Perfusion MRI in treatment evaluation of glioblastomas: Clinical relevance of current and future techniques

Abstract

Treatment evaluation of patients with glioblastomas is important to aid in clinical decisions. Conventional MRI with contrast is currently the standard method, but unable to differentiate tumor progression from treatment-related effects. Pseudoprogression appears as new enhancement, and thus mimics tumor progression on conventional MRI. Contrarily, a decrease in enhancement or edema on conventional MRI during antiangiogenic treatment can be due to pseudoresponse and is not necessarily reflective of a favorable outcome. Neovascularization is a hallmark of tumor progression but not for posttherapeutic effects. Perfusion-weighted MRI provides a plethora of additional parameters that can help to identify this neovascularization. This review shows that perfusion MRI aids to identify tumor progression, pseudoprogression, and pseudoresponse. The review provides an overview of the most applicable perfusion MRI methods and their limitations. Finally, future developments and remaining challenges of perfusion MRI in treatment evaluation in neuro-oncology are discussed. Level of Evidence: 3 Technical Efficacy: Stage 4 J. Magn. Reson. Imaging 2019;49:11-22.

Keywords: glioblastoma; magnetic resonance imaging; perfusion imaging; treatment evaluation.

Figure 1

Dynamic susceptibility contrast (DSC) case of tumor progression. A case of tumor progression in a 68‐year‐old male after 3 months postchemoradiotherapy. Anatomical MRI pre‐ (a) and postcontrast (b) T₁‐weighted imaging demonstrated new enhancement and increased FLAIR signal (c) Dynamic susceptibility contrast (DSC) perfusion imaging (d) confirmed tumor progression with elevated rCBV values located at the place of contrast enhancement as indicated by the white circles. DSC = dynamic susceptibility contrast, rCBV = relative cerebral blood volume.

Figure 2

Dynamic susceptibility contrast (DSC) in a patient with pseudoprogression. Pseudoprogression in a 35‐year‐old male 6 months after completion of chemoradiotherapy. Pre‐ (a) and postcontrast T₁‐weighted imaging (b) and FLAIR (c) were both suggestive of apparent progressive disease. However, DSC (d) correctly showed that these changes were due to pseudoprogression, as rCBV values were not elevated at the location of the enhancing lesion (white circles). DSC = dynamic susceptibility contrast, rCBV = relative cerebral blood volume.

Figure 3

Arterial spin labeling (ASL) in recurrent glioblastoma. Follow‐up imaging of a 40‐year‐old female with a glioblastoma 3 months after partial resection and chemoradiotherapy. Pre‐ (a) and postcontrast T₁‐weighted (b) and FLAIR (c) images showed a significant increase of the lesion. ASL perfusion imaging (d) was in accordance with the anatomical images, demonstrating increased CBF values (yellow) corresponding with tumor progression. ASL = arterial spin labeling, rCBF = cerebral blood flow.

Figure 4

Susceptibility artifact on dynamic susceptibility contrast (DSC) perfusion MRI. Postoperative imaging after resection of a glioblastoma in a 65‐year‐old female. The resection cavity contains a hemorrhage (circle) as demonstrated on precontrast T₁‐weighted imaging (a). Unprocessed DSC imaging demonstrated a large susceptibility artifact in the area of the blood products and surgical material after craniotomy (b). The calculated DSC‐rCBV is therefore not assessable with artifactual low values (c). Note also a susceptibility artifact frontally (asterisk) due to the skull base and frontal sinuses with bone‐air interfaces (b). DSC = dynamic susceptibility contrast, rCBV = relative cerebral blood volume.

Figure 5

Pseudoresponse identified by dynamic susceptibility contrast (DSC). Patient with a recurrent glioblastoma with new contrast enhancement on T₁‐weighted MRI after completion of chemotherapy (a). The patient received second‐line antiangiogenic treatment with bevacizumab. After the first course, follow‐up MRI (b) showed a decrease in contrast‐enhancing lesions (white circle), suggestive of apparent response. However, DSC demonstrated persisting high perfusion values (arrows) confirming the changes were due to pseudoresponse (c). Subsequent follow‐up scans demonstrated an increase in contrast enhancement and rCBV and the patient deteriorated. DSC = dynamic susceptibility contrast, rCBV = relative cerebral blood volume.

Figure 6

Intravoxel incoherent motion (IVIM) diffusion‐weighted imaging in glioblastoma. MRI of a 64‐year‐old female with a right frontal glioblastoma as shown on pre‐ (a) and postcontrast T₁‐weighted imaging (b). DSC demonstrated elevated perfusion at location of contrast enhancement (c) and diffusion‐weighted imaging showed decreased ADC laterally due to increased cellularity and elevated ADC in the necrotic core (d). IVIM imaging uses a biexponential model of signal decay (e). The diffusion signal is demonstrated in white for different b‐values. With IVIM this signal decay can be divided into the flow‐related pseudodiffusion (red dotted line) and the true diffusion (blue dotted line). The perfusion fraction (f) results from the signal difference between pseudodiffusion and true diffusion. The perfusion fraction demonstrated similar results to DSC‐rCBV (c). A pseudodiffusion map is also shown (g). IVIM‐derived true diffusion maps (h) are comparable to ADC with elevated values in the necrotic core. ADC = apparent diffusion coefficient, DSC = dynamic susceptibility contrast, IVIM = intravoxel incoherent motion, rCBV = relative cerebral blood volume.