Ducted Fuel Injection (DFI) is a concept of growing interest to abate soot
emissions in diesel combustion based on a small duct within the combustion
chamber in front of the injector nozzle. Despite ...the impressive potential of the
DFI proven in literature, its application for series production and the
complexity for the adaptation of existing Compression-Ignition (CI) engines need
to be extensively investigated. In this context, the aim of this study is to
numerically assess the potential of DFI implementation in a CI engine for
light-duty applications, highlighting the factors which can limit or facilitate
its integration in existing combustion chambers.
The numerical model for combustion simulation was based on a
One-Dimensional/Three-Dimensional Computational Fluid Dynamics (1D/3D-CFD)
coupled approach relying on a calibrated spray model, extensively validated
against experimental data. Once the coupling procedure had been assessed by
comparing the numerical results with experimental data of in-cylinder pressure
and heat release rate for both low- and high-load operating conditions, the
effect of the duct was investigated by introducing it in the computational
domain. It was observed that DFI did not yield any significant advantage to
engine-out soot emissions and fuel consumption with the existing combustion
system. Although soot formation was generally reduced, the soot oxidation
process was partially inhibited by the adopted duct keeping the fixed engine
calibration, suggesting the need for a complete optimization of the combustion
system design. On the other hand, a preliminary variation of engine calibration
highlighted several beneficial trends for DFI, whose operation was improved by a
simplified injection strategy.
The present numerical results indicate that DFI retrofit solutions without
specific optimization of the combustion system design do not guarantee soot
reduction. Nevertheless, there is still much room for improvement in terms of
DFI-targeted combustion chamber design and engine calibration to achieve the
full success of this technology for soot-free CI engines.
The design of diesel engine piston bowls plays a fundamental role in the optimization of the combustion process, to achieve ultra-low soot emissions. With this aim, an innovative piston bowl design ...for a 1.6-liter light-duty diesel engine was developed through a steel-based additive manufacturing (AM) technique, featuring both a sharp step and radial bumps in the inner bowl rim. The potential benefits of the proposed hybrid bowl were assessed through a validated three-dimensional computational fluid dynamics (3D-CFD) model, including a calibrated spray model and detailed chemistry. Firstly, the optimal spray targeting was identified for the novel hybrid bowl over different injector protrusions and two swirl ratio (SR) levels. Considering the optimal spray targeting, an analysis of the combustion process was carried out over different engine working points, both in terms of flame-wall interaction and soot formation. At rated power engine operating conditions, the hybrid bowl highlighted faster mixing-controlled combustion due to the reduced flame-to-flame interaction and the higher air entrainment into the flame front. At partial-load operating points, the hybrid bowl showed a remarkable soot reduction in comparison with the re-entrant bowl due to a more intense soot oxidation rate in the late combustion phase. Moreover, for the hybrid bowl, a robust Exhaust Gas Recirculation (EGR) tolerance was highlighted, leading to a flat soot-brake-specific oxides of nitrogen (BSNOₓ) trade-off. At constant BSNOₓ, a 70% soot reduction was achieved without any detrimental effect on fuel consumption, suggesting the high potential of the proposed innovative bowl for soot attenuation.
Background
Pathological complete response after neoadjuvant chemoradiotherapy in locally advanced rectal cancer (LARC) is achieved in 15–30% of cases. Our aim was to implement and externally validate ...a magnetic resonance imaging (MRI)-based radiomics pipeline to predict response to treatment and to investigate the impact of manual and automatic segmentations on the radiomics models.
Methods
Ninety-five patients with stage II/III LARC who underwent multiparametric MRI before chemoradiotherapy and surgical treatment were enrolled from three institutions. Patients were classified as responders if tumour regression grade was 1 or 2 and nonresponders otherwise. Sixty-seven patients composed the construction dataset, while 28 the external validation. Tumour volumes were manually and automatically segmented using a U-net algorithm. Three approaches for feature selection were tested and combined with four machine learning classifiers.
Results
Using manual segmentation, the best result reached an accuracy of 68% on the validation set, with sensitivity 60%, specificity 77%, negative predictive value (NPV) 63%, and positive predictive value (PPV) 75%. The automatic segmentation achieved an accuracy of 75% on the validation set, with sensitivity 80%, specificity 69%, and both NPV and PPV 75%. Sensitivity and NPV on the validation set were significantly higher (
p
= 0.047) for the automatic
versus
manual segmentation.
Conclusion
Our study showed that radiomics models can pave the way to help clinicians in the prediction of tumour response to chemoradiotherapy of LARC and to personalise per-patient treatment. The results from the external validation dataset are promising for further research into radiomics approaches using both manual and automatic segmentations.
Recently, Computer Aided Diagnosis (CAD) systems have been proposed to help radiologists in detecting and characterizing Prostate Cancer (PCa). However, few studies evaluated the performances of ...these systems in a clinical setting, especially when used by non-experienced readers. The main aim of this study is to assess the diagnostic performance of non-experienced readers when reporting assisted by the likelihood map generated by a CAD system, and to compare the results with the unassisted interpretation. Three resident radiologists were asked to review multiparametric-MRI of patients with and without PCa, both unassisted and assisted by a CAD system. In both reading sessions, residents recorded all positive cases, and sensitivity, specificity, negative and positive predictive values were computed and compared. The dataset comprised 90 patients (45 with at least one clinically significant biopsy-confirmed PCa). Sensitivity significantly increased in the CAD assisted mode for patients with at least one clinically significant lesion (GS > 6) (68.7% vs. 78.1%,
= 0.018). Overall specificity was not statistically different between unassisted and assisted sessions (94.8% vs. 89.6,
= 0.072). The use of the CAD system significantly increases the per-patient sensitivity of inexperienced readers in the detection of clinically significant PCa, without negatively affecting specificity, while significantly reducing overall reporting time.
Background
Radiomics is expected to improve the management of metastatic colorectal cancer (CRC). We aimed at evaluating the impact of liver lesion contouring as a source of variability on radiomic ...features (RFs).
Methods
After Ethics Committee approval, 70 liver metastases in 17 CRC patients were segmented on contrast-enhanced computed tomography scans by two residents and checked by experienced radiologists. RFs from grey level co-occurrence and run length matrices were extracted from three-dimensional (3D) regions of interest (ROIs) and the largest two-dimensional (2D) ROIs. Inter-reader variability was evaluated with Dice coefficient and Hausdorff distance, whilst its impact on RFs was assessed using mean relative change (MRC) and intraclass correlation coefficient (ICC). For the main lesion of each patient, one reader also segmented a circular ROI on the same image used for the 2D ROI.
Results
The best inter-reader contouring agreement was observed for 2D ROIs according to both Dice coefficient (median 0.85, interquartile range 0.78–0.89) and Hausdorff distance (0.21 mm, 0.14–0.31 mm). Comparing RF values, MRC ranged 0–752% for 2D and 0–1567% for 3D. For 24/32 RFs (75%), MRC was lower for 2D than for 3D. An ICC > 0.90 was observed for more RFs for 2D (53%) than for 3D (34%). Only 2/32 RFs (6%) showed a variability between 2D and circular ROIs higher than inter-reader variability.
Conclusions
A 2D contouring approach may help mitigate overall inter-reader variability, albeit stable RFs can be extracted from both 3D and 2D segmentations of CRC liver metastases.
A wide spectrum of anomalies of the pancreas, the pancreatic ductal system and the biliary tree are commonly encountered at radiologic evaluation. Pancreas bifidum, also known as bifid pancreas or ...fish-tail pancreas, is an extremely rare congenital branching anomaly of the main pancreatic duct characterized by its duplication. These 2 separate ducts are laid from the pancreatic tail to neck and they generally join at the pancreas body-tail draining via the major papilla; the pancreatic parenchyma is also bifurcated with separated dorsal and caudal buds. The clinical impact of this condition is not well established: although some authors sustained that probably does not cause or contribute to abdominal pain or overt pancreatic diseases, others argued that could be considered as a possible cause of acute pancreatitis.
We herewith describe the case of a 51-year-old woman presenting to our hospital with epigastric pain, nausea, and vomiting. Biochemical tests were suspicious for acute pancreatitis. Ultrasound examination was negative. MRI, including MR cholangiopancreatography revealed bifid pancreas characterized by duplication of the main pancreatic duct with 2 separate ducts that join at the pancreas head and draining via the minor papilla. On T2-weighted images the ventral bud of the pancreas was enlarged and characterized by slightly hyperintensity without peripancreatic fluid collections. The MRI findings were consistent with acute pancreatitis limited to the ventral bud of a bifid pancreas. Patient was treated with intravenous fluid resuscitation, pain control and institution of early enteral nutrition and discharged on the seventh day after admission.
Chemotherapy could induce benign liver alterations presenting as diffuse or focal lesions mimicking metastases. Oxaliplatin-induced vascular liver injury is described in literature, but the ...association with FNH-like lesions has been reported in a limited number of cases. We herewith describe the case of a 67-year-old male, who had laparoscopic right-sided hemicolectomy, 8 years ago, because of colonic adenocarcinoma (pT3N0M0) and subsequent adjuvant chemotherapy (capecitabine + oxaliplatin), who referred to the ultrasound service of our Radiology Unit because of abdominal pain. Five-years follow-up was negative for metastases. Ultrasound examination showed 2 small hypoechoic hepatic nodules, in segment VIII and VII, confirmed at CT, suspected for metastases. FDG-PET was negative, and blood tumor markers were within normal ranges. For further evaluation we performed gadoxetic acid (Gd-EOB-DTPA)-enhanced MRI that showed hyperintensity of the nodules in the hepatobiliary phase with central small hypointensity due to a central scar. Considering the previous oxaliplatin-based chemotherapy the findings were compatible with FNHlike lesions and the diagnostic suspicion was confirmed at ultrasound-guided core needle biopsy. Knowledge of the possible occurrence of FNH-like lesions in oncologic setting, along with the detection of typical MRI appearance, is important for appropriate management and may avoid unnecessary biopsy or surgery and reduce patients’ anxiety.
Peripheral neuroblastic tumors are extremely rare in the adult with less just over 20 cases involving adrenal gland described in the literature. We reported herewith the case of a 22-year-old young ...male who presented with epigastric pain and diarrhea. Imaging studies documented a 3.5cm x 3cm x 4cm solid well-circumscribed right adrenal mass, of heterogeneous structure and with fine calcifications. The lesion turned negative at MIBG scintigraphy. A right robotic-assisted adrenalectomy was performed leading to complete excision of the lesion without complications. Histology was consistent with intermixed stroma-rich ganglioneuroblastoma. A wait-and-see strategy was considered adequate. Two years after diagnosis patient is alive disease-free. Although the definitive diagnosis of a peripheral neuroblastic tumor is obtained after histopathological analysis, CT, and MRI are helpful to further characterize masses and useful in pretreatment risk stratification. Clinicians should be aware of the possibility of GNB development in adult population and its malignant potential.
Breast metastases are uncommon findings compared to primary breast cancer and in particular bilateral secondary breast lesions from neuroendocrine tumor (NET)s are extremely rare with just less over ...13 cases described in literature. We reported herewith the case of a 54-year-old woman who presented to our Breast Unit after noticing multiple, mobile, bilateral breast lumps. Imaging studies confirmed the presence of multiple, circumscribed, bilateral breast masses with slightly spiculated margins, classified as suspicious for malignancy (BI-RADS 4). A tru-cut biopsy was carried out on the largest lesion of each side and histopathologic and immunohistochemistry examination was consistent with metastases from pancreatic neuroendocrine tumor (PNET). Total-body CT revealed the presence of a mass located in the pancreatic body - tail with associated abdominal lymphadenopathies and multiple secondary nodules in bilateral breast and in the liver. Stage IV disease was diagnosed, patient did not undergo surgery and started LAR – octreotide therapy. Although rare, breast metastases from NETs represent an important diagnostic challenge for practitioners because of the difficulty to differentiate from a primary breast carcinoma or even from benign breast lesions. Clinicians should be aware of the possibility of bilateral breast metastases in differential diagnosis of breast lesions in order to ensure the correct diagnosis and the most appropriate management of these patients.
Rheumatoid arthritis (RA), a systemic inflammatory disease, may induce pulmonary manifestations. We describe a case of longstanding RA presenting with eosinophilic pneumonia (EP). Rare case reports ...of tissue eosinophilia involving isolated organs in the setting of RA exist in the literature. It has been shown that the production of proinflammatory cytokines activates different cell group and can simultaneously play a role in RA and induce eosinophils infiltration in target tissue. An appropriate lowest possible dosage of steroid therapy is essential, whereas EP may be a rare subset of pulmonary involvement in RA.
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