|ECR 2015 / C-0829|
|Latest Advancements in Real-time Fusion Imaging for Prostate|
|This poster is published under an open license. Please read the disclaimer for further details.|
Findings and procedure details
In recent years real-time Ultrasound image fusion with a pre-acquired second imaging dataset has become more common also in prostate diagnosis and biopsy guidance [17, 3, 18].
In our experiences, real-time fusion imaging was carried out by MyLabTwice Ultrasound system (Esaote S.p.A., Genova, Italy – Fig. 8) equipped with Virtual Navigator technology.
The endocavity probes used were TRT33 and EC1123.
TRT33 (Fig. 9) is Transrectal probe with a dual transducer: a Microconvex (6.5MHz center frequency) and a Linear array (7MHz center frequency) positioned along the probe shaft.
EC1123 (6.5MHz center frequency – Fig. 10) is an endfire Microconvex transducer with an ergonomic handle to improve user’s comfort.
Virtual Navigator technology enables the real-time fusion imaging between Ultrasound and a second reference imaging modality (MRI, PET/CT, 3D Ultrasound). See Fig. 11, Fig. 12 and Fig.13.
With a slight increase in the exam duration, the operator has the possibility to obtain enhanced diagnostic confidence, merging highly defined anatomical volume dataset imaging with any real-time Ultrasound modality, providing morphological (B-Mode), functional (Elastosonography and CEUS) and hemodynamic information (Color Doppler, Power Doppler).
Virtual Navigator fusion procedures were allowed by an electromagnetic tracking system, composed by a transmitter and a small receiver, mounted on the Ultrasound probe (Fig. 14). The transmitter’s position, which is the origin of the reference system, was fixed by a support and the receiver provided the position and the orientation of the Ultrasound probe in relation to the transmitter in the created 3D space. The electromagnetic field source tip was oriented to point to the phantom, in order to address the highest homogeneity of the created field to the Ultrasound scanning area.
A proper Motion Control Sensor (applied on the lower abdomen of the examined subject with a plaster strip – Fig. 15) was used, in order to identify patient movements after the registration procedure completion.
The fusion between real-time Ultrasound and second modality 3D DICOM dataset was carried out with the One plane-One point procedure.
After importing the 3D second imaging modality data on the Ultrasound system in DICOM format (through PACS, CD/DVD, LAN, USB Media), the system was ready to start the fusion procedure between MRI, PET/CT and/or 3D Ultrasound and real-time Ultrasound data.
One plane registration was performed selecting the same plane in axial view both on Ultrasound scan and on the 3D second imaging modality dataset. After this selection, the system roughly registered the two imaging modalities. Therefore, moving the Ultrasound probe, real-time Ultrasound scans and simultaneous navigation within the related second modality volume was achieved.
This procedure is mandatory in order to give the Ultrasound system the information about the examined area orientation and position within the electromagnetic field and with respect to the second modality volume dataset.
After that, the one point registration procedure is performed. One point registration consisted in real-time selection of the same point on Ultrasound scan and on the second imaging volume dataset.
One point registration corrected the spatial error in the three coordinates (X, Y, Z), even if the operator’s error, related to the point identification/selection accuracy, and the initial angular error, related to the probe position), were still present .
A fine-tuning adjustment, referring to anatomical points different from the previous ones, was necessary in order to achieve a further improvement of registration.
Multi dataset of the 3D DICOM second modality imaging can be loaded and merged directly on the Ultrasound system equipped with Virtual Navigator technology, in order to obtain multi-parametric information, both anatomical (MRI) and functional (PET), fused with Real-time Ultrasound.
During real-time Ultrasound image fusion with a pre-acquired second imaging dataset for prostate diagnosis and biopsy guidance, other Virtual Navigator functions were used in order to help the operator during the fusion imaging procedure.
AutoSwitch function selects automatically the best second imaging modality to show once the operator changes the probe scanning plane: this feature has been particularly useful when using the Transrectal dual array (convex-linear) TRT33 transducer, where one array is perpendicular to the other. When switching from the Microconvex array of TRT33 transducer to the linear one, the AutoSwitch automatically changes the best of two views in case of multiple 3D second imaging modality datasets related to the patient under examination.
Virtual Biopsy for targeted biopsies increases the confidence during real-time Ultrasound–guided biopsy procedures. Real needle position and identification is highlighted by the virtual needle indication directly on real-time Ultrasound and a proper 3D representation of the probe, scanning plane, needle in plane and off plane and path to the target is presented. Colored target can be shown as well. In order to plan in advance the best path of insertion to avoid vessels and structures, a virtual preview of the needle path can be visualized before the insertion of the real needle. Virtual Biopsy can be joined to real-time multimodality fusion imaging or solely with the Ultrasound real-time imaging guidance.
Biopsy Planning enables to schedule and manage the needle insertion (one or multiple) for the same target and for multiple targets. Thus to ensure the sample of the regions of interest which can be highlighted by functional information (MRI DWI and/or PET and/or Color/Power Doppler and/or CEUS) and morphological information (MRI T2). See Fig. 16.
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