Hyperspectral Imaging for Clinical Applications

Measuring morphological and biochemical features of tissue is crucial for disease diagnosis and surgical guidance, providing clinically significant information related to pathophysiology. Hyperspectral imaging (HSI) techniques obtain both spatial and spectral features of tissue without labeling molecules such as fluorescent dyes, which provides rich information for improved disease diagnosis and treatment. Recent advances in HSI systems have demonstrated its potential for clinical applications, especially in disease diagnosis and image-guided surgery. This review summarizes the basic principle of HSI and optical systems, deep-learning-based image analysis, and clinical applications of HSI to provide insight into this rapidly growing field of research. In addition, the challenges facing the clinical implementation of HSI techniques are discussed.

18F-Fluorocholine PET and 4D-CT in Patients with Persistent and Recurrent Primary Hyperparathyroidism

Patients with primary hyperparathyroidism (pHPT) can develop persistent (P-pHPT) or recurrent (R-pHPT) disease after parathyroidectomy. Before recommending reoperation, recurrence must be accurately identified because of the high risk of complications. Our study evaluates 18F-fluorocholine (18F-FCH) PET/CT and 4D-CT integrated in PET/4D-CT in patients with P-pHPT/R-pHPT. Patients with P-pHPT/R-pHPT investigated by 18F-FCH PET/4D-CT between May 2018 and March 2021 were retrospectively included. Forty-two patients were included, 37 of whom underwent 4D-CT. The sensitivity and detection rate (DR%) were 95% and 88% for 18F-FCH PET/CT and 70% and 63% for 4D-CT, respectively. PET/CT and 4D-CT were concordant in 18/24 glands and concordant and positive in 15/24 (63%) glands. Discordant results were obtained for 6/24 glands. The surgical success rate was 65%. PET/CT showed significantly higher sensitivity than 4D-CT. Dynamic CT allowed the identification of no additional glands missed by PET/CT, and the combination of the 2 techniques did not improve the sensitivity or DR%. 18F-FCH PET/CT appears to be a valuable technique to accurately detect hyperfunctioning parathyroid tissue in patients with P-pHPT/R-pHPT and is better than 4D-CT. Except for cases with doubtful locations of PET targets that may require 4D-CT for surgical guidance, standard nonenhanced 18F-FCH PET/CT can be effectively recommended in patients with P-pHPT/R-pHPT before reoperation.

EP.WE.334Value of including CT chest in the management of acute abdominal emergencies: Experience during first wave of COVID-19 pandemic at a District General Hospital

Aims The aim of this retrospective study was to assess the incidence of positive findings on CT chest in patients presenting with acute abdomen, who underwent CT thorax as part of the Intercollegiate General Surgical Guidance on COVID-19 during the first wave. To correlate CT chest findings with confirmed cases on RT-PCR; and to determine its influence on surgical management of abdominal emergencies. Methods A retrospective observational study of adult emergency surgical referrals (excluding trauma) for acute abdomen over a ten week period was performed. COVID changes on CT Chest were categorized as per the BSTI CT reporting criteria. Patient demographics, COVID RT-PCR, management and outcome were recorded. Statistical analysis was performed using Microsoft Excel with p value significant at ≤ 0.05. Results Of the 160 patients included, only 111(69.38%) had COVID RT-PCR. Of 24 (15%) patients with CT chest features of COVID, 45.83% demonstrated classic/probable CT features of COVID of which 36.36% had positive RT PCR. 54.17% had indeterminate pattern and none tested positive for COVID. There was a significant association between positive CT abdomen with normal CT chest findings (p = 0.03). Of 25 (15.63%) patients with normal CT abdomen, 7(28%) had CT features of COVID. Only 43(34.4%) patients needed surgical intervention of which 18.6% had COVID changes on CT, confirmed by positive RT PCR in 12.5%. Conclusions CT chest as an additional investigation modality in acute abdomen had clinically helped in triaging of patients to appropriate specialties but did not influence emergency surgical management.

91 Management and Outcomes of Appendicitis in The Pre-COVID-19, COVID-19 And Post-COVID-19 Periods

Aim The COVID-19 pandemic resulted in an upheaval of national surgical guidance on appendicitis, which has previously favoured surgical over conservative approaches. We analysed how these guidelines altered management and outcomes of appendicitis. Method A retrospective cohort study at Heartlands Hospital, Birmingham of all appendicitis admissions around and during the first COVID-19 peak was conducted, with analysis of electronic patient records using the acute surgical worklist. Results 48 admissions for appendicitis during the two-month period from 01/02/20 to 25/03/20 prior to the COVID-19 peak and 28 admissions in the two months during the peak itself from 30/03/20 to 24/05/20 were identified. Prior to the COVID-19 peak, a lower proportion of cases was managed conservatively (18.8%) compared to the latter (67.9%, p < 0.0001). This change also coincided with a switch from laparoscopic to open approaches in those managed surgically. We studied a further period post-COVID-19 peak from 01/06/20 to 26/07/20, where proportions of patients managed conservatively versus surgically did not significantly change following the COVID-19 peak, although surgical preference reverted from open to laparoscopic approaches. During the COVID-19 period, a reduced length of stay was seen in cases managed conservatively (1.65 days) compared to those managed surgically (4 days, p = 0.024). Differences in readmission rates were not statistically significant. Conclusions A reduction in numbers of appendicitis presentations as well as a switch to conservative approaches was seen during COVID-19. These findings furthermore support non-inferiority of conservative over open surgical approaches in most appendicitis cases at a time where laparoscopy was deemed unfeasible.

DIRECT PEDICLE SCREW INSERTION PULLOUT STRENGTH

ABSTRACT Objective: Study the in vitro pullout strength of SpineGuard/Zavation Dynamic Surgical Guidance Z-Direct Screw (DSG Screw), a screw pedicle designed to be inserted using a direct insertion technique. Methods: DSG Screws of 5.5 mm and 6.5 mm were introduced into polyurethane blocks with a density of 10 PCF (0,16 g/cm3). According to the experimental group, screws were inserted without pilot hole, with pilot without tapping, undertapping and line-to-line tapping. Screw pullout tests were performed using a universal test machine after screw insertion into polyurethane blocks. Results: Screws inserted directly into the polyurethane blocks without pilot hole and tapping showed a statistically higher pullout strength. Insertion of the screw without tapping or with undertapping increases the pullout screw strength compared to line-to-line tapping. Conclusion: DSG Screw showed the highest pullout strength after its insertion without pilot hole and tapping. Level of Evidence V, Expert Opinion.

O49 The use of augmented reality for surgical guidance: an assessment of the human error

Introduction Microsoft HoloLens® is an augmented-reality headset which is increasingly used for surgical guidance. This headset allows the overlay of patient-specific virtual models obtained from medical images onto the patient’s body surface using automatic marker-based alignment. This can guide surgeons during certain surgical tasks, e.g. determining biopsy needle entry points. This study aims to measure the human error in the localisation of virtual models with the headset and discuss its surgical implications. Method 59 adults were recruited between the ages of 20–59 years. A 12 cm2 digital marker was displayed on a monitor in 9 different positions, one at a time. This was repeated 3 times, resulting in 27 markers shown to each participant. Once a marker was detected by the headset’s camera, a virtual hexagon was rendered on the headset’s transparent lenses. Participants were tasked to click on the hexagon’s vertices using a mouse. The clicks’ coordinates were recorded by the system and compared to the predicted coordinates. This allowed for the calculation of the vertex localisation error. Result The mean vertex localisation error was found to be 5.19 mm (±3.56) with a range from 0.08 to 29.77 mm. There was a significant difference between marker positions as determined by a one-way ANOVA (P < 0.001). Conclusion This study suggests that the error in the localisation of virtual models depends on the position of the markers relative to the user wearing the headset. Further research is required to explore whether training can reduce the human error with this headset. Take-home Message The range of the human error in localising virtual models via the Microsoft HoloLens® headset is large and may be dependent on the position of the marker relative to the user of the headset. Further research is needed to investigate whether training with the headset can improve human performance.

Optical tissue measurements of invasive carcinoma and ductal carcinoma in situ for surgical guidance

Background Although the incidence of positive resection margins in breast-conserving surgery has decreased, both incomplete resection and unnecessary large resections still occur. This is especially the case in the surgical treatment of ductal carcinoma in situ (DCIS). Diffuse reflectance spectroscopy (DRS), an optical technology based on light tissue interactions, can potentially characterize tissue during surgery thereby guiding the surgeon intraoperatively. DRS has shown to be able to discriminate pure healthy breast tissue from pure invasive carcinoma (IC) but limited research has been done on (1) the actual optical characteristics of DCIS and (2) the ability of DRS to characterize measurements that are a mixture of tissue types. Methods In this study, DRS spectra were acquired from 107 breast specimens from 107 patients with proven IC and/or DCIS (1488 measurement locations). With a generalized estimating equation model, the differences between the DRS spectra of locations with DCIS and IC and only healthy tissue were compared to see if there were significant differences between these spectra. Subsequently, different classification models were developed to be able to predict if the DRS spectrum of a measurement location represented a measurement location with “healthy” or “malignant” tissue. In the development and testing of the models, different definitions for “healthy” and “malignant” were used. This allowed varying the level of homogeneity in the train and test data. Results It was found that the optical characteristics of IC and DCIS were similar. Regarding the classification of tissue with a mixture of tissue types, it was found that using mixed measurement locations in the development of the classification models did not tremendously improve the accuracy of the classification of other measurement locations with a mixture of tissue types. The evaluated classification models were able to classify measurement locations with > 5% malignant cells with a Matthews correlation coefficient of 0.41 or 0.40. Some models showed better sensitivity whereas others had better specificity. Conclusion The results suggest that DRS has the potential to detect malignant tissue, including DCIS, in healthy breast tissue and could thus be helpful for surgical guidance.