Breast CT is a promising modality whose inherent scatter could be used to reconstruct electron density (rho_e) images. This has led us to investigate the benefits of reconstructing linear attenuation coefficient (mu) and (rho_e) images of the breast. First generation CT provides a cost-effective and simple approach to reconstruct (rho_e) images in a laboratory but is limited by the anisotropic probability of scatter, attenuation, noise and contaminating scatter (coherent and multiple scatter). These issues were investigated using Monte Carlo (MC) simulations of a first generation breast scatter enhanced CT (B-SECT) system. A reconstruction algorithm was developed for the B-SECT system and is based on a ring of detectors which eliminates the scatter dependence on the relative position of the scattering centre. The algorithm incorporates an attenuation correction based on the (mu) image and was tested against analytical and MC simulations. MC simulations were also used to quantify the dose per scan. The ring measures a fraction of the total single incoherent scatter which is proportional to ray integrals of (rho_e) and can be quantified even when electron binding is non negligible. The algorithm typically reconstructs accurate (rho_e) images using a single correction for attenuation but has the capability for multiple iterations if required. MC simulations show that the dose coefficients are similar to those of cone beam breast CT. Coherent and multiple scatter can not be directly related to (rho_e) and lead to capping artifacts and overestimated (rho_e) by a factor greater than 2. This issue can be addressed using empirical corrections based on the radiological path of the incident beam and result in (rho_e) images of breast soft tissue with 1% accuracy, 3% precision and a mean glandular dose of 4 mGy for a 3D scan. The reconstructed (rho_e) image was more accurate than the (rho_e) estimate derived from the (mu) image. An alternative correction based on the thickness of breast traversed by the beam provides an enhanced contrast image reflecting the breast scatter properties. These results demonstrate the feasibility of detecting small (rho_e) changes in the intact breast and shows that further experimental evaluation of this technique is warranted.

The purpose of this study is the comparison of methods of image enhancement kinetics in breast MRI tomography, according to 4 models, that analyze dynamic image series. Specifically, the following models have been implemented: (a) the Kuhl empirical approach, (b) a 3-parameter empirical model, (c) the 3 parameter mathematical model of Jansen and (d) the 5-parameter mathematical model of Fan. These models have been tested in a classification task of breast lesions (benignity/malignancy), using a k-ΝΝ (k=3 and k=7) classifier. A case sample of 29 benign and 49 malignant lesions, originating from 1.5T system, were analyzed. A graphical user interface has been implemented, intended as a visual aid to guide the identification of the location of the analyzing Region of Interest (ROI) of the lesion. In this study, the enhancement kinetic features of the two empirical models, as well as the primary and the secondary kinetic features of the two mathematical models were calculated. For proper ROI selection, 2 feature maps (a) the initial enhancement and (b) the 3 Time Point (3TP) kinetic map (Hauth et al. 2006), were utilized as pre-processing step. To evaluate the classification performance, indices such as sensitivity, specificity and accuracy were utilized. Employing the initial enhancement map, classification performance obtained for Kuhl empirical approach (Kuhl et al. 1999), the 3-parameter empirical model, the mathematical model of Jansen et al (Jansen et al. 2008) and the mathematical model of Fan (Fan et al. 2004, 2007) was: (0.87, 0.34, 67.9%), (0.81, 0.65, 70.5%), (0.85, 0.55, 70.5%) and (0.81, 0.58, 67.9%), respectively. Classification results employing the 3TP kinetic map for the Kuhl empirical approach (Kuhl 1999), 3-parameter empirical model, the mathematical model of Jansen and the mathematical model of Fan were: (0.95, 0.58, 82.0%), (0.95, 0.82, 84.6%), (0.85, 0.68, 78.2%) and (0.93, 0.79, 79.4%), respectively. In conclusion, the 3TP kinetic contributed in the proper location of the analyzing ROI and subsequently in the improved classification of malignant from benign lesions for all enhancement kinetic models studied. / Σκοπός της παρούσας εργασίας είναι η σύγκριση μεταξύ μεθόδων ανάλυσης της κινητικής του σκιαγραφικού στην μαγνητική τομογραφία μαστού, σύμφωνα με 4 μοντέλα ανάλυσης που αξιοποιούν τα απεικονιστικά δεδομένα δυναμικών ακολουθιών εικόνων. Συγκεκριμένα, υλοποιήθηκαν: (α) η εμπειρική προσέγγιση Kuhl et al. (Kuhl et al. 1999), η οποία χρησιμοποιεί 1 ποσοτικό δείκτη της αρχικής ενίσχυσης του σήματος και ποιοτική εκτίμηση της κινητικής του σκιαγραφικού στη φάση έκπλυσης, (β) ένα εμπειρικό μοντέλο 3 ποσοτικών δεικτών που ποσοτικοποιούν την πρόσληψη και έκπλυση, (γ) το 3-παραμετρικό εμπειρικό μαθητικό φαρμακοκινητικό μοντέλο των Jansen et al. (Jansen 2008), (δ) το 5-παραμετρικό εμπειρικό φαρμακοκινητικό μαθητικό μοντέλο των Fan et al. (Fan et al. 2004, 2007), στα πλαίσια ταξινόμησης αλλοιώσεων του μαστού (καλοήθεια/κακοήθεια) με χρήση ταξινομητή k-ΝΝ (k=3 και k=7). Μελετήθηκαν 29 καλοήθεις και 49 κακοήθεις αλλοιώσεις, και οι λήψεις των εικόνων έγιναν από 1.5 T μαγνητικό τομογράφο. Υλοποιήθηκε γραφικό περιβάλλον διεπαφής (Graphical User Interface-GUI), προτεινόμενο ως εργαλείο υποβοήθησης για την επιλογή της τοποθέτησης της περιοχής ενδιαφέροντος για την αξιολόγηση των κινητικών χαρακτηριστικών της αλλοίωσης. Στα πλαίσια της παρούσας μελέτης, υπολογίστηκαν τα κινητικά χαρακτηριστικά για τα δύο εμπειρικά μοντέλα καθώς και τα πρωτεύοντα και δευτερεύοντα χαρακτηριστικά για τα μαθηματικά μοντέλα. Για την επιλογή της περιοχής ενδιαφέροντος υλοποιήθηκαν: (α) ένας κινητικός χάρτης πρώιμης ενίσχυσης σήματος, (β) ο κινητικός χάρτης 3TP (Hauth et al. 2006), οποίος εκφράζει τη συνολική κινητική του σκιαγραφικού. Για την αξιολόγηση της απόδοσης ταξινόμησης (διαφοροποίηση καλοήθειας/κακοήθειας) χρησιμοποιήθηκαν οι δείκτες ευαισθησία, ειδικότητα και ακρίβεια. Με χρήση του χάρτη πρώιμης ενίσχυσης για την επιλογή της περιοχής ενδιαφέροντος, η απόδοση ταξινόμησης, του εμπειρικού μοντέλου Kuhl et al. (1999), του εμπειρικού μοντέλου των 3 παραμέτρων, του μαθηματικού μοντέλου Jansen και του μαθηματικού μοντέλο Fan (Fan et al. 2004, 2007) ήταν: (0.87, 0.34, 67.9%), (0.81, 0.65, 70.5%), (0.85, 0.55, 70.5%) και (0.81, 0.58, 67.9%), αντιστοίχως. Με χρήση του κινητικού χάρτη 3TP η απόδοση ταξινόμησης του εμπειρικού μοντέλου Kuhl (Kuhl et al. 1999), του εμπειρικού μοντέλου των 3 παραμέτρων, του μαθηματικού φαρμακοκινητικού μοντέλου Jansen et al. (Jansen et al. 2008) και του μαθηματικού φαρμακοκινητικού μοντέλου Fan (Fan et al. 2004, 2007) ήταν: (0.95, 0.58, 82.0%), (0.95, 0.82, 84.6%), (0.85, 0.68, 78.2%) και (0.93, 0.79, 79.4%), αντιστοίχως. Συμπερασματικά, χρήση του κινητικού χάρτη 3TP συνεισφέρει σε ορθότερη επιλογή της θέσης της περιοχής ενδιαφέροντος προς ανάλυση, βελτιώνοντας αποτελέσματα της ταξινόμησης των κακοηθών από καλοήθεις αλλοιώσεις για όλα τα μοντέλα κινητικής σκιαγραφικού που μελετήθηκαν.

PURPOSE: The purpose of this study was to assess the ability of Micro Computed Tomography (Micro CT) to measure primary tumor size in breast lumpectomy specimens, as compared to the histopathological measurement. METHODS: This was a diagnostic study involving women who were scheduled to have breast lumpectomy surgery at the Massachusetts General Hospital (MGH) Department of surgery from June 2011 - September 2011. Those who met the study eligibility criteria were recruited to participate in the study. The study was approved by the MGH Institutional Review Board (IRB). All the participants provided consent prior to their participation in the study. The lumpectomy specimens of 45 subjects were scanned by Micro CT scan for no longer than 15 minutes, they were then delivered to the gross pathology lab for processing via the standard pathological protocol. Later on, the maximum dimension of the invasive breast tumor was obtained from the Micro CT image and was compared to the corresponding pathology report for each subject. RESULTS: We found that Micro CT tends to overestimate the breast malignant tumor size. However, there were few differences in T-stage classification between Micro CT and pathology. Overall, Micro CT demonstrated good agreement with pathological tumor size and staging. For Invasive ductal carcinoma, Micro CT showed a substantial agreement with pathological tumor size and staging. However, Micro CT showed no agreement with pathological tumor size and staging for invasive lobular carcinoma. CONCLUSIONS: Micro CT is a promising modality in measuring and staging the invasive ductal carcinoma.

Introdução: Os enxertos de gordura autóloga (lipoenxertia) são utilizados há muito tempo como material de preenchimento para correção de defeitos de tecido mole, sendo inicialmente utilizados para correção de defeitos faciais. Nos últimos anos, houve um crescente interesse no uso da lipoenxertia em mamas, tanto como método de reconstrução em pacientes submetidas a cirurgias por câncer de mama quanto em procedimentos estéticos. A gordura é considerada um material de preenchimento ideal em decorrência da facilidade de obtenção e da baixa reação imunogênica e alérgica, além de se tratar de material autólogo. Os principais problemas da lipoenxertia são as taxas de reabsorção imprevisíveis do material enxertado (40-60%), a preocupação quanto a sua segurança, principalmente pela hipótese de a gordura estimular o crescimento de células cancerígenas e o fato da necrose do material enxertado poder produzir fibrose, calcificações ou cistos oleosos na mama, os quais poderiam interferir na interpretação das imagens mamográficas. A partir da técnica desenvolvida por Coleman, diversos estudos surgiram mostrando a eficácia e a segurança da lipoenxertia, já que a mesma não parece interferir nas imagens radiológicas, demonstrando que alterações mamográficas após a lipoenxertia são facilmente interpretadas como alterações benignas por radiologistas experientes. Objetivo: Analisar se a lipoenxertia realizada durante a cirurgia conservadora por câncer de mama e posteriormente seguida de radioterapia causa modificações mamográficas. Método: Foi realizado seguimento de 171 pacientes com diagnóstico de câncer inicial submetidas a tratamento conservador e radioterapia no Hospital de Clínicas de Porto Alegre, no período de junho de 2010 a junho de 2013. Trinta e oito dessas pacientes foram submetidas a reconstrução imediata com lipoenxerto segundo a técnica de Coleman. Resultados: A média da idade das pacientes foi de 58,9 anos para as pacientes sem lipoenxerto e 52,5 anos para as com lipoenxerto, e a média do volume enxertado foi de 125 mL. Foram analisadas as alterações mamográficas dessas pacientes 6, 12, 18 e 24 meses após a radioterapia. Constatou-se uma maior incidência de alterações benignas, como cistos oleosos e esteatonecrose, nas pacientes submetidas a lipoenxertia. Não se detectou no presente estudo diferenças quanto a frequência de nódulos, achados suspeitos ou na classificação BI-RADS entre as pacientes com e sem lipoenxerto. Conclusão: Conclui-se, portanto, que a lipoenxertia causa alterações mamográficas facilmente percebidas como benignas, sem elevar a incidência de achados inconclusivos ou suspeitos. Trata-se de um estudo inédito, pois a reconstrução mamária com gordura é realizada no momento da cirurgia conservadora. / Background: Fat grafts have been used for a long time as a filling material for correction of soft tissue defects. There is growing interest in the use of fat grafting as a method of breast reconstruction in patients undergoing surgery for breast cancer. Fat is considered an ideal filler material due to its easy availability and low immunogenic and allergic reaction and because it is an autologous material. However, fat grafts often have high rates of reabsorption and replacement by fibrous scar tissue, calcifications or oily cysts, which can generate sequels and difficulties in the interpretation of radiological images of the breast. Based on the technique developed by Coleman, several studies have emerged showing the efficacy of fat grafting and that it does not seem to interfere with the early diagnosis of breast cancer. Studies have shown that the incidence of mammographic changes after fat grafting does not differ from other surgical procedures of the breast and that they are easily interpreted as benign changes by experienced radiologists in breast imaging. Aim: Analyze mammographic changes in fat grafting performed during conservative surgery for breast cancer and subsequently followed by radiotherapy. Methods: A total of 171 patients diagnosed with early-stage cancer who received conservative treatment and radiotherapy at the Hospital de Clínicas de Porto Alegre from June 2010 to July 2013 were followed in the present study. Thirty-eight of these also underwent immediate reconstruction with fat grafting, as described by Coleman. Results: Mean patient age was 58.9 years for those not exposed to lipomodeling, and 52.5 years in the remainder of the sample. The mean graft volume was 125 ml. In the present study, oncological follow-ups at 6, 12, 18 and 24 months revealed a higher incidence of benign mammographic findings, such as oil cysts and steatonecrosis, in women who had undergone lipomodeling. However, no between-group differences were identified on any other radiological parameter, including scarring, nodules, suspicious findings and BI-RADS categories. Conclusion: These findings suggest that the mammography alterations caused by lipomodeling are easily identified as benign, and that this procedure is not associated with an increased incidence of inconclusive or suspicious findings. This is a unique study because breast reconstruction with fat is conducted at the time of conservative surgery.

Introdução: Os enxertos de gordura autóloga (lipoenxertia) são utilizados há muito tempo como material de preenchimento para correção de defeitos de tecido mole, sendo inicialmente utilizados para correção de defeitos faciais. Nos últimos anos, houve um crescente interesse no uso da lipoenxertia em mamas, tanto como método de reconstrução em pacientes submetidas a cirurgias por câncer de mama quanto em procedimentos estéticos. A gordura é considerada um material de preenchimento ideal em decorrência da facilidade de obtenção e da baixa reação imunogênica e alérgica, além de se tratar de material autólogo. Os principais problemas da lipoenxertia são as taxas de reabsorção imprevisíveis do material enxertado (40-60%), a preocupação quanto a sua segurança, principalmente pela hipótese de a gordura estimular o crescimento de células cancerígenas e o fato da necrose do material enxertado poder produzir fibrose, calcificações ou cistos oleosos na mama, os quais poderiam interferir na interpretação das imagens mamográficas. A partir da técnica desenvolvida por Coleman, diversos estudos surgiram mostrando a eficácia e a segurança da lipoenxertia, já que a mesma não parece interferir nas imagens radiológicas, demonstrando que alterações mamográficas após a lipoenxertia são facilmente interpretadas como alterações benignas por radiologistas experientes. Objetivo: Analisar se a lipoenxertia realizada durante a cirurgia conservadora por câncer de mama e posteriormente seguida de radioterapia causa modificações mamográficas. Método: Foi realizado seguimento de 171 pacientes com diagnóstico de câncer inicial submetidas a tratamento conservador e radioterapia no Hospital de Clínicas de Porto Alegre, no período de junho de 2010 a junho de 2013. Trinta e oito dessas pacientes foram submetidas a reconstrução imediata com lipoenxerto segundo a técnica de Coleman. Resultados: A média da idade das pacientes foi de 58,9 anos para as pacientes sem lipoenxerto e 52,5 anos para as com lipoenxerto, e a média do volume enxertado foi de 125 mL. Foram analisadas as alterações mamográficas dessas pacientes 6, 12, 18 e 24 meses após a radioterapia. Constatou-se uma maior incidência de alterações benignas, como cistos oleosos e esteatonecrose, nas pacientes submetidas a lipoenxertia. Não se detectou no presente estudo diferenças quanto a frequência de nódulos, achados suspeitos ou na classificação BI-RADS entre as pacientes com e sem lipoenxerto. Conclusão: Conclui-se, portanto, que a lipoenxertia causa alterações mamográficas facilmente percebidas como benignas, sem elevar a incidência de achados inconclusivos ou suspeitos. Trata-se de um estudo inédito, pois a reconstrução mamária com gordura é realizada no momento da cirurgia conservadora. / Background: Fat grafts have been used for a long time as a filling material for correction of soft tissue defects. There is growing interest in the use of fat grafting as a method of breast reconstruction in patients undergoing surgery for breast cancer. Fat is considered an ideal filler material due to its easy availability and low immunogenic and allergic reaction and because it is an autologous material. However, fat grafts often have high rates of reabsorption and replacement by fibrous scar tissue, calcifications or oily cysts, which can generate sequels and difficulties in the interpretation of radiological images of the breast. Based on the technique developed by Coleman, several studies have emerged showing the efficacy of fat grafting and that it does not seem to interfere with the early diagnosis of breast cancer. Studies have shown that the incidence of mammographic changes after fat grafting does not differ from other surgical procedures of the breast and that they are easily interpreted as benign changes by experienced radiologists in breast imaging. Aim: Analyze mammographic changes in fat grafting performed during conservative surgery for breast cancer and subsequently followed by radiotherapy. Methods: A total of 171 patients diagnosed with early-stage cancer who received conservative treatment and radiotherapy at the Hospital de Clínicas de Porto Alegre from June 2010 to July 2013 were followed in the present study. Thirty-eight of these also underwent immediate reconstruction with fat grafting, as described by Coleman. Results: Mean patient age was 58.9 years for those not exposed to lipomodeling, and 52.5 years in the remainder of the sample. The mean graft volume was 125 ml. In the present study, oncological follow-ups at 6, 12, 18 and 24 months revealed a higher incidence of benign mammographic findings, such as oil cysts and steatonecrosis, in women who had undergone lipomodeling. However, no between-group differences were identified on any other radiological parameter, including scarring, nodules, suspicious findings and BI-RADS categories. Conclusion: These findings suggest that the mammography alterations caused by lipomodeling are easily identified as benign, and that this procedure is not associated with an increased incidence of inconclusive or suspicious findings. This is a unique study because breast reconstruction with fat is conducted at the time of conservative surgery.

In modern clinical practice, gamma camera is one of the most important imaging modalities for tumour diagnosis. The standard technique uses scintillator-based gamma cameras equipped with parallel-hole collimator to detect the planar position of γ photon interaction (scintillation). However, the positioning is of insufficient resolution and linearity for breast imaging. With the aim to improve spatial resolution and positioning linearity, a new gamma camera configuration was described specifically for breast-imaging. This breast-specific gamma camera was supposed to have the following technical features: variable angle slant-hole collimator; double SiPM arrays readout at the front and back sides of the scintillator; diffusive reflectors at the edges around the scintillator. Because slant-hole collimator was used, a new 3D scintillation positioning method was introduced and tested. The setup of the gamma detector was created in a Monte Carlo simulation toolkit, and a library of a number of light distributions from known positions was acquired through optical simulation. Two library-based positioning algorithms, similarity comparison and maximum likelihood, were developed to estimate the 3D scintillation position by comparing the responses from simulated gamma interactions and the responses from library. Results indicated that the planar spatial resolution and positioning linearity estimated with this gamma detector setup and positioning algorithm was higher than the conventional gamma detectors. The depth-of-interaction estimation was also of high linearity and resolution. With the results presented, the gamma detector setup and positioning method is promising in future breast cancer diagnosis.

No description available.

<p>Accurate knowledge of the frequency- and temperature-dependent dielectric properties of biological tissues is crucial in the development of ultra-wideband diagnostic and therapeutic technologies such as microwave breast cancer detection and hyperthermia treatments. This work examines the temperature dependence of the dielectric properties of the five tissue phantom-types developed by our group as well as porcine fat, muscle and liver tissues for the frequency range from 3 GHz to 10 GHz and for the temperature range from 5 °C to 45 °C. A systematic and simple measurement procedure is developed to measure the continuous temperature dependence of the dielectric properties of the various phantom and tissue types. The temperature trends of the dielectric properties of the different phantoms and tissues are investigated.</p> <p>Linear temperature coefficients at discrete frequencies are impractical and insufficient in ultra-wideband applications when realistic, non-linear numerical models of the dielectric properties are required. Therefore, a compact one-pole Cole-Cole model is used to model the frequency dependence of the dielectric properties of the measured samples at every temperature point. A second- or third-order polynomial is used to model the temperature dependence of the Cole-Cole parameters. The final model is a one-pole Cole-Cole model whose parameters are polynomial functions of temperature. This model enables the estimation of the relative permittivity and the conductivity of the measured phantom and tissue types at any temperature and frequency.</p> / Master of Applied Science (MASc)

No description available.

Diffuse optical tomography (DOT) is one of the promising imaging modalities that pro- vides functional information of the soft biological tissues in-vivo, such as breast and brain tissues. The near infrared (NIR) light (600-1000 nm) is the interrogating radiation, which is typically delivered and collected using fiber bundles placed on the boundary of the tissue. The internal optical property distribution is estimated via model-based image reconstruction algorithm using these limited boundary measurements. Image reconstruction problem in DOT is known to be non-linear, ill-posed, and some times under-determined due to the multiple scattering of NIR light in the tissue. Solving this inverse problem requires regularization to obtain meaningful results, with Tikhonov-type regularization being the most popular one. The choice of the regularization parameter dictates the reconstructed optical image quality and is typically chosen empirically or based on prior experience. An automated method for optimal selection of regularization parameter that is based on regularized minimal residual method (MRM) is proposed and is compared with the traditional generalized cross-validation method. The results obtained using numerical and gelatin phantom data indicate that the MRM-based method is capable of providing the optimal regularization parameter. A new approach that can easily incorporate any generic penalty function into the diffuse optical tomographic image reconstruction is introduced to show the utility of non-quadratic penalty functions. The penalty functions that were used include, quadratic (`2), absolute (`1), Cauchy, and Geman-McClure. The regularization parameter in each of these cases were obtained automatically using the generalized cross-validation (GCV) method. The reconstruction results were systematically compared with each other via utilization of quantitative metrics, such as relative error and Pearson correlation. The reconstruction results indicate that while quadratic penalty may be able to provide better separation between two closely spaced targets, it's contrast recovery capability is limited and the sparseness promoting penalties, such as `1, Cauchy, Geman-McClure have better utility in reconstructing high-contrast and complex-shaped targets with Geman-McClure penalty being the most optimal one. Effective usage of image guidance by incorporating the refractive index (RI) variation in computational modeling of light propagation in tissue is investigated to assess its impact on optical-property estimation. With the aid of realistic patient breast three-dimensional models, the variation in RI for different regions of tissue under investigation is shown to influence the estimation of optical properties in image-guided diffuse optical tomography (IG-DOT) using numerical simulations. It is also shown that by assuming identical RI for all regions of tissue would lead to erroneous estimation of optical properties. The a priori knowledge of the RI for the segmented regions of tissue in IG-DOT, which is difficult to obtain for the in vivo cases, leads to more accurate estimates of optical properties. Even inclusion of approximated RI values, obtained from the literature, for the regions of tissue resulted in better estimates of optical properties, with values comparable to that of having the correct knowledge of RI for different regions of tissue. Image reconstruction in IG-DOT procedure involves reduction of the number of optical parameters to be reconstructed equal to the number of distinct regions identified in the structural information provided by the traditional imaging modality. This makes the image reconstruction problem to be well-determined compared to traditional under- determined case. Still, the methods that are deployed in this case are same as the one used for traditional diffuse optical image reconstruction, which involves regularization term as well as computation of the Jacobian. A gradient-free Nelder-Mead simplex method was proposed here to perform the image reconstruction procedure and shown to be providing solutions that are closely matching with ones obtained using established methods. The proposed method also has the distinctive advantage of being more efficient due to being regularization free, involving only repeated forward calculations.