Adaptive Path Planning for Depth Constrained Bathymetric Mapping with an Autonomous Surface Vessel

This paper describes the design, implementation and testing of a suite of algorithms to enable depth constrained autonomous bathymetric (underwater topography) mapping by an Autonomous Surface Vessel (ASV). Given a target depth and a bounding polygon, the ASV will find and follow the intersection of the bounding polygon and the depth contour as modeled online with a Gaussian Process (GP). This intersection, once mapped, will then be used as a boundary within which a path will be planned for coverage to build a map of the Bathymetry. Methods for sequential updates to GP's are described allowing online fitting, prediction and hyper-parameter optimisation on a small embedded PC. New algorithms are introduced for the partitioning of convex polygons to allow efficient path planning for coverage. These algorithms are tested both in simulation and in the field with a small twin hull differential thrust vessel built for the task.Comment: 21 pages, 9 Figures, 1 Table. Submitted to The Journal of Field Robotic

Recommendations in Second Opinion Reports of Neurologic Head and Neck Imaging:Frequency, Referring Clinicians? Compliance, and Diagnostic Yield

BACKGROUND AND PURPOSE: Second opinion reports of neurologic head and neck imaging are requested with increased regularity, and they may contain a recommendation to the clinician. Our aim was to investigate the frequency and determinants of the presence of a recommendation and the adherence by the referring physician to the recommendation in a second opinion neurology head and neck imaging report and the diagnostic yield of these recommendations. MATERIALS AND METHODS: This retrospective study included 994 consecutive second opinion reports of neurology head and neck imaging examinations performed at a tertiary care center. RESULTS: Of the 994 second opinion reports, 12.2% (121/994) contained a recommendation. An oncologic imaging indication was significantly (P = .030) associated with a lower chance of a recommendation in the second opinion report (OR = .67; 95% CI, 0.46?0.96). Clinicians followed 65.7% (88/134) of the recommendations. None of the investigated variables (patient age, sex, hospitalization status, indication for the second opinion report, experience of the radiologist who signed the second opinion report, strength of the recommendation, and whether the recommendation was made due to apparent quality issues of the original examination) were significantly associated with the compliance of the referring physician to this recommendation. The 134 individual recommendations eventually led to the establishment of 52 (38.2%) benign diagnoses and 28 (20.6%) malignant diagnoses, while no definitive diagnosis could be established in 56 (41.2%) cases. CONCLUSIONS: Recommendations are relatively common in second opinion reports of neurology head and neck imaging examinations, though less for oncologic indications. They are mostly followed by requesting physicians, thus affecting patient management. In most cases, they also lead to the establishment of a diagnosis, hence adding value to patient care

Radiolabeled humanized anti-CD3 monoclonal antibody visilizumab for imaging human T-lymphocytes

Visilizumab is an IgG2 humanized monoclonal antibody (mAb) characterized by non-FcγR binding and specific to the CD3 antigen, expressed on more than 95% of circulating resting T-lymphocytes and on activated T-lymphocytes homing in inflamed tissues. We hypothesized that the use of a radiolabeled anti-CD3 antibody might serve as a diagnostic tool for imaging T-cell traffic and lymphocytic infiltration of tissues and organs affected by autoimmune diseases. Here we describe the results of in vitro and animal experiments with 99mTc-succinimidyl-6-hydrazinonicotinate hydrochloride (SHNH)-visilizumab. Methods: For mAb labeling, we used a 2-step method with a heterobifunctional linker SHNH. Several titrations were performed to obtain the best labeling efficiency. In vitro quality controls included stability assay, cysteine challenge, sodium dodecyl sulfate polyacrylamide gel electrophoresis, binding assay, and immunoreactivity assay. In vivo studies by high-resolution images were performed at 6 and 24 h after the injection of 99mTc-SHNH-visilizumab. These included cell-targeting experiments in BALB/c mice xenografted subcutaneously with an increasing number of HuT78 cells in the leg and displaced with an excess of cold antibody. We also studied irradiated severe combined immunodeficient (SCID) mice reconstituted with human peripheral blood mononuclear cells (hPBMCs) and injected with 99mTclabeled visilizumab or control mAb. After dynamic imaging for 3 h, major organs were removed, counted, and processed for immunohistologic examination. Results: Visilizumab was labeled with HYNIC with high labeling efficiency (>90%) and high specific activity (SA; 10,360-11,100 MBq/mg), with retained biochemical integrity and in vitro binding activity to CD3-positive cells. The in vivo targeting experiment showed a proportional increase of specific uptake with the number of injected cells, both at 6 and at 24 h, and the in vivo competition study demonstrated more than 60% decreased uptake after an excess of unlabeled antibody. In SCID mice, hPBMCs in different tissues were detected by 99mTc-labeled visilizumab and confirmed by histology. Conclusion: Visilizumab can be efficiently labeled with 99mTc with high efficiency and SA and could be a valuable tool for the study of human T-lymphocyte trafficking and lymphocytic infiltration of tissues and organs. Copyright © 2009 by the Society of Nuclear Medicine, Inc

Rapid reduction of sigma(1)-Receptor binding and F-18-FDG uptake in rat gliomas after in vivo treatment with doxorubicin

sigma-Receptors are strongly overexpressed in most rodent and human tumors and are proliferation markers. To evaluate the potential of a radiolabeled sigma(1)-ligand for therapy monitoring, we compared early changes of C-11-1-(3,4-dimethoxyphenethyl)-4-(3-phenylpropyl)piperazine (C-11-SA4503) binding and F-18-FDG uptake in gliomas after in vivo chemotherapy. Methods: C6 cells (2.5 x 10(6)) were subcutaneously injected into the right shoulder of male Wistar rats. After 7 cl, the tumor volume was 0.60 +/- 0.08 cm(3). Animals then received either saline or doxorubicin (8 mg/kg, intraperitoneally). One control and 1 treated rat were imaged simultaneously, 24 or 48 h after treatment, under pentobarbital anesthesia. Rodents (n = 20) were scanned first with C-11-SA4503 (25 MBq, intravenously) followed more than 100 min afterward by 18F-FDG (20 MBq, intravenously), using a dedicated small-animal PET camera (60-min protocol, tumors in the field of view). Tumor homogenates were prepared and subjected to sigma-receptor assays. The biodistribution of 18F-FDG was assessed. Results: Tumors appeared 4-5 d after inoculation and grew exponentially. No significant reduction of tumor growth was visible within 48 h after doxorubicin treatment. Both PET tracers visualized the tumors and showed reduced uptake after chemotherapy (C-11-SA4503: 26.5% +/- 6.5% at 24 h, 26.5% +/- 7.5% at 48 h; 18F-FDG: 22.6% +/- 3.2% at 24 h, 27.4% +/- 3.2% at 48 h; ex vivo F-18-FDG: 22.4% +/- 5.4% at 24 h, 31.7% +/- 12.7% at 48 h). sigma(1)-Receptor density in treated tumors was also reduced (from 172 +/- 35 to 125 +/- 28 fmol/mg of protein). Conclusion: Both C-11-SA4503 binding and 18F-FDG uptake declined in gliomas after chemotherapy. Decreased binding of C-11-SA4503 corresponded to a loss of (sigma(1)-receptors from the tumors. Changes in tracer uptake preceded the morphologic changes by at least 48 h

Time to Reconsider Routine Percutaneous Biopsy in Spondylodiscitis?

Percutaneous image-guided biopsy currently has a central role in the diagnostic work-up of patients with suspected spondylodiscitis. However, on the basis of recent evidence, the value of routine image-guided biopsy in this disease can be challenged. In this article, we discuss this recent evidence and also share a new diagnostic algorithm for spondylodiscitis that was recently introduced at our institution. Thus, we may move from a rather dogmatic approach in which routine image-guided biopsy is performed in any case to a more individualized use of this procedure. Percutaneous image-guided biopsy, while valuable, is an invasive procedure, and evidence has shown rather disappointing positive microbiologic culture yields of around 33%. Recent evidence also has shown that percutaneous image-guided biopsy rarely adds any new information when blood cultures have positive findings and that an effective empiric treatment can be started in most of cases even when the microbiologic culprit remains unknown. Finally, there is currently no evidence that percutaneous image-guided biopsy improves patient outcome

[18F]FDG PET in conditions associated with hyperkinetic movement disorders and ataxia:a systematic review

PURPOSE: To give a comprehensive literature overview of alterations in regional cerebral glucose metabolism, measured using [18F]FDG PET, in conditions associated with hyperkinetic movement disorders and ataxia. In addition, correlations between glucose metabolism and clinical variables as well as the effect of treatment on glucose metabolism are discussed.METHODS: A systematic literature search was performed according to PRISMA guidelines. Studies concerning tremors, tics, dystonia, ataxia, chorea, myoclonus, functional movement disorders, or mixed movement disorders due to autoimmune or metabolic aetiologies were eligible for inclusion. A PubMed search was performed up to November 2021.RESULTS: Of 1240 studies retrieved in the original search, 104 articles were included. Most articles concerned patients with chorea (n = 27), followed by ataxia (n = 25), dystonia (n = 20), tremor (n = 8), metabolic disease (n = 7), myoclonus (n = 6), tics (n = 6), and autoimmune disorders (n = 5). No papers on functional movement disorders were included. Altered glucose metabolism was detected in various brain regions in all movement disorders, with dystonia-related hypermetabolism of the lentiform nuclei and both hyper- and hypometabolism of the cerebellum; pronounced cerebellar hypometabolism in ataxia; and striatal hypometabolism in chorea (dominated by Huntington disease). Correlations between clinical characteristics and glucose metabolism were often described. [18F]FDG PET-showed normalization of metabolic alterations after treatment in tremors, ataxia, and chorea.CONCLUSION: In all conditions with hyperkinetic movement disorders, hypo- or hypermetabolism was found in multiple, partly overlapping brain regions, and clinical characteristics often correlated with glucose metabolism. For some movement disorders, [18F]FDG PET metabolic changes reflected the effect of treatment.</p

Ovariectomy-induced depressive-like behavior and brain glucose metabolism changes in female rats are not affected by chronic mild stress

The increased incidence of depression in women going through peri-menopause suggests that fluctuations in estrogen levels may increase the risk of developing depression. Nonetheless, this psychiatric disorder is likely to be multifactorial and consequently an additional trigger may be needed to induce depression in this population. Stress could be such a trigger. We therefore investigated the effect of ovarian estrogen depletion and chronic mild stress (CMS) on depressive-like behavior and brain metabolism in female rats. Approximately 2 and 9 weeks after estrogen depletion by ovariectomy, behavioral changes were assessed in the open-field test and the forced swim test, and brain metabolism was measured with [18F]FDG PET imaging. A subset of animals was subjected to a 6-weeks CMS protocol starting 17 days after ovariectomy. Short-term estrogen depletion had a significant effect on brain metabolism in subcortical areas, but not on behavior. Differences in depressive-like behavior were only found after prolonged estrogen depletion, leading to an increased immobility time in the forced swim test. Prolonged estrogen depletion also resulted in an increase in glucose metabolism in frontal cortical areas and hippocampus, whereas a decrease glucose metabolism was found in temporal cortical areas, hypothalamus and brainstem. Neither short-term nor prolonged estrogen depletion caused anxiety-like behavior. Changes in body weight, behavior and brain glucose metabolism were not significantly affected by CMS. In conclusion, ovarian estrogen depletion resulted in changes in brain metabolism and depressive-like behavior, but these changes were not enhanced by CMS

SMART (SiMulAtion and ReconsTruction) PET:an efficient PET simulation-reconstruction tool

Background: Positron-emission tomography (PET) simulators are frequently used for development and performance evaluation of segmentation methods or quantitative uptake metrics. To date, most PET simulation tools are based on Monte Carlo simulations, which are computationally demanding. Other analytical simulation tools lack the implementation of time of flight (TOF) or resolution modelling (RM). In this study, a fast and easy-to-use PET simulation-reconstruction package, SiMulAtion and ReconsTruction (SMART)-PET, is developed and validated, which includes both TOF and RM. SMART-PET, its documentation and instructions to calibrate the tool to a specific PET/CT system are available on Zenodo.SMART-PET allows the fast generation of 3D PET images. As input, it requires one image representing the activity distribution and one representing the corresponding CT image/attenuation map. It allows the user to adjust different parameters, such as reconstruction settings (TOF/RM), noise level or scan duration. Furthermore, a random spatial shift can be included, representing patient repositioning. To evaluate the tool, simulated images were compared with real scan data of the NEMA NU 2 image quality phantom. The scan was acquired as a 60-min list-mode scan and reconstructed with and without TOF and/or RM. For every reconstruction setting, ten statistically equivalent images, representing 30, 60, 120 and 300 s scan duration, were generated. Simulated and real-scan data were compared regarding coefficient of variation in the phantom background and activity recovery coefficients (RCs) of the spheres. Furthermore, standard deviation images of each of the ten statistically equivalent images were compared.Results: SMART-PET produces images comparable to actual phantom data. The image characteristics of simulated and real PET images varied in similar ways as function of reconstruction protocols and noise levels. The change in image noise with variation of simulated TOF settings followed the theoretically expected behaviour. RC as function of sphere size agreed within 0.3-11% between simulated and actual phantom data.Conclusions: SMART-PET allows for rapid and easy simulation of PET data. The user can change various acquisition and reconstruction settings (including RM and TOF) and noise levels. The images obtained show similar image characteristics as those seen in actual phantom data.</p

A retrospective analysis of the diagnostic performance of 11C-choline PET/CT for detection of hyperfunctioning parathyroid glands after prior negative or discordant imaging in primary hyperparathyroidism

BACKGROUND: Identifying the correct location of a parathyroid adenoma in patients with primary hyperparathyroidism (pHPT) is crucial as it can guide surgical treatment. This study aimed to determine the diagnostic performance of 11C-choline PET/CT in patients with pHPT as a next in-line scan after primary negative or discordant first-line imaging. METHODS: This was a retrospective single-center cohort study. All patients with pHPT that were scanned utilizing 11C-choline PET/CT, after prior negative or discordant imaging, between 2015 and 2019 and who subsequently underwent parathyroid surgery were included. The results of the 11C-choline PET/CT were evaluated lesion-based, with surgical exploration and histopathological examination as the gold standard. RESULTS: In total, 36 patients were included of which three patients were known to have Multiple Endocrine Neoplasia (MEN) syndrome. In these 36 patients, 40 lesions were identified on 11C-choline PET/CT and 37 parathyroid lesions were surgically removed. In 34/36 (94%) patients a focused parathyroidectomy was performed, in one patient a cervical exploration due to an ectopically identified adenoma, and in one patient a bilateral exploration was performed because of a double adenoma. Overall, per-lesion sensitivity of 11C-choline PET/CT was 97%, the positive predictive value was 95% and the accuracy was 94% for all parathyroid lesions. CONCLUSIONS: In patients with pHPT and prior negative or discordant first-line imaging results, pathological parathyroid glands can be localized by 11C-choline PET/CT with high sensitivity and accuracy

A light-responsive liposomal agent for MRI contrast enhancement and monitoring of cargo delivery

Medical magnetic resonance imaging (MRI) produces high-resolution anatomical images of the human body, but has limited capacity to provide useful molecular information. The light-responsive, liposomal MRI contrast agent described herein could be used to provide an intrinsic theranostic aspect to MRI and enable tracking the distribution and cargo release of drug delivery systems upon light-triggered activation