Efficacy of a Novel Respiratory Motion Reduction Block in Reducing Motion Artifact on Myocardial Perfusion Single-Photon Emission Computed Tomography.

PURPOSE: Motion artifacts caused by heart motion during myocardial perfusion single-photon emission computed tomography (SPECT) can compromise image quality and diagnostic accuracy. This study aimed to evaluate the efficacy of the novel respiratory motion reduction block (RRB) device in reducing motion artifacts by compressing the hypochondrium and improving SPECT image quality. METHODS: In total, 91 patients who underwent myocardial perfusion SPECT with 99mTc-sestamibi were retrospectively analyzed. Patients (n = 28) who underwent SPECT without the RRB were included in the control group, and those (n = 63) who underwent SPECT with the RRB were in the RRB group. The distance of heart motion during dynamic acquisition was measured, and projection data were assessed for patient motion and motion artifacts. Patient motion was classified into various levels, and motion artifacts on SPECT images were visually examined. RESULTS: The distances of heart motion without and with the RRB were 15.4 ± 5.3 and 7.5 ± 2.3, respectively. Compared with the control group, the RRB group had a lower frequency of heart motion based on the projection data, particularly in terms of creep and shift motion. The RRB group had a significantly lower incidence of motion artifacts on SPECT images than the control group. CONCLUSIONS: The RRB substantially reduced specific types of motion, such as shift and creep, and had a low influence on bounce motion. However, it could effectively suppress respiratory-induced heart motion and reduce motion artifacts on myocardial perfusion SPECT, thereby emphasizing its potential for improving image quality.

Monitoring the gasification area and its behavior in underground coal gasification by acoustic emission technique instead of temperature measurement.

Underground Coal Gasification (UCG) requires monitoring of the gasification area because the gasification process is invisible and the reaction temperature exceeds 1000 °C. Many fracturing events that occurred due to coal heating can be captured with Acoustic Emission (AE) monitoring technique during UCG. However, the temperature conditions to generate fracturing events during UCG have not yet been clarified. Therefore, the coal heating experiment and small-scale UCG experiment are conducted by measuring the temperature and AE activities in this research to examine the applicability of the AE technique instead of temperature measurement as a monitoring method during UCG. As a result, many fracturing events are generated when the temperature of coal is changed drastically, especially during coal gasification. Besides, AE events increase in the sensor near the heat source and AE sources are expanded widely with the expansion of the high-temperature region. AE monitoring is an effective technique for the estimation of the gasification area during UCG instead of temperature monitoring.

Comparison of the detectability of hot lesions on bone SPECT using six state-of-the-art SPECT/CT systems: a multicenter phantom study to optimize reconstruction parameters.

Single-photon emission computed tomography with X-ray computed tomography (SPECT/CT) systems have diversified due to the remarkable developments made by each manufacturer. This study aimed to optimize the reconstruction parameters of six state-of-the-art SPECT/CT systems and compare their image quality of bone SPECT. SPECT images were acquired on SPECT/CT systems, including Symbia Intevo, Discovery NM/CT 670, Discovery NM/CT 870 CZT, Brightview XCT, and VERITON-CT. SIM2 bone phantom with tough lung phantoms on both sides of the spinal inserts that simulate the thorax was used for image quality assessment. SPECT images were obtained at individual workstations using an ordered subset expectation maximization method with three-dimensional resolution recovery, as well as CT attenuation and scatter correction, subset 2, iteration 12-84, and a full width at half maximum 10-mm Gaussian smooth filter. An automatic image analysis software dedicated to SIM2 bone phantom was used to assess the contrast-to-noise ratio (CNR), relative recovery coefficient, percentage of coefficient of variance, contrast, and detectability. The optimal parameters for each system were defined with superior detectability of spherical lesions and noise characteristics, as well as the highest CNR. All systems exhibited better image quality indexes using the optimal parameters than using the manufacturer's recommended parameters. The detectability of all systems was in agreement while using the optimal parameters. Detectability agreement can be achieved by optimizing the reconstruction parameters for different reconstruction algorithms, which can further improve the image quality. Therefore, future research should focus on optimal reconstruction parameters for SPECT alone.

Feasibility of using counts-per-volume approach with a new SPECT phantom to optimize the relationship between administered dose and acquisition time.

We developed a phantom for single-photon emission computed tomography (SPECT), with the objective of assessing image quality to optimize administered dose and acquisition time. We investigated whether the concept of counts-per-volume (CPV), which is used as a predictor of visual image quality in positron emission tomography, can be used to estimate the acquisition time required for each SPECT image. QIRE phantoms for the head (QIRE-h) and torso (QIRE-t) were developed to measure four physical indicators of image quality in a single scan: uniformity, contrast of both hot and defective lesions with respect to the background, and linearity between radioactivity concentration and count density. The target organ's CPV (TCPV), sharpness index (SI), and contrast-to-noise ratio (CNR) were measured for QIRE-h and QIRE-t phantoms, and for anthropomorphic brain and torso phantoms. The SPECT image quality of the four phantoms was visually assessed on a 5-point scale. The acquisition time and TCPV were correlated for all four phantoms. The SI and CNR values were nearly identical for the QIRE and anthropomorphic phantoms with comparable TCPV. The agreement between the visual scores of QIRE-h and brain phantoms, as well as QIRE-t and torso phantoms, was moderate and substantial, respectively. Comparison of SPECT image quality between QIRE and anthropomorphic phantoms revealed close agreement in terms of physical indicators and visual assessments. Therefore, the TCPV concept can also be applied to SPECT images of QIRE phantoms, and optimization of imaging parameters for nuclear medicine examinations may be possible using QIRE phantoms alone.

The Incidence and Its Associated Factors Relevant to Brain Radionecrosis That Requires Intervention Following Single or Fractionated Stereotactic Radiosurgery Using Vero4DRT for Brain Metastases.

PURPOSE: Several factors, including the surrounding brain volume receiving specific doses, have hitherto been reported to correlate with brain radionecrosis (BR) after single or fractionated stereotactic radiosurgery (sSRS or fSRS) for brain metastases (BMs); however, those, especially for fSRS, have not yet been fully elucidated. Furthermore, the clinical outcome data of patients with BM treated with SRS using Vero4DRT are extremely limited. Therefore, this study aimed to demonstrate the incidence of BR requiring intervention (BRRI) and its highly correlated factors. MATERIALS AND METHODS: Patients with BMs treated with sSRS or fSRS using Vero4DRT at Toyohashi Municipal Hospital between July 2017 and June 2021 were retrospectively reviewed, of whom patients were available for at least 20 weeks of magnetic resonance imaging follow-up from SRS were included, and analyzed. The prescribed dose fractionation schemes to the planning target volume (PTV) boundary included 24 Gy (sSRS), 35 Gy (5 fractions [fr]), 42 Gy (10 fr), and 30 Gy (3 fr), according to the tumor volume and location. The volume of the surrounding normal brain receiving 84 Gy (V84 Gy, biologically effective dose [BED2] based on a linear-quadratic model with an alpha/beta ratio of 2, single-dose equivalent [SDE] to 12 Gy), V112 Gy (BED2, SDE to 14 Gy) for all lesions, and all irradiated volume, including gross tumor volume (GTV) receiving 81.6 Gy (81.6 Gy vol., BED2) for fSRS were calculated, for which cerebrospinal fluid and bone volumes were cautiously excluded. The diagnosis of tumor progression or BR dominance was based on serial T1/T2 matching. RESULTS: Sixty patients with 120 lesions (65 treated with sSRS and 55 treated with fSRS) were included in the final analysis, with a median follow-up period of 65 weeks. The local control rate at one year was 87.5%. The cumulative incidence of BRRI within two years was 11.5%. The risk of symptomatic BR was significantly higher for V84 Gy >10 cc (p <0.001) and V112 Gy >5 cc (p = 0.021). In the fSRS group, the cumulative incidence of Grade 3 BR and those requiring resection was significantly higher for 81.6 Gy vol. >14 cc (p = 0.003 and p = 0.004, respectively). The coexistence of viable tumor tissue and BR could not be ruled out for enlarging lesions after the nadir response, especially for fSRS, due to a lower BED10 to GTV margin (<80 Gy, BED10). CONCLUSIONS: Stereotactic irradiation with Vero4DRT provided efficacy and safety comparable to previous linear accelerator series, and most of the dose-volume thresholds for BRRI presented in this study were notably lower than those reported in previous studies. This study suggests that the indication of single and up to 5 frSRS should be limited to far smaller tumors than previously acknowledged to ensure long-term safety and efficacy.

Feasibility of ultra-high-speed acquisition in xSPECT bone algorithm: a phantom study with advanced bone SPECT-specific phantom.

OBJECTIVE: Although xSPECT Bone (xB) provides quantitative single-photon emission computed tomography (SPECT) high-resolution images, patients' burden remains high due to long acquisition time; therefore, this study aimed to investigate the feasibility of shortening the xB acquisition time using a custom-designed phantom. METHODS: A custom-designed xSPECT bone-specific (xSB) phantom with simulated cortical and spongious bones was developed based on the thoracic bone phantom. Both standard- and ultra-high-speed (UHS) xB acquisitions were performed in a male patient with lung cancer. In this phantom study, SPECT was acquired for 3, 6, 9, 12, and 30 min. The clinical SPECT acquisition time per rotation was 9 and 3 min for standard and UHS, respectively. SPECT images were reconstructed using ordered subset expectation maximization with three-dimensional resolution recovery (Flash3D; F3D) and xB algorithms. Quantitative SPECT value (QSV) and coefficient of variation (CV) were measured using the volume of interests (VOIs) placed at the center of the vertebral body and hot sphere. A linear profile was plotted on the spinous process at the center of the xSB phantom; then, the full width at half maximum (FWHM) was measured. The standardized uptake value (SUV) and standard deviation from the first thoracic to the fifth lumbar vertebrae in clinical standard- and UHS-xB images were measured using a 1-cm3 VOI. RESULTS: The QSV of F3D images was underestimated even in large regions, whereas those of xB images were close to actual radioactivity concentration. The CV was similar or lower for xB images than that for F3D images but was not decreased with increasing acquisition time for both reconstruction images. The FWHM of xB images was lower than those of F3D images at all acquisition times. The mean SUV values from the first thoracic to fifth lumbar vertebrae for standard- and UHS-xB images were 6.73 ± 0.64 and 6.19 ± 0.87, respectively, showing a strong positive correlation. CONCLUSIONS: Results of this phantom study suggest that xB imaging can be obtained in only one-third of the acquisition time without compromising the image quality. The SUV of UHS-xB images can be similar to that of standard-xB images in terms of clinical interpretation.

Optimization of cross-calibration factor for quantitative bone SPECT without attenuation and scatter correction in the lumbar spine: head-to-head comparison with attenuation and scatter correction.

OBJECTIVES: Quantitative single-photon emission computed tomography (SPECT) with computed tomography (SPECT/CT) is known to improve diagnostic performance. Although SPECT-alone systems are used widely, accurate quantitative SPECT using these systems is challenging. This study aimed to improve the accuracy of quantitative bone SPECT of the lumbar spine with the SPECT-alone system. METHODS: The cross-calibration factor (CCF) was measured using three kinds of phantoms and the optimal values were determined. The recovery coefficient with and without attenuation and scatter correction (ACSC) were compared. Bone SPECT/CT was performed on 93 consecutive patients with prostate cancer, and the standardized uptake values (SUVs) were compared using the respective CCFs. The first 60 patients were classified according to body weight, and the correlation coefficient between SUVs with and without ACSC were calculated; the slopes were defined as body weight-based coefficients (BWCs). In the remaining 33 patients, the SUV was adjusted according to BWC, and the accuracy of the adjustment was verified. RESULTS: The quantitative SPECT values obtained from the CCF using SIM2 bone phantom showed nearly accurate radioactivity concentrations, even without ACSC. The recovery coefficients with and without ACSC were similar. Unadjusted SUVs with and without ACSC were strongly correlated; however, SUVs without ACSC were significantly higher than those with ACSC (P < 0.0001). The mean difference between the SUVs with and without ACSC disappeared when the SUVs without ACSC were adjusted by BWC (P = 0.9814). CONCLUSIONS: Our cross-calibration method for quantitative bone SPECT enables interpretation with a harmonized SUV even in SPECT-alone systems.

Automatic quantification package (Hone Graph) for phantom-based image quality assessment in bone SPECT: computerized automatic classification of detectability.

OBJECTIVE: We previously developed a custom-design thoracic bone scintigraphy-specific phantom ("SIM2 bone phantom") to assess image quality in bone single-photon emission computed tomography (SPECT). We aimed to develop an automatic assessment system for imaging technology in bone SPECT and demonstrate the validity of this system. METHODS: Four spherical lesions of 13-, 17-, 22-, and 28-mm diameters in the vertebrae of SIM2 bone phantom simulating the thorax were filled with radioactivity (target-to-background ratio: 4). Dynamic SPECT acquisitions were performed for 15 min; reconstructions were performed using ordered subset expectation maximization at 3-15-min timepoints. Consequently, 216 lesions (54 SPECT images) were obtained: 120 and 96 lesions were used for software development and validation, respectively. The developed software used statistical parametric mapping to rigidly register and automatically calculate quantitative indexes (contrast-to-noise ratio, % coefficient of variance, % detectability equivalence volume, recovery coefficient, target-to-normal bone ratio, and full width at half maximum). A detectability score (DS) was used to define the four observation types (4, excellent; 3, adequate; 2, average; 1, poor) to score hot spherical lesions. The gold standard for DSs was independently classified by three experienced board-certified nuclear medicine technologists using the four observation types; thereafter, a consensus regarding the gold standard for DSs was reached. Using 120 lesions for development, decision tree analysis was performed to determine DS based on the quantitative indexes. We verified the validation of the quantitative indexes and their threshold values for automatic classification using 96 lesions for validation. RESULTS: The trends in the automatically calculated quantitative indices were consistent. Decision tree analysis produced four terminal groups; two quantitative indexes (% detectability equivalence volume and contrast-to-noise ratio) were used to classify DS. The automatically classified DSs exhibited an almost perfect agreement with the gold standard. The percentage agreement and kappa coefficient were 91.7% and 0.93, respectively, in 96 lesions for validation. CONCLUSIONS: The developed software automatically classified the detectability of hot lesions in the SIM2 bone phantom using the automatically calculated quantitative indexes, suggesting that this software could provide a means to automatically perform detectability analysis after data input that is excellent in reproducibility and accuracy.

[Usefulness of Post-processing Scatter Correction in Portable Abdominal Radiography Using a Low Ratio Anti-scatter Grid].

OBJECTIVES: The aim of this study was to evaluate an influence of post-processing scatter correction in portable abdominal radiography using a low ratio anti-scatter grid (grid). METHODS: To assess tube voltage on portable abdominal radiography, a burger phantom was used to measure for inverse of image quality figure (IQFinv). For evaluation of the influence on using or not the grid, IQFinv were measured. Abdominal phantom radiographies were assessed subjectively, in random order, by six radiologic technologists. The radiographies were performed without scatter correction [IG (-)] and with scatter correction at equivalent for grid ratio 6 [IG (6)] and 8 [IG (8)]. RESULTS: There was no significant decrease in IQFinv with 75 and 80 kV in comparison of 70 kV. Even processing scatter correction, IQFinv with using the grid was significantly higher than that without using the grid. The ability to detect nasogastric tube and stomach gas were significantly better in the scatter correction. Deviation index for IG (6) and IG (8) were significantly lower than that of IG (-). DISCUSSION: Portable abdominal radiographies will be improved image quality by utilizing scatter correction, although, it is necessary to consider the scatter correction processing as this may significant decrease deviation index in the practical situation. CONCLUSION: The post-processing scatter correction should be useful for detection nasogastric tube and stomach gas in portable abdominal radiography.

Examination for Effectiveness of Scatter Correction in Portable Chest Radiography.

OBJECTIVES: The aim of this study was to evaluate the effectiveness of scatter correction in the portable chest radiography. METHODS: Digital radiographies were performed without anti-scatter grid (grid), with the scatter correction and with the grid ratio of 3 : 1 in this study. The scatter fraction and the detectability of low contrast signals were measured using the four acrylic phantoms of different thicknesses. The chest phantom radiographs were assessed subjectively, in random order, by six radiologic technologists. RESULTS: The scatter fraction was higher in the no-grid technique, and was lower for the grid technique. The detectability of low contrast signals did not significantly differ between the scatter correction and the grid technique (p>0.05). The area under the receiver operating characteristic curve for the grid technique was higher than that for the scatter correction technique (0.888 vs. 0.855), although no significant difference was found between the grid and the scatter correction technique (p> 0.05). The ability to detect the nasogastric tube was significantly better in the grid technique (p<0.001). DISCUSSION: In the scatter correction technique, the ability of scatter removal increased as the scatter fraction increased. The scatter correction technique was unnecessary to extremely accurate alignment. In addition, patient dose can be reduced by the scatter correction technique. CONCLUSIONS: It seemed to be effective for the scatter correction in the portable chest radiography.

[Development of a Novel Body Phantom with Bone Equivalent Density for Evaluation of Bone SPECT].

We developed a custom-designed phantom for bone single photon emission computed tomography (SPECT)-specific radioactivity distribution and linear attenuation coefficient. The aim of this study was to evaluate the accuracy of the phantom. The lumbar phantom consisted of the trunk of a body phantom (background) containing a cylinder (vertebral body), a sphere (tumor), and a T-shaped container (processus). The vertebral body, tumor, and processus phantoms contained a K(2)HPO(4) solution of bone equivalent density and 50, 300 and 50 kBq/mL of (99m)Tc, respectively. The body phantom contained 8 kBq/mL of (99m)Tc solution. SPECT images were acquired using low-energy high-resolution collimation, a 128 × 128 matrix and 120 projections over 360° with a dwell time of 15 sec/view × 4 times. Thereafter, CT images were acquired at 130 kV and 70 ref mAs using adaptive dose modulation. The SPECT data were reconstructed with ordered subset expectation maximization with three-dimensional, scatter, and CT-based attenuation correction. Count ratio, linear attenuation coefficient (LAC), and full-width at half-maximum (FWHM) were measured. Count ratios between the background, the vertebral body, and the tumor in SPECT images were 463.8: 2888.0: 15150.3 (1: 6.23: 32.7). The LAC of the background and vertebral body in the CT-derived attenuation map were 0.155 cm⁻¹ and 0.284 cm⁻¹, respectively, and the FWHM measured from the processus was 15.27 mm. The precise counts and LAC indicated that the phantom was accurate and could serve as a tool for evaluating acquisition, reconstruction parameters, and quantitation in bone SPECT images.

[Usefulness of spatially adaptive noise reduction processing in computer-assisted diagnosis system for bone scintigraphy].

OBJECTIVES: The goal of this study was to assess the diagnostic accuracy of Pixon-processed images in comparison with raw images for computer-assisted interpretation of bone scintigraphy (BONENAVI). METHODS: Whole-body scans of 57 patients with prostate cancer who had undergone bone scintigraphy for suspected bone metastases were obtained approximately 3 h after intravenous injection of 740 MBq (99m)Tc-methylene diphosphonate. We obtained two image sets: raw images and images processed using the Pixon method. Artificial neural network (ANN) values, bone scan index (BSI), number of hotspots and regional ANN value of two images set were automatically calculated by the BONENAVI software. Areas under the receiver operator characteristic curves (AUC) were calculated in patient-based and lesion-based analyses. RESULTS: In ten cases with bone metastases, ANN, BSI and number of hotspots for processed images were equivalent to those in the raw images. However, in 47 cases without bone metastases, ANN, BSI and number of hotspots for processed images showed significantly lower values than those for the raw images (p<0.05). Sensitivity, specificity and accuracy of the raw images were 90.2, 44.7 and 65.9%, and those of the processed images were 90.2, 57.4 and 72.7%, respectively. The AUC for processed images was equivalent to that for raw images. CONCLUSIONS: Specificity and accuracy in the detection of bone metastases showed the Pixon-processed images to have high diagnostic performance. We conclude that the precision of computer-assisted interpretation of bone scintigraphy can be enhanced by using Pixon processing.

A double mutant between fission yeast telomerase and RecQ helicase is sensitive to thiabendazole, an anti-microtubule drug.

In the fission yeast Schizosaccharomyces pombe, deletion of trt1(+) causes gradual telomere shortening, while deletion of pot1(+) causes rapid telomere loss. The double mutant between pot1 and RecQ helicase rqh1 is synthetically lethal. We found that the trt1 rqh1 double mutant was not synthetically lethal. The chromosome end fragments in both the trt1Δ rqh1Δ and the trt1Δ rqh1-hd (helicase dead) double mutants did not enter a pulsed-field electrophoresis gel. Both the trt1Δ rqh1Δ and the trt1Δ rqh1-hd double mutants were sensitive to the anti-microtubule drug thiabendazole. Moreover, the trt1Δ rqh1-hd double mutant displayed RPA foci on the chromosome bridge at high frequency in M phase cells. These phenotypes are very similar to that of the pot1Δ rqh1-hd double mutant, in which recombination intermediates accumulate at the chromosme ends in the M phase. These results suggest that the entangled chromosome ends, most likely recombination intermediates, are present in the M phase in the trt1Δ rqh1-hd double mutant.

[Novel phantom for evaluating contrast resolution in single photon emission computed tomography (SPECT)].

OBJECTIVES: We have designed a phantom to evaluate acquisition and reconstruction parameters using contrast transfer function (CTF). The goal of this study was to evaluate the accuracy of the phantom for contrast resolution. METHODS: The phantom consisted of spaced (0-14 mm, 1 mm intervals) pairs of cubic containers (5 mm wide, 20 mm long, and 50 mm high). The phantom's accuracy was examined by comparing a real value of a measured count profile using the phantom with a theoretical value obtained by the line spread function (LSF) using a line source. A SPECT acquisition was 256×256 matrix (pixel size: 0.9×0.9 mm(2)), 360 degrees at 30 s/view. The radius of rotation was set to 15 cm, and the types of collimators were low energy high resolution (LEHR) and low middle energy general purpose (LMEGP). Reconstructions were performed with filtered backprojection and ordered subsets expectation maximization method (10 iterations, 10 subsets) with collimator-detector response correction. RESULTS: The actual measured count profile and CTF accorded closely with the theoretical one. DISCUSSION: The line pair (LP) phantom, obtained with smaller pixels, was really accurate. The size of cubic containers poses as a minimal problem for accurately evaluating the contrast resolution and plotted counts profile. CONCLUSIONS: This phantom could be a useful method for evaluating acquisition and reconstruction parameters in SPECT.

Involvement of Kv channel subtypes on GABA release in mechanically dissociated neurons from the rat substantia nigra.

The seven members of Shaker-related K(+) channel family, which are known to regulate membrane excitability and transmitter release, have been identified in the CNS. It is known that the substantia nigra pars reticulata (SNr) receives GABAergic inputs mainly from the striatum and sends GABAergic outputs to the thalamus. An immunohistochemical study shows that the Kv1 family, particularly Kv1.4, is expressed in the SNr, while it is reported that Kv1.2 mRNA is detected in the striatal neurons. Therefore, which Kv channels may be involved in the release of GABA in the SNr remains still controversial. To address this issue, we tested the effects of various K(+) channel blockers on the synaptic transmission using mechanically dissociated SNr neurons known as "synaptic bouton preparation", that retained functional presynaptic nerve terminals which enable us to examine miniature inhibitory postsynaptic currents (mIPSCs) by conventional whole-cell patch clamp recordings. Based on the sensitivities of mIPSCs to the Kv channel blockers, we concluded that Kv channels, in particular Kv1.2 subunit play the most significant role in the release of GABA at the presynaptic terminals projecting to the SNr neurons.

Activation of presynaptic GABAA receptors increases spontaneous glutamate release onto noradrenergic neurons of the rat locus coeruleus.

In order to further explore how GABA can modulate the excitability of noradrenergic neurons of the locus coeruleus (LC), we investigated the presence of GABA(A) receptors on glutamatergic nerve terminals and the functional consequences of their activation. We used mechanically dissociated immature rat LC neurons with adherent nerve terminals and patch-clamp recordings of spontaneous excitatory postsynaptic currents. Activation of presynaptic GABA(A) receptors by muscimol facilitated spontaneous glutamate release by activating tetrodotoxin-sensitive Na(+) channels and high-threshold Ca(2+) channels. Bumetanide (10 microM), a potent blocker of Na(+)-K(+)-Cl(-) cotransporter, diminished the muscimol-induced facilitatory action of glutamate release. Our results indicate that the Na(+)-K(+)-Cl(-) cotransporter accumulates Cl(-) inside the nerve terminals so that activation of presynaptic GABA(A) receptors causes depolarization. This GABA(A)-receptor-mediated modulation of spontaneous glutamatergic transmission is another mechanism by which GABA and its analogues can regulate the excitability and activity of noradrenergic neurons in the LC.