Deep Learning: A Primer for Radiologists Chartrand, Gabriel; Cheng, Phillip M; Vorontsov, Eugene ...
Radiographics,
2017 Nov-Dec, Letnik:
37, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Deep learning is a class of machine learning methods that are gaining success and attracting interest in many domains, including computer vision, speech recognition, natural language processing, and ...playing games. Deep learning methods produce a mapping from raw inputs to desired outputs (eg, image classes). Unlike traditional machine learning methods, which require hand-engineered feature extraction from inputs, deep learning methods learn these features directly from data. With the advent of large datasets and increased computing power, these methods can produce models with exceptional performance. These models are multilayer artificial neural networks, loosely inspired by biologic neural systems. Weighted connections between nodes (neurons) in the network are iteratively adjusted based on example pairs of inputs and target outputs by back-propagating a corrective error signal through the network. For computer vision tasks, convolutional neural networks (CNNs) have proven to be effective. Recently, several clinical applications of CNNs have been proposed and studied in radiology for classification, detection, and segmentation tasks. This article reviews the key concepts of deep learning for clinical radiologists, discusses technical requirements, describes emerging applications in clinical radiology, and outlines limitations and future directions in this field. Radiologists should become familiar with the principles and potential applications of deep learning in medical imaging.
RSNA, 2017.
Cet article présente les résultats de deux études semblables menées entre 2017 et 2020, au cours desquelles 68 entretiens de type récit de vie avec des femmes violentées ayant vécu une ou plusieurs ...situations d’itinérance ont été réalisés, ainsi que 17 groupes de discussion auprès d’intervenant·es communautaires oeuvrant auprès d’elles. Il expose une analyse féministe des obstacles rencontrés dans l’accès au logement dans certaines régions périphériques du Québec, au moment de quitter un contexte de violence conjugale. Il montre que la spirale de l’itinérance des femmes (Gélineau, 2008) peut être liée à leur fragilité économique à la sortie d’un contexte de violence, mais surtout aux inégalités (re)produites par le spatial fix. Les résultats illustrent 1) l’effet du développement économique, lequel est principalement axé autour des domaines traditionnellement masculins, sur le prix des logements, et 2) les difficultés à accéder, principalement pour les femmes seules, à un logement social. Par conséquent, les femmes tentant d’échapper à un contexte de violence sont contraintes 1) de se reloger dans un secteur éloigné des centres, loin des pôles de développement, renforçant du même coup leur précarité ; 2) de résider dans un logement vétuste ou d’être sujette aux abus d’un propriétaire ou d’un concierge dans les centres urbains régionaux ; ou 3) de retourner dans un contexte de violence.
BackgroundIL-27 is a heterodimeric cytokine consisting of IL 27p28 and Epstein-Barr virus-induced gene 3 (EBI3) that binds the IL-27 receptor subunit alpha and glycoprotein 130. IL-27 is produced by ...activated macrophages and dendritic cells and limits the intensity and duration of immune responses in the tumor microenvironment by inducing the expression of immunoregulatory receptors (PD-L1, TIM3, LAG-3, TIGIT) and inhibiting production of proinflammatory cytokines (IFNγ, IL-17, TNFα). The IL-27 subunit EBI3 is elevated in plasma from patients with certain cancers including renal cell carcinoma, where it correlates with poor outcome. Based on high expression of IL-27 transcript in tumors from patients with hepatocellular carcinoma (HCC), the role of IL-27 was further explored in patient samples and a mouse model of HCC.MethodsGene expression profiles from the Cancer Genome Atlas (TCGA) were analyzed to identify tumors with elevated IL-27 transcripts. Serum from patients with HCC was analyzed for levels of the IL-27 subunit EBI3. The ability of SRF388, a first-in-class IL-27-blocking antibody that binds to IL-27p28, to reverse IL-27-induced inhibition of cytokine production in human immune cell cultures from patients with HCC was assessed in vitro. Finally, the anti-tumor activity of SRF388 was assessed in an orthotopic murine model of HCC.ResultsTCGA expression data revealed that IL-27p28 transcripts were elevated in tumors from patients with HCC relative to other indications. Serum levels of EBI3 were: 1) elevated in a subset of HCC patients; 2) inversely correlated with survival; 3) independent of serum alpha-fetoprotein levels; and 4) elevated in both hepatitis B/C virus positive and negative patients. Treatment with SRF388 stimulated increased cytokine production in activated peripheral blood mononuclear cells from patients with HCC that was further enhanced when combined with PD-1 blockade. Furthermore, SRF388 inhibited the growth of orthotopic Hepa1-6 liver tumors. mRNA transcriptional profiling of treated tumors revealed that SRF388 profoundly altered the transcriptional landscape in this model. In particular, treatment with SRF388 inhibited expression of immunoregulatory receptors PD-L1 and TIGIT, repressed transcripts associated with TGF-β signaling, and altered myeloid and natural killer cell transcripts.ConclusionsThese data indicate that elevated IL-27 subunit EBI3 is a hallmark of HCC and is associated with poor outcomes in these patients. Blockade of IL-27 with SRF388, currently being evaluated in a Phase 1 clinical trial in patients with advanced solid tumors (NCT04374877), may represent a promising therapy for patients with HCC where it can potentiate anti-tumor immune responses.
Background Patients with von Hippel-Lindau disease (VHL) commonly develop pancreatic cysts and neuroendocrine neoplasms (PNENs or PNETs). Solid microcystic serous adenoma (SMSA), a rare neoplasm ...described in VHL patients, can be mistaken for PNEN on imaging. Methods Clinical, pathologic, and radiologic data were reviewed on VHL patients who underwent surgery for a preoperative diagnosis of PNEN since 1994 at 1 institution. Blinded to the pathologic diagnoses, radiologists reassessed available imaging. Results For 55 patients, 79 pancreatectomies were performed for presumed PNENs. Ten (18%) patients underwent 12 (15%) resections for neoplasms diagnosed as SMSA on final pathology. The average size of a SMSA leading to operation was 3.6 ± 0.4 cm. Four out of 11 SMSAs were still mistaken for PNENs when imaging was reassessed. The mean FDG-positron emission tomography (PET) standardized uptake value was greater for 17 PNENs (12.1 ± 1.2) compared with 6 SMSAs (4.2 ± 0.5; P = .002). The mean doubling time of SMSAs and PNENs was similar. Seven (15%) patients with pathologically proven PNENs had malignant disease. Conclusion SMSAs can mimic PNENs on nonfunctional imaging; FDG-PET may help to differentiate them. A high index of suspicion is needed to minimize operations performed for SMSA and to counsel VHL patients of their risks of undergoing operation for a lesion with no known malignant potential.
Abstract Background Despite the beneficial effects of epidurals in intra-abdominal surgery, the incidence of anastomotic leak remains controversial when used. Moreover, studies have also shown that ...fluid overload may be deleterious to anastomoses. The purpose of this paper is to evaluate the effects of varying intraoperative fluid protocols, in the presence of an epidural, on the burst pressure strength of colonic anastomoses. Methods An epidural was installed in 18 rabbits, divided into three groups. Group 1 received 30 mL/kg/h Ringer's lactate, Group 2 received 100 mL/kg/h Ringer's lactate, and Group 3 received 30 mL/kg/h Pentaspan. Two colo-colonic anastomoses were performed per rabbit. On postoperative day 7 the anastomoses were resected and their burst pressures measured as a surrogate for anastomotic leak. Results When comparing the average burst pressures of all three groups, there was a significant difference ( P = 0.04). The anastomoses in the 100 mL/kg/h Ringer's lactate group were shown to be the weakest, with 64% of the anastomoses having burst under 120 mm Hg. The rabbits hydrated with Pentaspan had the highest strength, with no anastomoses bursting under 120 mm Hg. This translated into significant burst pressure differences ( P = 0.02) between Group 2 and Group 3. Conclusion These results suggest that fluid overload with a crystalloid, in the presence of an epidural, may be deleterious to the healing of colonic anastomoses, creating a higher risk of anastomotic leak. Intraoperative resuscitation should thus focus on goal-directed euvolemia with appropriate amounts of colloids and/or crystalloids to prevent the risk of weakening anastomoses, especially in patients with epidurals.
Response to immune checkpoint blockade cancer immunotherapy is variable, but the mechanisms that underlie this variability remain unclear. In a recent issue of Nature Medicine, Yu et al. demonstrate ...that liver metastases limit immunotherapy efficacy by promoting macrophage-mediated elimination of tumor-specific CD8+ T cells. Liver-directed radiotherapy in preclinical models could partially overcome this effect.
Response to immune checkpoint blockade cancer immunotherapy is variable, but the mechanisms that underlie this variability remain unclear. In a recent issue of Nature Medicine, Yu et al. demonstrate that liver metastases limit immunotherapy efficacy by promoting macrophage-mediated elimination of tumor-specific CD8+ T cells. Liver-directed radiotherapy in preclinical models could partially overcome this effect.
Limited evidence exists that humans mount a mutation-specific T cell response to epithelial cancers. We used a whole-exomic-sequencing-based approach to demonstrate that tumor-infiltrating ...lymphocytes (TIL) from a patient with metastatic cholangiocarcinoma contained CD4+ T helper 1 (TH1) cells recognizing a mutation in erbb2 interacting protein (ERBB2IP) expressed by the cancer. After adoptive transfer of TIL containing about 25% mutation-specific polyfunctional TH1 cells, the patient achieved a decrease in target lesions with prolonged stabilization of disease. Upon disease progression, the patient was retreated with a >95% pure population of mutation-reactive TH1 cells and again experienced tumor regression. These results provide evidence that a CD4+ T cell response against a mutated antigen can be harnessed to mediate regression of a metastatic epithelial cancer.
To assess the optimal pancreatic phase delay in terms of parenchymal enhancement and tumor-to-pancreas contrast with a bolus-tracking method.
Patients referred for suspicion of pancreatic tumor and ...undergoing 64-detector computed tomography scanner were randomized to an individualized scan delay of 10, 20, or 30 seconds of nonionic contrast material (370 mg I/mL) after aortic enhancement above 150 Hounsfield units. The volume of contrast was adjusted to patient weight. Pancreatic and tumor enhancements were measured. Statistical analysis included analysis of variance and post hoc Tukey tests.
One hundred and fifty patients were randomized to individualized scan delays of 10, 20, or 30 seconds. Pancreatic parenchymal enhancement in all patients (n = 150) was significantly higher with a delay of 20 or 30 seconds than that with 10 seconds (P < .001 for both). Tumor-to-pancreas contrast for solid tumors (n = 59) was significantly higher with a delay of 30 seconds than that with 10 seconds (P = .015). Adenocarcinoma-to-pancreas contrast during pancreatic phase was significantly higher for a 20- or 30-second delay than for a 10-second delay (P = .027 and .011, respectively) for one reader.
With a flow rate of 4 mL/s and weight-adjusted contrast volume, an individualized scan delay of 30 seconds after aortic transit time revealed higher pancreatic enhancement and tumor-to-pancreas contrast than that with a delay of 10 seconds.
The liver is a highly specialized organ involved in regulating systemic metabolism. Understanding metabolic reprogramming of liver disease is key in discovering clinical biomarkers, which relies on ...robust tissue biobanks. However, sample collection and storage procedures pose a threat to obtaining reliable results, as metabolic alterations may occur during sample handling. This study aimed to elucidate the impact of pre-analytical delay during liver resection surgery on liver tissue metabolomics. Patients were enrolled for liver resection during which normal tissue was collected and snap-frozen at three timepoints: before transection, after transection, and after analysis in Pathology. Metabolomics analyses were performed using .sup.1 H Nuclear Magnetic Resonance (NMR) and Liquid Chromatography-Mass Spectrometry (LC-MS). Time at cryopreservation was the principal variable contributing to differences between liver specimen metabolomes, which superseded even interindividual variability. NMR revealed global changes in the abundance of an array of metabolites, namely a decrease in most metabolites and an increase in beta-glucose and lactate. LC-MS revealed that succinate, alanine, glutamine, arginine, leucine, glycerol-3-phosphate, lactate, AMP, glutathione, and NADP were enhanced during cryopreservation delay (all p<0.05), whereas aspartate, iso(citrate), ADP, and ATP, decreased (all p<0.05). Cryopreservation delays occurring during liver tissue biobanking significantly alter an array of metabolites. Indeed, such alterations compromise the integrity of metabolomic data from liver specimens, underlining the importance of standardized protocols for tissue biobanking in hepatology.
Prostate-derived Ets transcription factor (PDEF) has recently been associated with invasive breast cancer, but no expression profile has been defined in clinical specimens. We undertook a ...comprehensive PDEF transcriptional expression study of 86 breast cancer clinical specimens, several cell lines, normal tissues. PDEF expression profile was analyzed according to standard clinicopathologic parameters, compared with hormonal receptor, HER-2/neu status, to the expression of the new tumor biomarker Dikkopf-1 (DKK1). Wide ranging PDEF overexpression was observed in 74% of tested tumors, at higher levels than the average expression found in normal breasts. High PDEF expression was associated with hormone receptor positivity (P < .001), moderate to good differentiation (less than grade III, P = .01), dissemination to axillary lymph nodes (P = .002). PDEF was an independent risk factor for nodal involvement (multivariate analysis, odds ratio 1.250, P = .002). It was expressed in a different subgroup compared to DKK1-expressing tumors (P < .001). Our data imply that PDEF mRNA expression could be useful in breast cancer molecular staging. Further insights into PDEF functions at the protein level, possible links with hormone receptors biology, bear great potential for new therapeutic avenues.
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