METODI PER L\u2019ANALISI DELLA TEXTURE DI REGIONI DI INTERESSE (ROIs) DI FORMA IRREGOLARE PER IMMAGINI BIOMEDICHE

In questa tesi sono presentati algoritmi per le stime, in ROIs irregolari di immagini a scale di grigio, della dimensione frattale(DF) e di indici per la caratterizzazione dei loro istogrammi. Tali strumenti sono stati testati in due lavori. Il primo riguarda un nuovo metodo di valutazione dell\u2019hepato-renal ratio(HRR) per la valutazione quantitativa della steatosi epatica con immagini ecografiche. L\u2019HRR \ue8 stato definito come il rapporto dell\u2019intensit\ue0 media di due ROIs rispettivamente del fegato e del rene. Il metodo proposto prevede la selezione di ROIs a \u201cmano libera\u201d(ROIs fh).Le ROIs sono quindi sottoposte a pre-processing(PP), consistente nella\u201cnormalizzazione delle ROIs\u201d,per rendere le due aree pi\uf9 comparabili, e nello smoothing dei relativi istogrammi normalizzati.L\u2019HRR \ue8 stato calcolato sulla base del PP delle ROIs. Per testare l\u2019efficacia del PP, il procedimento \ue8 stato ripetuto da un secondo operatore con ROIs di forma ellittica o circolare(ROIs e/c).Il dataset analizzato \ue8 di 98 scansioni di 32 pazienti(23 pazienti con pi\uf9 scansioni).L\u2019efficacia della tecnica \ue8 stata valutata confrontandola con un metodo(metodo di riferimento,MR)sviluppato sulla base di precedenti lavori. La variabilit\ue0 inter-scansione \ue8 stata valutata calcolando il massimo tra i valori assoluti delle differenze degli HRRs delle scansioni di uno stesso paziente. Gli HRRs ottenuti con il PP delle ROIs non hanno mostrato differenze significative rispetto a quelli ottenuti con il MR(p-value=0.52 per ROIs fh e p-value=0.14 per ROIs e/c).Un analogo risultato \ue8 stato conseguito nel confronto tra gli HRRs ottenuti dal PP delle ROIs e/c e quelli risultanti dal PP delle ROIs fh,(p-value=0.46).Il metodo presentato(con PP di ROIs fh )ha mostrato una variabilit\ue0 inter-scansione minore del MR(p-value<0.001).I risultati preliminari sembrano confermare che il metodo proposto \ue8 riproducibile ed ha un\u2019efficacia clinica comparabile al MR. L\u2019oggetto del secondo lavoro \ue8 la valutazione quantitativa delle alterazioni ecografiche dello sfintere anale interno(IAS) associate l\u2019invecchiamento.62 soggetti sani di et\ue0 tra i 19 e gli 87anni sono stati sottoposti a endosonografia anale 3D.La parte mediale dell\u2019IAS \ue8 stata valutata con misurazioni di volume, dell\u2019intensit\ue0 mediana(IM) e della DF.L\u2019et\ue0 dei soggetti \ue8 stata rappresentata attraverso una variabile a tre livelli(19-59, 60-69 e 70-87anni).Per lo studio delle associazioni tra l\u2019et\ue0 e le caratteristiche dell\u2019IAS \ue8 stata impiegata la \u201cpath analysis\u201d(PA).L\u2019IM e la DF sono state incluse nella PA come potenziali mediatori dell\u2019effetto dell\u2019et\ue0 sul volume se, nell\u2019analisi descrittiva, essi mostravano un andamento crescente con l\u2019et\ue0. L\u2019associazione tra ogni coppia di variabili \ue8 stata espressa mediante il rapporto tra i valori attesi(REV:1=nessuna associazione,1=associazione positiva).Nell\u2019analisi descrittiva, contrariamente all\u2019IM ed al volume, la DF non ha mostrato un andamento crescente con l\u2019et\ue0 ed \ue8 stata quindi esclusa dalla PA.Nella PA, l\u2019IM ha mostrato un aumento significativo solo tra i soggetti pi\uf9 anziani e quelli pi\uf9 giovani(70-87vs.19-59anni,REV=1.21, p-value=0.048).\uc8 stato osservato solo un effetto diretto dell\u2019et\ue0 sul volume(60-69vs.19-59anni,REV=1.21, p-value=0.070 e 70-87vs.19-59anni,REV=1.32,p-value=0.015).L\u2019IM appare efficace nel rilevare alterazioni della texture dell\u2019IAS legate all\u2019invecchiamento.I risultati ottenuti, sembrano non supportare l\u2019ipotesi di un\u2019associazione tra il processo di fibrosi dell\u2019IAS legato all\u2019invecchiamento e l\u2019aumento di volume muscolare legato all\u2019et\ue0. In entrambi i lavori la verifica dei risultati ottenuti,e/o delle relative interpretazioni, richieder\ue0 ulteriori indagini con studi che validino le misurazioni ecografiche attraverso rilevazioni istologiche su un largo campione di soggetti. I due studi sono esempi di come l\u2019analisi della texture possa contribuire a realizzare nuovi strumenti clinici in grado di produrre valutazioni oggettive e quantitativeThis thesis presents algorithms for the assessment, in irregular gray scale image ROIs, of the fractal dimension (FD) and indices aimed at the characterization of the related histograms. The tools were tested by their applications in the two studies. The first study shows the preliminary results obtained in the experimentation of a new method for liver steatosis quantification by means of ultrasound image analysis. This method is based on hepato-renal ratio (HRR) assessment. HRR was assessed as the ratio between the mean intensities of pixels belonging to two ROIs located respectively in the liver and the kidney. In the method outlined here, the operator selects two ROIs by \u201cfreehand\u201d(fh ROIs).The ROIs were subsequently pre-processed, via \u201cROI normalization\u201d, to make the two areas more comparable, and smoothing out the related normalized histograms. Then HRRs were calculated on the basis of the histograms obtained from pre-processing(PP). In order to test the efficacy of the PP, the procedure was repeated by a second operator, using elliptical and/or circular ROIs(e/c ROIs). The dataset comprised 98 images of 32 patients(for 23 patients more than one scan was performed). The efficacy of the technique presented was tested by comparison with a method developed on the basis of previous works. The HRRs obtained with ROIs pre-processing did not differ significantly from those of the reference method (for the fh ROIs and e/c ROIs the p-values were 0.52 and 0.14 respectively). A similar result was obtained by comparing the HRRs derived from the PP of the e/c ROIs and those resulting from the PP of fh ROIs (p- value=0.46).The method for HRR assessment presented here (on the basis of the PP of fh ROIs) gave a smaller inter-scan variability than the reference method (p-value<0.001). Preliminary results seem to confirm that the proposed method is reproducible and has clinical efficacy comparable to the reference method. The second study aimed at the quantitative assessment of the ultrasound alterations of the internal anal sphincter(IAS), associated with aging. 62 healthy subjects aged between 19 and 87 underwent 3D endoanal ultrasonography. The medial part of the IAS was characterized by assessments of the volume, median voxel intensity (MI) and FD. The age of the subjects under analysis was classified as a three-level variable(19-59, 60-69 and 70-87years). The associations between age and IAS characteristics were evaluated by a path analysis(PA).The MI and the FD were included in the PA as potential mediators of the effect of age on the volume only if they showed an increasing trend according to aging by descriptive analysis. The association between each pair of variables was summarized using the ratio of expected values(REV: 1=no association, 1=positive association).In descriptive analysis, unlike for volume and MI, the FD did not show an increasing trend according to aging, therefore it was excluded from PA. In the PA, the MI showed a statistically significant difference between older and younger subjects only(70-87vs.19-59 years, REV= 1.21, p-value=0.048). Furthermore solely a direct positive effect of age on volume was observed(60-69 vs.19-59 years, REV=1.21, p-value=0.070 and 70-87vs.19-59 years, REV=1.32, p-value=0.015).The MI seems to be an appropriate measure of echotexture alterations in the IAS related to aging.The findings obtained appear not to support the hypothesis that there is an association between the age-related physiological process of fibrosis and a volume increase with age. For both works presented, the results obtained and/or related interpretations require verification by further investigation via studies aimed at the validation of ultrasound assessments by histological findings, analyzing a large sample of subjects. These studies are examples of how texture analysis can be used to provide new tools able to perform objective and quantitative assessments for clinical purpos

An Improved Method for Hepato-Renal Ratio Assessment: a Feasibility Study

Hepato-Renal Ratio (HRR) is a method for the quantitative assessment of liver steatosis based on the processing of ultrasound images. Its reliability has been validated in literature through biopsy and 1H magnetic resonance spectroscopy.This paper describes a new method for ROI segmentation and HRR assessment, designed to minimize both inter-observer and inter-scan variability

An improved method for hepato-renal ratio assessment in the diagnosis of hepatosteatosis: a feasibility study

The hepato-renal ratio is a non-invasive method for liver steatosis quantification based on ultrasound image analysis. Its effectiveness has been validated in literature by means of liver biopsy and 1H magnetic resonance spectroscopy. We propose a new and improved method for ROI selection and HRR assessment, designed to minimize both interobserver and inter-scan variability

New method for internal anal sphincter measurements: Feasibility study

The aim of this paper is to provide a method for measuring the internal anal sphincter on the basis of the quantitative analysis of three-dimensional endosonographic images. A software calculates a large set of measurements which are able to describe the three-dimensional shape of the muscle. The software provides four types of measurements: thickness, length, area and volume. The different magnitudes are estimated using the same reference system. The measurements obtained are modeled by functions that describe their spatial tren

Liver iron measurements with less expensive technology: comparison of a room-temperature susceptometer with SQUID in 84 subjects

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Correlazione tra parametri TC ed analisi istologica nell\u2019eterogenit\ue0 di placca carotidea: studio pilota

Scopo di questo studio pilota \ue8 identificare parametri TC con mezzo di contrasto (TCMdC) in grado diidentificare placche carotidee (PC) ad alto grado di eterogenicit\ue0 istologic

Relaciones genéticas entre las carbonatitas y las rocas nefèlinicas del Complejo El Picacho, Sierra de Tamaulipas, NE de Mèxico

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Imaging of the Internal Anal Sphincter: Study of Healthy Subject: Review Article

Introduction: The internal anal sphincter is a smooth muscle that works with other muscles to control defecation. The identification of morphological changes, defects or the precise definition of the level of tumor infiltration of muscle have significant importance in clinical practice. For these reasons the evaluation of shape and volume of muscle in healthy subjects has been studied for many years. The main used imaging techniques are the anal endosonografy, the endoanal coil magnetic resonance imaging and the phase-array coil magnetic resonance. The small size of muscle, the high irregularity in shape, the variability associated with factors such as age and sex, the use of different imaging techniques, including non-invasive ones, and the lack of a standardized method of measurement, can make difficult the correct comparison of the results. In this chapter we will discuss the results reported in the literature concerning the evaluation of muscle in healthy subjects and the advantages and disadvantages of different methods adopted. Normal IAS Variations: Age-related variations:the thickening of the muscle associated to aging is particularly noticeable when the measurements is performed with the EAU and MR with endoanal coil. Sex-related variations: The characterization of the shape of the muscle in relation to sex appears to be controversial with all methods. The only common result is the greater length of the anterior quadrant in males when measured with the EAU. Variations related to other factors: In a study of nulliparous women with the EAU, it is reported a positive correlation between the thickness, measured in the mid anal canal, and BMI. By contrast, in a similar study carried out with MRI without the introduction of endoanal coil the average thickness of the muscle does not appear to be correlated with BMI. The thickness of the IAS in relation to height appears to increase with both methods of MR. Conclusion: The MRI allows a better visualization of the entirety of the pelvic perineal floor compared to EAU, which is extremely effective in imaging the IAS. Even the lower cost and facility and speed of EAU are the basis of most of the research with anal endosonografy. Normal range have been specifically formulated in only a few works for thickness and length. We believe that new studies and a process of standardization of methods of measurement could provide significant advances in the study of muscle either in a state of normality or pathology

Correlation Between Multidetector Computed Tomography Angiography and Carotid Plaque Histologic Heterogeneity

The aim of this pilot study was to identify multidetector computed tomography angiography (MDCTA) features that may help identify carotid atherosclerotic plaques (CAPs) with severe histological heterogeneity