A scheme for assessing the performance characteristics of small field-of-view gamma cameras

Existing protocols for assessing the performance characteristics of large field-of-view (LFOV) gamma cameras can be inappropriate and require modification for use with small field-of-view (SFOV) gamma camera systems. This communication proposes a generic scheme suitable for evaluating the performance characteristics of SFOV gamma cameras, based on modifications to the standard procedures of NEMA NU1-2007. Key differences in methodology between tests for LFOV and SFOV gamma cameras are highlighted along with the rationale for these changes. It is envisaged that this scheme will provide more appropriate methods for equipment characterisation, ensuring quality and consistency for all SFOV cameras.     

Intraoperative gamma cameras for radioguided surgery: Technical characteristics,performance parameters,and clinical applications

Several small gamma cameras (SGCs) intended for surgical use are now in development or currently being marketed. In this review, we discuss the characteristics, performance, and clinical use of SGCs which are hand-held and small enough to be easily managed by surgeons during their procedures. We expect that SGCs have the potential to be used more widely in radioguided surgery. As advancing molecular imaging technologies will broaden clinical indications, SGCs will likely be used and integrated with other imaging modalities into numerous types of radioguided surgery in the near future.     

Quality assurance procedure for a gamma guided stereotactic breast biopsy system

A quality assurance procedure has been developed for a prototype gamma-ray guided stereotactic biopsy system. The system consists of a compact small-field-of-view gamma-ray camera mounted to the rotational arm of a Lorad stereotactic biopsy system. The small-field-of-view gamma-ray camera has been developed for clinical applications where mammographic X-ray localization is not possible. Marker sources that can be imaged with the gamma-camera have been designed and built for quality assurance testing and to provide a fiducial reference mark. An algorithm for determining the three dimensional location of a region of interest, such as a lesion, relative to the fiducial mark has been implemented into the software control of the camera. This system can be used to determine the three-dimensional location of a region of interest from a stereo pair of images and that information can be used to guide a biopsy needle to that site. Point source phantom tests performed with the system have demonstrated that the camera can be used to localize a point of interest to within 1 mm, which is satisfactory for its use in needle localization.     

In vivo quantification of renal function in mice using clinical gamma cameras

IntroductionIn preclinical research, the growing number of transgenic models has led to the need for renal-function studies in mice. Many efforts have been made to develop dedicated SPECT systems for rodents, but their availability is limited due to high capital costs. The aim of this work is to demonstrate the feasibility of mouse renal imaging by using an inexpensive alternative based on clinical gamma-cameras.MethodsA healthy mouse was scanned 3 h after injection of 6 mCi of Dimercaptosuccinic acid (DMSA) labeled with 99mTc by using a single-head gamma-camera in conjunction with a dedicated pinhole collimator. List-mode data were binned to emulate multiple injections of 1 mCi, 0.1 mCi and 0.01 mCi of 99mTc-DMSA and 6-min ventral and dorsal planar images were acquired and SPECT imaging (60 projection images acquired over 60 min) was performed. An optimization of the protocols in terms of injected activity, time scan, renal cortex uniformity and cortex-to-pelvis contrast was carried out.ResultsThe appropriate protocols were an injected activity of 0.6 mCi, combined with duration of scanning of 1 min for planar and 60 min for SPECT imaging. Our results were validated through the relative quantification of renal function, which showed that both kidneys contributed equally to the total function. They showed that functional structures of the mouse kidneys can be visually distinguished as easily as in human studies.ConclusionsOur findings showed the feasibility of conducting quantitative DMSA SPECT studies of anesthetized mice on clinical gamma cameras.     

Kilovoltage beam model for flat panel imaging system with bow-tie filter for scatter prediction and correction

PurposeKilovoltage flat-panel imaging systems are used for cone-beam Computed Tomography (CBCT) and digital Tomosynthesis (DTS). Hereby, the presence of scatter and relatively large dose from imaging are challenging factors. In this study a phenomenological beam model was developed to characterize imager response to imaging beams with a bow-tie filter (Varian OBI system).Materials and methodThe kilovoltage beam model was based on dose ratio formalism and thus was using standard concepts of megavoltage dose calculation such as scatter factors, tissue maximum ratio and off-axis ratio. Primary and scatter (head and phantom scatter) were modeled with three Gaussian kernels. Parameters were based on measured transmission images for slabs of solid water of different total thickness and various jaw settings.ResultsThe beam model was used to evaluate contributions from primary, secondary and tertiary contributions for different geometrical objects such as cylinders and step-like phantoms. Theoretical predictions of radiographs using the model for known objects are consistent with the measurements.ConclusionSecondary and tertiary contributions were interpreted as scatter and can be subtracted from CBCT projections based on the analytical model. Therefore our model can provide a basis for improvement of image quality (less artifacts due to scatter, better contrast and resolution) in CBCT reconstruction.     

Quality assurance of isocentres for passive proton beam nozzles using motion capture cameras

PurposeThe objective of this work is to determine mechanical, radiation, and imaging isocentres in three-dimensional (3D) coordinates and verifying coincidence of isocentres of passively scattered proton beam using a visual tracking system (VTS) and an in-house developed phantom named the Eagle.MethodsThe Eagle phantom consists of two modules: The first, named Eagle-head, is used for determining 3D mechanical isocentre of gantry rotation. The second, named Eagle-body, is used for determining 3D radiation and imaging isocentres. The Eagle-body has four slots wherein radiochromic films were inserted for measuring the 3D radiation isocentre and a metal bead was embedded in the centre of one cube to determine the imaging isocentre; this was determined by analysing cone-beam computed tomography images of the cube. Infrared reflective markers that can be tracked by VTS were attached to the Eagle at predetermined locations. The tracked data were converted into 3D treatment room coordinates. The developed method was compared with other methods to assess accuracy.ResultsThe isocentres were determined in mm with respect to the laser isocentre. The mechanical, radiation, and imaging isocentres were (−0.289, 0.189, 0.096), (−0.436, −0.217, 0.009), and (0.134, 0.142, 0.103), respectively. When compared with other methods, the difference in coordinates was (−0.033, −0.107, 0.014) and (0.003, 0.067, 0.039) for radiation and imaging isocentres, respectively.ConclusionThe developed system was found to be useful in providing fast and accurate measurements of the three isocentres in the 3D treatment room coordinate system.     

A real-time feed rate control system for pilot plant baker's yeast production

Summary An on-line feed rate control system for baker's yeast production using the molasses uptake rate as a feeding index was developed. The optimal feed rate was obtained by maximising the feeding index. The experiments were performed to test this control system in fermenter of 30 m³ total capacity. In baker's yeast process 2760 kg M₅₀ was consumed and 2852 kg compressed yeast (D_c) was produced. Cell yield, final molasses dilution and final yeast concentration were 1.0 kg D_c/kg M₅₀, 1:6.5 and 52 g D₁₀₀/l, respectively. These results found that the developed feed rate control system is to be successful.     

Stereometry in very close-range stereophotogrammetry with non-metric cameras for human movement analysis

In this paper a stereophotogrammetric algorithm based on a black-box approach to the modelling of object to image spaces relationship is proposed. The algorithm is well suited for 'very close-range photogrammetry', with respect to experiments in which the measurement field is 0.5 X 0.5 X 0.5 m or smaller, as in the analysis of a few or small body segments movements. The attainable accuracy is high, better than 0.1% of the observation distance. Non-professional and even different cameras can be used. Consequently an inexpensive experimental set-up can be realized. A very simple, cheap and easily usable calibration object is needed. Computation time for the reconstruction of object-space co-ordinates of point body landmarks is one order of magnitude lower than in the case of the Direct Linear Transformation (DLT) (Abdel Aziz and Karara, Proceedings of the ASP/U1 Symposium on Close-Range Photogrammetry, pp. 1-18. American Society of Photogrammetry, 1971; Marzan and Karara, Proceedings of the Symposium on close-range Photogrammetric Systems, pp. 420-467. American Society of Photogrammetry, 1975). Computation time for calibration is two-fold in respect of the DLT. An example of application to the recording of the movements of the index finger with respect to the metacarpophalangeal joint is given.     

Quality control of cervical cytology in high-risk women. PAPNET system compared with manual rescreening

OBJECTIVE: To compare the effectiveness of the PAPNET System with conventional rescreening of negative cervical smears in a high-risk population. STUDY DESIGN: Three thousand ninety-seven negative cervical smears from women with past history of cervical abnormalities were rescreened manually and with the PAPNET System. There were two reviews of PAPNET images: the first by two cytotechnologists with limited exposure to the instrument, and the second, limited to smears with discrepant diagnoses, by an expert in the use of the system. The remaining discrepant smears were submitted to a blinded microscopic review by a third party. The a priori consensus diagnosis was arbitrarily established when the result of two of the three reviews--manual, PAPNET and the independent third review--were concordant. The results of rescreening were compared with available biopsies. RESULTS: On manual rescreening of the 3,097 smears, 2,901 (93.66%) were reported as negative and 170 (5.49%) as abnormal. On the first PAPNET review, 2,938 (94.87%) were reported as negative and 150 (4.84%) as abnormal. There were 144 smears with discrepant diagnoses. After the second PAPNET review of these discrepant smears, the agreement between manual and PAPNET rescreening rose from 94.27% to 95.58%. A final, blinded review of 89 residual discrepant smears was used to establish consensus diagnoses. The diagnoses made by PAPNET-assisted rescreening agreed much better with the consensus diagnoses than did manual rescreening (Kappa = .61 vs. Kappa = -.32, P < .001). When compared with the results of 50 available biopsies, PAPNET-assisted rescreening also had a somewhat lower false negative rate (sensitivity 58.82% vs. 41.18%, P = .17) and a statistically significant lower false positive rate (specificity 63.64% vs. 36.36%, P = .01). CONCLUSION: PAPNET-assisted rescreening, when carried out by an experienced person, is more efficient than manual rescreening.     

实验动物的质量管理与控制

我国通过建立的实验动物法律法规、管理制度、技术标准、许可证制度、动物质量检测体系等一系列措施,加大了对实验动物的管理力度。目的是提高和保证实验动物质量,提高实验动物科技水平和生命科学研究水平。同时,随着管理力度的加大和人们认识水平的提高及动物环境设施的改善,动物的福利也得到了很大的改善和提高,更有利于提高动物试验结果的准确性和可信性。     

Quality control in databanks for molecular biology

Using a scientific measurement without an estimate of its error is like lending money to a stranger. Given the explosion in nucleic acid and protein sequence and structural data, what risks are the scientific and medical communities running in using these databases. Is there an ‘ombudsman’ who speaks for the users of the data? CODATA, the Committee on Data for Science and Technology of the International Council of Scientific Unions was established to improve the quality, reliability, processing, management, and accessibility of data for science and technology. The CODATA Task Group on Biological Macromolecules has surveyed quality control procedures of archival databanks in molecular biology. Our role is ‘to advise, to be consulted, and to warn.’ This report describes the kinds and extents of errors that may appear in nucleic acid and protein databases, and presents an agenda for future work to improve the quality of these databases. The results of the survey appear on the web http://www.codata.org/codata/tgreports/tg_reps.html . BioEssays 22:1024–1034, 2000. © 2000 John Wiley & Sons, Inc.     

Quality control of an unreliable flexible manufacturing system with scrapping and infinite buffer capacity

Manufacturing multiple part types on a flexible manufacturing system (FMS) is increasingly becoming a rule rather than an exception. In such systems, attention has been drawn to the application of zero-defect technologies. However, in practice, this goal has remained elusive and costly. As a result, even though FMSs may be more reliable, producing fewer defective parts, system complexity and more stringent quality standards are rendering quality control in FMSs potentially useful. The goals of this article are threefold. First, we introduce a procedure for measuring and managing the in-process quality control of an FMS, which is described by an Open Queueing Network (OQN), bridging thereby a gap between queueing theory and quality control. Second, by focusing attention on the potential unreliabilities of FMSs, we provide some managerial insights regarding the role, position, and distribution of the quality control effort in an FMS. Finally, we stress the intricate relations between an FMS's operating characteristics and the manufactured quality and its control. Using numerical analyses, we draw some inferences regarding the design of such FMSs when both quality and quantity issues in the FMSs are considered. These simultaneous considerations of quantity and quality flows in an FMS have not been previously considered in the study of FMSs.     

A Deep Learning-based correction to EPID dosimetry for attenuation and scatter in the Unity MR-Linac system

PurposeEPID dosimetry in the Unity MR-Linac system allows for reconstruction of absolute dose distributions within the patient geometry. Dose reconstruction is accurate for the parts of the beam arriving at the EPID through the MRI central unattenuated region, free of gradient coils, resulting in a maximum field size of ~10 × 22 cm² at isocentre. The purpose of this study is to develop a Deep Learning-based method to improve the accuracy of 2D EPID reconstructed dose distributions outside this central region, accounting for the effects of the extra attenuation and scatter.MethodsA U-Net was trained to correct EPID dose images calculated at the isocenter inside a cylindrical phantom using the corresponding TPS dose images as ground truth for training. The model was evaluated using a 5-fold cross validation procedure. The clinical validity of the U-Net corrected dose images (the so-called DEEPID dose images) was assessed with in vivo verification data of 45 large rectum IMRT fields. The sensitivity of DEEPID to leaf bank position errors (±1.5 mm) and ±5% MU delivery errors was also tested.ResultsCompared to the TPS, in vivo 2D DEEPID dose images showed an average γ-pass rate of 90.2% (72.6%–99.4%) outside the central unattenuated region. Without DEEPID correction, this number was 44.5% (4.0%–78.4%). DEEPID correctly detected the introduced delivery errors.ConclusionsDEEPID allows for accurate dose reconstruction using the entire EPID image, thus enabling dosimetric verification for field sizes up to ~19 × 22 cm² at isocentre. The method can be used to detect clinically relevant errors.     

Fluorescence correlation spectroscopy with high count rate and low background: analysis of translational diffusion

An epi-illuminated microscope configuration for use in fluorescence correlation spectroscopy in bulk solutions has been analyzed. For determining the effective sample dimensions the spatial distribution of the molecule detection efficiency has been computed and conditions for achieving quasi-cylindrical sample shape have been derived. Model experiments on translational diffusion of rhodamine 6G have been carried out using strong focusing of the laser beam, small pinhole size and an avalanche photodiode in single photon counting mode as the detector. A considerable decrease in background light intensity and measurement time has been observed. The background light is 40 times weaker than the fluorescence signal from one molecule of Rh6G, and the correlation function with signal-to-noise ratio of 150 can be collected in 1 second. The effect of the shape of the sample volume on the autocorrelation function has been discussed. Correspondence to: R. Rigler     

Quality control system of the endoplasmic reticulum and related diseases

The quality control (QC) system of the endoplasmic reticulum (ER) is an important monitoringmechanism in the protein maturation process,which ensures export of properly folded proteins from the ER.Incorrectly or incompletely folded proteins are retained in the ER for refolding or degradation by the ER-residing proteasome.The calnexin/calreticulin cycle and ER-associated degradation are the key elements inQC.These two mechanisms work together to allow incorrectly folded proteins have additional opportunitiesto achieve their native conformations.The QC dysfunction is involved in many diseases caused by mutantproteins,many of which are causes of neurodegenerative disorders.A better understanding of molecularregulation in the QC system will uncover the molecular pathogenic mechanisms of many diseases caused byprotein misfolding and help discover novel strategies for preventing or treating these diseases.