Slice-stacking T2-weighted MRI for fast determination of internal target volume for liver tumor

Non-contrast-enhanced breast MRI for evaluation of tumor volume change after neoadjuvant chemotherapy

PURPOSE

Three-dimensional contrast-enhanced magnetic resonance imaging (3D-Ce-MRI) is a most powerful tool for evaluation of neoadjuvant chemotherapy (NAC). However, the use of contrast agent is invasive, expensive, and time consuming, Thus, contrast agent-free imaging is preferable. We aimed to investigate the tumor volume change after NAC using maximum intensity projection diffusion-weighted image (MIP-DWI) and 3D-Ce-MRI.

METHOD

We finally enrolled 55 breast cancer patients who underwent NAC in 2018. All MRI analyses were performed using SYNAPSE VINCENT® medical imaging system (Fujifilm Medical, Tokyo, Japan). We evaluated the tumor volumes before, during, and after NAC. Tumor volume before NAC on 3D-Ce-MRI was termed Pre-CE and those during and after NAC were termed Post-CE. The observer raised the lower end of the window width until the tumor was clearly visible and then manually deleted the non-tumor tissues. A month thereafter, the same observer who was blinded to the 3D-Ce-MRI results randomly evaluated the tumor volumes (Pre-DWI and Post-DWI) using MIP-DWI with the same method. Tumor volume change between ΔCE (Pre-CE - Post-CE/Pre-CE) and ΔDWI (Pre-DWI - Post-DWI/Pre-DWI) and the processing time for both methods (Time-DWI and Time-CE) were compared.

RESULTS

We enrolled 55 patients. Spearman's rho between ΔDWI and ΔCE for pure mass lesions, and non-mass enhancement (NME) was 0.89 (p < 0.01), 0.63(p < 0.01) respectively. Time-DWI was significantly shorter than Time-CE (41.3 ± 21.2 and 199.5 ± 98.3 respectively, p < 0.01).

CONCLUSIONS

Non-contrast-enhanced Breast MRI enables appropriate and faster evaluation of tumor volume change after NAC than 3D-Ce-MRI especially for mass lesions.

Contrast-enhanced 4D-MRI for internal target volume generation in treatment planning for liver tumors

BACKGROUND

Liver tumors are often invisible on four-dimensional commuted tomography (4D-CT). Imperfect imaging surrogates are used to estimate the tumor motion. Here, we assessed multiple 4D magnetic resonance (MR) binning algorithms for directly visualizing liver tumor motion for radiotherapy planning.

METHODS

Patients were simulated using a 3 Tesla MR and CT scanner. Three prototype binning algorithms (phase, amplitude, and two-directional) were applied to the 4D-MRIs, and the image quality was assessed using a qualitative clarity score and quantitative sharpness score. Radiation plans were generated for internal target volumes (ITVs) derived using 4D-MRI and 4D-CT, and the dosimetry of targets were compared. Paired t-tests were used to compare sharpness scores and dosimetric data.

RESULTS

Twelve patients with 17 liver tumors were scanned between May and November 2021. Compared to phase binning, two-directional demonstrated equal or better clarity and sharpness scores (end-expiration: 0.33 vs. 0.38, p=0.018, end-inspiration: 0.28 vs. 0.31, p=0.010). Compared to amplitude binning, two-directional binning captured hysteresis of ≥3 mm in 35% of patients. Evaluation of dosimetry CT-optimized plans revealed that PTV coverage of MR-derived targets were significantly lower than CT-derived targets (PTV receiving 90% of prescription: 75.56% vs. 89.38%, p=0.002).

CONCLUSION

Using contrast-enhanced 4D-MRI is feasible for directly delineating liver tumors throughout the respiratory cycle. The current standard of using radiation plans optimized for 4D-CT-derived targets achieved lower coverage of directly visualized MRI targets, suggesting that adopting MRI for motion management may improve radiation treatment of liver lesions and reduce the risk of marginal misses.

Novel monodisperse FePt nanocomposites for T2-weighted magnetic resonance imaging: biomedical theranostics applications

Given the high incidence and mortality of cancer, current research is focused on designing efficient diagnostic methods. At present, clinical diagnoses are made based on X-ray, computed tomography, magnetic resonance imaging (MRI), ultrasound, and fiber optic endoscopy. MRI is a powerful diagnostic tool because it is non-invasive, has a high spatial resolution, uses non-ionizing radiation, and has good soft-tissue contrast. However, the long relaxation time of water protons may result in the inability to distinguish different tissues. To overcome this drawback of MRI, magnetic resonance contrast agents can enhance the contrast, improve the sensitivity of MRI-based diagnoses, increase the success rate of surgery, and reduce tumor recurrence. This review focuses on using iron-platinum (FePt) nanoparticles (NPs) in T2-weighted MRI to detect tumor location based on dark-field changes. In addition, existing methods for optimizing and improving FePt NPs are reviewed, and the MRI applications of FePt NPs are discussed. FePT NPs are expected to strengthen MRI resolution, thereby helping to inhibit tumor development.