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Published on: August 14, 2019
Diffusion-weighted MRI features of brain abscess and cystic or necrotic brain tumors: comparison with conventional
Shih Chin Chang1, Ping Hong Lai, Wei Liang Chen
1Department of Radiology, Veterans General Hospital-Kaohsiung, National Yang-Ming University, National Sun Yat-Sen University, 386 Ta-Chung First Road, Kaohsiung, Taiwan, ROC.
Background And Purpose:
The purpose of this study was to determine whether diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) can be used to distinguish brain abscesses from cystic or necrotic brain tumors, which are difficult to distinguish by conventional magnetic resonance imaging (MRI) techniques.
Methods:
Eleven consecutive patients with brain abscesses [10 pyogenic and 1 toxoplasmosis (in an AIDS patient)] and 15 with cystic or necrotic brain gliomas or metastases were enrolled in this study. None of these lesions had apparent hemorrhage based on T1-weighted image (T1WI). The DWI was performed using a 1.5-T system, single-shot spin-echo echo-planar pulse sequence with b=1000 s/mm(2). The ADC was calculated using a two-point linear regression method at b=0 and b=1000 s/mm(2). The ratio (ADCR) of the lesion ADC to control region ADC was also measured.
Results:
Increased signal was seen in all of the pyogenic abscess cavities to variable degrees on DWI. In vivo ADC maps showed restricted diffusion in the abscess cavity in all pyogenic abscesses [0.65+/-0.16 x 10(-3) (mean+/-S.D.) mm(2)/s, mean ADCR=0.63]. The case with multiple toxoplasmosis abscesses showed low signal intensity on DWI and high ADC values (mean 1.9 x 10(-3) mm(2)/s, ADCR=2.24). All cystic or necrotic tumors but one showed low signal intensity on DWI and their cystic or necrotic areas had high ADC values (2.70+/-0.31 x 10(-3) mm(2)/s, mean ADCR=3.42). One fibrillary low-grade astrocytoma had a high DWI signal intensity and a low ADC value in its central cystic area (0.44 x 10(-3) mm(2)/s, ADCR=0.49). Postcontrast T1WIs yielded a sensitivity of 60%, a specificity of 27.27%, a positive predictive value (PPV) of 52.94%, and a negative predictive value (NPV) of 33.33% in the diagnosis of necrotic tumors. DWI yielded a sensitivity of 93.33%, a specificity of 90.91%, a PPV of 93.33%, and a NPV of 90.91%. The area under receiver operating characteristic (ROC) curves for postcontrast T1WI was 0.44 and DWI was 0.92. Analysis of these areas under the ROC curves indicates significant difference between postcontrast T1WI and DWI (P<.001).
Conclusion:
With some exceptions, DWI is useful in providing a greater degree of confidence in distinguishing brain abscesses from cystic or necrotic brain tumors than conventional MRI and seems to be a valuable diagnostic tool.
Insights
Diffusion-weighted imaging (DWI) effectively distinguishes brain abscesses from cystic or necrotic tumors, unlike conventional MRI. DWI offers higher diagnostic confidence and accuracy for these challenging brain lesions.
Area of Science:
- Neuroradiology
- Medical Imaging
- Neuro-oncology
Background:
- Distinguishing brain abscesses from cystic or necrotic tumors is challenging with conventional MRI.
- Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping offer advanced techniques for characterizing brain lesions.
Purpose of the Study:
- To evaluate the efficacy of DWI and ADC in differentiating brain abscesses from cystic or necrotic brain tumors.
- To compare the diagnostic performance of DWI with conventional MRI techniques.
Main Methods:
- Eleven patients with brain abscesses and 15 with cystic/necrotic brain tumors were included.
- DWI was performed using a 1.5-T system with b=1000 s/mm(2).
- ADC values and ADC ratios (ADCR) were calculated and analyzed.
Main Results:
- Pyogenic abscesses showed restricted diffusion (low ADC values) on DWI, while toxoplasmosis abscesses had high ADC values.
- Cystic/necrotic tumors generally exhibited high ADC values, except for one low-grade astrocytoma.
- DWI demonstrated significantly higher sensitivity (93.33%) and specificity (90.91%) than postcontrast T1WI (60% and 27.27%) in differentiating these lesions.
Conclusions:
- DWI is a valuable tool for distinguishing brain abscesses from cystic or necrotic tumors.
- DWI provides greater diagnostic confidence compared to conventional MRI techniques.
- The study highlights DWI's potential to improve diagnostic accuracy in neuroimaging.
Related Concept Videos
01:26Brain Abscess l: Introduction
01:24Magnetic Resonance Imaging
01:14Brain Imaging
These technologies include computerized axial tomography (CAT or CT scans), positron-emission tomography (PET scans), magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), and Transcranial Magnetic Stimulation (TMS).