CHINA—A recent study published in Radiotherapy and Oncology showed that delayed MRI sequences improve brain tumor visualization after contrast administration.

This approach, aimed at determining the gross tumor target volume (GTV) for radiation therapy treatments of brain metastases (BM), provides valuable insights into tumor size and shape.

This method can optimize treatment strategies for patients with brain tumors by offering improved visualization.

The study, led by corresponding author Yong Yin from the Department of Oncology at the Affiliated Hospital of Southwest Medical University in China, emphasizes the limitations of single-phase static enhancement scans in accurately delineating tumor boundaries and determining GTV.

According to Yin and colleagues, these scans only capture a snapshot of the contrast agent’s presence in the tumor, failing to depict the dynamic process of contrast agent penetration and removal.

To address this limitation, the research team conducted contrast-enhanced T1-weighted imaging scans at various time intervals post-gadolinium-based contrast agent injection on 155 patients with brain metastases. 

The intervals included 1, 3, 5, 10, 18, and 20 minutes. By comparing the volume, shape, and signal intensity of GTVs and brain white matter at each interval, the researchers aimed to identify optimal delay times for improved visualization.

Results revealed a consistent increase in tumor volume with longer delay times post-contrast injection. 

Specifically, starting from the 3-minute delay and extending to the 20-minute delay, there was a steady increase in tumor volume. 

The study noted a peak in the contrast ratio between the GTV and white matter at the 5-minute interval, indicating enhanced visibility of tumors at this stage.

Yin and colleagues explained that the prolonged delay allows for better contrast agent penetration and removal, increasing tumor visibility and improved detection rates. 

These findings challenge previous recommendations suggesting scans begin 10 minutes after contrast injection. 

The study proposes the inclusion of multiple scan phases beyond the 10-minute mark to assess the extent of brain metastases accurately.

The study’s methodology involved fusing the GTVs obtained at different delay times into a single reference GTV-total

Results indicated significant differences in tumor boundaries and shapes across different delay times, highlighting the effectiveness of time-delayed multi-phase contrast-enhanced scanning in GTV determination.

Notably, time phases equal to or exceeding 10 minutes post-contrast injection were deemed mandatory for optimal results.

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