Strahlenschutz durch alternative Bildgebungsverfahren MRT

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1 3. Berliner Strahlenschutzseminar 26. April 2012 Strahlenschutz durch alternative Bildgebungsverfahren MRT Bernhard Schnackenburg Senior Clinical Scientist 2012 Einleitung/Sicherheit im MRT Technische Entwicklungen Diagnostik koronarer Herzerkrankungen Diagnostik angeborener Herzfehler 1

2 RF shield cooling magnet gradient coils RF coil X-gradient Y-gradient Z-gradient Patient table RF coil gradient coils magnet RF transmitter RF receiver Wasserstoffatomkerne computer 1. Gradienten ein + HF-Puls senden magnet gradient coils RF coil B 0 Patient table RF coil gradient coils magnet 2

3 2. Gradienten ein + HF-Signal empfangen magnet gradient coils RF coil B 0 Patient table RF coil gradient coils magnet 3. Bild berechnen FT Signale digitalisieren Analoge Signale (Echos) k-raum Bild [1/m] (Orts)frequenz [m] 3

4 water image (H 2 O) fat image (CH 2 ) Sicherheit Statisches Magnetfeld (B 4T) - Reversible Effekte (EKG-Verzerrungen, Schwindel, Magneto-Phosphene) - Ferromagnetische Materialien werden angezogen Gradientenfelder (Schwellwerte für db/dt in abh. von der Schaltzeit) - Reversible Effekte (Stimulation von peripheren Nerven) - Schallemission (Hörschutz obligatorisch) Hochfrequenzfeld (SAR* 4 W/kg) - Reversible Effekte (Erwärmung, 1 C Körperkerntemperatur-Erhöhung) - Erwärmung von Implantaten möglich *SAR = specific absorbtion rate 4

5 Technische Entwicklungen Klassisches Design 5

6 Panorama 1Tesla 60 cm 70 cm 6

7 Field strength. Higher field strength: benefits and challenges SNR field strength Wavelength inside the body For homogeneous rf- excitation: object must be smaller than wavelength Bernhard Schnackenburg, 01/

8 Standing 3T dielectric shading Torso Reality (3.0T) Simulation (3.0T) Spine, cardiac, brain Dielectric shading (3T) 8

9 Parallel RF 3T The RF Shimming (B1 calibration) Procedure Survey B1 calibration (1 slice) B1 Map Scanning with MultiTransmit B1 ShimTool 1. pla 2. 9

10 Patient adaptive RF shimming Note: BSA = Body Surface Area ISMRM 2011 #3353 Krishnamurthy et al. Phased Array Spulen (ADC in der Spule) ADC SNR 10

11 Kardio MRT Cardiovascular MRI: Indications/methods Coronary artery disease: ischemia, viability Heart valve disease Congenital heart disease Cardiomyopathies Pericardial disease Tumors, thrombi and masses MR angiography MR spectroscopy MR guided cardiovascular interventions 11

12 Darstellung des Herzens Kurzachse (SA) Vierkammerblick (4Ch) Zweikammerblick (2Ch) Dreikammerblick (3Ch) Motion Beating of the heart Respiration 12

13 Diagnostik koronarer Herzerkrankungen (Ischämiediagnostik) 5. Strategies for pre-intervention diagnosis and imaging... In summary, documentation of ischaemia using functional testing is strongly recommended before elective invasive procedures, preferably using non-invasive testing before invasive angiography. Cardiovascular magnetic resonance and singlephoton emission computed tomography for diagnosis of coronary heart disease (CE-MARC): a prospective trial Greenwood JP et al, LANCET December 2011 CMR sensitivity 86.5 % vs. SPECT sensitivity 66.5 % Bernhard Schnackenburg IACSM

14 Ischämie Kaskade Myocardial infarction Chest pain ECG alterations Systolic dysfunction Diastolic dysfunction Metabolic alterations Perfusion abnormality Duration of ischemia Courtesy: Ingo Paetsch, Cosima Jahnke Perfusion Methods: First pass of a CA (T1-effect) Time Sequential measurement of several slices/heartbeat (at least 3 slices) Single shot technique n spatial resolution: < 3 x 3 x 8 mm Rest and stress (Adenosin) i. e. heart rate up to 120 bpm Short Axis Apical Mid Basal LAD RCA LCX 14

15 Perfusion (Beurteilung visuell) signal Perfusionsdefekt time Sensitivität: 88% Spezifität: 82% Diagnostische Genauigkeit: 85% CMR-Perfusion during adenosin stress 65 y/o man with suspected CAD, atypical chest pain Arterial hypertension, diabetes, hyperlipidemia ergometry inconclusive High grade stenosis: CX and LAD Courtesy: DHZ Berlin 15

16 Saturation recovery 3D T1-TFE (patch from ETH Zürich 1) ) 10 x k-t acceleration (effective 6.5) k-t SENSE reconstruction (WIP: PCA reconstruction 2) ) TR/TE = 1.85 / 0.74 ms, Flip angle = 15 o Spatial resolution: 2.30 x 2.30 mm² 8 slices with 10 mm (reconstructed to 16 slices with 5 mm) Typical FOV: 380 x 380 x 80 mm 3 30 dynamics Breathhold in inspiration (up to 30 s) Acquisition window per heart beat: 220 ms WET* saturation pulse (120, 90, 180, 230 ; delay 150 ms) 0.5 molar CA (0.1 mmol/kg/bw, 4 ml/s) *WET water suppression enhanced through T1 effects 1) Vitanis V et al: MRM ) Pedersen H et al: MRM 2009 Saturation recovery 3D T1-TFE (Adenosin stress) Patient with suspected CAD, atypical chest pain k-t acceleration: 10; 16 slices 2.3 x 2.3 x 5 mm³ Courtesy: DHZ Berlin 16

17 Saturation recovery 3D T1-TFE Patient with suspected CAD, atypical chest pain No perfusion defect at rest Diagnostik angeborener Herzfehler 17

18 Strahlenrisiko bei Kindern Importantly, children are at much greater risk than adults from a given dose of radiation both because they are inherently more radiosensitive and because they have more remaining years of life during which a radiationinduced cancer could develop. Prakash A et al: Circ Cardiovasc Imaging. 2010;3: Part 1 Prakash A et al: Circ Cardiovasc Imaging. 2010;3:

19 Part 2 Prakash A et al: Circ Cardiovasc Imaging. 2010;3: Children s Hospital Boston Prakash A et al: Circ Cardiovasc Imaging. 2010;3:

20 Children s Hospital Boston Prakash A et al: Circ Cardiovasc Imaging. 2010;3: Fortschr Röntgenstr 2012; 184:

21 Bei angeborenen Herzfehlern sind 23 Fragestellungen aufgeführt: MRT 8 x I1 13 x I2 2 x I3 CT 0 x I1 7 x I2 10 x I3 6 x U I1 Zuverlässig einsetzbar und anderen Verfahren überlegen I2 Diagnostische Genauigkeit vergleichbar mit anderen Verfahren I3 Einsatz technisch möglich und validiert, Indikation aber nur in Einzelfällen gegeben U unklare Indikation, keine oder nicht kongruente Studienergebnisse Fortschr Röntgenstr 2012; 184: D balanced SSFP (free breathing) Sørensen T et al: Circulation. 2004;110:

22 Transposition of the great arteries Sørensen T et al: Circulation. 2004;110: Kinking aortic arch Sørensen T et al: Circulation. 2004;110:

23 CINE Imaging (Panorama 1T) 11 year, girl artificial pulmonary valve aneurysm of the RVOT Courtesy Dr. Junge, AKK Quantitative 2D 3T insufficiency of the aortic valve Stroke volume (SV) 86.3 ml Forward SV ml Backward SV 66.9 ml Regurgitant Fraction: 43.7 % 23

24 Vorhofseptumdefekt AAO RUPV SVC IVC ASD LV Flussmessung ASD Courtesy Philipp Beerbaum Planung der Flussmessungen Ao Ao Aorta PA PA Pulmonalis Courtesy Philipp Beerbaum 24

25 Quantifizierung der Fluss- und Schlagvolumina PA Ao Qp/Qs=2.45 PA = 58.5 ml (range, ml) Ao = 23.7 ml (range, ml) Q p Q s - pulmonalis Schlagvolumen - aortales Schlagvolumen PA - Flussvolumen in der Pulmonalis Ao - Flussvolumen in der Aorta a. Relevanter Links-Rechts-Shunt (Q p /Q s > 1.5) Courtesy Philipp Beerbaum 3D Flow Peak systolic flow through the aortic valves (streamlines). Helical flow pattern in a patient with dilated ascending aorta (pathlines) courtesy: Gerard Crelier, GyroTools LLC 25

26 Coronaries Coronary anomaly 26

27 Vielen Dank für Ihre Aufmerksamkeit 27