When performing MRI to rule out brain tumors, which weighted images are typically acquired to evaluate lesion involvement after the injection of gadolinium?

When evaluating brain tumors, especially after the administration of gadolinium contrast, T1 weighted images are typically acquired. This is because T1 weighted imaging provides detailed anatomical information and allows for the visualization of the enhancement patterns of lesions, which are crucial in identifying and assessing tumor involvement. The presence of gadolinium enhances the T1 signal of areas where the blood-brain barrier is disrupted, which is common in tumors. This enhancement can help differentiate between tumor tissue, edema, and necrosis, making T1 weighted imaging particularly valuable for post-contrast evaluation.

While other imaging techniques such as proton density and T2 weighted images can provide useful information regarding brain tissue characteristics and fluid content, they are less effective in visualizing the enhancement that occurs with gadolinium. T2 weighted images, for instance, are more sensitive to edema and fluid changes but do not show the same contrast between tumor and surrounding tissue as effectively as T1 images following contrast administration. Inversion recovery sequences might be used in specific situations to suppress signals from certain tissues, but they are not the primary choice for assessing tumor involvement post-contrast. This specificity makes T1 weighted images the standard protocol for this context.