Real-time Intraoperative Guidance Research Articles

Enhancing surgical planning for abdominal tumors in children through advanced 3D visualization techniques: a systematic review of future prospects.

Preoperative three-dimensional (3D) reconstruction using sectional imaging is increasingly used in challenging pediatric cases to aid in surgical planning. Many case series have described various teams' experiences, discussing feasibility and realism, while emphasizing the technological potential for children. Nonetheless, general knowledge on this topic remains limited compared to the broader research landscape. The aim of this review was to explore the current devices and new opportunities provided by preoperative Computed Tomography (CT) scans or Magnetic Resonance Imaging (MRI). A systematic review was conducted to screen pediatric cases of abdominal and pelvic tumors with preoperative 3D reconstruction published between 2000 and 2023. Surgical planning was facilitated through virtual reconstruction or 3D printing. Virtual reconstruction of complex tumors enables precise delineation of solid masses, formulation of dissection plans, and suggests dedicated vessel ligation, optimizing tissue preservation. Vascular mapping is particularly relevant for liver surgery, large neuroblastoma with imaging-defined risk factors (IDRFs), and tumors encasing major vessels, such as complex median retroperitoneal malignant masses. 3D printing can facilitate specific tissue preservation, now accessible with minimally invasive procedures like partial nephrectomy. The latest advancements enable neural plexus reconstruction to guide surgical nerve sparing, for example, hypogastric nerve modelling, typically adjacent to large pelvic tumors. New insights will soon incorporate nerve plexus images into anatomical segmentation reconstructions, facilitated by non-irradiating imaging modalities like MRI. Although not yet published in pediatric surgical procedures, the next anticipated advancement is augmented reality, enhancing real-time intraoperative guidance: the surgeon will use a robotic console overlaying functional and anatomical data onto a magnified surgical field, enhancing robotic precision in confined spaces.

PitSurgRT: real-time localization of critical anatomical structures in endoscopic pituitary surgery.

Endoscopic pituitary surgery entails navigating through the nasal cavity and sphenoid sinus to access the sella using an endoscope. This procedure is intricate due to the proximity of crucial anatomical structures (e.g. carotid arteries and optic nerves) to pituitary tumours, and any unintended damage can lead to severe complications including blindness and death. Intraoperative guidance during this surgery could support improved localization of the critical structures leading to reducing the risk of complications. A deep learning network PitSurgRT is proposed for real-time localization of critical structures in endoscopic pituitary surgery. The network uses high-resolution net (HRNet) as a backbone with a multi-head for jointly localizing critical anatomical structures while segmenting larger structures simultaneously. Moreover, the trained model is optimized and accelerated by using TensorRT. Finally, the model predictions are shown to neurosurgeons, to test their guidance capabilities. Compared with the state-of-the-art method, our model significantly reduces the mean error in landmark detection of the critical structures from 138.76 to 54.40 pixels in a 1280 720-pixel image. Furthermore, the semantic segmentation of the most critical structure, sella, is improved by 4.39% IoU. The inference speed of the accelerated model achieves 298 frames per second with floating-point-16 precision. In the study of 15 neurosurgeons, 88.67% of predictions are considered accurate enough for real-time guidance. The results from the quantitative evaluation, real-time acceleration, and neurosurgeon study demonstrate the proposed method is highly promising in providing real-time intraoperative guidance of the critical anatomical structures in endoscopic pituitary surgery.

Toward the use of diffuse reflection spectroscopy for intra-operative tissue discrimination during sarcoma surgery.

Accurately distinguishing tumor tissue from normal tissue is crucial to achieve complete resections during soft tissue sarcoma (STS) surgery while preserving critical structures. Incomplete tumor resections are associated with an increased risk of local recurrence and worse patient prognosis. We evaluate the performance of diffuse reflectance spectroscopy (DRS) to distinguish tumor tissue from healthy tissue in STSs. DRS spectra were acquired from different tissue types on multiple locations in 20 freshly excised sarcoma specimens. A -nearest neighbors classification model was trained to predict the tissue types of the measured locations, using binary and multiclass approaches. Tumor tissue could be distinguished from healthy tissue with a classification accuracy of 0.90, sensitivity of 0.88, and specificity of 0.93 when well-differentiated liposarcomas were included. Excluding this subtype, the classification performance increased to an accuracy of 0.93, sensitivity of 0.94, and specificity of 0.93. The developed model showed a consistent performance over different histological subtypes and tumor locations. Automatic tissue discrimination using DRS enables real-time intra-operative guidance, contributing to more accurate STS resections.

5-aminolevulinic acid-guided endoscopic biopsy with violet light-emitting diode flashlight in malignant glioma: Technical note.

5-aminolevulinic acid (5-ALA) photodynamic diagnosis (PDD) has enabled better identification of malignant tumor cells and real-time intraoperative guidance. Here, we report a reasonable procedure for 5-ALA-guided endoscopic biopsy with a violet light-emitting diode (LED) flashlight for deep-seated malignant gliomas. A 63-year-old man presented with a headache and left upper homonymous quadrantanopia. Imaging studies showed atypical lesions with non-significant and partial contrast enhancement in the right deep temporo-occipital lobe. An endoscopic biopsy was performed under the guidance of 5-ALA PDD with a violet LED flashlight. The tumor tissues, which were difficult to distinguish from normal brain parenchyma under white light, were positive for 5-ALA fluorescence. The histopathological diagnosis was astrocytoma (the World Health Organization grade 3). The patient underwent adjuvant chemoradiation therapy. Headache and anopia improved, and no recurrence was observed at 12 months follow-up. This technique of neuroendoscopic biopsy guided by 5-ALA PDD fluorescence with a violet LED flashlight may allow a safe and accurate diagnosis of deep-seated malignant gliomas.

Artificial Intelligence in Ophthalmic Surgery: Current Applications and Expectations.

Artificial Intelligence (AI) has found rapidly growing applications in ophthalmology, achieving robust recognition and classification in most kind of ocular diseases. Ophthalmic surgery is one of the most delicate microsurgery, requiring high fineness and stability of surgeons. The massive demand of the AI assist ophthalmic surgery will constitute an important factor in boosting accelerate precision medicine. In clinical practice, it is instrumental to update and review the considerable evidence of the current AI technologies utilized in the investigation of ophthalmic surgery involved in both the progression and innovation of precision medicine. Bibliographic databases including PubMed and Google Scholar were searched using keywords such as "ophthalmic surgery", "surgical selection", "candidate screening", and "robot-assisted surgery" to find articles about AI technology published from 2018 to 2023. In addition to the Editorials and letters to the editor, all types of approaches are considered. In this paper, we will provide an up-to-date review of artificial intelligence in eye surgery, with a specific focus on its application to candidate screening, surgery selection, postoperative prediction, and real-time intraoperative guidance.

Development of an Artificial Intelligence Tool for Intraoperative Guidance During Endovascular Abdominal Aortic Aneurysm Repair

Adverse events during surgery can occur in part due to errors in visual perception and judgment. Deep learning is a branch of artificial intelligence (AI) that has shown promise in providing real-time intraoperative guidance. This study aims to train and test the performance of a deep learning model that can identify inappropriate landing zones during endovascular aneurysm repair (EVAR). A deep learning model was trained to identify a "No-Go" landing zone during EVAR, defined by coverage of the lowest renal artery by the stent graft. Fluoroscopic images from elective EVAR procedures performed at a single institution and from open access sources were selected. Annotations of the "No-Go" zone were performed by trained annotators. A 10-fold cross-validation technique was used to evaluate the performance of the model against human annotations. Primary outcomes were intersection-over-union (IoU) and F1 score and secondary outcomes were pixel-wise accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). The AI model was trained using 369 images procured from 110 different patients/videos, including 18 patients/videos (44 images) from open access sources. For the primary outcomes, IoU and F1 were 0.43 (standard deviation ±0.29) and 0.53 (±0.32) respectively. For the secondary outcomes, accuracy, sensitivity, specificity, NPV, and PPV were 0.97 (±0.002), 0.51 (±0.34), 0.99 (±0.001). 0.99 (±0.002), and 0.62 (±0.34) respectively. AI can effectively identify sub-optimal areas of stent deployment during EVAR. Further directions include validating the model on datasets from other institutions and assessing its ability to predict optimal stent graft placement and clinical outcomes.

Micro-Doppler for venous sinus localization in approaches to the cerebello-pontine angle.

Main anatomical landmarks of retrosigmoid craniotomy are transverse sinus (TS), sigmoid sinus (SS), and the confluence of both. Anatomical references and guidance based on preoperative imaging studies are less reliable in the posterior fossa than in the supratentorial region. Simple intraoperative real-time guidance methods are in demand to increase safety. This manuscript describes the localization of TS, SS, and TS-SS junction by audio blood flow detection with a micro-Doppler system. This is an additional technique to increase safety during craniotomy and dura opening, widening the surgical corridor to secure margins without carrying risks nor increase surgical time.

Real-time intraoperative surgical guidance system in the da Vinci surgical robot based on transrectal ultrasound/photoacoustic imaging with photoacoustic markers: an ex vivo demonstration.

This paper introduces the first integrated real-time intraoperative surgical guidance system, in which an endoscope camera of da Vinci surgical robot and a transrectal ultrasound (TRUS) transducer are co-registered using photoacoustic markers that are detected in both fluorescence (FL) and photoacoustic (PA) imaging. The co-registered system enables the TRUS transducer to track the laser spot illuminated by a pulsed-laser-diode attached to the surgical instrument, providing both FL and PA images of the surgical region-of-interest (ROI). As a result, the generated photoacoustic marker is visualized and localized in the da Vinci endoscopic FL images, and the corresponding tracking can be conducted by rotating the TRUS transducer to display the PA image of the marker. A quantitative evaluation revealed that the average registration and tracking errors were 0.84 mm and 1.16°, respectively. This study shows that the co-registered photoacoustic marker tracking can be effectively deployed intraoperatively using TRUS+PA imaging providing functional guidance of the surgical ROI.

Development of an Artificial Intelligence Tool for Intraoperative Guidance During Endovascular Aneurysm Repair

Adverse events during surgery can occur in part owing to errors in visual perception and judgment. Deep learning is a branch of artificial intelligence (AI) that has shown promise to provide real-time intraoperative guidance and augment surgical performance. This study aims to train and test the performance of a deep learning model that can identify inappropriate landing zones on fluoroscopy during endovascular aneurysm repair (EVAR).

Overview and Future Perspectives on Tumor-Targeted Positron Emission Tomography and Fluorescence Imaging of Pancreatic Cancer in the Era of Neoadjuvant Therapy.

Simple SummaryPatients diagnosed with pancreatic cancer have a poor prognosis at time of diagnosis, with a 5-year survival rate of merely 10%. The only treatment with curative intent is surgical resection of the tumor and adjacent tumor-containing lymph nodes. To improve surgical outcome and survival, additional (imaging) tools are needed that support complete surgical tumor resection. Firstly, more accurate monitoring of tumor response to neoadjuvant treatment and subsequent determination of resectability is needed. Secondly, an imaging tool is needed for intraoperative guidance allowing accurate identification, delineation, and complete resection of the tumor and suspected lymph nodes. Therefore, both tumor-targeted PET/CT before surgery and real time fluorescence-guidance during surgery could be helpful to improve patient outcome. This review focusses on literature considering tumor-targeted PET/CT and near-infrared fluorescence (NIRF) imaging. Several tumor-targeted agents are under clinical evaluation, and several other promising agents are currently tested preclinically, both with promising results. Their additional diagnostic value and feasibility for future implementation in standard clinical care of PDAC has yet to be established in phase III clinical trials.Background: Despite recent advances in the multimodal treatment of pancreatic ductal adenocarcinoma (PDAC), overall survival remains poor with a 5-year cumulative survival of approximately 10%. Neoadjuvant (chemo- and/or radio-) therapy is increasingly incorporated in treatment strategies for patients with (borderline) resectable and locally advanced disease. Neoadjuvant therapy aims to improve radical resection rates by reducing tumor mass and (partial) encasement of important vascular structures, as well as eradicating occult micrometastases. Results from recent multicenter clinical trials evaluating this approach demonstrate prolonged survival and increased complete surgical resection rates (R0). Currently, tumor response to neoadjuvant therapy is monitored using computed tomography (CT) following the RECIST 1.1 criteria. Accurate assessment of neoadjuvant treatment response and tumor resectability is considered a major challenge, as current conventional imaging modalities provide limited accuracy and specificity for discrimination between necrosis, fibrosis, and remaining vital tumor tissue. As a consequence, resections with tumor-positive margins and subsequent early locoregional tumor recurrences are observed in a substantial number of patients following surgical resection with curative intent. Of these patients, up to 80% are diagnosed with recurrent disease after a median disease-free interval of merely 8 months. These numbers underline the urgent need to improve imaging modalities for more accurate assessment of therapy response and subsequent re-staging of disease, thereby aiming to optimize individual patient’s treatment strategy. In cases of curative intent resection, additional intra-operative real-time guidance could aid surgeons during complex procedures and potentially reduce the rate of incomplete resections and early (locoregional) tumor recurrences. In recent years intraoperative imaging in cancer has made a shift towards tumor-specific molecular targeting. Several important molecular targets have been identified that show overexpression in PDAC, for example: CA19.9, CEA, EGFR, VEGFR/VEGF-A, uPA/uPAR, and various integrins. Tumor-targeted PET/CT combined with intraoperative fluorescence imaging, could provide valuable information for tumor detection and staging, therapy response evaluation with re-staging of disease and intraoperative guidance during surgical resection of PDAC. Methods: A literature search in the PubMed database and (inter)national trial registers was conducted, focusing on studies published over the last 15 years. Data and information of eligible articles regarding PET/CT as well as fluorescence imaging in PDAC were reviewed. Areas covered: This review covers the current strategies, obstacles, challenges, and developments in targeted tumor imaging, focusing on the feasibility and value of PET/CT and fluorescence imaging for integration in the work-up and treatment of PDAC. An overview is given of identified targets and their characteristics, as well as the available literature of conducted and ongoing clinical and preclinical trials evaluating PDAC-targeted nuclear and fluorescent tracers.

Laparoscopic anatomical liver resection for malignancies using positive or negative staining technique with intraoperative indocyanine green-fluorescence imaging.

Indications for a minimally invasive resections are increasing worldwide, but respecting anatomical planes during intraparenchymal transection is demanding. Intraoperative ICG fluorescence staining of liver parenchyma has been introduced as a tool for real-time intraoperative guidance. The aim of this study is to make a systematic review of the current relevant literature on indications, techniques, and results of laparoscopic anatomical liver resection (LALR) using intraoperative indocyanine green (ICG) fluorescence for positive and negative staining of liver segments in patients affected by liver malignancies. Electronic bibliographical databases (MEDLINE and PubMed) were searched according to the PRISMA criteria. English language articles meeting the selection criteria and published until June 2020 were retrieved and reviewed. a total of 86 articles were initially found and 11 articles were finally included in the analysis with a total of 83 patients treated. Sixty-two patients (74.6%) underwent mono-segmentectomies. Thirty-five patients (42.1%) underwent the positive staining technique, and forty-eight patients (57.8%) the negative staining technique. The positive or negative indocyanine green staining technique with real-time fluorescence guidance is an emerging and promising approach. However, the technique has to be standardized and advantages in terms of oncologic results still need validation in further studies.

Machine Vision for Real-Time Intraoperative Anatomic Guidance: A Proof-of-Concept Study in Endoscopic Pituitary Surgery.

Current intraoperative orientation methods either rely on preoperative imaging, are resource-intensive to implement, or difficult to interpret. Real-time, reliable anatomic recognition would constitute another strong pillar on which neurosurgeons could rest for intraoperative orientation. To assess the feasibility of machine vision algorithms to identify anatomic structures using only the endoscopic camera without prior explicit anatomo-topographic knowledge in a proof-of-concept study. We developed and validated a deep learning algorithm to detect the nasal septum, the middle turbinate, and the inferior turbinate during endoscopic endonasal approaches based on endoscopy videos from 23 different patients. The model was trained in a weakly supervised manner on 18 and validated on 5 patients. Performance was compared against a baseline consisting of the average positions of the training ground truth labels using a semiquantitative 3-tiered system. We used 367 images extracted from the videos of 18 patients for training, as well as 182 test images extracted from the videos of another 5 patients for testing the fully developed model. The prototype machine vision algorithm was able to identify the 3 endonasal structures qualitatively well. Compared to the baseline model based on location priors, the algorithm demonstrated slightly but statistically significantly (P < .001) improved annotation performance. Automated recognition of anatomic structures in endoscopic videos by means of a machine vision model using only the endoscopic camera without prior explicit anatomo-topographic knowledge is feasible. This proof of concept encourages further development of fully automated software for real-time intraoperative anatomic guidance during surgery.

Mixed Reality Intraoperative Navigation in Craniomaxillofacial Surgery.

We report our early experience with the HoloLens 2 (Microsoft Corp., Redmond, Wash.) mixed reality device1 in the management of patients with craniomaxillofacial trauma. Preoperative planning is performed using iPlan Cranial Version 2.6 (Brainlab, Munich, Germany). The contralateral uninjured facial skeleton is mirrored for use as a template for reconstruction. This skull reference model is exported as a Standard Tessellation Language file. This is uploaded onto the HoloLens 2 system by means of the software Virtual Surgery Intelligence (apoQlar GmbH, Hamburg, Germany), which generates a skull reference hologram. Intraoperatively, superimposition of the skull reference hologram onto the patient is performed after fracture exposure (Fig. 1). Predetermined exposed bony landmarks on the patient were matched. These were visually verified on the frontal, lateral, and worm’s-eye views. Having the hologram projected directly on the operative field allows surgeons to have a better appreciation of the vector and magnitude of movement required for fracture reduction. Surgeons can visualize structures beyond the area of exposure. Adequacy of fracture reduction can be validated immediately. Adjustments can be made and validations repeated. Fixation is performed once reduction is satisfactory.Fig. 1.: Alignment of skull reference hologram is performed using multiple exposed bony landmarks to improve accuracy.The main advantage of mixed reality is its ability to allow visualization and manipulation of superimposed holograms on patients in real time. The experience is akin to a live “in-flight” image-guided surgery. There is immediate feedback on the adequacy of reduction. Surgeons are able to directly visualize the skull reference hologram superimposed on the patient’s skull through the lens, without changes in line of sight. Limitations include the arbitrary nature of aligning the skull reference hologram onto the patient. Mitsuno et al.2 described a three-point technique of alignment. A more precise technique is required in craniomaxillofacial surgery. Our described technique is adapted from the registration process with current navigation devices. Greater accuracy can be attained by aligning a larger number of landmarks directly on exposed bones that are to be operated on. Advances that we are developing include the following: Automated stereoscopic registration and alignment of skull reference hologram: This removes the subjectivity and time involved in the process of superimposing the hologram onto the patient. Automated and objective validation of fracture reduction: A system that automatically detects the extent of deviation of the reduced fracture fragments from the skull reference hologram. Adjustments and reduction can be made more accurately. Soft-tissue segmentation and visualization: Critical soft-tissue structures such as nerves can be superimposed alongside the skull reference model, visualized, and preserved intraoperatively. Instrument recognition and early warning system: Instruments can be registered onto the system and be recognized intraoperatively. When positioned in close proximity to critical structures such as the optic nerve, the system detects this and sends out an early warning signal such that inadvertent injury to these structures can be avoided. Mixed reality devices provide surgeons with real-time intraoperative guidance. It has the potential to decrease operative time and improve patient outcomes. DISCLOSURE The authors have no financial interest in any of the products or devices mentioned in this article.

A narrative review of fluorescence imaging in robotic-assisted surgery.

Objective:In this review, we provide examples of applications of fluorescence imaging in urologic, gynecologic, general, and endocrine surgeries.Background:While robotic-assisted surgery has helped increase the availability of minimally invasive procedures across surgical specialties, there remains an opportunity to reduce adverse events associated with open, laparoscopic, and robotic-assisted methods. In 2011, fluorescence imaging was introduced as an option to the da Vinci Surgical System, and has been standard equipment since 2014. Without interfering with surgical workflow, this fluorescence technology named Firefly® allows for acquisition and display of near-infrared fluorescent signals that are co-registered with white light endoscopic images. As a result, robotic surgeons of all specialties have been able to explore the clinical utility of fluorescence guided surgery.Methods:Literature searches were performed using the PubMed and MEDLINE databases using the keywords “robotic-assisted fluorescence surgery”, “ICG robotic surgery”, and “fluorescence guided surgery” covering the years 2011–2020.Conclusions:Real-time intraoperative fluorescence guidance has shown great potential in helping guide surgeons in both simple and complex surgical interventions. Indocyanine green is one of the most widely-used imaging agents in fluorescence guided surgery, and other targeted, near-infrared imaging agents are in various stages of development. Fluorescence is becoming a reliable tool that can help surgeons in their decision-making process in some specialties, while explorations continue in others.

The real-time intraoperative guidance of the new HIFU Focal-One® platform allows to minimize the perioperative adverse events in salvage setting.

To assess the use of the new Focal-One® HIFU platform in salvage setting to evaluate the occurrence of postoperative complications. Patients who underwent salvage HIFU (sHIFU) with Focal-One® platform were enrolled prospectively (Candiolo cancer institute-FPO IRCCS; registry number: 258/2018). Perioperative and postoperative outcomes (in terms of oncological and functional ones) were recorded during the first year of follow-up. In particular postoperative complications were classified according to Clavien-Dindo system. 20 patients were enrolled. No grade 3 complications were recorded. Referring to grade 2 complications, eight patients reported urgency after 3months of follow-up, and in 4 cases, a low urinary tract infection occurred. Evaluating the impact of sHIFU on patients' sexual potency, micturition and quality of life, no significant deterioration was recorded during the follow-up as proven using the ANOVA analysis for repeated measurements. Only two patient had a biochemical failure after 12months of follow-up. The real-time intraoperative guidance with Focal-One® platform, allows a continuous monitoring and tailoring of the treatment, with a minimization of the adverse events even in a salvage setting.

Machine vision for real-time intraoperative anatomical guidance: a proof-of-concept study in endoscopic pituitary surgery

Machine vision for real-time intraoperative anatomical guidance: a proof-of-concept study in endoscopic pituitary surgery

3D cone-beam tomosynthesis provides axial imaging of the spine with lower radiation compared to computed tomography

Three imaging techniques were compared using porcine spines. To compare image acquisition time, radiation exposure, pedicle width measurement, assessment of screw breach, and image artifact between cone-beam tomosynthesis (CBT) single mode, CBT dual mode (stereotactic CBT), and computed tomography (CT) imaging with and without spinal implants. CT is the standard for axial imaging of orthopedic procedures. CBT technology is being developed, allowing real-time intraoperative imaging and 3D surgical guidance. CBT may deliver useful axial imaging quicker with less radiation than current technologies. Six porcine spines were instrumented with bilateral pedicle screws at six levels connected with 5.5mm rods. Dosimeters were attached to four surfaces of spines. CT, CBT single and CBT dual images were acquired pre-implant and post-implant. Image acquisition and 3D reconstruction times were recorded. Pedicle widths were measured before and after instrumentation. Screw medial breaches were graded (0: no breach, 1: < 2mm, 2: 2-4mm, 3: > 4mm). Artifact and/or distortion of each image was ranked (0 = none, 1 = mild, 2 = moderate, 3 = large). Image acquisition and reconstruction times, radiation dose, pedicle width, screw breach and artifact were compared between techniques. Total image acquisition and reconstruction times of CBT was significantly less (single: 9.9 ± 0.2s, p < 0.001; dual: 60.0 ± 8.7 s, p < 0.001) than CT (250.3 ± 36.7s). CBT had significantly less radiation exposure than CT (CT: 0.7 ± 0.1rad, single: 0.03 ± 0.02rad, dual: 0.07 ± 0.03rad; p < 0.001). No difference in pedicle width change pre-implant to post-implant was found (CT: p = 0.449, single: p = 0.430, dual: p = 0.528). Pedicle width (pre-implant: p > 0.5, post-implant: p > 0.9) and pedicle width change (p > 0.4) was similar amongst all techniques. Breach assessment was not different between groups (p = 0.257). CBT images had consistently lower artifact grades than CT. Although CBT axial image quality appeared subjectively inferior to CT, it enabled consistent assessment of pedicle width and screw breach, at half time and 10× lower radiation exposure. With continued refinements, CBT technology may allow for adequate intra-operative axial imaging using low radiation exposure.

Comprehensive Case Review of a Diabetic Patient With Chronic Limb-Threatening Ischemia

Vascular technologists can play a comprehensive role in the management of complex chronic limb-threatening ischemia diabetic patients. This includes preoperative planning, intraoperative real-time guidance of therapy, and postoperative surveillance. This case will demonstrate the importance of dedicated vascular ultrasound technology.

Simulations and human cadaver head studies to identify optimal acoustic receiver locations for minimally invasive photoacoustic-guided neurosurgery

Real-time intraoperative guidance during minimally invasive neurosurgical procedures (e.g., endonasal transsphenoidal surgery) is often limited to endoscopy and CT-guided image navigation, which can be suboptimal at locating underlying blood vessels and nerves. Accidental damage to these critical structures can have severe surgical complications, including patient blindness and death. Photoacoustic image guidance was previously proposed as a method to prevent accidental injury. While the proposed technique remains promising, the original light delivery and sound reception components of this technology require alterations to make the technique suitable for patient use. This paper presents simulation and experimental studies performed with both an intact human skull (which was cleaned from tissue attachments) and a complete human cadaver head (with contents and surrounding tissue intact) in order to investigate optimal locations for ultrasound probe placement during photoacoustic imaging and to test the feasibility of a modified light delivery design. Volumetric x-ray CT images of the human skull were used to create k-Wave simulations of acoustic wave propagation within this cranial environment. Photoacoustic imaging of the internal carotid artery (ICA) was performed with this same skull. Optical fibers emitting 750 nm light were inserted into the nasal cavity for ICA illumination. The ultrasound probe was placed on three optimal regions identified by simulations: (1) nasal cavity, (2) ocular region, and (3) 1 mm-thick temporal bone (which received 9.2%, 4.7%, and 3.8% of the initial photoacoustic pressure, respectively, in simulations). For these three probe locations, the contrast of the ICA in comparative experimental photoacoustic images was 27 dB, 19 dB, and 12 dB, respectively, with delay-and-sum (DAS) beamforming and laser pulse energies of 3 mJ, 5 mJ, and 4.2 mJ, respectively. Short-lag spatial coherence (SLSC) beamforming improved the contrast of these DAS images by up to 15 dB, enabled visualization of multiple cross-sectional ICA views in a single image, and enabled the use of lower laser energies. Combined simulation and experimental results with the emptied skull and >1 mm-thick temporal bone indicated that the ocular and nasal regions were more optimal probe locations than the temporal ultrasound probe location. Results from both the same skull filled with ovine brains and eyes and the human cadaver head validate the ocular region as an optimal acoustic window for our current system setup, producing high-contrast (i.e., up to 35 dB) DAS and SLSC photoacoustic images within the laser safety limits of a novel, compact light delivery system design that is independent of surgical tools (i.e., a fiber bundle with 6.8 mm outer diameter, 2 mm-diameter optical aperture, and an air gap spacing between the sphenoid bone and fiber tips). These results are promising toward identifying, quantifying, and overcoming major system design barriers to proceed with future patient testing.

Impact of suboptimal tandem implantation on local control and complications in intracavitary brachytherapy for cervix cancer

PURPOSECorrect tandem implantation for cervix cancer intracavitary brachytherapy may be challenging. We investigated whether suboptimal implantation can be related to patient and disease characteristics and may result in subsequent underutilization of brachytherapy in cervical cancer. METHODS AND MATERIALSConsecutive cervix cancer patients referred for intracavitary brachytherapy after external beam radiation therapy performed in several general hospitals from 2013 to 2017 were included. ResultsIn 172 patients having 301 procedures, 95 implantations were suboptimal (15% inadequate tandem insertions, 10% subserosal insertion, and 6% uterine perforation on postimplant CT scan). Risk factors were age, myometrium invasion, and uterine retroversion. Median followup was 21 months. Three-year local control and survival rates were 72% and 85%, respectively. Forty-seven patients (27%) failed to receive brachytherapy. Failure to perform brachytherapy was associated with poorer local control (OR = 0.34 [0.17–0.67], p = 0.001). By contrast, suboptimal implantation did not increase local failure or toxicity rates in patients undergoing brachytherapy. No peritoneal carcinomatosis occurred after uterine perforation in our cohort. CONCLUSIONSSuboptimal implantation was frequent. In the absence of image guidance during implantation, conversion to other treatment modalities (including external beam radiation therapy) due to insertion difficulties resulted in worse local control. With optimization, however, suboptimal brachytherapy implantation did not result in suboptimal dose coverage or poorer local control. Failure to perform a brachytherapy boost correlates with increased local failure risk in patients with cervix cancer, whereas tandem malposition does not. Real-time intraoperative ultrasound guidance may be useful to reduce uterine perforation rates and thus increase brachytherapy use.