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Diffusion-weighted imaging of brain metastases: their potential to be misinterpreted as focal ischaemic lesions
1Department of Radiology, University Hospital, 22185 Lund, Sweden. bo.geijer@drad.lu.se
Abstract:
Small focal ischaemic brain lesions are said to be easy to identify in the acute stage and to differentiate from older lesions using diffusion-weighted imaging (DWI). Brain metastases are common and the aim of this study was to evaluate the risk of misinterpretation as ischaemic lesions in a standard MRI protocol for clinical stroke. Of 26 patients investigated with MRI for possible metastases, 12 did have metastatic brain lesions, including most of the common tumours. On a 1.5 tesla imager, we obtained DWI, plus T2- and T1-weighted images, the latter before and after triple-dose contrast medium. Well-circumscribed brain lesions with a decreased apparent diffusion coefficient and a slightly or moderately increased signal on T2-weighted images were found in patients with metastases from a small-cell bronchial carcinoma and a pulmonary adenocarcinoma. The same features were also found in metastases from a breast carcinoma but the lesions were surrounded by oedema. With a standard DWI protocol, the features of common brain metastases may overlap with those of small acute and subacute ischaemic lesions.
Insights
Diffusion-weighted imaging (DWI) can misdiagnose brain metastases as acute ischemic lesions. This study highlights the risk of misinterpreting metastatic brain tumors on standard MRI scans, potentially delaying critical treatment.
Area of Science:
- Neuroradiology
- Oncology
- Neurology
Background:
- Small focal ischemic brain lesions are typically identifiable in acute stages using diffusion-weighted imaging (DWI).
- Brain metastases are a common clinical finding, necessitating accurate differentiation from other pathologies.
Purpose of the Study:
- To evaluate the risk of misinterpreting brain metastases as ischemic lesions within a standard magnetic resonance imaging (MRI) protocol for clinical stroke assessment.
Main Methods:
- A cohort of 26 patients with suspected brain metastases underwent MRI, including DWI, T2-weighted, and T1-weighted sequences (pre- and post-contrast).
- Analysis focused on lesion characteristics such as circumscription, apparent diffusion coefficient (ADC) values, T2 signal intensity, and surrounding edema.
Main Results:
- Brain metastases from small-cell bronchial carcinoma, pulmonary adenocarcinoma, and breast carcinoma exhibited features mimicking acute ischemic lesions.
- Specific findings included well-circumscribed lesions with decreased ADC and increased T2 signal, with edema present in some cases (e.g., breast carcinoma).
- Overlap in imaging features between metastases and acute/subacute ischemic lesions was observed with standard DWI protocols.
Conclusions:
- Standard DWI protocols may lead to misinterpretation of common brain metastases as small acute or subacute ischemic lesions.
- Careful evaluation of lesion characteristics, including surrounding edema, is crucial for differentiating brain metastases from ischemic events on MRI.