https://www.icimagingsociety.org.uk
Giovanni Morana1, Elena Tornari2, Andrea Rossi1
1Neuroradiology Unit, Istituto Giannina Gaslini, Genoa, GE, 16145, Italy; 2Department of Radiotherapy, Ospedale Policlinico San Martino, Genoa, GE, 16132, Italy
Radiation-induced CNS toxicity comprises a wide spectrum of clinical and radiological complications determining variable neurological manifestations.
Effects of brain radiation can be focal or diffuse and are influenced by different factors such as patient age, cumulative dose of irradiation, type of irradiation (i.e. accelerated vs hyperfractionated, photon vs proton therapy), duration of exposure and association with chemotherapy.
Classification of radiation-induced CNS toxicity is based on timing of clinical presentation and comprises three main categories: acute (within 1-6 weeks), subacute or "early" delayed (3 weeks to 6 months) and chronic or "late" delayed (after 6-12 months to years) [2].
Early injuries are usually reversible and tend to resolve spontaneously, whereas late delayed effects are generally irreversible.
Among radiation-induced complications pseudoprogression and radiation necrosis are respectively early and late delayed effects, enhanced by concomitant chemotherapy, that can be associated with clinical worsening mimicking disease progression [3,4].
Late delayed radiation-induced complications include also diffuse radiation leukoencephalopathy, vascular injuries, mineralizing microangiopathy and pituitary disfunction, which are extremely common in the paediatric population [5,6].
Conventional MRI is the imaging method of choice for evaluating radiation-induced brain alterations. Advanced imaging modalities such as, Diffusion Weighted Imaging, Magnetic Resonance Spectroscopy and Perfusion Weighted Imaging, as well as Positron Emission Tomography with amino-acid tracers, may be of help in differentiating pseudoprogression and radiation necrosis from true disease progression.
Evaluation and depiction of the main manifestations of brain injury induced by radiation therapy is the focus of the present work.
References
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2. Pruzincová L, Steno J, Srbecký M, Kalina P, Rychlý B, Boljesíková E, et al. MR imaging of late radiation therapy- and chemotherapy-induced injury: a pictorial essay. Eur Radiol 2009, 19:2716-27.
3. Fatterpekar GM, Galheigo D, Narayana A, Johnson G, Knopp E. Treatment-related change versus tumour recurrence in high-grade gliomas: a diagnostic conundrum-use of dynamic susceptibility contrast-enhanced (DSC) perfusion MRI. AJR Am J Roentgenol 2012, 198:19-26.
4. Faraci M, Morana G, Bagnasco F, Barra S, Polo P, Hanau G, et al. Magnetic resonance imaging in childhood leukemia survivors treated with cranial radiotherapy: a cross sectional, single center study. Pediatr Blood Cancer 2011, 57:240-6.
5. Di Giannatale A, Morana G, Rossi A, Cama A, Bertoluzzo L, Barra S, et al. Natural history of cavernous malformations in children with brain tumours treated with radiotherapy and chemotherapy. J Neurooncol 2014, 117:311-20.