A robust motion correction technique for infrared thermography during awake craniotomy

PURPOSE

Intraoperative infrared thermography is an emerging technique for image-guided neurosurgery, whereby physiological and pathological processes result in temperature changes over space and time. However, motion during data collection leads to downstream artifacts in thermography analyses. We develop a fast, robust technique for motion estimation and correction as a preprocessing step for brain surface thermography recordings.

METHODS

A motion correction technique for thermography was developed which approximates the deformation field associated with motion as a grid of two-dimensional bilinear splines (Bispline registration), and a regularization function was designed to constrain motion to biomechanically feasible solutions. The performance of the proposed Bispline registration technique was compared to phase correlation, a band-stop filter, demons registration, and the Horn-Schunck and Lucas-Kanade optical flow techniques.

RESULTS

All methods were analyzed using thermography data from ten patients undergoing awake craniotomy for brain tumor resection, and performance was compared using image quality metrics. The proposed method had the lowest mean-squared error and the highest peak-signal-to-noise ratio of all methods tested and performed slightly worse than phase correlation and Demons registration on the structural similarity index metric (p < 0.01, Wilcoxon signed-rank test). Band-stop filtering and the Lucas-Kanade method were not strong attenuators of motion, while the Horn-Schunck method was well-performing initially but weakened over time.

CONCLUSION

Bispline registration had the most consistently strong performance out of all the techniques tested. It is relatively fast for a nonrigid motion correction technique, capable of processing ten frames per second, and could be a viable option for real-time use. Constraining the deformation cost function through regularization and interpolation appears sufficient for fast, monomodal motion correction of thermal data during awake craniotomy.

A Novel Intraoperative Mapping Device Detects the Thermodynamic Response Function

Functional activation leads to an increase in local brain temperature via an increase in local perfusion. In the intraoperative setting, these cortical surface temperature fluctuations may be imaged using infrared thermography such that the activated brain areas are inferred. While it is known that temperature increases as a result of activation, a quantitative spatiotemporal description has yet to be achieved. A novel intraoperative infrared thermography device with data collection software was developed to isolate the thermal impulse response function. Device performance was validated using data from six patients undergoing awake craniotomy who participated in motor and sensory mapping tasks during infrared imaging following standard mapping with direct electrical stimulation. Shared spatiotemporal patterns of cortical temperature changes across patients were identified using group principal component analysis. Analysis of component time series revealed a thermal activation peak present across all patients with an onset delay of five seconds and a peak duration of ten seconds. Spatial loadings were converted to a functional map which showed strong correspondence to positive stimulation results for similar tasks. This component demonstrates the presence of a previously unknown impulse response function for functional mapping with infrared thermography.

Labeling Noncontrast Head CT Reports for Common Findings Using Natural Language Processing

BACKGROUND AND PURPOSE

Prioritizing reading of noncontrast head CT examinations through an automated triage system may improve time to care for patients with acute neuroradiologic findings. We present a natural language-processing approach for labeling findings in noncontrast head CT reports, which permits creation of a large, labeled dataset of head CT images for development of emergent-finding detection and reading-prioritization algorithms.

MATERIALS AND METHODS

In this retrospective study, 1002 clinical radiology reports from noncontrast head CTs collected between 2008 and 2013 were manually labeled across 12 common neuroradiologic finding categories. Each report was then encoded using an n-gram model of unigrams, bigrams, and trigrams. A logistic regression model was then trained to label each report for every common finding. Models were trained and assessed using a combination of L2 regularization and 5-fold cross-validation.

RESULTS

Model performance was strongest for the fracture, hemorrhage, herniation, mass effect, pneumocephalus, postoperative status, and volume loss models in which the area under the receiver operating characteristic curve exceeded 0.95. Performance was relatively weaker for the edema, hydrocephalus, infarct, tumor, and white-matter disease models (area under the receiver operating characteristic curve > 0.85). Analysis of coefficients revealed finding-specific words among the top coefficients in each model. Class output probabilities were found to be a useful indicator of predictive error on individual report examples in higher-performing models.

CONCLUSIONS

Combining logistic regression with n-gram encoding is a robust approach to labeling common findings in noncontrast head CT reports.

The Two-Point Technique for Fluoroscopic-Guided Endoscopic Procedures in Urology: A Validation Study

Introduction: The widespread use of diagnostic and therapeutic ionizing radiation raises concerns regarding excessive occupational and patient exposure. In this study, we test a novel fluoroscopic technique that has the potential to minimize radiation dose during urologic procedures. Materials and Methods: A prospective evaluation of all patients undergoing endoscopic urologic procedures in our institution was conducted. A "two-point technique (TPT)" is described in which the fluoroscope image intensifier (c-arm) is shifted between caudal and cephalad set points of the operative field. We wished to determine whether patient radiation exposure was lower with TPT than with a non-structured conventional technique, referred to as the cognitive fluoroscopic technique (CFT), in which the manipulation of the c-arm was at the discretion of the user. We obtained all clinical, radiographic, and fluoroscopic data of patients in the study period and used unpaired nonparametric statistical analysis of univariates entered stepwise into a logistic regression model. Results: A total of 106 endoscopic urologic procedures from January 2016 to November 2018 were reviewed. Forty-four (41.5%) cases were performed using TPT and 62 (58.5%) using CFT. The mean fluoroscopy time of TPT vs CFT was 71.1 (±60.8) seconds vs 104.5 (±91.6) seconds, respectively (p = 0.04), and the mean radiation dose on TPT vs CFT was 11.6 (±10.6) mGy vs 20.3 (±24.3) mGy, respectively (p = 0.03). TPT was an independent predictor of reduced operative room (OR) time and fluoro time (p < 0.05), while body mass index, age, and operator were not. Conclusion: The "TPT" helps reducing radiation dose and fluoroscopic time during endoscopic urologic procedures. The TPT is useful to lower radiation exposure to patients and OR staff.

Device Malfunctions and Complications Associated with Benign Prostatic Hyperplasia Surgery: Review of the Manufacturer and User Facility Device Experience Database

Introduction and Objectives: Multiple surgical therapies for benign prostatic hyperplasia (BPH) have been developed to decrease complications and increase provider efficiency. We investigated contemporary BPH treatment device-related adverse events by searching a publicly available database. Materials and Methods: The Manufacturer and User Facility Device Experience (MAUDE) database was queried for contemporary BPH treatments. All devices were evaluated for malfunction, patient complications, and manufacturer review. The MAUDE adverse event classification system was used to standardize complications. Univariate analysis was performed to identify associations between BPH devices and adverse events. Results: A total of 2567 reports were identified: transurethral resection of the prostate (TURP) 197 (7.67%), holmium laser enucleation of the prostate (HoLEP) 39 (1.52%), GreenLight™ 2315 (90.2%), and UroLift^® 16 (0.62%). The most common deviations for each modality included cutting loop detachment during TURP 116 (58.9%), morcellator dysfunction for HoLEP 23 (58.9%), tip fracture/detachment for GreenLight (68.8%), and failure to deploy during UroLift 10 (62.5%). Only 18 (0.7%) patients required medical/surgical management (MAUDE II-IV) due to a device complication. No significant relationship was seen between each modality and complications; however, morcellator use (27.8%) was observed in higher grade complications. Manufacturer review occurred in 61.7% of cases, with 41.3% of reviewed cases finding the operator the cause of the malfunction. Conclusion: Each BPH modality investigated had minimal patient harm with over 99% of patients experiencing no complication after device malfunction. Of note, great care should be taken with morcellator use during HoLEP as it had the greatest number of MAUDE II to IV complications among all devices. Manufacturer review revealed that over 40% of cases were due to misuse by the user. Therefore, urologists should select the modalities they are most familiar with to decrease patient harm and prevent device malfunctions.

Percutaneous and Endoscopic Management of Nephrolithiasis in a Patient with Five Native Ureters (Trifid Right and Bifid Left Collecting System)

Triplication of the ureter is a rare urologic finding that has been well described in the literature. Patients can present with urinary tract infections, incontinence, and calculi. We present the case of a patient with extensive stone burden with right trifid and left bifid collecting systems. Stone management was performed with a multimodal approach using a combination of endoscopic and percutaneous approaches. Our systematic and staged approach highlights a method for efficacious stone treatment in a complex endourologic case.

IgM-Dependent Phagocytosis in Microglia Is Mediated by Complement Receptor 3, Not Fcα/μ Receptor

Microglia play an important role in receptor-mediated phagocytosis in the CNS. In brain abscess and other CNS infections, invading bacteria undergo opsonization with Igs or complement. Microglia recognize these opsonized pathogens by Fc or complement receptors triggering phagocytosis. In this study, we investigated the role of Fcα/μR, the less-studied receptor for IgM and IgA, in microglial phagocytosis. We showed that primary microglia, as well as N9 microglial cells, express Fcα/μR. We also showed that anti-Staphylococcus aureus IgM markedly increased the rate of microglial S. aureus phagocytosis. To unequivocally test the role of Fcα/μR in IgM-mediated phagocytosis, we performed experiments in microglia from Fcα/μR(-/-) mice. Surprisingly, we found that IgM-dependent phagocytosis of S. aureus was similar in microglia derived from wild-type or Fcα/μR(-/-) mice. We hypothesized that IgM-dependent activation of complement receptors might contribute to the IgM-mediated increase in phagocytosis. To test this, we used immunologic and genetic inactivation of complement receptor 3 components (CD11b and CD18) as well as C3. IgM-, but not IgG-mediated phagocytosis of S. aureus was reduced in wild-type microglia and macrophages following preincubation with an anti-CD11b blocking Ab. IgM-dependent phagocytosis of S. aureus was also reduced in microglia derived from CD18(-/-) and C3(-/-) mice. Taken together, our findings implicate complement receptor 3 and C3, but not Fcα/μR, in IgM-mediated phagocytosis of S. aureus by microglia.