Attractive new technologies for 7-wavelength time domain optical mammography

An 8-channel Silicon PhotoMultiplier (SiPM) probe and Time-to-Digital-Converter (TDC) realize a higher-throughput, cheaper and compact detection chain for time-resolved optical mammography than photomultiplier tubes (PMTs) and Time Correlated Single Photon Counting (TCSPC) boards, providing comparable estimate of optical properties with increased optical responsivity

High throughput detection chain for time domain optical mammography

A novel detection chain, based on 8 Silicon Photomultipliers (forming a wide-area custom-made detection probe) and on a time-to-digital converter, was developed to improve the signal level in multi-wavelength (635-1060 nm) time domain optical mammography. The performances of individual components and of the overall chain were assessed using established protocols (BIP and MEDPHOT). The photon detection efficiency was improved by up to 3 orders of magnitude, and the maximum count rate level was increased by a factor of 10 when compared to the previous system, based on photomultiplier tubes and conventional time-correlated single-photon counting boards. In the estimate of optical parameters, the novel detection chain provides performances comparable to the previous system, widely validated in clinics, but with higher signal level, higher robustness, and at a lower price per channel, thus targeting important requirements for clinical applications

Novel approaches to photon detection and timing for 7-wavelength time domain optical mammography

An 8-channel Silicon Photomultiplier probe and a Time-to-Digital Converter are used to build a higher-throughput, cheaper and compact detection chain for time-resolved optical mammography as compared with conventional PhotoMultiplier Tubes and Time-Correlated Single-Photon Counting boards, still providing comparable performance in the estimation of optical properties, but with higher optical responsivity

High-throughput multi-wavelength time-resolved optical mammograph: importance of in vivo performance assessment

The use of technologies still under development for the upgrade of our multi-wavelength time-resolved optical mammograph, such as silicon photomultipliers and a Time-to-Digital Converter (TDC), highlighted the crucial need for a thorough and progressive instrument characterization: from extensive laboratory tests on phantoms to in vivo measurements. Despite satisfying results on phantoms, in vivo tests urged a significant instrumental change to obtain high-quality breast scans. The setup was upgraded with the adoption of a just-released high-throughput TDC and now grants much wider scan area, better day-by-day reproducibility, and improved signal quality. These results point out the importance of in vivo performance assessment as a general approach for instrument characterization, not limited only to our optical mammograph. After the successful outcomes of the preliminary tests, a clinical study on neoadjuvant chemotherapy monitoring is now ongoing at the San Raffaele Hospital, Milan

Advances in single-photon detection and timing for Time Domain multi-wavelength Optical Mammography

To enhance photon harvesting and improve data quality, an 8-channel compact SiPM probe and TDC acquisition replace PMTs and TCSPC boards in a time-resolved optical mammograph still providing similar performances for optical properties estimation

Fitting a spectral model for component analysis in diffuse optical tomography

Time Domain Diffuse Optical Tomography (TD-DOT) at different wavelengths can be used to retrieve tissue reconstructing the components of a two-region system starting from self-normalized time-dependent measurements performed in reflectivity geometry over multiple wavelengths. The proposed method performs a fit of a limited number of tissues parameters providing a good quantification of the components’ concentrations by applying a FEM-based Diffusion approximation of the TD-DOT direct model

Multi-wavelength time domain diffuse optical tomography for breast cancer: initial results on silicone phantoms

Time domain Diffuse Optical Tomography (TD-DOT) non-invasively probes the optical proprieties of biological tissue. These can be related to changes in tissue composition, thus making TD-DOT potentially valuable for cancer imaging. In particular, an application of interest is therapy monitoring for breast cancer. Thus, we developed a software tool for multi-wavelength TD-DOT in reflectance geometry. While the use of multiple wavelengths probes the main components of the breast, the chosen geometry offers the advantage of linking the photon flight time to the investigated depth. We validated the tool on silicone phantoms embedding an absorbing inclusion to simulate a malignant lesion in breast tissue. Also, we exploited the a priori information on position and geometry of the inclusion by using a morphological prior constraint. The results show a good localization of the depth of inclusion but a reduced quantification. When the morphological constraint is used, though, the localization improves dramatically, also reducing surface artifacts and improving quantification as well. Still, there is room for improvement in the quantification of the “lesion” properties

Spectral approach to time domain diffuse optical tomography for breast cancer: validation on meat phantoms

Time Domain Diffuse Optical Tomography (TD-DOT) performed at multiple wavelengths can be used to non-invasively probe tissue composition. Then, tissue composition can be related to breast tissue and lesion type. Thus, TD-DOT could be used for therapy monitoring for breast cancer. We developed a software tool for multi-wavelength TD-DOT and performed a validation on meat phantoms to mimic tissue heterogeneity. An inclusion of different meat was exploited to mimic the presence of a lesion in the breast. Results show good localization of the inclusion, but poor quantification of the reconstructed breast composition. The use of a morphological prior constraint, providing information on inclusion geometry and position, significantly improves both localization and composition estimate

A novel approach to online Physics refresher courses at Politecnico di Milano

Among the challenges that universities are facing nowadays, one that deserves special attention is the increasing number of dropouts. Refresher courses for perspective freshmen have regularly been organised at Politecnico di Milano over the last years as a means to tackle this issue. Due to the Covid-19 pandemic, the present situation posed serious limitations to traditional teaching methods this year, especially for long (3-4 hours) lectures which may be difficult to follow online. In this paper we present a novel approach based on a blend of non-interactive conventional lectures in large groups and interactive lessons in smaller groups. The course was delivered online using the Microsoft Teams software according to the following structure: first, a live video of a 1-hour lecture was streamed by a single tutor for the whole pool of approximately 1000 students. During this streaming, the students were not allowed to interact with the tutor or with one another by any means. Afterwards, 8 teams of students were formed and assigned to different tutors for the following three hours of more interactive lectures. Each tutor presented examples and exercises of their own choice (mainly on the same topic as the streamed video) and delivered guided solutions while promoting the interaction among students. Furthermore, a common set of short problems was given to each team: this activity could be performed at any time during the second part of the block, as decided by each tutor. In order to span among different teaching styles, the student teams were assigned to a different tutor every day for the interactive part of the lesson. As an additional resource, an online forum was activated on a dedicated website, which allowed students to ask questions on the course topics in an asynchronous way. At the end of the course, every student was invited to fill in an anonymous survey to express their satisfaction with the course. The results of the survey indicate an overall degree of satisfaction with a mean rating over 75%

Multi-wavelength time domain diffuse optical tomography for breast cancer: initial results on silicone phantoms

Time domain Diffuse Optical Tomography (TD-DOT) non-invasively probes the optical proprieties of biological tissue. These can be related to changes in tissue composition, thus making TD-DOT potentially valuable for cancer imaging. In particular, an application of interest is therapy monitoring for breast cancer. Thus, we developed a software tool for multi-wavelength TD-DOT in reflectance geometry. While the use of multiple wavelengths probes the main components of the breast, the chosen geometry offers the advantage of linking the photon flight time to the investigated depth. We validated the tool on silicone phantoms embedding an absorbing inclusion to simulate a malignant lesion in breast tissue. Also, we exploited the a priori information on position and geometry of the inclusion by using a morphological prior constraint. The results show a good localization of the depth of inclusion but a reduced quantification. When the morphological constraint is used, though, the localization improves dramatically, also reducing surface artifacts and improving quantification as well. Still, there is room for improvement in the quantification of the “lesion” properties