses indicating improved image quality with the research CBCT:
- Accuracy of Automated Tissue Delineation (Photon Therapy Participants): The mean difference in Dice Similarity Coefficient between Research CBCT and Standard CBCT was -0.065 (95% Confidence Interval: -0.099 to -0.032, p-value: 0.0001). This indicates improved accuracy of auto-segmented contours with the research CBCT.
- Ratio of Standard CBCT to Research CBCT HU Error (Photon Therapy Participants): The mean ratio was 1.768 (95% Confidence Interval: 1.466 to 2.132, p-value: 0.0001). A ratio greater than 1 indicates higher HU error in standard CBCT relative to research CBCT, signifying improved accuracy with the research CBCT.
- Median Shift in Hounsfield Unit (HU) Error (Proton Therapy Participants): The median paired shift in HU error between standard CBCT and research CBCT was -128.8 (95% Confidence Interval: -137.9 to -123.3, p-value: 0.001953). This significant negative shift indicates a reduction in HU error with research CBCT.
- Ratio of Artifact Amplitude (Photon Therapy Participants): The mean ratio of artifact amplitude between Standard CBCT and Research CBCT was 1.489 (95% Confidence Interval: 1.255 to 1.767, p-value: 0.0001). This suggests a reduction in artifact amplitude with research CBCT.
- Median Shift in Artifact Amplitude (Proton Therapy Participants): The median paired shift in artifact amplitude was -235.9 (95% Confidence Interval: -269.1 to -182.4, p-value: 0.001953), indicating significantly less artifact amplitude in research CBCT scans.
- Ratio of Contrast-To-Noise Ratio (CNR) (Photon Therapy Participants): The mean ratio of CNR between Standard CBCT and Research CBCT was 1.199 (95% Confidence Interval: 1.082 to 1.329, p-value: 0.0001). A ratio greater than 1 indicates improved CNR with research CBCT.
- Median Shift in Contrast to Noise Ratio (CNR) (Proton Therapy Participants): The median shift in CNR between standard CBCT and research CBCT was 0.56.
What this means
The consistent improvements observed across multiple image quality metrics, including reduced Hounsfield Unit error, decreased artifact amplitude, enhanced contrast-to-noise ratio, and improved accuracy of automated tissue delineation, suggest that 2D antiscatter grid technology significantly enhances CBCT image quality. For patients undergoing radiation therapy for prostate, head and neck, and upper abdomen cancers, improved image quality can lead to more precise tumor targeting, better visualization of anatomical structures, and potentially more accurate dose delivery. These findings support the potential for 2D antiscatter grids to optimize image guidance in radiation oncology.
Source
The information regarding these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT04565457, titled "A Pilot Study Evaluating the Effect of 2D Antiscatter Grids on CBCT Image Quality," were posted on 2026-05-06 on clinicaltrials.gov.