Brain MRI for Cancer Screening
For cancer screening purposes, the type of brain MRI depends critically on your risk profile: high-risk patients with cancer predisposition syndromes require a dedicated brain protocol with multiple sequences and contrast administration, while lower-risk individuals may use a short brain protocol with FLAIR sequences only. 1
Risk-Stratified Approach to Brain MRI Screening
High-Risk Patients (Cancer Predisposition Syndromes)
When there is an increased risk of central nervous system (CNS) tumors, a dedicated brain sub-protocol is performed, with multiple sequences and with contrast administration. 1
This applies specifically to patients with:
- Li-Fraumeni syndrome (LFS) - where brain tumors are among the common malignancies alongside sarcoma, breast cancer, leukemia, and adrenocortical carcinoma 1
- Neurofibromatosis (NF) - requiring assessment for CNS involvement 1
- Constitutional Mismatch Repair Deficiency Syndrome (CMMR-D) - necessitating dedicated brain evaluation 1
The National Comprehensive Cancer Network (NCCN) and American Association for Cancer Research (AACR) recommend annual brain MRI with contrast as the screening technique of choice in the management of adult and pediatric subjects with LFS. 1
Lower-Risk Patients
In subjects with a low risk of CNS tumors, the assessment of the brain can be improved with a short brain protocol, including fluid attenuated inversion recovery (FLAIR) sequences. 1
Dedicated Brain MRI Protocol Components
Core Sequences Required
The recommended minimum requirements for brain tumor screening include: 1
- Precontrast 3-dimensional, isotropic, IR-prepped T1-weighted gradient echo (IR-GRE) sequence 1
- Axial 2-dimensional T2-weighted fluid-attenuated inversion recovery (FLAIR) sequence obtained using turbo-spin-echo (TSE) readout 1
- Axial 2-dimensional, 3-directional (isotropic) diffusion-weighted imaging (DWI) sequence 1
- Axial 2-dimensional T2-weighted TSE sequence 1
- Postcontrast 3-dimensional, isotropic, T1-weighted IR-GRE sequence with matching acquisition parameters to precontrast T1-weighted images 1
Technical Specifications
Magnetic field strength should be a minimum of 1.5T (preferably 3.0T). 2
Maximum slice thickness should be 3mm with in-plane spatial resolution of 1 × 1 mm (voxel size 3 × 1 × 1 mm). 2
Total acquisition time should be 25-30 minutes. 2
Contrast Administration Guidelines
When Contrast Is Required
For high-risk cancer screening, contrast agents should be administered when additional dedicated brain evaluations are performed. 1
Gadolinium dose should be 0.1 mmol/kg body weight (0.2 mL/kg). 2, 3
Minimum delay time of 5 minutes between gadolinium injection and T1-weighted sequence acquisition is required. 2
When Contrast May Be Avoided
The routine use of contrast agents when performing whole-body MRI for cancer screening in asymptomatic subjects of the general population is strongly discouraged. 1
This recommendation is based on:
- Medical and public concerns related to long-term gadolinium deposition in the brain 1
- Possible adverse effects in subjects with undisclosed acute kidney injury, including nephrogenic systemic fibrosis 1
- Patient discomfort related to intravenous puncture 1
In the largest study with contrast administration including 2500 subjects, all malignant tumors were detected on whole-body unenhanced MR images, with the exception of a myocardial tumor found in targeted contrast-enhanced cardiac MRI. 1
Screening for Brain Metastases
Asymptomatic Patients with Extracranial Malignancy
For secondary screening for brain metastases in patients with systemic malignancy, MRI of the brain without and with IV contrast is recommended. 1
MRI brain without IV contrast may demonstrate vasogenic edema and mass effect often associated with metastases, but IV contrast is typically preferred for improved delineation of intraaxial and extraaxial (leptomeningeal and/or dural-based) lesions. 1
Whole-Body MRI Integration
When brain screening is part of a comprehensive whole-body MRI cancer screening protocol:
The core protocol should cover from head to pelvis and include T1-weighted GRE (preferably with Dixon technique), T2-weighted TSE, and diffusion-weighted imaging (DWI) sequences. 1
The study should be completed within 30 to 40 minutes for head to pelvis coverage. 1
Common Pitfalls and Caveats
CT head without IV contrast is not supported for screening for brain metastases in asymptomatic patients with extracranial malignancy. 1
FDG-PET/CT and FDG-PET/MRI have no relevant literature support for use in brain metastases screening in asymptomatic patients. 1
The recently published Oncologically Relevant Findings Reporting and Data System (ONCO-RADS) guidelines represent a comprehensive effort towards the standardization of whole-body MRI reporting in the setting of cancer screening. 1
Gadolinium is retained for months or years in brain, bone, skin, and other organs in patients with normal renal function, though the clinical consequences of retention are unknown. 3