Effects of CT FOV displacement and acquisition parameters variation on texture analysis features.

Texture analysis (TA) applied to CT imaging is an intensely studied topic and many studies suggested TA potential value in imaging characterisation for diagnostic purposes in different fields. However, often authors do not consider the reproducibility and the robustness versus variations in acquisition parameters; in this work, we wanted to explore the robustness of the TA features extracted from CT images. We scanned a commercial phantom (CIRS model 062M) containing plugs with nine different tissue equivalent electron densities using two different CT scanners of the same vendor and changing tube current (100 and 200 mA without modulation) and peak voltage (80 and 140 kVp). After the segmentation, we extracted TA features with LifeX and data were then statistically analysed using the generic estimate equations (GEE) method. Our results suggest that only seven out of 37 TA features extracted are not affected by variation in acquisition parameters considered in this study: GLRLM lgre, GLRLM srlge, GLRLM lrgle, GLZLM lze, GLZLM lgze, GLZLM szlge, GLZLM lzlge. Definitively, we highlighted the importance of a careful study of the dependence of TA parameters on acquisition modalities and analysis before their application in clinical studies.

Bone texture analysis using CT-simulation scans to individuate risk parameters for radiation-induced insufficiency fractures.

This study deals with the role of texture analysis as a predictive factor of radiation-induced insufficiency fractures in patients undergoing pelvic radiation. INTRODUCTION: This study aims to assess the texture analysis (TA) of computed tomography (CT) simulation scans as a predictive factor of insufficiency fractures (IFs) in patients with pelvic malignancies undergoing radiation therapy (RT). METHODS: We performed an analysis of patients undergoing pelvic RT from January 2010 to December 2014, 24 of whom had developed pelvic bone IFs. We analyzed CT-simulation images using ImageJ macro software and selected two regions of interest (ROIs), which are L5 body and the femoral head. TA parameters included mean (m), standard deviation (SD), skewness (sk), kurtosis (k), entropy (e), and uniformity (u). The IFs patients were compared (1:2 ratio) with controlled patients who had not developed IFs and matched for sex, age, menopausal status, type of tumor, use of chemotherapy, and RT dose. A reliability test of intra- and inter-reader ROI TA reproducibility with the intra-class correlation coefficient (ICC) was performed. Univariate and multivariate analyses (logistic regression) were applied for TA parameters observed both in the IFs and the controlled groups. RESULTS: Inter- and intra-reader ROI TA was highly reproducible (ICC > 0.90). Significant TA parameters on paired t test included L5 m (p = 0.001), SD (p = 0.002), k (p = 0.006), e (p = 0.004), and u (p = 0.015) and femoral head m (p < 0.001) and SD (p = 0.001), whereas on logistic regression analysis, L5 e (p = 0.003) and u (p = 0.010) and femoral head m (p = 0.027), SD (p = 0.015), and sex (p = 0.044). CONCLUSIONS: In our experience, bone CT TA could be correlated to the risk of radiation-induced IFs. Studies on a large patient series and methodological refinements are warranted.

Water/cortical bone decomposition: A new approach in dual energy CT imaging for bone marrow oedema detection. A feasibility study.

INTRODUCTION: Many studies aimed at validating the application of Dual Energy Computed Tomography (DECT) in clinical practice where conventional CT is not exhaustive. An example is given by bone marrow oedema detection, in which DECT based on water/calcium (W/Ca) decomposition was applied. In this paper a new DECT approach, based on water/cortical bone (W/CB) decomposition, was investigated. MATERIALS AND METHODS: Eight patients suffering from marrow oedema were scanned with MRI and DECT. Two-materials density decomposition was performed in ROIs corresponding to normal bone marrow and oedema. These regions were drawn on DECT images using MRI informations. Both W/Ca and W/CB were considered as material basis. Scatter plots of W/Ca and W/CB concentrations were made for each ROI in order to evaluate if oedema could be distinguished from normal bone marrow. Thresholds were defined on the scatter plots in order to produce DECT images where oedema regions were highlighted through color maps. The agreement between these images and MR was scored by two expert radiologists. RESULTS: For all the patients, the best scores were obtained using W/CB density decomposition. CONCLUSIONS: In all cases, DECT color map images based on W/CB decomposition showed better agreement with MR in bone marrow oedema identification with respect to W/Ca decomposition. This result encourages further studies in order to evaluate if DECT based on W/CB decomposition could be an alternative technique to MR, which would be important when short scanning duration is relevant, as in the case of aged or traumatic patients.

Type II congenital pulmonary airway malformation associated with intralobar pulmonary sequestration: report of a case and review of classification criteria.

Pulmonary congenital abnormalities are rare disorders including congenital pulmonary airway malformations (CPAM) and pulmonary sequestration (PS). CPAM is a lesion characterized by the presence of anomalous bronchiolar or acinar structures, variable in size, either cystic or not cystic. PS is generally defined as nonfunctioning lung tissue that is not in normal continuity with the tracheobronchial tree and that derives its blood supply from systemic vessels. We describe a case of a baby girl with a very rare association between CPAM type 2 and intralobar pulmonary sequestration (IPS) focusing on the cystic lesions typical of CPAM and on the lymphatic and blood vessels. The cells lining the cysts often were positive for D2-40 (oncofetal protein M2A). Lymphatic endothelial cells, positive for D2-40, were widely present in the lung parenchyma and dilated lymphatic vessels were present also in the inter-alveolar septa. Moreover, we discuss the pathogenesis of CPAM and its classification criteria.

Assessment of response to chemoradiation therapy in rectal cancer using MR volumetry based on diffusion-weighted data sets: a preliminary report.

PURPOSE: This study evaluated the feasibility of magnetic resonance (MR) volumetry using a diffusion-weighted data set (V(DWI)) and compared it with conventional T2-weighted volumetry (V(C)) in patients affected by rectal cancer treated with chemoradiation therapy (CHRT). MATERIALS AND METHODS: Fourteen patients with a biopsy diagnosis of rectal cancer underwent MR examination before and after CHRT. T2-weighted images were used to extrapolate V(C). A diffusion-weighted (DW) sequence was acquired [spin-echo diffusion-weighted echo-planar imaging (SE-DW-EPI)] with a b-value of 800 s/mm(2) and volume (V(DWI)) was calculated by semiautomatic segmentation of tumour hyperintensity. Two radiologists independently assessed volumes and analysed data in order to establish interobserver agreement and compare and correlate volumes to tumour regression grade (TRG), as evaluable at pathological examination of the surgical specimen. RESULTS: Interobserver agreement was 0.977 [(95% confidence interval (CI) 0.954-0.989) and 0.956 (95% CI 0.905-0.980) for V(C) and V(DWI) and 0.964 (95% CI 0.896-0.988) and 0.271 (95% CI-0.267 to 0.686) between V(C) and V(DWI) before and after CHRT. The correlation between TRG and V(C) and V(DWI) was, respectively, rho = 0.597 (p<0.05) and r(2)=0.156 (p=0.162) and rho=0.847 (p<0.001). CONCLUSIONS: V(DWI) seems to be a promising tool for assessing response to CHRT in rectal cancer. Further studies on large series of patients are needed to refine the technique and evaluate its potential predictive value.

Diffusion-weighted magnetic resonance imaging in the evaluation of renal function: a preliminary study.

PURPOSE: Magnetic resonance diffusion-weighted imaging (MR-DWI) is useful to assess proton motion by the computation of an apparent diffusion coefficient (ADC). This property could be used to assess renal damage, with special regard to unilateral dysfunction. The aim of this study was to estimate the correlation between ADC and the stage of chronic renal failure (CRF) using a spin-echo echo-planar imaging (SE-EPI) sequence with the sensitivity encoding (SENSE) technique. MATERIALS AND METHODS: Fourteen patients (nine men and five women, mean age 49 years, range 22-66 years) underwent an MR examination on a 1.5-T system. Seven patients had a history of hypertension or CRF, one had Takayasu disease and one had nephrovascular hypertension. Five subjects without known kidney disease were used as controls. The glomerular filtration rate (GFR) assessed by Cockcroft-Gault's equation was used as a functional marker. The imaging protocol consisted of T1- and T2-weighted sequences followed by a SE-EPI acquisition with a diffusion gradient of 600 s/mm(2) and SENSE factor 2 and pixel-by-pixel ADC map reconstruction. In five patients, the SE-EPI-DWI sequence was repeated after i.v. administration of 1 mg of furosemide. RESULTS: ADC was of 2.44+/-0.24 x 10(-3) mm(2)/s in patients with normal GFR and of 2.05+/-0.33 x 10(-3) mm(2)/s (p<0.05) in subjects with altered GFR; a significant difference was found between stage III and IV (p<0.01), whereas no differences were found between stage I and II (p=0.27) and between stage II and III (p=0.39). A good correlation was found between GFR and ADC (r=0.79; p<0.01), with no significant change after furosemide administration (p=0.7). CONCLUSIONS: DWI is a feasible MR technique for assessing renal damage. Further studies with scintigraphic correlation are needed to confirm these results and to establish reference values for this imaging technique.

Three-dimensional analysis of pulmonary nodules by MSCT with Advanced Lung Analysis (ALA1) software.

PURPOSE: The purpose of this study was to test the reproducibility of the three-dimensional (3D) Advanced Lung Analysis software (3D-ALA, GE Healthcare) in the estimation of pulmonary nodule volume. MATERIALS AND METHODS: We retrospectively reviewed the unenhanced multislice CT scans (Lightspeed Pro 16 GE) of 77 patients with a solitary pulmonary nodule (n=71) or metastatic pulmonary disease (n=6). A total of 103 pulmonary nodules (19 well-circumscribed, 45 juxtavascular and 39 juxtapleural) were analysed grouped into five classes based on diameter: <5 mm, 10 nodules (9.7%); >or=5 to <10 mm, 25 nodules (24.2%); >or=10 mm to <15 mm, 41 nodules (39.8%); >or=5 to <18 mm, 14 nodules (13.6% ); >or=8 to <30 mm, 13 nodules (12.62%). The following acquisition parameters were used: slice thickness 0.625 mm, reconstruction interval 0.4 mm, pitch 0.562:1, 140 kV, 300 mAs, field of view 13 cm, bone kernel. For each of the 103 nodules three, 3D volume measurements were obtained by the 3D-ALA software. The reproducibility of nodule segmentation was evaluated according to a visual score (1=optimal, >or=95%; 2=fair, 90-95%; 3=poor, 0.05). CONCLUSIONS: Three-dimensional volume measurement with ALARiassunto 1 software is reproducible for all nodules as regards dimension and site. ALA-1 software provided a good and reproducible volume measurement in well-circumscribed and most juxtavascular nodules. Volumetric evaluation and reproducibility of volume estimation in juxtapleural pulmonary nodules, particularly those adjacent to diaphragmatic pleura, is inadequate, and software improvement is needed.

Magnetic resonance diffusion-weighted imaging: extraneurological applications.

Diffusion-weighted (Dw) imaging has for a number of years been a diagnostic tool in the field of neuroradiology, yet only since the end of the 1990s, with the introduction of echoplanar imaging (EPI) and the use of sequences capable of performing diffusion studies during a single breath hold, has it found diagnostic applications at the level of the abdomen. The inherent sensitivity to motion and the magnetic susceptibility of Dw sequences nonetheless still create problems in the study of the abdomen due to artefacts caused by the heartbeat and intestinal peristalsis, as well as the presence of various parenchymal-gas interfaces. With regard to focal liver lesions, a review of the literature reveals that Dw imaging is able to differentiate lesions with high water content (cysts and angiomas) from solid lesions. With regard to the latter, although there are differences between benign forms [focal nodular hyperplasia (FNH), adenoma] and malignant forms [metastasis, hepatocellular carcinoma (HCC)] in their apparent diffusion coefficient (ADC) in the average values for histological type, there is a significant overlap in values when lesions are assessed individually, with the consequent problem of their correct identification. One promising aspect is the possibility of quantifying the degree of fibrosis in patients with chronic liver disease and cirrhosis given that the deposit of collagen fibres "restricts" the motion of water molecules and therefore reduces ADC values. However, even in this field, studies can only be considered preliminary and far from real clinical applications. The retroperitoneum is less affected by motion artefacts and similarly deserves the attention of Dw imaging. Here it is possible to differentiate mucin-producing tumours of the pancreas from pseudocystic forms on the basis of ADC values even though the limited spatial resolution of Dw imaging does not enable the identification of small lesions. Dw imaging may be applied to the study of the kidney to differentiate hydronephrosis from pyonephrosis and with regard to tumours, solid from pseudocystic forms. In addition, given that renal parenchyma has significantly variable ADC values on the basis of the anatomic section and physiological conditions, the possibility of assessing functional alterations is currently being studied. Indeed, a good correlation has been found between ADC values and glomerular filtration rate. With regard to musculoskeletal applications, the absence of motion artefacts in the regions studied has enabled the development of sequences less sensitive to magnetic susceptibility and with greater spatial resolution than EPI. Attempts have therefore been made to use Dw imaging in the characterization of soft-tissue tumours although the findings so far have been disputed. Greater agreement has been found regarding sensitivity of the technique in assessing response of these tumours to chemotherapy: tumour necrosis is thought to increase ADC whereas the persistence of vital neoplastic tissue tends to lower it. One of the most promising applications of Dw imaging is without doubt the assessment of vertebral collapse where a high ADC has been shown to be associated with an osteoporotic cause and a low ADC with a neoplastic cause. Nonetheless, even here, a moderate overlap between ADC values of the two types has been encountered. Dw imaging has also been used in the assessment of bone marrow cellularity: areas of tightly packed cells show a higher ADC value than hypocellular areas. In particular, no significant difference in ADC is noted between normal hypercellular bone marrow and hypercellular bone marrow secondary to lymphomatous infiltration whereas this difference is significant between hypocellular, normocellular and haematopoietic hypercellular bone marrow. With regard to the study of joints, the limited structure dimensions, particularly cartilage, creates technical difficulties related to spatial resolution and an adequate signal-to-noise ratio, problems that can only be solved by further technological developments. Lastly, a significant difference in ADC values between degenerative and inflammatory effusion has been found, a fact that may be explained as the result of the activity of hyaluronidase present in inflammatory forms, which causes a reduction in the concentration of hyaluronic acid with a consequent decrease in viscosity.