Un Sistema di Navigazione basato su Mixed Reality per Trattamenti HIFU

Transcription

1 La Medicina Incontra la Realtà Virtuale MIMOS Un Sistema di Navigazione basato su Mixed Reality per Trattamenti HIFU C. Freschi, V. Ferrari*, F. Porcelli, A. Peri, L. Pugliese, L. Morelli, M. Ferrari, F. Mosca Università di Pisa

2 High Intensity Focused Ultrasound (HIFU) Focused transducer Emitting ultrasound waves Acoustical pressure Normalized Peak-to-Peak Pressure through the Focus Tissue heating Over 85 C Peak-to-Peak Pressure (MPa) x (mm) y (mm)

3 Tissue Lesion Thermal effects Temperature Simulation + Cavitation effects INSERM U 557 HIFUIFU INDUCED CAVITATION + Time exposure Thermal Dose Simulation INSERM U 557 = Tissue lesion

4 Completely non invasive burning of lesions!!! Skin Lesion of coagulation necrosis at focus (12x3mm) Target organ (e.g. liver) Transducer Tumour Undamaged tissue in front of focus

5 HIFU Clinical Indications Prostate cancer Blana, et al. Urology 2004;63(2): Uterine fibroids Stewart, et al. Am J Obstet Gynecol 2003;189(1):48-54 Pancreatic cancer Feng Wu, et al. Radiology 2005 Liver lesions (at our hospital) G. Di Candio, et al.. Proc. Of Second European Conference on interventional Oncology (ECIO 2010), to be appear

6 Imaging guidance Insightec ( MRI guided Israel & GE) Aishen (China, US guided) China Medical Technologies (China US guided) Mianyang (China US guided)

7 JC200 Haifu (HIFU) by Tech Co., Ltd, Chongqing

8 The localization/targeting system

9 Remote movement of the loc./targeting sys. HIFU Reference Frame

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11 Trouble Lesions that are clearly visible during a traditional ultrasound examination, are sometimes difficult to detect with the localization probe integrated in the HIFU system.

12 Troubles Movement limits of the localization/targeting system: 4 DOF for the probe and one for the patient (tilting bed). limited range of motion requires often the (manual) repositioning of the patient. Orientation difficulties using the remote motion of the location/targeting system, which is unnatural for doctors in respect to traditional freehand ultrasound. Inability to see the probe (drowned in the tank inside the bed) respect to the patient. The doctor often "loses itself" and takes a long time to locate the treatment area.

13 Troubles 28 % of the selected patients are positioned on the HIFU table but are not treated due to not founding of the lesion! Up two hours to search (and find in 72%) the lesion!

14 Goal To develop a navigation system with the aim to overcome these limitations and then to increase the number of possible treatments and to reduce the times of sittings and the risk of potential errors

15 Choosing the solution It is necessary other source of morphological information that allow to better find and localize (in respect to the HIFU frame) the target to burn. Among several types of imaging used to integrate the HIFU location/targeting system, including MRI and CT, an additional traditional ultrasound to use freehand is a good choice because: it allows to identify clearly and simply the treatment area. Its integration with the HIFU system requires no changes to machinery and requires no special spatial needs (such as MRI and CT).

16 Localization Our navigation system has been designed using an additional free hand US probe coupled with a localizer.

17 Components calibration

18 Our solution: two sub-systems 1) Traditional free-hand 2D US probe localized and calibrated with the HIFU reference frame 2) 3D virtual scene (on a workstation) containing: the patient-specific virtual anatomy, reconstructed from CT radiological images, the position of the additional free-hand ultrasound probe, the US 2D image instantaneously projected on the current US scan plane. It will also provide the classical 2D ultrasound image visualization.

19 VIRTUAL pre-operative 3D CT model Registration 3D model

20 Patient specific 3D model

21 Virtual to real anatomy registration First roughly point based registration in two steps: radio opaque fiducial markers in correspondence of the sternum (one marker) and of the iliac spines (two markers). Fiducial markers are acquired in the CT reference frames and registered with the corresponding points acquired before the treatment on the patient, positioned and fixed on the bed, in the Clinical Space using a digitizer. A second registration using internal anatomical reference points, close to the target zone: some points are acquired inside the patient using the localized ultrasound probe and registered with the corresponding points selected on the CT images.

22 FIRST SISTEM EVALUATIONS

23 In-vitro and in-vivo experiments In vitro setup (phantom) to evaluete US sensor calibration: error +- 2 mm In vitro setup to evaluete the transformation and calibration chain accuracy: error < 5 mm Simulation experiment using a volunteer was performed to test the efficacy of the navigation system (we didn t burned him!) Two clinicians tried the navigation system on the volunter and evaluate it very positively considering the system very useful to help the clinician to orient in the 3D space.

24 In-vivo evaluation of the navigation system

25 Target searching in our navigation system The clinician can search the target using the additional ultrasound probe. Restoring the a free-hand manipulation of the US. He/she can view the current position of the US scan plane in respect to the virtual anatomy. Eventually, if the target is not visible by the additional ultrasound probe, for example due to patient decubitus, he/she can localize the zone to treat using just the virtual anatomy. The user can select the target zone clicking on the scan plane of the additional ultrasound probe, or directly on the CT images.

26 Target identification at the HIFU console The system indicates to the surgeon how to position the HIFU localization/targeting system to reach the target zone selected (on the virtual scene). Then the clinician verifies the target using the traditional HIFU localization probe and accurately plan the zone to burn searching the lesion borders.

27 CONCLUSION The work demonstrates the feasibility and the potentiality of the use of an augmented reality navigation system to facilitate the target localization in the HIFU treatment and consequently to: reduce the times of sittings to increase the number of possible treatments to decrease the risk of potential errors A rigorous clinical experimentation is necessary to quantify the efficacy of the system

28 Acknoledgments The authors wish like to thank OV, which offers to biomedical research its work, day by day, in another sector, that in this case he (patiently) offered his unlucky situation to test the navigator. This project is supported by Cassa di Risparmio di Pisa Fundation (Software for generation of abdominal patient specific 3D models from volumetric radiological images) and Arpa Fundation (new US)

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