Risonanza Magnetica. Evoluzione in ambito della Neuroradiologia Pediatrica: aspetti caratterizzanti. Neuroradiologia Pediatrica oggi.

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1 I raggi X fanno male.. Evoluzione in ambito della Neuroradiologia Pediatrica: aspetti caratterizzanti Fabio Triulzi soprattutto ai bambini Neuroradiologia Pediatrica oggi Esame Dose effettiva (msv) N di RX torace per dose equivalente Rischio di cancro Periodo equivalente di radiazione del fondo ambientale Rx Torace 0,02 1 1/1milione 3 giorni Cistografia / mesi TC encefalo / anno TC addome / anni e 6 mesi US Risonanza Magnetica TC

2 Ultrasuoni nel neonato MR T2 MR T1 US Anatomia normale cono cauda SACRAL DIMPLE Sacral Pit Normal

3 Intradural lipoma CSF TAC 3D Malformazioni cranio facciali Applicazioni Neuro Urgenze vascolari Urgenze traumatiche Monitoraggio chirurgico Calcificazioni intracraniche Studio del cranio e del basicranio Studio del massiccio facciale Studio delle rocche petrose Rachide solo alcune malformazioni o tumori

4 Accorgimenti per ridurre la dose Importante usare spessori adeguati, pitch ampi e valori di kv e ma bassi Studi multifase da evitare o comunque solo con indicazioni specifiche Sistemi di riduzione dose radiante CARE DOSE 4D Sistemi di ricostruzione iterattiva ma ~ spessore del corpo del Paziente mantenendo costante qualità di immagine! ma e kv in funzione del peso Peso ma kv < > Consenso informato! ImPACT CT Patient Dosimetry Calculator version 0.99v, 17/6/2004 Scanner Model: Acquisition Parameters: Manufacturer: Siemens ma 30 ma Scanner: Siemens Sensation 16 Rotation time 0.00 s kv: 120 mas / Rotation 30 mas Scan Region: Body Collimation mm Data Set MCSET16 Update Data Set Slice Width mm Current Data MCSET16 Pitch 3 Scan range Rel. CTDI Look up 2,15 (assumed Start Position 43 cm Get From Phantom CTDI (air) Look up 32,8 mgy/100 End Position 68,5 cm Diagram CTDI (soft tissue) 35,1 mgy/100 Patient Sex: nctdi w Look up 14,7 mgy/100 Se RX torace = 0.02 msv TC torace tra 40 e 50 RX Organ w T H T w T.H T Remainder Organs Gonads 0,2 0,0015 0,0003 Adrenals Bone Marrow (red) 0,12 0,54 0,064 Brain Colon 0,12 0,0033 0,00039 Upper Large Intestine Lung 0,12 2 0,24 Small Intestine Stomach 0,12 0,2 0,024 Kidney Bladder 0,05 0, , Pancreas Breast 0,05 1,7 0,085 Spleen Liver 0,05 0,3 0,015 Thymus Oesophagus (Thymus) 0,05 2,2 0,11 Uterus Thyroid 0,05 0,32 0,016 Muscle Skin 0,01 0,36 0,0036 Bone Surface 0,01 1 0,01 CTDI w (mgy) Thymus 0,025 2,2 0,056 CDTI vol (mgy) Remainder 2 0,025 0,36 0,0089 DLP (mgy.cm) Total Effective Dose (msv) 0,63 esposizione con dati non corretti è pari a 385 RX

5 RM in Neuroradiologia Pediatrica Prerequisito High Resolution: WHY? Radiological history is a continous research to improve the three faces of resolution: SPACE, CONTRAST and TIME ALTO CAMPO MAGNETICO This is exceedingly true in neonatal and pediatric BRAIN: it is SMALL with a DIFFERENT CONTRAST between gray and white matter and we have FEW TIME to scan patients before they are going to move Pediatric MRI: the MYTH Spatial Resolution: how it works Low field, open MRI enables to scan children without sedation. Up to now the great majority of kids under 6 years of age needs sedation. Children with neurological disease needs often sedation even older than 6 years of age MRI brain imaging in kids at low field are of very poor utility and in many cases a second MRI at high field is needed PIXEL SIZE = FOV / MATRIX VOXEL SIZE = PIXEL SIZE x SLICE THICKNESS The standard FOV 240 mm / MATRIX 256² = PIXEL 0.93² SLICE THICKNESS 5 mm = VOXEL 4.7 mm³

6 Pediatric Brain MRI: the standard T2 WI T2 = 0.7x0.7x4 = 1.96 ml FLAIR = 0.8x0.9x4 = 2.88 ml Magnet 1.5 T FOV 20 (newborn) to 24 cm Slice thickness 3 to 4 mm Matrix size 256² to 380² 400² rarely 512² Voxel size at the best 0.6x0.6x3.0 mm (adult) Voxel size 1,08 mm³ or 1,08 ml Standard adult 0.8x0.8x5.0 mm (3,2 mm³) T1 = 0.8x0.8x4 = 2.56 ml ADC ~ 2x2x5 = 20 ml Neonatal MRI 0.82x0.7x3.0 mm = 1.72 ml

7 1-2 m 3-4 m 5-6 m m m m 7-8 m 9-10 m Fetal MRI FOV 350 mm! m Voxel > 4.5 ml 22 23

8 Fetal MRI T 32ch is it a real improvement? S/N MORE SIGNAL Less TIME equal Spatial RES Equal TIME more Spatial RES MORE NOISE Same parameters more artifacts 3.0 T 32 ch the standard 0.45 x 0.57 x 3.0 mm ~ 6 min Gennari Stripe

9 Baillarger Stria (4th layer) MR FETAL AUTOPSY 0.3x0.3x1.2 = ml, 108 nl 22SG 21SG 22SG 19SG

10 0.4x0.48x2.0 mm = ml Neonatal MRI 0.82x0.7x3.0 mm = ml 0.38 ml imaging 1.7 ml imaging 0.38 ml imaging 1.7 ml imaging 0.38 ml imaging 1.7 ml imaging

11 Isotropic 3D T1 at 0.9 mm³ (0.72 ml) 3.0 T 32 ch is it a real improvement? Standard T2 W sequences (5 6 min) 0.76 ml in children 0.38 ml in newborn Yes it is! Is it possible some further improvement? Is it possible some further improvement? 0.45 x 0.57 x 3.0 mm 0.3x0.3x1.1 0,099 ml (99nl) Pushing the acquisition time up to 18 min (sedated pts) it is possibile to further reduce the spatial resolution below the limit of 0.1 ml (100 nl)

12 Leukoencephalopathy with calcifications and cysts Leukoencephalopathy with calcifications and cysts 0,099 ml 0,099 ml

13 Band heterotopia Band heterotopia

14 Band heterotopia 0,099 ml Band heterotopia 0,099 ml Agyria pachigyria 0,099 ml

15 Agyria pachigyria Agyria pachigyria 0,099 ml Partial CC agenesis in NF1

16 Partial CC agenesis in NF1 0,099 ml Partial CC agenesis in NF1 0,099 ml

17 Molar tooth

18 Molar tooth 0,099 ml Molar tooth Molar tooth 0,099 ml

19 Near drowning 0,099 ml 0,099 ml 7 T

20 7 T 3 T HR Imaging of cortical layering Conclusion 1.5 T 3 T 3 T HR 7 T Standard high res imaging with 3T32ch allows to obtain voxel size of about ml Particular sequences in sedated patients can further reduce voxel size below the limit of 0.1 ml, very close to the typical voxel size in 7T imaging This new imaging techniques diclose a new horizon in MR morphological studies of the developing brain ~ 1.8 ml ~ 0.8 ml ~ 0.1 ml ~ 0.05 ml