Preoperative Magnetic Resonance and Intraoperative Ultrasound Fusion Imaging for Real-Time Neuronavigation in Brain Tumor Surgery = Präoperative MRI- und intraoperative Ultraschallfusion für die Echtzeit-Neuronavigation in der Neurochirurgie von Hirntumoren

Purpose: Brain shift and tissue deformation during surgery for intracranial lesions are the main actual limitations of neuro-navigation (NN), which currently relies mainly on preoperative imaging. Ultrasound (US), being a real-time imaging modality, is becoming progressively more widespread during neurosurgical procedures, but most neurosurgeons, trained on axial computed tomography (CT) and magnetic resonance imaging (MRI) slices, lack specific US training and have difficulties recognizing anatomic structures with the same confidence as in preoperative imaging. Therefore real-time intraoperative fusion imaging (FI) between preoperative imaging and intraoperative ultrasound (ioUS) for virtual navigation (VN) is highly desirable. We describe our procedure for real-time navigation during surgery for different cerebral lesions. Materials and Methods: We performed fusion imaging with virtual navigation for patients undergoing surgery for brain lesion removal using an ultrasound-based real-time neuro-navigation system that fuses intraoperative cerebral ultrasound with preoperative MRI and simultaneously displays an MRI slice coplanar to an ioUS image. Results: 58 patients underwent surgery at our institution for intracranial lesion removal with image guidance using a US system equipped with fusion imaging for neuro-navigation. In all cases the initial (external) registration error obtained by the corresponding anatomical landmark procedure was below 2mm and the craniotomy was correctly placed. The transdural window gave satisfactory US image quality and the lesion was always detectable and measurable on both axes. Brain shift/deformation correction has been successfully employed in 42 cases to restore the co-registration during surgery. The accuracy of ioUS/MRI fusion/overlapping was confirmed intraoperatively under direct visualization of anatomic landmarks and the error was < \u30083mm in all cases (100%). Conclusion: Neuro-navigation using intraoperative US integrated with preoperative MRI is reliable, accurate and user-friendly. Moreover, the adjustments are very helpful in correcting brain shift and tissue distortion. This integrated system allows true real-time feedback during surgery and is less expensive and time-consuming than other intraoperative imaging techniques, offering high precision and orientation.Brain Shift und Gewebeverschiebung w\ue4hrend der chirurgischen Entfernung intrakranialer Raumforderungen sind die limitierenden Faktoren bei der Neuronavigation (NN), welche aktuell haupts\ue4chlich pr\ue4operative Bilder einsetzt. Ultraschall (US) als Echtzeit-Bildgebung wird bei neurochirurgischen Prozeduren zunehmend angewandt. Vielen Neurochirurgen fehlt aber die US Expertise, da schon in der Ausbildung standarisierte (typisch axiale) CT und MRT Schnittbilder f\ufcr die Navigation bevorzugt eingesetzt werden und somit die Sicherheit bei der sonografischen Identifikation anatomischer Strukturen fehlt. Daher ist eine intraoperative Echtzeitfusion zwischen pr\ue4operativen CT bzw. MRT Bildern und intraoperativem Ultraschall (ioUS) im Rahmen der virtuellen Navigation (VN) au ferordentlich w\ufcnschenswert. Wir pr\ue4sentieren hier die bei uns angewandte Methode f\ufcr dieEchtzeitnavigation bei der Entfernung verschiedener Hirntumoren. Material und Methoden: Wir wandten die Bildfusion mit virtueller Navigation bei der chirurgischen Entfernung von Hirntumoren an. Zum Einsatz kam ein Neuronavigationssystem, welches intraoperative Ultraschallbilder mit pr\ue4operativen MRT Bildern in Echtzeit \ufcberlagert und zu jedem US Bild simultan die dazu passende ko-planare MRTSchnittebene anzeigt. Ergebnisse: Die US-basierte Neuronavigation wurde bei der Operation von 58 Patienten mit Hirntumoren eingesetzt. In allen F\ue4llen war der Fehler der initialen (externen) Registrierung, welche anhand von anatomischen Landmarken erfolgte, unterhalb von 2mm und die Kraniotomie konnte korrekt angesetzt werden. Die Bildqualit\ue4t des transduralen Ultraschalls war gut und die L\ue4sion konnte bei allen Patienten detektiert und in allen Achsen vermessen werden. Die Korrektur von Brain Shift sowie Gewebeverschiebung gelang erfolgreich in 42 F\ue4llen zur Wiederherstel lung der intraoperativen Co-Registrierung. Die Genauigkeit der cberlagerung von ioUS und MRT wurde intraoperativ anhand der Visualisierung anatomischerLandmarken \ufcberpr\ufcft und der Fehler lag in allen F\ue4llen (100 %) unterhalb von 3mm. Schlussfolgerung: Neuronavigation mit Hilfe von in pr\ue4operative MRT Bilder integrierten intraoperativen US Bildern ist eine zuverl\ue4ssige, genaue und anwenderfreundliche neue Technologie. Brain Shift und Gewebeverlagerungen k\uf6nnen anhand verschiedener Einstellungsm\uf6glichkeiten am System erfolgreich intraoperativ korrigiert werden. Das integrierte System erm\uf6glicht eine intraoperative cberpr\ufcfung der Navigation in Echtzeit und ist dabei kosteng\ufcnstiger und weniger Zeit aufw\ue4ndig als andere intraoperative Bild-gebende Verfahren, trotzdem aber hoch pr\ue4zise

Three-dimensional breast assessment by multiple stereophotogrammetry after breast reconstruction with latissimus dorsi flap

Introduction: Numerous methods exist for the assessment of the female breast. Traditionally, a subjective approach was taken for surgical planning and evaluation of the postoperative outcome. Several objective methods have been developed to support this procedure, among which are laser scanning, MRI, mammography, ultrasound and photography. Recently, 3D imaging technology has been developed. Material & Method: 3D breast assessment by multiple stereophotogrammetry was examined. A custom-made imaging system with eight digital cameras arranged in four camera pods was utilised. This system was used for breast capture, resulting in eight images obtained by the cameras. The merging of these images and 3D image construction was carried out by C3D software and the volume assessment of the 3D images was made using breast analysis tool (BAT) software, developed by Glasgow University. A validation study was conducted. Nine plaster models were investigated and their volume determined by 3D stereophotogrammetry and water displacement method. Water displacement was considered to be the gold standard for comparison. The plaster models were specially made in order to represent a variety of shapes and sizes of the female breast. Each plaster model was examined 10 times by each method. Further, the volumes of the breasts of six female volunteer live models were investigated by the same two methods and the results compared. A special focus was placed on the reproducibility of the assessment. Each live model was captured with the 3D capture system three times at two different time points after retaking a special pose in a custom-made positioning frame. Altogether, each live model was captured six times, resulting in six 3D images, each of which was measured three times with BAT software. A patient study was conducted in 44 patients after unilateral immediate breast reconstruction with Latissimus dorsi flap and no contra-lateral surgery. Each patient underwent 3D imaging with the multiple stereophotogrammetry system. During capture, the special pose in the custom-made positioning frame was taken by the patient’s leaning forward almost horizontally with the upper body for the breasts to rise off the chest wall to enable full breast coverage by the cameras. 3D images were constructed with C3D software and volumes measured with BAT. For each patient, one 3D image was constructed and measured four times with BAT software. In addition to the volume determination, a shape analysis was conducted. For this purpose, 10 landmarks were determined according to recommendations in the literature. Two landmarks, sternal notch and xiphoid, were marked, forming an imaginary midline between each other and four landmarks on each breast, i.e. the medial and lateral ends of the infra-mammary fold, and the most prominent and most inferior breast points were utilised for symmetry assessment between the right and left breasts. Each landmark was recorded four times by the operator on the 3D image and three-dimensional coordinates obtained. By assessment of the left and right breasts a breast asymmetry score was calculated. Firstly, breast asymmetry was assessed objectively on the 3D images through the centroid size, which was determined as the square root of the sum of squared Euclidian distances from each landmark to the centroid. The centroid was the geometric mean of the landmarks. Secondly, asymmetry was assessed through breast volume by application of BAT software. Thirdly, asymmetry was examined through the landmarks themselves by investigation of the mismatch of the landmark configuration of one breast and its relabelled and matched reflection. The non-operated and reconstructed sides were compared and landmarks were recorded by the operator in three dimensions in four repeated tests. A decomposition of the total landmark asymmetry into its factors was conducted by fixation of the surface of the non-operated side and translation, rotation and scaling of the surface of the reconstructed side. For comparison, a subjective breast assessment was conducted by six expert observers who rated the results after breast reconstruction by subjective qualitative assessment of the symmetry in 2D images of the same 44 patients in six poses. For this purpose the Harris scale was utilised, providing a score of 1 to 4 for poor to excellent symmetry. Results: The results revealed that differences in the obtained volumes in the plaster models were not significant. In contrast, differences in the breast volumes measured in the live models were significant. The examination of the reproducibility revealed that overall reproducibility obtained by stereophotogrammetry was better than that obtained by water displacement. No correlation between breast size and reproducibility of the measurements was found. The results of the patient study demonstrated that the reproducibility of the landmarks was within 5 mm. There was a non-significant difference of the centroid sizes between both breasts. There was a significant difference of the volumes between the two breasts, with the non-operated side being larger than the reconstructed side. Volume was considered to be a more accurate measure for comparison of both breasts than centroid size as it was based on thousands of data points for the calculation as opposed to only four points of the centroid size. The statistical analysis of the landmark data provided a mathematical formula for determination of the breast asymmetry score. The average asymmetry score, derived by landmark assessment as the degree of mismatch between both sides, was 0.052 with scores ranging from 0.019 (lowest score) to 0.136 (highest score). The decomposition of the landmark-based asymmetry revealed that location was the most important factor contributing to breast asymmetry, ahead of intrinsic breast asymmetry, orientation and scale. When investigating the subjective assessment, the inter-observer agreement was good or substantial. There was moderate agreement on the controls and fair to substantial intra-observer agreement. When comparing the objective and subjective assessments, it was found that the relationship between the two scores was highly significant. Conclusion: We concluded that 3D breast assessment by multiple stereophotogrammetry was reliable for a comparative analysis and provided objective data to breast volume, shape and symmetry. A breast asymmetry score was developed, enabling an objective measurement of breast asymmetry after breast reconstruction. 3D breast assessment served as an objective method for comparison to subjective breast assessment

Image-based registration methods for quantification and compensation of prostate motion during trans-rectal ultrasound (TRUS)-guided biopsy

Prostate biopsy is the clinical standard for cancer diagnosis and is typically performed under two-dimensional (2D) transrectal ultrasound (TRUS) for needle guidance. Unfortunately, most early stage prostate cancers are not visible on ultrasound and the procedure suffers from high false negative rates due to the lack of visible targets. Fusion of pre-biopsy MRI to 3D TRUS for targeted biopsy could improve cancer detection rates and volume of tumor sampled. In MRI-TRUS fusion biopsy systems, patient or prostate motion during the procedure causes misalignments in the MR targets mapped to the live 2D TRUS images, limiting the targeting accuracy of the biopsy system. In order to sample smallest clinically significant tumours of 0.5 cm3with 95% confidence, the root mean square (RMS) error of the biopsy system needs to be The target misalignments due to intermittent prostate motion during the procedure can be compensated by registering the live 2D TRUS images acquired during the biopsy procedure to the pre-acquired baseline 3D TRUS image. The registration must be performed both accurately and quickly in order to be useful during the clinical procedure. We developed an intensity-based 2D-3D rigid registration algorithm and validated it by calculating the target registration error (TRE) using manually identified fiducials within the prostate. We discuss two different approaches that can be used to improve the robustness of this registration to meet the clinical requirements. Firstly, we evaluated the impact of intra-procedural 3D TRUS imaging on motion compensation accuracy since the limited anatomical context available in live 2D TRUS images could limit the robustness of the 2D-3D registration. The results indicated that TRE improved when intra-procedural 3D TRUS images were used in registration, with larger improvements in the base and apex regions as compared with the mid-gland region. Secondly, we developed and evaluated a registration algorithm whose optimization is based on learned prostate motion characteristics. Compared to our initial approach, the updated optimization improved the robustness during 2D-3D registration by reducing the number of registrations with a TRE \u3e 5 mm from 9.2% to 1.2% with an overall RMS TRE of 2.3 mm. The methods developed in this work were intended to improve the needle targeting accuracy of 3D TRUS-guided biopsy systems. The successful integration of the techniques into current 3D TRUS-guided systems could improve the overall cancer detection rate during the biopsy and help to achieve earlier diagnosis and fewer repeat biopsy procedures in prostate cancer diagnosis

Colonoscopy and Colorectal Cancer Screening

Colorectal cancer (CRC) represents a major public health problem worldwide. Fortunately most CRCs originate from a precursor lesion, the adenoma, which is accessible and removable. This is the rationale for CRC screening programs, which are aimed to diagnose CRC at an early stage or even better to detect and resect the advanced adenoma before CRC has developed. In this background colonoscopy emerges as the main tool to achieve these goals with recent evidence supporting its role in CRC prevention. This book deals with several topics to be faced when implementing a CRC screening program. The interested reader will learn about the rationale and challenges of implementing such a program, the management of the detected lesions, the prevention of complications of colonoscopy, and finally the use of other screening modalities that are emerging as valuable alternatives. The relevance of the topics covered in it and the updated evidence included by the authors turn this book into a very useful tool to introduce the reader in this amazing and evolving field

Instruction with 3D Computer Generated Anatomy

Research objectives. 1) To create an original and useful software application; 2) to investigate the utility of dyna-linking for teaching upper limb anatomy. Dyna-linking is an arrangement whereby interaction with one representation automatically drives the behaviour of another representation. Method. An iterative user-centred software development methodology was used to build, test and refine successive prototypes of an upper limb software tutorial. A randomised trial then tested the null hypothesis: There will be no significant difference in learning outcomes between participants using dyna-linked 2D and 3D representations of the upper limb and those using non dyna-linked representations. Data was analysed in SPSS using factorial analysis of variance (ANOVA). Results and analysis. The study failed to reject the null hypothesis as there was no signi cant di fference between experimental conditions. Post-hoc analysis revealed that participants with low prior knowledge performed significantly better (p = 0.036) without dyna-linking (mean gain = 7.45) than with dyna-linking (mean gain = 4.58). Participants with high prior knowledge performed equally well with or without dyna-linking. These findings reveal an aptitude by treatment interaction (ATI) whereby the effectiveness of dyna-linking varies according to learner ability. On average, participants using the non dyna-linked system spent 3 minutes and 4 seconds longer studying the tutorial. Participants using the non dyna-linked system clicked 30% more on the representations. Dyna-linking had a high perceived value in questionnaire surveys (n=48) and a focus group (n=7). Conclusion. Dyna-linking has a high perceived value but may actually over-automate learning by prematurely giving novice learners a fully worked solution. Further research is required to confirm if this finding is repeated in other domains, with different learners and more sophisticated implementations of dyna-linking