Bert, C.

Constantinescu, A.

Durante, M.

Graeff, C.

Kaderka, R.

Lehmann, H. I.

Packer, D.

GSI Repository

Heart beat modelling in a water and anthropomorphic phantomR. Kaderka1, A. Constantinescu1,2, H.I. Lehmann3, D. Packer3, M. Durante1,2, C. Graeff1, and C.Bert1,41GSI, Germany; 2TU Darmstadt, Germany; 3Mayo Clinic College of Medicine, USA; 4Universita¨tsklinik Erlangen,GermanyIntroductionAtrial fibrillation represents the most common cardiacarrythmia. AV node ablation requiring an invasive proce-dure is the commonly used treatment choice at the moment.However, animal studies have shown that a similar resultcan be achieved non-invasively using ionising radiation. Amethod was described by Sharma et al [1] using photons toachieve AV node ablation.As known from cancer patients using the Bragg peak char-acteristic of charged particles can lead to a more favorabledose deposition. In order to explore the potential of car-bon ions for treatment of atrial fibrillation animal studieswith swines are planned for 2014 at GSI. In this report amethod for determining the dose deposition under influ-ence of breathing and cardiac motion with the help of aphantom is described.Materials and methodsThe main challenge when irradiating the AV node is themotion of the target. The target exhibits two interferingmotion types: a slow motion (several seconds) with largeamplitude due to breathing as well as a fast motion (around120 beats per minute for swines) coming from the heart it-self. The treatment procedure must incorporate means tomitigate the motion of the AV node.Moving phantoms need to be used in order to experimen-tally study the dosimetric effects of breathing, heartbeatand motion mitigation techniques. For this purpose the tar-get area is simulated by a PMMA block containing pinpointionisation chambers. The ion chamber block is mounted onan industrial robot Kuka KR5 sixx R850. The robot is ca-pable of 6D motion and holds the target block either in wa-ter or an anthropomorphic breathing phantom. The latterphantom consists of a thorax and is actuated with a step-per motor to simulate the moving of the chest wall whilebreathing (Fig. 1).The breathing functionality of the anthropomorphic phan-tom has been used for several years at GSI and is docu-mented in [2]. The motion of the AV node has now beenincorporated into the phantom motion mimicking patternsextracted from 4DCTs of four swines. The 4DCTs weretaken by Mayo Clinic College of Medicine. The AV nodedisplacement can be traced with sufficient accuracy (< 0.5mm) by the robot. In order to study the effects of the dif-ferent motion components, the robot control software canenable each movement type individually (Fig. 2).Figure 1: Picture of the Kuka robot holding the PMMAblock with ionisation chambers inside the anthropomorphicbreathing phantom.Figure 2: Motion trajectory of the target in superior-inferiordirection showing breathing and heartbeat motion individ-ually as well as the superposition.DiscussionThe robot is able to reliably reproduce a target trajectorycoming from both breathing and cardiac motion in a phan-tom. The motion parameters can easily be manipulated inthe control software to allow both quality assurance as wellas research for a large variety of patients or animals.References[1] Sharma et al., HeartRhythm 7(6), 2010[2] Steidl et al., Phys Med Biol 57(8), 2012GSI SCIENTIFIC REPORT 2013 BIOPHYSICS-47doi:10.15120/GR-2014-1-BIOPHYSICS-47 249

Heart beat modelling in a water and anthropomorphic phantom

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Heart beat modelling in a water and anthropomorphic phantom

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