IMAGING BRAIN TUMORS IN IMAGING BRAIN TUMORS IN NEWBORNS AND EARLY NEWBORNS AND EARLY CHILDHOOD: UTILITY OF CHILDHOOD: UTILITY OF

COMBINING MR COMBINING MR TECHNIQUESTECHNIQUES

IMAGING BRAIN TUMORS IN IMAGING BRAIN TUMORS IN NEWBORNS AND EARLY NEWBORNS AND EARLY CHILDHOOD: UTILITY OF CHILDHOOD: UTILITY OF

COMBINING MR COMBINING MR TECHNIQUESTECHNIQUES

M. MORTILLA, M. ANTONELLO, C. CESARINI, M. MORTILLA, M. ANTONELLO, C. CESARINI, L. TASCIOTTI, C. FONDAL. TASCIOTTI, C. FONDA

UNIVERSITY CHILDREN’S HOSPITAL A. UNIVERSITY CHILDREN’S HOSPITAL A. MEYERMEYER

FIRENZE, ITALYFIRENZE, ITALY

M. MORTILLA, M. ANTONELLO, C. CESARINI, M. MORTILLA, M. ANTONELLO, C. CESARINI, L. TASCIOTTI, C. FONDAL. TASCIOTTI, C. FONDA

UNIVERSITY CHILDREN’S HOSPITAL A. UNIVERSITY CHILDREN’S HOSPITAL A. MEYERMEYER

FIRENZE, ITALYFIRENZE, ITALY

INTRODUCTIONINTRODUCTION

In the childhood CNS tumors are the leading cause of cancer-related death.In the last 20 years the advances in neuroimaging, neurosurgery, radiation therapy and chemotherapy have considerably improved the long term survival of children with brain tumors.Conventional MR images show definite details of brain tumor location, extension and morphological characteristics. Therefore MR imaging is widely used in the diagnosis and follow-up of pediatric patients with brain tumors.

Since conventional MRI does not provide information about tissue chemistry and the interpretation of these images may lead to poor estimation of the extent of active tumor, non conventional techniques, such as diffusion images and proton spectroscopy, may be used contributing to more accurate diagnosis, prognostication and treatment planning.Tissue diagnosis remains the gold standard.

The purpose of the study is to find a role of Diffusion-weighted Imaging (DWI) and proton Spectroscopy in characterizing intracerebral masses and finding a correlation between these techniques and histologic analysis of tumors.

PATIENTS & PATIENTS & METHODSMETHODS

62 patients affected with brain tumors aged 1 month-6 years, were studied with a 1.5T MR scanner (Eclipse, Philips) operating at 27mT/m gradient strenght and 40 mT/m/ms slew rate. A quadrature head coil was used.T2w SE images, FLAIR, T1w SE pre and post Gadolinium injection and sometimes GE T2* were obtained.Proton Spectroscopy studies included single voxel studies (PRESS TE 40/135/270ms, STEAM TE 20ms) and/or CSI (PRESS TE 135/270.

Spectroscopy acquisition were performed before the injection of the contrast media.

Eight children were able to undergo to the MR without need of sedation despite the long duration of the exam (50-60 minutes).The other children were sedated with different modalities regarding weight, age and critical conditions: patients up to 18 months of age (if the weight was below 10Kg) were sedated with chlorale hydrate (50-100 mg/Kg), while from 18mo. to 6yrs. patients were sedated using Sevoflurane through laringeal mask or, rarely, with barbiturates i.v.

Echo planar Imaging of Diffusion were obtained with sensitization along the slice select, read out and phase encoding axes (b- value of 800/1000/1200) with Echo Planar Single Shot sequences (TR 6450ms, TE 145.8ms, FA 90°, 5mm/1mm slice thickness/gap, 81x81 > 128x 128 reconstruction matrix, 1 NEX, chemical saturation at FA 180°, FAT saturation) with a total acquisition time of 32 seconds/15 slices.

In all patients a set of 3 images along the long orthogonal axes of gradient sensitization were obtained and the DWI TRACE images were post-processed. Apparent Diffusion Coefficient (ADC) images along the same orthogonal axes were also obtained and synthetic ADC map was produced (ADC TRACE.ADC values are expressed as a number x 10-3mm2/sec.

Multivoxel (CSI) were acquired with PRESS sequence, TR 1500ms, TE 135ms, FA 90°, thickness 1-1.5 cm, FOV 15 to 20cm.Chemical shift imaging matrix size 16x16, signal averages 1/2 with 1 slice per batch.

Single voxel were acquired with PRESS sequence, TR 1500/2000ms, TE 270/135/40ms and with STEAM TE 20ms, FA 90°; acquisition volume from 20x20x20mm, signal averages 128 and reference averages 8.

Multivoxel (CSI) were acquired with PRESS sequence, TR 1500ms, TE 135ms, FA 90°, thickness 1-1.5 cm, FOV 15 to 20cm.Chemical shift imaging matrix size 16x16, signal averages 1/2 with 1 slice per batch.

Single voxel were acquired with PRESS sequence, TR 1500/2000ms, TE 270/135/40ms and with STEAM TE 20ms, FA 90°; acquisition volume from 20x20x20mm, signal averages 128 and reference averages 8.

Most of the tumors underwent to surgery excisionand the specimens were analyzed by an expertise in pathology in order to make diagnosis following the WHO classification and to determine cell counting expressed as mean value (m.v.) over an are of 0.083mm2.Some tumors were biopsied only, such as germinoma because they are highly responsive to therapy.Biopsy or surgical excision was not performed when the tumor arised from non resectable regions (hypotalamus, brainstem,..)

OUR CASES

•Craniopharingioma 5•Low grade glioma (WHO I) 11•Glioma WHO II 2•High grade glioma 1•Pylocitic astrocytoma 10•Medulloblastoma (MB-PNET) 11•Germinoma 1•Subependimal gigantic astrocytoma 2•Ganglioblastoma 1•Ganglioglioma 1•Dysplasia 3•DNET 2 •Teratoma 1•Metastasi 1•Altri 10

Diffusion-weighted Imaging

It has been reported that the ADC characterizes the biophysical characteristics of tissue microstructure and microdynamics and that it provides information (based on pathophysiologic characteristics) that differs from that obtained with contrast-enhancing imaging.It has been suggested that the minimum ADC value of high-grade gliomas is significantly higher than that of low-grade gliomas and that low ADC values were found in areas of increased cellularity.

Others have suggested that the ADC may assist in the early detection of responses to anticancer therapy, because an increase in ADC values has been noted after treatment.DWI measures the molecular mobility of extracellular water,alterations in water mobility appear to reflect treatment-induced changes in tissue structure.Current understanding is that water diffusion increases acutely in tumor responsive to therapy. This precede changes in tumor volume.

11H-MRS (proton magnetic H-MRS (proton magnetic resonance spectroscopy)resonance spectroscopy)

11H-MRS (proton magnetic H-MRS (proton magnetic resonance spectroscopy)resonance spectroscopy)

11H-MRS (H-MRS (Magnetic Resonance Magnetic Resonance SpectroscopySpectroscopy) provides a qualitative ) provides a qualitative and quantitative evaluation of brain and quantitative evaluation of brain chemistrychemistryIn a proton spectrum at 1.5T the In a proton spectrum at 1.5T the metabolites are spread out between 63 metabolites are spread out between 63 and 64 MHz, and near 300 MHz at 7Tand 64 MHz, and near 300 MHz at 7TThe resonant frequencies are expressed The resonant frequencies are expressed in part per million (ppm), and are read in part per million (ppm), and are read from right to leftfrom right to left

11H-MRS (H-MRS (Magnetic Resonance Magnetic Resonance SpectroscopySpectroscopy) provides a qualitative ) provides a qualitative and quantitative evaluation of brain and quantitative evaluation of brain chemistrychemistryIn a proton spectrum at 1.5T the In a proton spectrum at 1.5T the metabolites are spread out between 63 metabolites are spread out between 63 and 64 MHz, and near 300 MHz at 7Tand 64 MHz, and near 300 MHz at 7TThe resonant frequencies are expressed The resonant frequencies are expressed in part per million (ppm), and are read in part per million (ppm), and are read from right to leftfrom right to left

11H-MRSH-MRSFat and water are eliminated, because their Fat and water are eliminated, because their peaks are to high and in spectrum scaling peaks are to high and in spectrum scaling the brain metabolites would be invisiblethe brain metabolites would be invisibleThe water suppression is obtained with The water suppression is obtained with CHESS (Chemical Shift Selective) or IR CHESS (Chemical Shift Selective) or IR (Inversion Recovery) techniques(Inversion Recovery) techniquesThe peaks are separated into the individual The peaks are separated into the individual frequencies through a Fourier Transformfrequencies through a Fourier TransformThe magnetic field felt by the Protons in The magnetic field felt by the Protons in different molecules depends on electron different molecules depends on electron clouds related to their different molecular clouds related to their different molecular position -> different chemical shift -> spread position -> different chemical shift -> spread of single peaks over the ppm or hertz scale of single peaks over the ppm or hertz scale

Sequences in 1H-MRSSequences in 1H-MRS

STEAMSTEAM (Stimulated Echo Acquisition Mode): 90 (Stimulated Echo Acquisition Mode): 90oo refocusing pulse, short echo time, less signal-to-refocusing pulse, short echo time, less signal-to-noise rationoise ratio PRESSPRESS (Point Resolved Spectroscopy): 180 (Point Resolved Spectroscopy): 180o o

refocusing pulse, short and long echo timerefocusing pulse, short and long echo time

With short echo time (TE 20-40 ms) metabolites of With short echo time (TE 20-40 ms) metabolites of both short and long T2 are visualizedboth short and long T2 are visualizedWith long echo time (TE 270 ms) only metabolites With long echo time (TE 270 ms) only metabolites with long T2 are seen . Echo Time of 135 ms with long T2 are seen . Echo Time of 135 ms allows the separation of lactate doublet from allows the separation of lactate doublet from lipids peaks with phase inversion. lipids peaks with phase inversion. TE 65 ms increases sensitivity in lipid detection TE 65 ms increases sensitivity in lipid detection nulling lactatenulling lactate

voxelvoxel

MR Spectra may be acquired with a MR Spectra may be acquired with a single single voxelvoxel localized in region of interest (normal localized in region of interest (normal or pathological) with variable volume or pathological) with variable volume (usually of 2x2x2 cm or more). Small (usually of 2x2x2 cm or more). Small volume are characterized by less signal to volume are characterized by less signal to noise ratio. Large volumes experience noise ratio. Large volumes experience higher averaging and are not indicated for higher averaging and are not indicated for higher resolution data collection, but only higher resolution data collection, but only for mean value in a defined areafor mean value in a defined area

multivoxelmultivoxel

MR Spectra may be acquired within a MR Spectra may be acquired within a brain slice in 2D acquisition or more slices brain slice in 2D acquisition or more slices in 3D acquisition) with variable matrix and in 3D acquisition) with variable matrix and variable volume (usually of 1x1x1 cm or variable volume (usually of 1x1x1 cm or more) Small volume of voxels experience more) Small volume of voxels experience lower averaging than single voxel with lower averaging than single voxel with larger volume. larger volume. Chemical Shift Imaging Chemical Shift Imaging (CSI)(CSI) may create the metabolite maps may create the metabolite maps with direct visualization of peak with direct visualization of peak concentrationconcentrationMagnetic field inhomogeneity, insufficient Magnetic field inhomogeneity, insufficient shimming and lipids contamination shimming and lipids contamination frequently alter the quality of multivoxel frequently alter the quality of multivoxel spectra. spectra.

Many metabolites may be Many metabolites may be identified in the proton identified in the proton magnetic resonance at 1.5 tesla, magnetic resonance at 1.5 tesla, NAA, Cho, Cr, Lactate, myo-NAA, Cho, Cr, Lactate, myo-Inositol, Lipids are currently Inositol, Lipids are currently evaluatedevaluated

In the following slides there is a In the following slides there is a list brain peaks:list brain peaks:

List of metabolites that can be List of metabolites that can be individualizedindividualized by by 11H-MRS H-MRS

N-acetyl methylgroups N-acetyl methylgroups (NAA –N-acetylaspartate and NAAG – N-(NAA –N-acetylaspartate and NAAG – N-acetylaspartylglutamate)acetylaspartylglutamate)

Methyl and Methylene protons of total creatine (Cr +PCr)Methyl and Methylene protons of total creatine (Cr +PCr)Trimethylammonium groups –Choline containing (Cho)Trimethylammonium groups –Choline containing (Cho)Myo-Inositol (mI)Myo-Inositol (mI)Glycine co-resonating with main mI peak (Gly)Glycine co-resonating with main mI peak (Gly)Glutamate & Glutamine with a and b-/g- protons (Glu/Gln)Glutamate & Glutamine with a and b-/g- protons (Glu/Gln)GlucoseGlucoseScyllo-inositolScyllo-inositolLactateLactateGABAGABAGlutathioneGlutathioneTaurineTaurineHomo-carnosineHomo-carnosinePhospho-ethanolaminePhospho-ethanolamineMacromoleculesMacromoleculesLipidsLipids

Resonance intensitiesResonance intensitiesexpressed in ppm at 1.5Texpressed in ppm at 1.5T

– Lactate/lipids1.33– NAA 2.02– Glx 2.2-2.4– Cr/PCr 3.02– Cho 3.22– mI 3.56

Control 5 yrs old: CSI PRESS TE 135ms

NAA(N-acetyl aspartate)NAA(N-acetyl aspartate): free : free aminoacid, high CNS concentration aminoacid, high CNS concentration (just less to glutamate) (just less to glutamate)

in adults in neural tissue, axons in adults in neural tissue, axons and dendritesand dendrites

in brain maturation also in in brain maturation also in oligodendrocytes type 2 and in non oligodendrocytes type 2 and in non neuronal cellsneuronal cells (mast cells)(mast cells)

used as used as neuronalneuronal marker marker

NAA(N-acetyl aspartate)NAA(N-acetyl aspartate): free : free aminoacid, high CNS concentration aminoacid, high CNS concentration (just less to glutamate) (just less to glutamate)

in adults in neural tissue, axons in adults in neural tissue, axons and dendritesand dendrites

in brain maturation also in in brain maturation also in oligodendrocytes type 2 and in non oligodendrocytes type 2 and in non neuronal cellsneuronal cells (mast cells)(mast cells)

used as used as neuronalneuronal marker marker

ChoCho (choline - N(CH(choline - N(CH33))3 3 GPC,PC)GPC,PC)

cellularcellular membrane turnover marker membrane turnover marker High in tumors, demyelinating High in tumors, demyelinating processes, inflammationprocesses, inflammationCrCr ( creatine - Cr + PCr = k),( creatine - Cr + PCr = k), reference internalreference internal due to its due to its stability,stability, marker of byproducts of marker of byproducts of energy energy chainschains >ATP >ATPLac (Lactate)Lac (Lactate) expresses the expresses the anaerobic metabolismanaerobic metabolism

mI (myo inositol)mI (myo inositol) glial pool glial pool markermarker. Small amounts from . Small amounts from glycineglycine

Glu or Glx (glutamate)Glu or Glx (glutamate) neurotransmitter, neurotransmitter, intermediate in aminoacid intermediate in aminoacid catabolism catabolism

Gln (glutamine)Gln (glutamine) metabolism of metabolism of glutamate glutamate glial markerglial marker

PRESS TE 135ms

STEAM TE 20ms

a

b

c

4 years old girl: 4 years old girl: pilocytic astrocytomapilocytic astrocytomaLactate in solid noduleLactate in solid noduleHigh choline peak High choline peak In P.A. the Choline In P.A. the Choline Levels are usually belowLevels are usually below3.0, while in MB-PNET3.0, while in MB-PNETare usually higherare usually higher

Cho Lac NAA

DWI TRACEDWI TRACE ADC TRACEADC TRACE

Nr. of cell: 0.083mm2

215 m.v.215 m.v.

185 m.v185 m.v.

Mean ADC valueMean ADC value1.68 101.68 10-3 -3 mmmm2 2 /sec /sec

4y.o. girl:4y.o. girl:pilocytic astrocytomapilocytic astrocytoma.. Histologic surgicalHistologic surgicalspecimen and cell density specimen and cell density counting over mixoid (185 cells) counting over mixoid (185 cells) and more compact (215 cells) and more compact (215 cells) portion of the tumor. portion of the tumor.

Boy, 13 monthsBRAINSTEM GLIOMACho/CrNAA/CrLac : MRS data indicates that it could be a pilocytic astrocytoma

PRESS TE 135ms

PRESS TE 270ms

1st MRI:diagnosis(WHO I)

2nd:afterchemoHigh Cho

3rd:6mo.after StopTherapyHigher Cho, low NAA, high lac

PRESS TE 270ms

6 years old boy: Brainstem glioma years old boy: Brainstem glioma

FLAIR C.E. FSE T1 ADC TRACE

b= 800b= 800

DWI TRACE ADC TRACEDWI TRACE ADC TRACE

At diagnosis b = 800At diagnosis b = 800DWIDWIADCADC

DWI TRACE ADC TRACEDWI TRACE ADC TRACE

After chemotherapy

6 years old girl: glioma of the midbrain (WHO I)

PRESS TE 40ms

Mild reduction of NAA/Cr and mI/Cr

Boy, 4 years old:Astrocytoma WHO II-III

Important reduction of NAA/Cr and moderate increase of Cho/Cr

CSI PRESS TE 270 ms

VOXEL 8

STEAM TE 20 msSTEAM TE 20 ms

CSI PRESS TE 270ms: CSI PRESS TE 270ms: high choline peak (Cho/Cr high choline peak (Cho/Cr 4.09), low NAA intensity 4.09), low NAA intensity signal.signal.Small amount of lactate. Small amount of lactate. STEAM TE 20ms: STEAM TE 20ms: evident lipids peak.evident lipids peak.

a

b

6 years old boy: medulloblastoma6 years old boy: medulloblastoma

MedulloblastomaMedulloblastoma.

a

Nr. of cell: 0.083mm2

750 m.v.750 m.v.

Mean ADC valueMean ADC value1.2 101.2 10-3 -3 mmmm2 2 /sec/sec

DWI DWI TRACETRACE

ADC ADC TRACETRACE

PRESS TE 135ms

STEAM TE 20ms

6 years old girl.: PNET-MB6 years old girl.: PNET-MB

a

b

..STEAM 20: evident mI, STEAM 20: evident mI, lipids and Glx peaks lipids and Glx peaks PRESS TE 135ms: high PRESS TE 135ms: high choline peak (Cho/Cr 12.4)choline peak (Cho/Cr 12.4)and low NAA intensity and low NAA intensity signal.signal.

PRESS TE 135ms

STEAM TE 20ms

PRESS 135: high choline peak PRESS 135: high choline peak (Cho/Cr 2.6), (Cho/Cr 2.6), low NAA signal intensity.low NAA signal intensity.Presence of lactate. Presence of lactate. STEAM 20: STEAM 20: evident lipids and mI peaks.evident lipids and mI peaks.

11 months old girl: 11 months old girl: pinealoblastoma. pinealoblastoma.

PinealoblastomaPinealoblastoma

DWI TRACEDWI TRACE ADC TRACEADC TRACE

Mean ADC valueMean ADC value0.4 x 100.4 x 10-3 -3 mmmm2 2 /sec/sec

Nr. of cell: 0.083mm2

900 m.v900 m.v..

PRESS TE 135ms

6 years old girl: choroid plexus carcinoma.

Mean ADC valueMean ADC value1.0 101.0 10-3 -3 mmmm2 2

/sec/sec

reducedreduced CrCr

All metabolites, includedCreatine, but Choline arereduced Cho/Cr 31.5 Cho/Cr 31.5

neoplasm do not neoplasm do not produce NAAproduce NAA

5 years old girl: germinoma5 years old girl: germinoma.

high lipids signalhigh lipids signal..

PRESS TE 135ms

320 m.v.320 m.v.

Nr. of cell: 0.083mm2

Mean ADC valueMean ADC value0.57 100.57 10-3 -3 mmmm2 2

/sec/sec

PRESS TE 270ms

CSI PRESS TE 135ms

Girl, 23 monthsmetastasis from rabdomyosarcoma

Cho/Cr 6.1Lac/Cr 6.8NAA/Cr

STEAM TE 20ms

Cortical DysplasiaTAYLOR TYPE

Increased mI/Cr ratio

Boy, 20 months: Tuberous sclerosisIncreased mI/Cr ratio

PRESS TE 40ms STEAM TE 20ms

GerminomaGerminoma

JDGGJDGG

PinealoblastomaPinealoblastoma

PNETPNET

MB-PNETMB-PNET

Pylocitic Astrocytoma (solid portion)Pylocitic Astrocytoma (solid portion)

ADC vs.Cells number correlationADC vs.Cells number correlation

Regression95% confid.

ADC vs. CELLS (Casewise MD deletion)

CELLS = 1024.6 - 420.8 * ADC

Correlation: r = -.6023

ADC

CE

LLS

100

300

500

700

900

1100

1300

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

more highly cellular >smaller intercellular spaces > lower ADC

BRAIN ABSCESSBRAIN ABSCESSvs. TUMORvs. TUMOR

BRAIN ABSCESSBRAIN ABSCESSvs. TUMORvs. TUMOR

DWI is able to discriminate between abscesses and tumors:a) brain abscess; b) supratentorial ependymoma

ab

DWIADC

Boy, 6 years old: brain abscess

Most of the metabolites are reduced.Lipids and lactate are present

ConclusionsConclusionsConclusionsConclusionsBrain tumors in children are highly heterogeneous for histology, prognosis and therapeutic response.Diagnosis and therapy of those, most of which are low grade, can be complicated because of their frequent adjacent location to crucial structures that limits biopsy.The utility of combining data from biologically important intracellular molecules, obtained with proton MR spectroscopy and from water mobility, obtained with diffusion imaging, is clearly addressed to increase the diagnostic accuracy in determining the clinical grade of pediatric brain tumors.

DWI enable to better differenciate between low- grade and high-grade tumor: high-grade gliomas have lower ADC values than low-grade gliomas.ADC maps are easily generated from routine fast diffusion-weighted imaging by use of software available on many MR systems.ADC may be a more direct indicator of changes in the brain than are other physical parameters. The degree of diffusion is strongly affected by microscopic biological structures such as the number, type and spatial arrangement of cells. These structures create barriers to the free diffusion of water so changes in diffusion may more directly reflect changes occurring within and between cells.

It still debating if ADC measurement can be used to determine the extent of tumor infiltration and to differentiate infiltration from peritumoral edema. It has been suggested that tumor infiltration is characterized by lower ADC values than edema.In our experience we found that quite often this is true but we always prefer to be cautious adding spectroscopy data when is possible to perform CSI.We also utilize high-b-value DWI that increase the anisotropy so is more accurate in the assessment of infiltration. Since infiltration occurs within and along white matter tracts, diffusion tensor imaging may yield more useful information.

Proton MR Spectroscopy enables the measurements of multiple chemical metabolites in normal and abnormal brain parenchyma.Cho/Cr or Cho/NAA in a lesion correlate with higher cellular proliferation rate and reflect the presence of a more malignant and rapidly growing tumor. It is necessary to correlate MRI data since pilocytic astrocytoma has high Choline and lactate despite it is considered benign: usually Cho/Cr ratio is less than 3.NAA is considered a neuronal marker, which decreases with replacement of neurons by tumor (or other non-neuronal tissue, including necrosis).In choroid plexus carcinoma a very low NAA/Cr is characteristic since the tumor does not produce NAA.

MRS can be used to follow tumors over time, since patients can serve as their own control after obtaining a baseline scan.CSI may be useful in monitoring the surgical scar: elevation of Cho/Cr ratio is index of a relapse. We have found this index reliable mostly in anaplastic ependymoma. It has been suggested that children with higher total creatine levels are more responsive to radiation or chemotherapy.In our experience children with low-grade gliomas that have significantly higher baseline Cho/Cr ratio have more chance to have tumor that progress over 2 years than those that have stable tumors.Lactate is no more considered an indicator of malignancy since it is found in benign tumors such as pilocytic astrocytoma.

Lipids may be detected in enhancing and non enhancing tumor regions. For a reliable detection of lipid peak it would be better to use acquisition protocols with a TE 65ms that null lactate peak.Lipids represent microscopic tumor cell necrosis or membrane breakdown that may precede necrosis.Lipids may be present in viable tumor, presumably because of poor perfusion and hypoxia and they undergo major intensity changes during apoptosis.They are found also in radiation necrosis.Because glial tumors are grade according to their cellularity, proliferative activity and degree of necrosis, Cho mapping (increased cellularity and proliferative activity) may added value to MRI in childrens with brain tumors, especially when it is combined with lipid mapping (necrosis and/or apoptosis).

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