Elsevier

Journal of Neuroradiology

Volume 35, Issue 4, October 2008, Pages 224-229
Journal of Neuroradiology

Original article
Contribution of the apparent diffusion coefficient in perilesional edema for the assessment of brain tumorsApport du coefficient de diffusion apparent de l’œdème périlésionnel pour l’étude des tumeurs cérébrales

https://doi.org/10.1016/j.neurad.2008.02.003Get rights and content

Summary

Objectives

Diffusion-weighted MRI is sensitive to molecular motion and has been applied to the diagnosis of stroke. Our intention was to investigate its usefulness in patients with brain tumor and, in particular, in the perilesional edema.

Methods

We performed MRI of the brain, including diffusion-weighted imaging and mapping of the apparent diffusion coefficient (ADC), in 16 patients with brain tumors (glioblastomas, low-grade gliomas and metastases). ADC values were determined by the use of regions of interest positioned in areas of high signal intensities as seen on T2-weighted images and ADC maps. Measurements were taken in the tumor itself, in the area of perilesional edema and in the healthy contralateral brain.

Results

ADC mapping showed higher values of peritumoral edema in patients with glioblastoma (1.75 × 10−3 mm2/s) and metastatic lesions (1.61 × 10−3 mm2/s) compared with those who had low-grade glioma (1.40 × 10−3 mm2/s). The higher ADC values in the peritumoral zone were associated with lower ADC values in the tumor itself.

Conclusions

The higher ADC values in the more malignant tumors probably reflect vasogenic edema, thereby allowing their differentiation from other lesions.

Résumé

Objectif

L’IRM de diffusion est sensible aux mouvements moléculaires et a été appliquée avec succès pour le diagnostic des accidents vasculaires cérébraux. Notre objectif était d’étudier son intérêt chez les patients présentant des tumeurs cérébrales, avec une attention particulière au niveau de l’œdème périlésionnel.

Méthodes

Une IRM cérébrale comportant des séquences de diffusion et des cartographies du coefficient de diffusion apparent (ADC) était réalisée chez 16 patients présentant des tumeurs cérébrales (glioblastomes, gliomes de bas grade et métastases). Les valeurs d’ADC étaient déterminées à l’aide de régions d’intérêt définies au niveau des zones de signal élevé visibles sur les images T2 et les cartographies ADC. Les mesures étaient réalisées au niveau de la tumeur elle-même, dans l’œdème périlésionnel et dans le cerveau sain controlatéral.

Résultats

Les cartographies ADC ont montré des valeurs plus élevées au niveau de l’œdème péritumoral chez les patients présentant un glioblastome (1,75 × 10−3 mm2/s) ou une lésion métastatique (1,61 × 10−3 mm2/s) comparées à ceux présentant un gliome de bas grade (1,40 × 10−3 mm2/s). Ces valeurs plus élevées en zone péritumorale étaient associées à un ADC bas dans la tumeur elle-même.

Conclusions

L’augmentation des valeurs d’ADC au niveau de l’œdème périlésionnel des tumeurs plus malignes reflète probablement un œdème vasogénique plus important permettant de les différencier des autres lésions.

Introduction

Diffusion-weighted imaging (DWI) has become a standard routine sequence in most clinical investigations [1], [2]. It involves a simple modification of a spin-echo sequence, where two gradient sensitizing pulses are applied before and after the 180 pulse. Diffusion imaging is sensitive to the molecular motion of tissues, allowing it to be used with great success in the setting of stroke [3], [4], where it is thought to be able to differentiate between cytotoxic and vasogenic edema. The occurrence of acute ischemia is accompanied by a decrease in the so-called apparent diffusion coefficient (ADC), which allows quantification of the diffusion characteristics of a given tissue. This has been applied to other pathologies such as brain abscess [5] and some tumors, and brain development [6] and aging [7], as well as for monitoring interventions [8]. The possibility of mapping the ADC allows the quantification of water movement. This has already been applied to tumors of the brain, head and neck [9], [10]. Previous studies have shown that ADC values reflect both cellularity and edema [11]. The present study aimed to address its capacity to determine the type of intracranial tumor based on the ADC values from the perilesional edema. To do this, we investigated a series of patients who had different types of intracranial tumors.

Section snippets

Patients

Sixteen consecutive patients (nine men, seven women; ages 35 to 82, mean age 58 years) were prospectively included, having been recruited from the neurosurgical clinic of our hospital over a period of six months (January to July 2001). All patients had undergone brain MRI because of an intracranial tumor. They were informed of the examination they were about to undergo and had given their consent.

The patients all subsequently underwent craniotomy and biopsy/surgery to obtain samples of tumor

Results

On histology, eight patients showed high-grade gliomas, four had cerebral metastases and four had low-grade gliomas (Fig. 3).

Discussion

This study showed that both high-grade gliomas and metastatic brain tumors have higher ADC values in the perilesional edema than do low-grade gliomas, indicating a higher water content and greater tissue displacement due to vasogenic edema, and probably secondary to a more aggressive histological reaction. Also, there is a tendency for the more malignant lesions to have lower ADC values within the tumor itself, probably due to necrosis. Therefore, DWI-derived ADC maps can be helpful in

Conclusion

ADC mapping of brain tumors and assessment of the ADC in the peritumoral lesion appears to be promising in the differentiation of tumors and in the assessment of local invasiveness. Glioblastomas, while having a low central ADC, have a high ADC in the periphery, reflecting a central high cellularity and peripheral vasogenic edema.

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      Lee et al. (10) explained this finding by the increased cellularity in the peritumoral region in primary tumors as a result of infiltration, while in metastatic tumors there is vasogenic edema with no infiltration. It is noted that the Guzman et al. (13) reported the ability of peritumoral ADC values to differentiate low from high grade tumors, contradicting our results. This contradiction could be attributed to the limitation of having a small population in this study.

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      The DWI technique has become present in clinical practice because it is helpful and sensitive for the detection of acute ischemic stroke in the early phase [3,4] while other imaging techniques, such as computed tomography, fail due to their reduced sensitivity for diffusion disorders. ADC measurements are useful for the quantitative assessment of pathological states of the brain, such as neurological disorders of the brain [5,6], the detection of tumours, the characterisation of lesions, and the evaluation of the treatment response [7,8]. Moreover, DWI has been used as a noninvasive, accurate tool for the evaluation of age-related differences and morphologic changes in brain structures [9,10] as a sensitive technique responsive to incoherent water motion, which depends on the brain's microstructure.

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