Computed Tomography Perfusion Imaging for the Assessment of Brain Tumors

Computed Tomography Perfusion Imaging for the Assessment of Brain Tumors

Perspectives Commentary on: Perfusion Computed Tomography: An Imaging Biomarker for Brain Tumors’ Grading by Tomasello et al. pp. E831-E832. Russell ...

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Perspectives Commentary on: Perfusion Computed Tomography: An Imaging Biomarker for Brain Tumors’ Grading by Tomasello et al. pp. E831-E832.

Russell R. Lonser, M.D. Chair, The Ohio State University Wexner Medical Center Department of Neurological Surgery

Computed Tomography Perfusion Imaging for the Assessment of Brain Tumors J. Bradley Elder and Russell R. Lonser

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he radiographic characterization of intra-axial brain tumors is a critical component in the clinical management of patients. Magnetic resonance (MR) and computed tomography (CT) imaging are fundamental imaging techniques used in the initial diagnosis and subsequent surveillance during/after treatment. On the basis of diagnostic imaging (often after the development of symptoms/signs), surgical intervention often is performed that frequently is followed by adjuvant chemotherapy or radiation. Serial imaging, typically MR imaging, is used to assess the response to adjuvant therapy and to monitor for recurrence or progression. Currently, CT imaging (nonperfusion) often is reserved for acute neurologic decline that results from hemorrhage, hydrocephalus, or other mass lesions. Emerging data indicate that advanced imaging techniques, including CT perfusion, may enhance imaging information at multiple points during diagnosis, treatment, and follow-up in patients with brain tumors. Although CT perfusion has been used commonly to assess the effects cerebrovascular disorders and treatment, its potential utility in neuro-oncology is the subject of ongoing research (2, 4). Specifically, data suggest that defined CT perfusion imaging characteristics may be used to improve the diagnostic accuracy and tumor grading before surgery (1). Although the gold standard for primary brain tumor diagnosis is histopathologic analysis, correlation with CT perfusion imaging could reduce the risk of misdiagnosis caused by sampling error. Preoperative CT perfusion imaging could potentially guide surgical resection of intrinsic brain tumors. Information regarding tumor hemodynamics derived from CT perfusion (3) can be used in conjunction with standard MR imaging to plan the surgical approach and the tumor volume targeted for safe resection. With

Key words Brain tumors - Contrast enhancement - Perfusion computed tomography - Perfusion MRI - Tumour grading -

Abbreviations and Acronyms CT: Computed tomography MRI: Magnetic resonance imaging

WORLD NEUROSURGERY 82 [6]: e723-e724, DECEMBER 2014

the use of neuronavigation imaging and tools, tissue could potentially be resected from various areas of differing perfusion and analyzed separately to not only further subclassify the tumor but also determine options for adjuvant therapy. Alternatively, CT perfusion imaging could be used to define higher-grade tumor regions to guide biopsy and enhance diagnostic accuracy in lesions that are not amenable to resection. Currently, serial MR imaging most frequently is used to assess for tumor recurrence and response to therapy after tumor biopsy or resection. Nevertheless, it is often difficult to definitively determine whether progressive enhancement on MR imaging is caused by the progression of the tumor or “treatment effect.” Accurately distinguishing between true tumor progression or pseudoprogression is difficult, because either circumstance can appear similar on MR imaging. The accurate diagnosis of true progression or pseudoprogression is critical because the therapeutic management can be different. CT perfusion imaging could potentially be used to distinguish between these 2 entities, although additional studies are needed to assess the accuracy of this imaging modality in distinguishing either situation. An additional and potentially important application of CT perfusion imaging in the postoperative period also is to provide information regarding response to various therapies. Antiangiogenic agents may have a very different and defined response on CT perfusion imaging compared with cytotoxic agents. Novel therapies, including viral vectors, may have a very different CT perfusion profile. Ultimately, therapeutic profiles based on CT perfusion imaging may provide early and potent insights into therapeutic effects and molecular biologic changes. These findings may inform and enhance development of putative agents for treatment of brain tumors.

Department of Neurological Surgery, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA To whom correspondence should be addressed: J. Bradley Elder, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2014) 82, 6:e723-e724. http://dx.doi.org/10.1016/j.wneu.2014.08.029

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Overall, the role that CT perfusion imaging will play in the assessment and management will require further study. The accompanying article, entitled “Perfusion CT: an Imaging Biomarker of Brain Tumors’ Grading,” provides an outline of recent and emerging research. The authors underscore interesting and evolving features of this imaging modality with regard

REFERENCES 1. Ding B, Ling HW, Chen KM, Jiang H, Zhu YB: Comparison of cerebral blood volume and permeability in preoperative grading of intracranial glioma using CT perfusion imaging. Neuroradiology 48: 773-781, 2006. 2. Eastwood JD, Provenzale JM: Cerebral blood flow, blood volume, and vascular permeability of cerebral glioma assessed with dynamic CT perfusion imaging. Neuroradiology 45:373-376, 2003.

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to brain tumors. The article provides a primer for neuro-oncologists and neurosurgical oncologists to better understand CT perfusion imaging. Ultimately, further efforts into understanding CT perfusion imaging and other brain tumor imaging methods are important steps towards optimizing noninvasive diagnostic capabilities and patient outcomes.

3. Ellika SK, Jain R, Patel SC, Scarpace L, Schultz LR, Rock JP, Mikkelsen T: Role of perfusion CT in glioma grading and comparison with conventional MR imaging features. AJNR Am J Neuroradiol 28:1981-1987, 2007.

4. Lu N, Di Y, Feng XY, Qiang JW, Zhang JW, Wang YG, Guo QY: Comparison between acetazolamide challenge and 10% carbon dioxide challenge perfusion CT in rat C6 glioma. Acad Radiol 19:159-165, 2012.

Citation: World Neurosurg. (2014) 82, 6:e723-e724. http://dx.doi.org/10.1016/j.wneu.2014.08.029 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2014 Elsevier Inc. All rights reserved.

WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.08.029