Safety aspects of a new Hybrid

Angio-MR: P3-Stroke-Horizon 2020 project of EIT Health

Michiel Dehairs1, Nicholas Marshall1,2, Hilde Bosmans1,2

1 Medical Imaging Research Center, Medical Physics and Quality Assessment , Katholieke Universiteit Leuven, 3000 Leuven, Belgium2 Department of Radiology, UZ Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium

The concepts and information presented in this presentation are based on research and are not commercially available

Angio-MR system

• Hybrid system combining an MRI with an Angio x-ray source and

detector

• One combined system not two systems next to each other

Siemens nexaris Angio-CT

© Siemens Healthcare GmbH, 2018

Angio-MR system

Mock-up of the system

18426 P3-Stroke - Predictive Prevention and Personalized Interventional Stroke

Therapy

• Project partners

• UK Erlangen, Prof Arnd Dörfler

• FAU Erlangen, Prof Andreas Maier

• KU Leuven, Prof Hilde Bosmans

• Univ Bordeaux *, Prof Pierre Jais

• ESTESC Coimbra * Prof Graciano Paulo

• Siemens Healthcare GmbH, Dr Martino Leghissa

• * External project partners

Purpose• Increasing the efficiency of Stroke treatment

o Stroke remains the second leading cause of death worldwide

o Rapid treatment may minimize the long-term effects of a stroke and prevent death

o By combining both imaging modalities into one hybrid system it is possible to reduce treatment

time significantly no more time delay between diagnosis and treatment

o Immediate verification whether treatment is successful

• Electro Physiology (EP)

• Interventional oncology

• Percutaneous RF ablation

• Trans Arterial Chemo-Embolization (TACE)

• Selective Internal Radio Therapy (SIRT)

Take advantage of the Hybrid System

• Make use of the MRI system when possible

• Find ways to reduce the use of X-rays

immediate reduction of dose

• Task for the physicians to help with this

• MRI should/could replace CT scan when possible

Safety

• It’s a hybrid system look at the safety measures for:

o MRI

o Angio

• MRI safety: deal with magnetic fields

• Angio safety deal with the X-rays

Magnetic Safety

• Testing of MR compatibility and safety of neuro-interventional devices

• Metallic coating of catheter artifacts in MRI (similar for guidewires)

Various stent retrievers Guidewires Catheters

X-ray Safety

• Under couch vs Over couch configuration

patient eye lens becomes a risk factor

Eye lens dose

• Threshold for developing lens opacities: 0.5 - 2.0 Gy

• Threshold for developing cataract: 5.0 Gy

The Peak Skin Dose (PSD),

averaged over 60 patients

undergoing a thrombectomy

procedure in our hospital was

0.26 Gy with a maximum value of

1.97 Gy. In total four patients had

a PSD above 0.5 Gy.

Eye lens dose

Simulation TLD Measurements

Eye lens dose Results• Simulation ratio Anterior-Posterior/Posterior-Anterior:

o Small FOV: ~4

o Large FOV: ~40

• TLD Measurement ratio AP/PA:

o Small FOV: ~4

o Large FOV: ~35

• Bismuth eye shield lowered eye lens dose by factor ~3

Eye lens dose Conclusion• Patient eye lens dose is significantly increased in the Angio-MR system

meaning necessary precautions need to be considered:

good collimation, eye shields, head tilt, larger primary angulations,…

Secondary

angulation is not

possible with the

Angio-MRI

Tilting the head

when possible

removes the eyes

from the primary

FOV

Physician Dose

• Comparative study of the scattered radiation towards the primary

physician was performed

Bore exit

Safe position for theinterventionalist

Patient table

3D Dose Distribution(eV/g) per history

Patient table

No lead shields in thissimulation

Head

Head

Feet

Feet

3D Dose Distribution(eV/g) per history

Physician Dose Results:• The scattered radiation towards the physician reduced by a factor: 2 - 4

• When taking a step back the scatter reduced a further factor of 15 for the

Angio-MRI setup

• After adding both a ceiling mounted and table mounted radiation shield in the

conventional setup, the MRI setup had factor 2 lower dose

• The head of the physician is also protected when standing close enough to the

MRI bore exit

possible reduction in eye lens dose

Physician Dose Conclusion

• The presence of the MRI can serve as a radiation shield

• When possible, the medical personnel should step outside the

scattered x-ray field during irradiation

• Adding a ceiling mounted shield could reduce the scatter even more

• Physician eye lens dose could potentially be lowered

Thank You!