Brain Tumor Imaging

Caribbean Medical Providers Practicing Abroad

June 13, 2015

Asante M. Dickson, MD

CAQ Neuroradiology

Washington Adventist Hospital

Takoma Park, MD

Role of Imaging

Diagnosis Grade Guide Biopsy Monitor treatment response and prognosis

Post-operative base-line

Imaging Modalities Available

CT MRI PET

Pediatric

Supratentorial JPA juvenile pilocytic astrocytoma, Ganglioglioma,

PXA pleomorphic xanthoastrocytoma, PNET primitive neuroectodermal tumor, DNT dysembroplastic neuroepithelial tumor

Infratentorial JPA, Medulloblastoma, ATRT, Ependymoma,

Diffuse pontine glioma (Not usually intra-axial but don’t forget about

LCH and Neuroblastoma)

Medulloblastoma

4 year old

Brainstem Glioma

26 yo M

Craniopharyngioma

56 yo M

FLAIRT2

DWI

ADC

Intravascular Lymphoma

Post Gad

Okay, it’s a brain tumor – But then what ? WHO divides CNS neoplasms into 9 primary groups and mets

Neuroepithelial tumours (astrocytic, oligo, astroblastoma, ependymal, choroid plexus)

Neuronal, mixed glial-neuronal and neurocytic Pineal parenchymal tumors Embryonal tumors (PNET, medullo, ATRT) Peripheral neuroblastic tumors (neuroblastoma) Tumors of cranial, spinal or peripheral nerves Meningeal tumors (meningioma, chondrosarcoma,

hemangioblastoma) Lymphoma, hematopoietic tumors (leukemia, plasmacytoma) Germ Cell Tumors Metastases

The Approach to Differential Diagnosis

Where is it? Intra-axial Vs Extra-axial Cortical, white matter or deep grey matter, Intraventricular Supra-tentorial or Infra-tentorial

Solitary or Multiple How old is the patient?

Child, Young Adult, Older Adult, Ready to die of other causes Primary vs Secondary Is the patient immunocompromised? Other clinical history...

E.g. Lymphoma Imaging features – T2, DWI, PWI, MRS, Gad

Gamuts

Tumors in children <2yo Astrocytoma, CPP, Teratoma, Embryonal tumors

Cortically based tumors DNET, Ganglioglioma, Oligo, PXA(pleomorphic xanthoastrocytoma)

Intraventricular tumors Pineal Region tumors Dural Based tumors Intracranial extension from extracranial

Chordoma, paraganglioma, carcinomas (NPCA), sarcomas (rhabdo)

Cyst + Nodule Pilocytic, Craniopharyngioma, Ganglioglioma, Hemangioblastoma

Intra-axial vs Extra-axial Features Intra-axial

Surrounded by white matter

Expands cortex May destroy GM/WM jx Effaces CSF cisterns Internal vascular supply

Extra-axial CSF Cleft Widening of CSF cisterns Buckling of grey matter GM/WM junction

preserved Continuity with bone or

falx Bony changes External vascular supply

12yoM – Intra or Extra-axial?

Differential Diagnosis – Extra-axial Skull-base/calvarium Dural Sellar/Parasellar/Optic chiasm Perineural Intra-ventricular

Central neurocytoma, ependymoma, subependymoma, oligo, pilocytic astro, meningioma, choroid plexus tumour, epidermoid, subependymal giant cell astrocytoma, colloid cyst, arachnoid cyst

Pineal Region CP Angle

Pre T1 Post T1

Post T1 Post T1 Post T1

Post T1

56 yo M

Primary CNS Lymphoma

Diagnosis – Is it neoplastic?

Mass Lesions – The standard Ddx (Congenital) Infectious Inflammatory Neoplastic Vascular – Ischemic, Hemorrhagic (Toxic, Metabolic) (Traumatic) (Degenerative)

56year old male history of lung CA

FSE T2 DWI ADC

Post-Gad

Abscesses

19 yo Male, Previously well, presents with new onset of seizures x 3

MRI Same Day

DWI ADC GRE Post-Gad

5 Days Later

Post-Gad Pre-GadFSE T2

10 days after presentation

DWI ADC FSE T2

Post Gad Perfusion

15 days after presentation

FLAIR

GRE

Post-Gad

Supratentorial Neoplasms – Adults Metastases Infiltrative (Diffuse or fibrillary) astrocytic tumours

Astrocytoma, anaplastic astrocytoma, GBM, gliomatosis Localized/Noninfiltrative astrocytic tumours

(Pilocytic astrocytoma - peds), Pleomorphic xanthoastrocytoma, (supependymal giant cell astrocytoma)

Oligodendroglioma and anaplastic oligo Neuronal and Glial-neuronal composition

Gangliocytoma and ganglioglioma, (desmoplastic infantile ganglioglioma <1yo), (central neurocytoma), DNT

Primary CNS Lymphoma

GBM

Epithelioid Hemangioendothelioma

Mets from lung

Infratentorial Neoplasms - Adults Metastases Hemangioblastoma Medulloblastoma (Cerebellar astrocytoma, Ependymoma)

JPA

Proton MRS

Elevated choline:Creatine ratio and reduced NAA considered “tumor spectrum” but non-specific

Metabolic ratios for glioma grading remains investigational May be useful to help differentiate high vs low grade

gliomas (II vs III/IV) Lactate (high and low grades, ?radioresistance) vs Mobile

Lipids (high grade only) – can’t separate on standard MRS Imaging brain tumor after therapy – elevated choline

(>50% contralateral oe Ch:Cr >2) – moderate to high sensitivity and high specificity for identifying active tumor (but no large series)

MRS

TE 144 TE 35

Lactate inversion

NAA

ChoCr

Single Voxel

67 yo M

MR Perfusion – elevated relative CBV

MR Spectroscopy – increased choline, reduced NAA

Multivoxel

Grading of Brain Tumors

WHO grading revised in 2000 Based on histological appearance

Does not take into account anatomic location and size of tumor which influence resectability

Primary basis for guiding therapy, prognosis, scientific study

Diffusion Weighted Imaging and Grade Tumor grade and cellularity reflected by ADC values

But most astrocytomas are too heterogeneous for ADC values to be helpful

Post-operative injury Enhancement post-surgery may be subacute infarction

Peritumoral edema Vasogenic edema (mets and meningiomas) vs Tumoral

edema – not so helpful Integrity and Position of White Matter Tracts (DTI)

Tumor grade and cellularity

Higher cellularity, reduced ADC Minimum ADC may correlate inversely with

grade Limit due to tumor heterogeneity Non-glial neoplasms – Meningioma,

Lymphoma

MR Perfusion

Measures Degree of tumour angiogenesis and capillary permeability

CBV is proportional to the area under the contrast agent concentration-time curve Contrast concentration is proportional to the

change in relaxation rate (dR2*) Assumptions of negligible recirculation and

contrast leakage – generally violated Measurement is relative therefore compare to

contralateral white matter

MR Perfusion continued

Oligo’s – high CBV regardless of grade Astrocytomas – higher CBV = high grade Choroid plexus tumours, some meningiomas,

mets – may not return to baseline – contrast leakage/leaky capillaries

CNS Lymphoma – high but not as high as GBM

Tumefactive MS – intralesional venous enhancement, possible mild elevation of CBV

Permeability imaging (DCE steady-state T1 measurement or DSC) Endothelial permeability of vessels in brain tumors

gives info about BBB integrity, vascular morphology and nature of neovascularization

Quantitative estimates of microvascular permeability (Ktrans) correlate with brain tumour grade

Ktrans (endothelial transfer coefficient) is a generalized measure to decribe the relationship between the time course of blood plasma Gad concentration (arterial input function) and Gad concentration changes in the voxel Affected by blood flow, blood volume, endothelial surface

area, endothelial permeability

Monitoring Response to Therapy Post-operative Baseline Tumour recurrence vs radiation necrosis

48year old previously well

DWI Post-GadFLAIR

3 months later - Following one course of steroids

1 year following more steroids

11 months after presentation

13 months after initial presentation

MR Perfusion

11 months Perfusion

13 months Perfusion

FDG-18

Thank You very much !

Special thanks to Dr. Talia Vertinsky