Effect of X-ray tube on image quality and pancreatic ductal adenocarcinoma conspicuity in pancreatic protocol dual-energy CT.

AIM: To compare the radiation dose, image quality, and conspicuity of pancreatic ductal adenocarcinoma (PDAC) in pancreatic protocol dual-energy computed tomography (CT) between two X-ray tubes mounted in the same CT machine. MATERIAL AND METHODS: This retrospective study comprised 80 patients (median age, 73 years; 45 men) who underwent pancreatic protocol dual-energy CT from January 2019 to March 2022 using either old (Group A, n=41) or new (Group B, n=39) X-ray tubes mounted in the same CT machine. The imaging parameters were completely matched between the two groups, and CT data were reconstructed at 70 and 40 keV. The CT dose-index volume (CTDIvol); CT attenuation of the abdominal aorta, pancreas, and PDAC; background noise; and qualitative scores for the image noise, overall image quality, and PDAC conspicuity were compared between the two groups. RESULTS: The CTDIvol was lower in Group B than Group A (7.9 versus 9.2 mGy; p<0.001). The CT attenuation of all anatomical structures at 70 and 40 keV was comparable between the two groups (p=0.06-0.78). The background noise was lower in Group B than Group A (12 versus 14 HU at 70 keV, p=0.046; and 26 versus 30 HU at 40 keV, p<0.001). Qualitative scores for image noise and overall image quality at 70 and 40 keV and PDAC conspicuity at 40 keV were higher in Group B than Group A (p<0.001-0.045). CONCLUSION: The latest X-ray tube could reduce the radiation dose and improve image quality in pancreatic protocol dual-energy CT.

Low-tube-voltage whole-body CT angiography with extremely low iodine dose: a comparison between hybrid-iterative reconstruction and deep-learning image-reconstruction algorithms.

AIM: To evaluate arterial enhancement, its depiction, and image quality in low-tube potential whole-body computed tomography (CT) angiography (CTA) with extremely low iodine dose and compare the results with those obtained by hybrid-iterative reconstruction (IR) and deep-learning image-reconstruction (DLIR) methods. MATERIALS AND METHODS: This prospective study included 34 consecutive participants (27 men; mean age, 74.2 years) who underwent whole-body CTA at 80 kVp for evaluating aortic diseases between January and July 2020. Contrast material (240 mg iodine/ml) with simultaneous administration of its quarter volume of saline, which corresponded to 192 mg iodine/ml, was administered. CT raw data were reconstructed using adaptive statistical IR-Veo of 40% (hybrid-IR), DLIR with medium- (DLIR-M), and high-strength level (DLIR-H). A radiologist measured CT attenuation of the arteries and background noise, and the signal-to-noise ratio (SNR) was then calculated. Two reviewers qualitatively evaluated the arterial depictions and diagnostic acceptability on axial, multiplanar-reformatted (MPR), and volume-rendered (VR) images. RESULTS: Mean contrast material volume and iodine weight administered were 64.1 ml and 15.4 g, respectively. The SNRs of the arteries were significantly higher in the following order of the DLIR-H, DLIR-M, and hybrid-IR (p<0.001). Depictions of six arteries on axial, three arteries on MPR, and four arteries on VR images were significantly superior in the DLIR-M or hybrid-IR than in the DLIR-H (p≤0.009 for each). Diagnostic acceptability was significantly better in the DLIR-M and DLIR-H than in the hybrid-IR (p<0.001-0.005). CONCLUSION: DLIR-M showed well-balanced arterial depictions and image quality compared with the hybrid-IR and DLIR-H.

A nearby long gamma-ray burst from a merger of compact objects.

Gamma-ray bursts (GRBs) are flashes of high-energy radiation arising from energetic cosmic explosions. Bursts of long (greater than two seconds) duration are produced by the core-collapse of massive stars1, and those of short (less than two seconds) duration by the merger of compact objects, such as two neutron stars2. A third class of events with hybrid high-energy properties was identified3, but never conclusively linked to a stellar progenitor. The lack of bright supernovae rules out typical core-collapse explosions4-6, but their distance scales prevent sensitive searches for direct signatures of a progenitor system. Only tentative evidence for a kilonova has been presented7,8. Here we report observations of the exceptionally bright GRB 211211A, which classify it as a hybrid event and constrain its distance scale to only 346 megaparsecs. Our measurements indicate that its lower-energy (from ultraviolet to near-infrared) counterpart is powered by a luminous (approximately 1042 erg per second) kilonova possibly formed in the ejecta of a compact object merger.

Deep-learning image-reconstruction algorithm for dual-energy CT angiography with reduced iodine dose: preliminary results.

AIM: To evaluate the computed tomography (CT) attenuation values, background noise, arterial depiction, and image quality in whole-body dual-energy CT angiography (DECTA) at 40 keV with a reduced iodine dose using deep-learning image reconstruction (DLIR) and compare them with hybrid iterative reconstruction (IR). MATERIAL AND METHODS: Whole-body DECTA with a reduced iodine dose (200 mg iodine/kg) was performed in 22 patients, and DECTA data at 1.25-mm section thickness with 50% overlap were reconstructed at 40 keV using 40% adaptive statistical iterative reconstruction with Veo (hybrid-IR group), and DLIR at medium and high levels (DLIR-M and DLIR-H groups). The CT attenuation values of the thoracic and abdominal aortas and iliac artery and background noise were measured. Arterial depiction and image quality on axial, multiplanar reformatted (MPR), and volume-rendered (VR) images were assessed by two readers. Quantitative and qualitative parameters were compared between the hybrid-IR, DLIR-M, and DLIR-H groups. RESULTS: The vascular CT attenuation values were almost comparable between the three groups (p=0.013-0.97), but the background noise was significantly lower in the DLIR-H group than in the hybrid-IR and DLIR-M groups (p<0.001). The arterial depictions on axial and MPR images and in almost all arteries on VR images were comparable (p=0.14-1). The image quality of axial, MPR, and VR images was significantly better in the DLIR-H group (p<0.001-0.015). CONCLUSION: DLIR significantly reduced background noise and improved image quality in DECTA at 40 keV compared with hybrid-IR, while maintaining the arterial depiction in almost all arteries.

Deep-learning-based image reconstruction in dynamic contrast-enhanced abdominal CT: image quality and lesion detection among reconstruction strength levels.

AIM: To evaluate the use of deep-learning-based image reconstruction (DLIR) algorithms in dynamic contrast-enhanced computed tomography (CT) of the abdomen, and to compare the image quality and lesion conspicuity among the reconstruction strength levels. MATERIALS AND METHODS: This prospective study included 59 patients with 373 hepatic lesions who underwent dynamic contrast-enhanced CT of the abdomen. All images were reconstructed using four reconstruction algorithms, including 40% adaptive statistical iterative reconstruction-Veo (ASiR-V) and DLIR at low, medium, and high-strength levels (DLIR-L, DLIR-M, and DLIR-H, respectively). The signal-to-noise ratio (SNR) of the abdominal aorta, portal vein, liver, pancreas, and spleen and the lesion-to-liver contrast-to-noise ratio (CNR) were calculated and compared among the four reconstruction algorithms. The diagnostic acceptability was qualitatively assessed and compared among the four reconstruction algorithms and the conspicuity of hepatic lesions was compared between <5 and ≥5 mm lesions. RESULTS: The SNR of each anatomical structure (p<0.0001) and CNR (p<0.0001) were significantly higher in DLIR-H than the other reconstruction algorithms. Diagnostic acceptability was significantly better in DLIR-M than the other reconstruction algorithms (p<0.0001). The conspicuity of hepatic lesions was highest when using 40% ASiR-V and tended to lessen as the reconstruction strength level was getting higher in DLIR, especially in <5 mm lesions; however, all hepatic lesions could be detected. CONCLUSIONS: DLIR improved the SNR, CNR, and image quality compared with 40% ASiR-V, while making it possible to decrease lesion conspicuity using higher reconstruction strength.

Virtual monochromatic image at lower energy level for assessing pancreatic ductal adenocarcinoma in fast kV-switching dual-energy CT.

AIM: To evaluate the value of virtual monochromatic images (VMIs) at lower energy levels in fast-voltage-switching dual-energy computed tomography (DECT) for assessing pancreatic ductal adenocarcinoma (PDAC). MATERIALS AND METHODS: The institutional review board approved this prospective study. Written informed consent was obtained from all patients. Seventy-four consecutive patients with PDAC underwent dynamic contrast-enhanced DECT. Two radiologists reviewed eight energy levels (40, 45, 50, 55, 60, 65, 70, and 75 keV) of the pancreatic parenchymal phase VMIs. CT attenuation of the PDAC and pancreatic parenchyma, background noise, signal-to-noise ratio (SNR) of the pancreas, tumour-to-pancreas contrast-to-noise ratio (CNR), major and minor axes of PDAC, and qualitative tumour conspicuity were compared among the VMIs at eight energy levels. RESULTS: CT attenuation of PDAC and pancreatic parenchyma, background noise, SNR, and CNR peaked on VMIs at 40 keV with statistically significant difference (p<0.0001) and gradually decreased with increasing energy levels. The reproducibility in measuring tumour size was better on VMIs at 40 keV (28.8 and 29.2 mm of major axis in readers 1 and 2, respectively) and tended to be overestimated at higher energy levels (29.8 and 30.9 mm of major axis at 75 keV in readers 1 and 2, respectively). Qualitative tumour conspicuity was also significantly superior on VMIs at 40 keV than at all other energy levels (p<0.0001). CONCLUSION: VMIs at 40 keV demonstrated significantly increased SNR of the pancreas, CNR, and tumour conspicuity and high reproducibility in measuring tumour size for assessing PDAC.

Pancreatic MRI associated with pancreatic fibrosis and postoperative fistula: comparison between pancreatic cancer and non-pancreatic cancer tissue.

AIM: To evaluate the potential value of magnetic resonance imaging (MRI) for predicting postoperative pancreatic fistula (POPF) in patients with pancreatic cancer (PC) and non-pancreatic cancer (non-PC). MATERIAL AND METHODS: This retrospective study was approved by the institutional review board and written informed consent was waived. Forty patients underwent pancreatoduodenectomy due to PC (n=31) and non-PC (n=9). The pancreas-to-muscle signal intensity ratio (SIR) on three-dimensional (3D)- fast field echo (FFE) T1-, in- and opposed-phase T1-, and T2-weighted images, as well as the apparent diffusion coefficient (ADC) value of the pancreas were measured. The frequency of POPF and MRI measurements were compared between patients with PC and non-PC. The MRI measurements were also compared with the grade of pancreatic fibrosis on pathological findings, fat deposition, and interstitial oedema. RESULTS: The frequency of POPF was significantly higher in patients with non-PC than in those with PC (p=0.0067), with an odds ratio of 10.4. The SIR on 3D-FFE T1-weighted images was significantly higher in patients with non-PC (p=0.0001) and those with POPF (p=0.017) than in those with PC and those without POPF, respectively. Multiple regression analysis demonstrated that the SIR on 3D-FFE T1-weighted image was independently associated with the grade of pancreatic fibrosis (p<0.0001). CONCLUSION: The frequency of POPF was significantly higher in patients with non-PC than in those with PC was inversely related to the grade of pancreatic fibrosis. The SIR on 3D-FFE T1-weighted image might be a potential imaging biomarker for predicting POPF.

Right adrenal vein: comparison between adaptive statistical iterative reconstruction and model-based iterative reconstruction.

AIM: To compare right adrenal vein (RAV) visualisation and contrast enhancement degree on adrenal venous phase images reconstructed using adaptive statistical iterative reconstruction (ASiR) and model-based iterative reconstruction (MBIR) techniques. MATERIAL AND METHODS: This prospective study was approved by the institutional review board, and written informed consent was waived. Fifty-seven consecutive patients who underwent adrenal venous phase imaging were enrolled. The same raw data were reconstructed using ASiR 40% and MBIR. The expert and beginner independently reviewed computed tomography (CT) images. RAV visualisation rates, background noise, and CT attenuation of the RAV, right adrenal gland, inferior vena cava (IVC), hepatic vein, and bilateral renal veins were compared between the two reconstruction techniques. RESULTS: RAV visualisation rates were higher with MBIR than with ASiR (95% versus 88%, p=0.13 in expert and 93% versus 75%, p=0.002 in beginner, respectively). RAV visualisation confidence ratings with MBIR were significantly greater than with ASiR (p<0.0001, both in the beginner and the expert). The mean background noise was significantly lower with MBIR than with ASiR (p<0.0001). Mean CT attenuation values of the RAV, right adrenal gland, IVC, and hepatic vein were comparable between the two techniques (p=0.12-0.91). Mean CT attenuation values of the bilateral renal veins were significantly higher with MBIR than with ASiR (p=0.0013 and 0.02). CONCLUSION: Reconstruction of adrenal venous phase images using MBIR significantly reduces background noise, leading to an improvement in the RAV visualisation compared with ASiR.

Renovascular CT: comparison between adaptive statistical iterative reconstruction and model-based iterative reconstruction.

AIM: To compare contrast enhancement and image quality between renovascular computed tomography (CT) images with adaptive statistical iterative reconstruction (ASiR) and that with model-based iterative reconstruction (MBIR). MATERIAL AND METHODS: This retrospective study was approved by the institutional review board and written informed consent was waived. Twenty-five consecutive patients who underwent renovascular CT were enrolled in this study. The same raw projection data were reconstructed using ASiR 40%, 100%, and MBIR. Background noise, CT attenuation, and signal-to-noise ratio (SNR) of the renal vessels and kidneys, and image quality were compared among the three reconstruction techniques. RESULTS: Mean background noise was significantly lower with MBIR at the first and second phases than those with ASiR 40% and 100% (p<0.0001). Mean CT attenuation of the abdominal aorta, renal artery, and renal cortex obtained at the first phase and those of the renal vein and renal medulla at the second phase were comparable among the three techniques (p=0.051-1.00). Mean SNRs of the abdominal aorta, renal artery, renal cortex, renal vein, and renal medulla were significantly higher with MBIR than with ASiR 40% or 100% (both p<0.0001). The depiction of the renal artery and vein as well as image quality significantly improved with MBIR compared with those with ASiR 40% and 100% (p<0.0001-0.0016). CONCLUSION: Reconstruction of renovascular CT images with MBIR significantly reduces background noise, leading to an improvement in SNR and image quality compared with that using ASiR.

Meteorology in ruptured abdominal aortic aneurysm: an institutional study and a meta-analysis of published studies reporting atmospheric pressure.

The aim of this paper was to determine whether weather factors including atmospheric pressure are associated with the occurrence of ruptured abdominal aortic aneurysm (RAAA). We investigated our institutional experiences of RAAA in more than 150 patients during 8 years. Further, we performed a meta-analysis of published studies reporting the influence of atmospheric pressure on RAAA. We retrospectively evaluated 152 patients who underwent surgery for RAAA (including ruptured iliac arterial aneurysm) at our institute between 1 January 2006 and 31 December 2013. Daily regional meteorological data (in the nearest weather station located 3.5 km from the hospital) were obtained online from Japan Meteorological Agency. To identify comparative studies of mean atmospheric pressure on the day with RAAA versus that on the day without RAAA, MEDLINE and EMBASE were searched through January 2014 using Web-based search engines (PubMed and OVID). Mean sea level atmospheric pressure, delta mean atmospheric pressure (difference between mean sea level atmospheric pressure on the day and that on the previous day), and sunshine duration on the day with RAAA were significantly lower than those on the day without RAAA: 1012.43±7.44 versus 1013.71±6.49 hPa, P=0.039, -1.18±5.15 versus 0.05±5.62 hPa, P=0.005; and 4.76±3.76 versus 5.47±3.88 h, P=0.026; respectively. A pooled analysis of 8 studies (including our institutional study) demonstrated that mean atmospheric pressure on the day with RAAA was significantly lower than that on the day without RAAA: standardized mean difference, -0.09; 95% confidence interval, -0.14 to -0.04; P=0.0009. Atmospheric pressure on the day with RAAA appears lower than that on the day without RAAA. Atmospheric pressure may be associated with the occurrence of RAAA.

Effects of the masticatory demand on the rat mandibular development.

The influence of masticatory loading stimulus on mandibular development is not fully clear. In this paper, experimental alterations in the daily muscle use, caused by a changed diet consistency, were continuously monitored, while adaptations in bone and cartilage were examined. It is hypothesised that decreased muscular loading will result in a decrease in the growth factor expression and mandible growth. Fourteen 21-day-old Wistar strain male rats were randomly divided into two groups and fed on either a hard or soft diet for 14 weeks. An implanted radio-telemetric device recorded continuously muscle activity of the superficial masseter muscle. Chondroblast proliferation in the condylar cartilage was identified by insulin-like growth factor-1 receptor (IGF-1r) immunostaining. Furthermore, an X-ray was taken for cephalometric analysis. In the soft-diet group, the duty time of the superficial masseter muscle at higher activity levels was significantly lower than that in the hard-diet group. This decrease in muscular loading of the jaw system was accompanied by: a significant reduction in (i) articular cartilage thickness, (ii) expression of IGF-1r immunopositive cells and (iii) mandible ramus height. In conclusion, a decrease in masticatory demand during the growth period leads to insufficient mandibular development.

GRB 130427A: a nearby ordinary monster.

Long-duration gamma-ray bursts (GRBs) are an extremely rare outcome of the collapse of massive stars and are typically found in the distant universe. Because of its intrinsic luminosity (L ~ 3 × 10(53) ergs per second) and its relative proximity (z = 0.34), GRB 130427A reached the highest fluence observed in the γ-ray band. Here, we present a comprehensive multiwavelength view of GRB 130427A with Swift, the 2-meter Liverpool and Faulkes telescopes, and by other ground-based facilities, highlighting the evolution of the burst emission from the prompt to the afterglow phase. The properties of GRB 130427A are similar to those of the most luminous, high-redshift GRBs, suggesting that a common central engine is responsible for producing GRBs in both the contemporary and the early universe and over the full range of GRB isotropic energies.

Paraneoplastic cerebellar degeneration caused by ovarian clear-cell carcinoma.

Paraneoplastic cerebellar degeneration is a paraneoplastic neurological syndrome caused by the remote effect of certain systemic cancers and is characterized by subacute cerebellar symptoms. A 62-year-old woman suffering from unidentified cerebellar symptoms was admitted to our hospital. Paraneoplastic cerebellar degeneration was suspected and ovarian cancer was detected after the systemic examination for malignancy. The symptoms of vertigo and dysarthria were improved a little after surgical operation and treatments of γ-globulin, steroid pulse and tacrolimus hydrate. The cerebellar symptoms of paraneoplastic cerebellar degeneration are often evident prior to detection of malignancy. It is important to perform systemic examination for malignancy in case of unidentified cerebellar symptoms.

MRI findings of granulomatous prostatitis developing after intravesical Bacillus Calmette-Guérin therapy.

AIM: To evaluate magnetic resonance imaging (MRI) findings of granulomatous prostatitis (GP) developing after intravesical Bacillus Calmette-Guérin (BCG) therapy. MATERIALS AND METHODS: Ten patients with pathologically proven GP underwent prostatic MRI. Lesion shape and signal intensity (SI) were evaluated on T2-weighted (T2WI), T1WI, and diffusion-weighted imaging (DWI). RESULTS: Polygonal nodular lesions with notches, diffuse lesions, and cystic lesions with mural nodules were seen in two, six, and one patients, respectively. The remaining patient had a diffuse and cystic lesion. All diffuse lesions showed higher SI than muscle on T1WI and higher SI than the normal peripheral zone (PZ) on DWI. On T2WI, six of seven diffuse lesions showed a slightly lower SI than bone marrow and the remaining one lesion was iso-intense. All nodular lesions showed a low SI similar to muscle on T2WI and were iso-intense to muscle on T1WI. On DWI, two each of the four nodular lesions showed slightly lower SI and slightly higher SI than the normal PZ, respectively. All contents within the cyst and mural nodules showed markedly high and low SI on T2WI, respectively. On DWI, all fluids within cysts showed markedly high SI. One each of the mural nodules showed slightly higher SI and slightly lower SI than the normal PZ on DWI. CONCLUSION: Three main MRI patterns of GP were identified: diffuse, nodular, and cystic with mural nodule; among them, the diffuse type was the most common. Cystic lesions with mural nodules could accompany the lesion.

Changes in activity and structure of jaw muscles in Parkinson's disease model rats.

Parkinson's disease (PD), a major neurological disease, is characterised by a marked loss of dopaminergic neurons in the substantia nigra. Patients with PD frequently show chewing and swallowing dysfunctions, but little is known about the characteristics of their stomatognathic functions. The purpose of this study was to evaluate the influence of PD on jaw muscle fibre and functions. PD model rats were made by means of the injection of 6-hydroxydopamine (6-OHDA) into the striatum of 8-week-old Sprague-Dawley male rats. Five weeks after the injection, a radio-telemetric device was implanted to record muscle activity continuously from the superficial masseter and anterior belly of digastric muscles. Muscle activity was recorded for 3 days and was evaluated by the total duration of muscle activity per day (duty time). After recording the muscle activities, jaw muscles were isolated for immunohistochemical and PCR analyses. In PD model rats, the following findings of the digastrics muscles verify that compared to the control group: (i) the higher duty time exceeding 5% of the peak activity level, (ii) the higher expression of the mRNA of myosin heavy chain type I, and (iii) the tendency for fast to slow fibre-type transition. With respect to the masseter muscle, there were no significant differences in all analyses. In conclusion, PD leads to the changes in the jaw behaviours, resulting in a PD-specific chewing and swallowing dysfunctions.

Cerebral blood flow and metabolism measurement using positron emission tomography before and during internal carotid artery test occlusions: feasibility of rapid quantitative measurement of CBF and OEF/CMRO(2).

Balloon test occlusion (BTO) of the internal carotid artery (ICA) combined with cerebral blood flow (CBF) study is a sensitive test for predicting the outcome of permanent ICA occlusion. However, false negative results sometimes occur using single photon emission tomography (SPECT). We have recently developed a rapid positron emission tomography (PET) protocol that measures not only the CBF but also the cerebral oxygen metabolism before and during BTO in succession. We measured acute changes in regional CBF and OEF/CMRO(2) before and during BTO in three cases with large or giant cerebral aneurysms using the rapid PET protocol. Although no patients showed ischemic symptoms during BTO, PET studies exhibited mildly to moderately decreased CBF (9∼34%) compared to the values obtained before BTO in all cases. The average OEF during BTO was significantly increased (21% and 43%) than that of before BTO in two cases. The two cases were considered to be non-tolerant for permanent ICA occlusion and treated without ICA sacrifice. Measurement of the CBF and OEF/CMRO(2) using a rapid PET protocol before and during BTO is feasible and can be used for accurate assessment of tolerance prediction in ICA occlusion.

Allogeneic hematopoietic stem cell transplantation for adult AML patients with granulocytic sarcoma.

We recently reported that adult acute myeloid leukemia (AML) patients with granulocytic sarcoma (GS) possessed unique clinical features and poor prognosis. However, the optimal therapeutic strategy for this entity has not been established. Therefore, the aim of this study was to assess the efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for the management of AML with GS. We retrospectively analyzed 503 consecutive adult AML patients (median age, 44 years; range, 15-73 years) who received allo-HSCT. A total of 44 patients (8.7%) had GS before transplantation. Patients with GS achieved comparable survival to those without GS (5-year overall survival (OS), 47% vs 44%, respectively, P=0.621). In patients with GS, excellent outcomes were seen in those that underwent allo-HSCT while in complete remission, whereas nine out of ten patients with GS at the time of transplant experienced a relapse within 6 months after allo-HSCT. Local irradiation for GS prior to allo-HSCT and acute and chronic graft-versus-host disease did not affect survival significantly. Multivariate analysis identified age, disease status and the use of myeloablative conditioning as independent prognostic factors for OS. These data suggest that better control of GS prior to allo-HSCT is crucial to improve the outcome of transplantation for those with GS.

Relativistic jet activity from the tidal disruption of a star by a massive black hole.

Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.