Image-guided stereotactic body radiation therapy (SBRT): an emerging treatment paradigm with a new promise in radiation oncology

Internal Target Volume Estimation for Liver Cancer Radiation Therapy Using an Ultra Quality 4-Dimensional Magnetic Resonance Imaging

Purpose

Accurate internal target volume (ITV) estimation is essential for effective and safe radiation therapy in liver cancer. This study evaluates the clinical value of an ultraquality 4-dimensional magnetic resonance imaging (UQ 4D-MRI) technique for ITV estimation.

Methods and Materials

The UQ 4D-MRI technique maps motion information from a low spatial resolution dynamic volumetric MRI onto a high-resolution 3-dimensional MRI used for radiation treatment planning. It was validated using a motion phantom and data from 13 patients with liver cancer. ITV generated from UQ 4D-MRI (ITV4D) was compared with those obtained through isotropic expansions (ITV2 mm and ITV5 mm) and those measured using conventional 4D-computed tomography (computed tomography-based ITV, ITVCT) for each patient.

Results

Phantom studies showed a displacement measurement difference of <5% between UQ 4D-MRI and single-slice 2-dimensional cine MRI. In patient studies, the maximum superior-inferior displacements of the tumor on UQ 4D-MRI showed no significant difference compared with single-slice 2-dimensional cine imaging (P = .985). Computed tomography-based ITV showed no significant difference (P = .72) with ITV4D, whereas ITV2 mm and ITV5 mm significantly overestimated the volume by 29.0% (P = .002) and 120.7% (P < .001) compared with ITV4D, respectively.

Conclusions

UQ 4D-MRI enables accurate motion assessment for liver tumors, facilitating precise ITV delineation for radiation treatment planning. Despite uncertainties from artificial intelligence-based delineation and variations in patients' respiratory patterns, UQ 4D-MRI excels at capturing tumor motion trajectories, potentially improving treatment planning accuracy and reducing margins in liver cancer radiation therapy.

Updates on Neuronavigation: Emerging tools for tumor resection

Multiple studies have been conducted to properly elucidate the various tools available to help enhance the resection of tumor tissue, aneurysms, and arteriovenous malformations (AVM). Diffusion tensor imaging (DTI) tractography is useful in providing a map of the tumor borders, allowing the optimal preservation of function and structure of specific regions of the brain. During neurosurgery, especially craniotomies, the possibility of the brain shifting due to swelling or gravity is high. Thus, tools for intraoperative imaging such as high-frequency linear array ultrasound transducers and doppler ultrasonography are utilized for high resolution images and detecting frequency shifts. 4D-digital subtraction angiography (DSA) is another technique used to create spatial resolutions and 3D maps for aneurysms. These similar techniques can also be utilized to assess the integrity of white matter in AVM. By implementing effective evaluation strategies, healthcare professionals can make informed decisions regarding treatment options, preventive measures, and long-term care plans tailored to individual patients.

Patterns of metastatic progression after definitive radiation therapy for early-stage and locally advanced non-small cell lung cancer

Current preclinical models of metastatic disease (particularly oligometastases) suggest that metastases appear in a hierarchical order. We attempted to identify systematic patterns of metastasis in non-small cell lung cancer (NSCLC) after radiation therapy (XRT). We analyzed 1074 patients treated from 12/21/1998 through 8/20/2012 with ≥60 Gy definitive radiation for initially non-metastatic NSCLC. Location and time of metastases were recorded. Regional nodal failure was noted, as was subsequent distal failure. For further analysis, we considered only the five most common sites of metastasis (bone, brain, liver, adrenal, and lung). Metastatic progression over time was defined and patterns elucidated with Chi square tests. Histologic findings were analyzed with Wilcoxon rank sum tests. A significant multistep linear progression was not apparent. Having a first metastasis in lung or bone was associated with respective 16% (median 2.4 months) and 15% likelihoods (median 7.9 months) of secondary brain metastasis. Initial metastasis in the brain led to metastasis in another organ 29.3% of the time, most often in the lung, bone, and liver (medians 3.6, 7.9, and 3.1 months). Adenocarcinoma was more likely than squamous to metastasize to the brain (18 vs. 9%) and any of the five major sites (41 vs. 27%). We did not appreciate dominant patterns suggesting a multi-step hierarchical order of metastasis. Rather, our findings suggest that certain subgroups may develop different patterns of spread depending on a variety of factors.