| 1. |
- Axelsson, Johan, et al.
(författare)
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Prior information in fluorescence molecular tomography based on multispectral fluorescence emission
- 2007
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1042-4687 .- 1605-7422. - 9780819465474 ; 6434, s. 4340-4340
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Konferensbidrag (refereegranskat)abstract
- Fluorescence molecular tomography (FMT) suffers from inherent ill-posedness due to the vast number of possible solutions to the reconstruction problem. To increase the robustness of such a problem one need prior information. We present here a method for rendering a priori information of the position of a fluorescent inclusion inside turbid media. The method utilizes solely two spectral bands within the fluorescence spectrum emitted from the fluorophore. The method is presented and verified using experimental data from a tissue phantom. The confinement is also used to impose weights onto the voxels before the inversion of the linear set of equations describing the FMT problem.
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| 2. |
- Johansson, Ann, et al.
(författare)
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Interstitial photodynamic therapy for primary prostate cancer incorporating realtime treatment dosimetry
- 2007
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1042-4687 .- 1605-7422. ; 6427, s. 4270-4270
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Konferensbidrag (refereegranskat)abstract
- Photodynamic therapy (PDT) for the treatment of prostate cancer has been demonstrated to be a safe treatment option capable of inducing tissue necrosis and decrease in prostate specific antigen (PSA). Research groups report on large variations in treatment response, possibly due to biological variations in tissue composition and shortterm response to the therapeutic irradiation. Within our group, an instrument for interstitial PDT on prostate tissue that incorporates realtime treatment feedback is being developed. The treatment protocol consists of two parts. The first part incorporates the pre-treatment plan with ultrasound investigations, providing the geometry for the prostate gland and surrounding risk organs, an iterative random-search algorithm to determine near-optimal fiber positions within the reconstructed geometry and a Block-Cimmino optimization algorithm for predicting individual fiber irradiation times. During the second part, the therapeutic light delivery is combined with measurements of the light transmission signals between the optical fibers, thus monitoring the tissue effective attenuation coefficient by means of spatially resolved spectroscopy. These data are then used as input for repeated runs of the Block-Cimmino optimization algorithm. Thus, the irradiation times for individual fibers are updated throughout the treatment in order to compensate for the influence of changes in tissue composition on the light distribution at the therapeutic wavelength.
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| 3. |
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| 4. |
- Ruschin, Mark, et al.
(författare)
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Improved in-plane visibility of tumors using breast tomosynthesis
- 2007
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422 .- 1042-4687. ; 6510
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this work was to evaluate and compare the visibility of simulated tumors in 2D digital mammography (DM) and breast tomosynthesis (BT) images of patients. Images of the same women were acquired on both a DM system (Mammomat Novation, Siemens) and a BT prototype system adapted from the same type of DM system. Using the geometrical properties of the two systems, simulated, ellipsoid-shaped tumors (average dimension: 8.4 mm × 6.6 mm × 5 mm) with irregular margins were projected and added to each DM image as well as each BT projection image prior to 3D reconstruction. The same beam quality and approximately the same total absorbed dose were used for each breast image acquisition on both systems. Two simulated tumors were added to each of thirty patient scans, yielding sixty cases. A series of 4-alternative forced choice (4-AFC) human observer experiments were conducted in order to determine what projected signal intensity (contrast) of the tumors in the DM images would be needed to achieve the same detectability as in the reconstructed BT images. Nine observers participated. For the BT 4-AFC experiment, when the signal intensity of the tumor on the central projection was 0.010 (natural logarithmic units) the mean percent of correct responses (PC) was measured to be 81.5%, which converted to a detectability index value (d') of 1.96. For the DM system, the same detectability was achieved at a signal intensity determined to be 0.038. Equivalent levels of tumor detection in BT images were thus achieved at around four times less projected signal intensity than in DM images, indicating that the use of BT may lead to earlier detection of breast cancer.
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| 5. |
- Shen, Li, et al.
(författare)
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An interactive 3D visualization and manipulation tool foreffective assessment of angiogenesis and arteriogenesis usingcomputed tomographic angiography
- 2005
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Ingår i: Progress in Biomedical Optics and Imaging. - : SPIE. - 1605-7422 .- 1042-4687. ; 5744:II, s. 848-858
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents IVM, an Interactive Vessel Manipulation tool that can help make effective and efficient assessmentof angiogenesis and arteriogenesis in computed tomographic angiography (CTA) studies. IVM consistsof three fundamental components: (1) a visualization component, (2) a tracing component, and (3) a measurementcomponent. Given a user-specified threshold, IVM can create a 3D surface visualization based on it. Sincevessels are thin and tubular structures, using standard isosurface extraction techniques usually cannot yieldsatisfactory reconstructions. Instead, IVM directly renders the surface of a derived binary 3D image. The imagevolumes collected in CTA studies often have a relatively high resolution. Thus, compared with more complicatedvessel extraction and visualization techniques, rendering the binary image surface has the advantages of beingeffective, simple and fast. IVM employs a semi-automatic approach to determine the threshold: a user can adjustthe threshold by checking the corresponding 3D surface reconstruction and make the choice. Typical tracingsoftware often defines ROIs on 3D image volumes using three orthogonal views. The tracing component in IVMtakes one step further: it can perform tracing not only on image slices but also in a 3D view. We observe thatdirectly operating on a 3D view can help a tracer identify ROIs more easily. After setting a threshold and tracingan ROI, a user can use IVM’s measurement component to estimate the volume and other parameters of vesselsin the ROI. The effectiveness of the IVM tool is demonstrated on rat vessel/bone images collected in a previousCTA study.
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| 6. |
- Svahn, Tony, et al.
(författare)
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In-plane artifacts in breast tomosynthesis quantified with a novel contrast-detail phantom
- 2007
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422 .- 1042-4687. ; 6510:PART 3, s. 1853-1864
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Konferensbidrag (refereegranskat)abstract
- The purpose of this work was to develop a contrast-detail phantom that can be used to evaluate image quality in breast tomosynthesis (BT) and as a first step use it to evaluate in-plane artifacts with respect to object size and contrast. The phantom was constructed using a Polylite [registered trademark] resin as bulk material, as it has x-ray mass attenuation properties similar to polymethyl methacrylate (PMMA), a common phantom material in mammography. Six different materials polyoxymethylene (POM), bakelite [registered trademark] , nylon, polycarbonate (PC), acrylonitrilebutadienestyrene (ABS) and polyethene (PE) - were selected to form the phantom details. For each of the six materials, five spherical objects were manufactured (diameters of 4, 8, 12, 16, and 20 mm) resulting in 30 objects that were embedded with their centres approximately aligned at the central plane of a 26 mm thick Polylite [registered trademark] block (210 mm × 300 mm). A 20 mm thick PMMA block was added to yield a phantom with attenuation properties similar to 45 mm PMMA that could simulate a so-called standard breast (50 mm thick, 50% glandular tissue). Images of the phantom were acquired using a BT prototype system that employs filtered backprojection for image reconstruction. The magnitude of the in-plane artifacts was evaluated and was found to increase linearly with increasing contrast (signal) level and size of the embedded objects. The contrast-detail phantom was found to be a useful tool for evaluating BT in-plane artifacts and might also be used to study out-of-plane artifacts and the effect of different acquisition and reconstruction parameters on image quality in BT.
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| 7. |
- Svensson, Jenny, et al.
(författare)
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Pharmacokinetic study of a systemically administered novel liposomal Temoporfin formulation in an animal tumor model
- 2007
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422 .- 1042-4687. ; 6427, s. 4270-4270
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Konferensbidrag (refereegranskat)abstract
- Meso-tetra(hydroxyphenyl)chlorin (mTHPC) (international generic name Temoporfin) is a potent photosensitizer used for photodynamic therapy (PDT). In this study the pharmacokinetics of a systemically administered novel lipid formulation of Temoporfin in a murine tumor model has been investigated. Fluorescence spectroscopy measurements were performed at several time intervals following drug administration, yielding information on the Temoporfin concentration within excised internal organs as a function of time after injection. Both point-monitoring and imaging setups were used. The acquired fluorescence data were correlated to the concentration of Temoporfin obtained with High Performance Liquid Chromatography (HPLC). There was a significant correlation between the fluorescence methods and HPLC for most organs investigated. The pharmacokinetics of this new liposomal formulation of Temoporfin exhibited a rather flat temporal profile in the time interval 2-8 hours in this study.
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| 8. |
- Timberg, Pontus, et al.
(författare)
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Optimization of image quality in breast tomosynthesis using lumpectomy and mastectomy specimens
- 2007
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1042-4687 .- 1605-7422. ; 6510:PART 2, s. 1379-1386
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Konferensbidrag (refereegranskat)abstract
- The purpose of this study was to determine how image quality in breast tomosynthesis (BT) is affected when acquisition modes are varied, using human breast specimens containing malignant tumors and/or microcalcifications. Images of thirty-one breast lumpectomy and mastectomy specimens were acquired on a BT prototype based on a Mammomat Novation (Siemens) full-field digital mammography system. BT image acquisitions of the same specimens were performed varying the number of projections, angular range, and detector signal collection mode (binned and non-binned in the scan direction). An enhanced filtered back projection reconstruction method was applied with constant settings of spectral and slice thickness filters. The quality of these images was evaluated via relative visual grading analysis (VGA) human observer performance experiments using image quality criteria. Results from the relative VGA study indicate that image quality increases with number of projections and angular range. A binned detector collecting mode results in less noise, but reduced resolution of structures. Human breast specimens seem to be suitable for comparing image sets in BT with image quality criteria.
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| 9. |
- Yavari, Nazila, et al.
(författare)
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Measurements of optical properties of pig brain tissue in vitro using a novel compact device
- 2005
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422 .- 1042-4687. ; 5864, s. 1-11
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Konferensbidrag (refereegranskat)abstract
- In numerous medical and scientific fields, knowledge of the optical properties of tissues can be applied. Among many different ways of determining the optical properties of turbid media; integrating sphere measurements are widely used. However, this technique is associated with bulky equipment, complicated measuring techniques, interference compensation techniques, and inconvenient sample handling. This paper describes measurements of the optical properties of porcine brain tissue using novel instrumentation for simultaneous absorption and scattering characterization of small turbid samples. The system used measures both angularly and spatially resolved transmission and reflection and is called Combined Angular and Spatially-resolved Head (CASH) sensor. The results compare very well with data obtained with an integrating sphere for well-defined samples. The instrument was shown to be accurate to within 12 % for μa. and 1 % for μs' in measurements of intralipid-ink samples. The corresponding variations of data were 17 %, and 2 %, respectively. The reduced scattering coefficient for porcine white matter was measured to be 100 cm-1, while the value for coagulated brain tissue was 65 cm-1. The corresponding absorption coefficients were 2 and 3 cm-1, respectively. © 2005 SPIE and OSA.
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| 10. |
- Arvidsson, Ida, et al.
(författare)
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Detection of left bundle branch block and obstructive coronary artery disease from myocardial perfusion scintigraphy using deep neural networks
- 2021
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Ingår i: Medical Imaging 2021 : Computer-Aided Diagnosis - Computer-Aided Diagnosis. - : SPIE. - 1605-7422. - 9781510640238 ; 11597
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Konferensbidrag (refereegranskat)abstract
- Myocardial perfusion scintigraphy, which is a non-invasive imaging technique, is one of the most common cardiological examinations performed today, and is used for diagnosis of coronary artery disease. Currently the analysis is performed visually by physicians, but this is both a very time consuming and a subjective approach. These are two of the motivations for why an automatic tool to support the decisions would be useful. We have developed a deep neural network which predicts the occurrence of obstructive coronary artery disease in each of the three major arteries as well as left bundle branch block. Since multiple, or none, of these could have a defect, this is treated as a multi-label classification problem. Due to the highly imbalanced labels, the training loss is weighted accordingly. The prediction is based on two polar maps, captured during stress in upright and supine position, together with additional information such as BMI and angina symptoms. The polar maps are constructed from myocardial perfusion scintigraphy examinations conducted in a dedicated Cadmium-Zinc-Telluride cardio camera (D-SPECT Spectrum Dynamics). The study includes data from 759 patients. Using 5-fold cross-validation we achieve an area under the receiver operating characteristics curve of 0.89 as average on per-vessel level for the three major arteries, 0.94 on per-patient level and 0.82 for left bundle branch block.
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