Course objectives. Head Ultrasound. Introduction

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1 Disclosure Information AACPDM 68 th Annual Meeting September 10-13, 2014 Imaging of the pediatric brain, spinal cord and muscle: Tools and clinical applications Andrea Poretti, MD Research Associate Section of Pediatric Neuroradiology The Johns Hopkins School of Medicine Alec Hoon, MD Associate Professor of Pediatrics The Johns Hopkins School of Medicine Director, Phelps Center Kennedy Krieger Institute Avner Meoded, MD Research Associate Section of Pediatric Neuroradiology The Johns Hopkins School of Medicine Speakers Names: Andrea Poretti, Avner Meoded and Alec Hoon Disclosure of Relevant Financial Relationships: We have no financial relationships to disclose Disclosure of Off-Label and/or investigative uses: We will not discuss off label use and/or investigational use in our presentation AACPDM 68 th Annual Meeting, San Diego, September 10-13, 2014 Course objectives The participant will: 1. Identify the principles of the various imaging modalities available to clinicians 2. Recognize clinical settings when specific imaging tools are appropriate/indicated 3. Recognize clinical applications of the imaging techniques 4. Consider the use of these techniques in his/her clinical practice Introduction Head Ultrasound Neuroimaging techniques: Conventional-anatomical: US, CT, MRI: T1, T2, FLAIR, Advanced-functional: DWI, DTI, SWI, 1 H-MRS, Pro No ionizing radiation No sedation Bedside Relatively inexpensive Serial imaging easy Contra Age-dependent = only newborn + infants Investigator dependent Limited for the evaluation of brain periphery abnormalities at the brain convexity can be missed 1

2 Head ultrasound P R E T E R M T E R M Venous hemorrhagic infarction with follow-up (2 months) in a preterm neonate Head ultrasound Head ultrasound Anterior fontanel Mastoid fontanel Acute hypoxic-ischemic injury in a term neonate Cerebellar hemorrhage: Best seen on images through the mastoid fontanel Head ultrasound Computed tomography (CT) Resistive index (RI) of the intracranial vasculature: Correlates with brain perfusion Measurement: Anterior circulation (e.g. ACA) Normal values: (term neonates) HIE: RI values (<0.5) correlation with poor outcome Pro Widely available Rapid Usually no sedation Contra Limited ability to distinguish between tissues with subtle differences in densities Ionizing radiation Side effects (short/long term) Impact on developing brain CT should be used with caution in children and alternative imaging modalities should be used whenever possible 2

3 CT: Indications CT: Calcifications Calcifications: Congenital infections: CMV, Toxoplasmosis, Metabolic: Aicardi-Goutières syndrome, Cockayne syndrome, Brain tumors Skull abnormalities: Craniosynostosis Trauma Confirmed congenital CMV infection Congenital CMV infection CT: Calcifications Congenital toxoplasmosis infection Congenital HIV infection CT: Calcifications Conventional MRI: T1, T2 T1 = Myelin-weighted Myelin = bright H 2 0 = dark T2 = H 2 0-weighted H 2 0 = bright Myelin = dark Aicardi-Goutières syndrome 3

4 Conventional MRI: T1 Useful for delineation of anatomy Bright on T1: Blood (sub-acute hemorrhage) Fat Melanin Contrast agent CT T1 Conventional MRI: myelination Unmyelinated white matter = H Myelinated white matter = fat/myelin +++ T2w T1w T2w T1w T2w T1w newborn 5 months 2 years Conventional MRI: T1, T2 Conventional MRI: T1, T2 Patient Patient Congenital Pelizaeus-Merzbacher disease (PLP1 mutation) Conventional MRI: T1, T2 Conventional MRI: T1, T2 Lissencephaly posterior > anterior gradient Sequelae after acute neonatal hypoxic-ischemic injury 4

5 T1 + contrast agent Periventricular leukomalacia Contrast agent = paramagnetic (T1-shortening bright signal) Within brain tissue = abnormal Enhancement = damage of the blood-brain barrier: Brain tumors Infections Inflammations T1 + contrast agent T1 + contrast agent T2 T2 T1c T1+c Neonatal HSV infection X-linked adrenoleukodystrophy FLAIR = FLuid Attenuated Inversion Recovery FLAIR H 2 0-weighted + suppression of CSF = T2w image with dark CSF FLAIR T2 Allows a better evaluation of the structure close to CSF spaces: Periventricular white matter Dentate nuclei 5

6 FLAIR FLAIR FLAIR T2 FLAIR T2 Late-infantile neuronal ceroid lipofuscinosis Vanishing white matter disease (EIF2B5 mutation) Magnetic resonance angiography (MRA) and venography (MRV) MRA + MRV Allows studying the macro-vasculature of the brain Various techniques available MRA MRV Indication: Vascular disorders: stroke, malformations, posttraumatic, vasculitis, MRA Cerebrospinal Fluid (CSF) Flow Imaging Study of the direction, amplitude and pulsatility of CSF flow Systole Blood into cranial vault CSF spinal canal Diastole Blood out of cranial vault CSF back into cranial vault Moyamoya syndrome in neurofibromatosis type 1 Bidirectional CSF flow 6

7 CSF Flow Imaging CSF Flow Imaging Magnitude images Phase images Indication: CSF flow study: Craniovertebral junction: Chiari malformations Sylvian aqueduct Patency of a third ventriculostomy CSF Flow Imaging Diffusion-weighted imaging (DWI) Differences in diffusion properties of protons (H + ) Degree of diffusion depends on: Physiological micro-structural properties of tissue Pathological changes of tissue Chiari 1 malformation CSF = high degree of mobility DWI White matter = less degree of mobility DWI ADC ADC = apparent diffusion coefficient Values, calculated by post-processing Advantage compared to DWI: Represents only local diffusion without contamination by other physical phenomenon such as T2 relaxation Diffusion CSF > brain tissue 7

8 DWI ADC DWI ADC DWI DWI ADC High diffusion Dark Bright Low diffusion Bright Dark ADC Pathological diffusion characteristics DWI / ADC Restricted diffusion Represents cytotoxic edema = low diffusion DWI = bright ADC = dark T2 DWI Increased diffusion Represents vasogenic edema = high diffusion DWI = dark ADC = bright ADC Indication: Ischemic injury Inflammatory process Infection Brain tumor Metabolic disorder DWI / ADC DWI / ADC DWI ADC DWI ADC Acute hypoxic-ischemic encephalopathy 8

9 DWI / ADC Diffusion tensor imaging (DTI) Characterization of 3D shape of diffusion Diffusion = in all directions: isotropic Diffusion in all directions: anisotropic Brain abscess DTI DTI z λ 1 y x Measure diffusion along various directions (> 6) λ 2 λ 3 Calculate shape of the ellipsoid Fractional anisotropy (FA) = proportion of anisotropic diffusion relative to total diffusion Values range: 0-1 FA DTI DTI Principal diffusion/fiber direction can be color coded: Red: right left Green: anterior posterior Blue: superior inferior 9

10 DTI: qualitative evaluation DTI: qualitative evaluation Joubert syndrome Old right MCA stroke DTI: qualitative evaluation Fiber tractography (FT) Joubert syndrome FT = complex post-processing technique enables the reconstruction of the course of major fibers within the brain FT application FT application Joubert syndrome 10

11 FT application 1 H-Magnetic resonance spectroscopy (MRS) Allows studying brain metabolites qualitatively and quantitatively mi Cr Cho NAA Aberrant course of the right corticospinal tract 1 H-MRS 1 H-MRS Metabolite Significance Patient N-Acetylaspartate (NAA, 2.0 ppm) Glutamate/-mine (2.3 ppm) Creatine (3.0 ppm) Choline (3.2 ppm) Myo-Inositol (3.5 ppm) Neuronal marker Neurotransmitter Energy metabolism Cell membrane turnover Osmoregulation Cr Cho mi NAA Patient Lactate (1.33 ppm) Anaerobic glycolysis Creatine deficiency syndrome (GAMT mutation) 1 H-MRS 1 H-MRS Patient Patient Cr Cho mi NAA Cr Cho mi NAA Lactate Canavan disease Complex 1 deficiency 11

12 Perfusion-weighted imaging (PWI) Dynamic contrast susceptibility PWI Maps the micro-perfusion of the brain tissue Two techniques: Dynamic first pass contrast enhanced magnetic susceptibility imaging Arterial spin labeling (ASL) CBV!! Courtesy of Dr. T. Huisman Arterial spin labeling Non-invasive hemodynamic imaging No IV contrast, radiofrequency labelling Arterial spin labeling Can be repeated as often as necessary Absolute quantification Selective vascular territory studies CBF!! Wintermark M et al, Stroke, 2005 Van Laar PJ et al, Radiology, 2008 PWI PWI Clinical applications Indication: Stroke: identification of regions of critical perfusion (PWI-DWI=tissue risk of infarction) Tumors: high-perfusion = high-grade Hypoxic-ischemic injury 1-day-old male (39 weeks of gestation) with acute neonatal stroke Huisman TA et al, Eur Radiol,

13 Susceptibility weighted imaging (SWI) SWI MRI technique accentuating magnetic properties of blood, blood products, non-heme iron, and calcifications Difference in the magnetic properties of oxygenated and deoxygenated hemoglobin phase difference between regions with various concentrations of oxygen SWI SWI: application Blood, blood products: Hemorrhagic disorders, stroke, traumatic brain injury, brain tumors, vascular malformation Calcifications: Infections, brain tumors, metabolic/ neurodegenerative disorders Non-heme iron: Neurometabolic/neurodegenerative disorders SO2 80% SO2 100% SWI: application SWI: application Traumatic brain injury (DAI) Sturge-Weber syndrome 13

14 Imaging of the spinal cord Nervous system includes not only the brain, but also: Spinal cord Peripheral nerves Muscles Diastematomyelia Imaging of the spinal cord Imaging of the peripheral nerves Foramen magnum stenosis in patient with mucopolysaccharidosis type 2 Neurofibromas in patient with NF1 Imaging of the muscles Imaging of the muscles Courtesy of Dr. A. Klein Courtesy of Dr. A. Klein 14

15 Imaging of the muscles Imaging of the muscles RYR1-related myopathy Courtesy of Dr. A. Klein Mercuri E et al, Ann Neurol, 2010 Conclusion Take home messages 1 Multimodality diagnostic imaging Anatomical imaging: T1, T2, FLAIR, Functional imaging: DWI, DTI, 1 H-MRS, 1. Speak to neuroradiologists to insure that the right sequences are obtained to answer your questions 2. In specific clinical situations - certain sequences are key to diagnosis: White matter disorders = T2 + FLAIR Cerebellar atrophy = coronal T2 Calcifications/blood in consideration = SWI Metabolic disorder in consideration = 1 H-MRS Acute neurology = DWI Inflammation, infections, tumors = T1+contrast 3. Possible artifacts of imaging should always be considered in image interpretation Take home messages 2 4. Always look at ventricular size and shape carefully 5. Brain maturation during the first months of life are reflected in changes in brain myelination on MRI 6. As a generalization: T1 weighted images = anatomic considerations FLAIR and T2 = pathology 7. Use a neuroimaging based pattern-recognition if possible: White matter disorders Cerebellar atrophy Calcifications 15