48 research outputs found
Assessment of the hybridization chain reaction for the amplification of signal on DNA microarrays
No full textThe hybridization chain reaction (HCR), in which stable DNA monomers assemble only upon exposure to a target DNA fragment, has been introduced earlier for reactions in solution. Two species of DNA hairpins are present in solution without interaction, until an initiator DNA triggers a cascade of hybridization events resulting in an elongated strand of alternating opened hairpins forming a double helix. Hybridization chain reaction (HCR) was introduced as an attractive method to amplify the signal of targeted nucleic acids.
We report here the results of the HCR for the amplification of DNA microarray signals. Hairpins were fluorescently labelled with Cy3 or Cy5, or with alternative couples of fluorophors. First results indicate that the HCR-induced fluorescence at the surface might be hard to detect directly. Protocols involving the removal of the amplification product from the surface evidence an amplification factor of about 5. Performing the HCR in solution before hybridizing the product to the DNA microarray, i.e. using HCR for multiple labelling the target for the detection, produces a signal amplification of a factor 3-4. The effect of buffer composition, initiator concentration and hairpin concentration was investigated. The low sensitivity that is currently attainable (approximately 0,05 μM) severely limits the practical use of the HCR
Assessment of pelvic organ prolapse with the Pelvic Inclination Correction System: defining the normal range and threshold to pathology.
No full textPURPOSE
To define the normal range and threshold values for pathologic prolapse on MRI using the PICS line and assess its correlation with the pubococcygeal line (PCL).
METHODS
This prospective, IRB-approved study included 20 nulliparous volunteers and 18 prolapse patients (POP-Q Stage ≥ 2). Organ positions (bladder, cervix, anorectal junction) relative to PICS and PCL were measured on dynamic MRI. Differences in organ position were compared. Receiver-operating characteristic (ROC) analysis was performed to identify cutoff values for prolapse using the PICS line. The correlation between PICS and PCL measurements was tested with Spearman's rank correlation.
RESULTS
In volunteers, median bladder and cervix positions measured to the PICS at rest were - 2.7 cm and - 5.3 cm compared to - 1.9 cm and - 2.7 cm in patients (p < 0.001). During straining, bladder and cervix were at - 0.9 cm and - 3.2 cm in volunteers versus + 2.5 cm and + 2.5 cm in patients (p < 0.001). Correlation was strong for PICS and PCL measurements for all three compartments (δ = 0.883-0.970, p ≤ 0.001). AUCs of PICS for the anterior and middle compartment were 0.98 (95% confidence interval [CI] 0.96-1.00, p < 0.001) and 0.96 (95% CI 0.89-1.00, p < 0.001) for differentiating patients from healthy volunteers. AUC for the posterior compartment was 0.76 (95% CI 0.57-0.96, p = 0.034).
CONCLUSION
PICS measurements reliably differentiate patients from volunteers in the anterior and middle compartment. Future studies need to identify a reliable threshold for the posterior compartment. PICS and PCL measurements are strongly correlated
Design study of a Split-Coaxial RFQ for IsoDAR
No full text© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). The Isotope Decay-At-Rest experiment (IsoDAR) is a proposed experiment to search for sterile neutrinos by measuring neutrino oscillations. The electron-antineutrino generation requires a high intensity primary proton beam impinging on a beryllium target surrounded by lithium . In IsoDAR, H2+ ions are generated and accelerated to avoid space charge effects in the low energy region, which will be stripped into protons after extraction from a cyclotron. As part of the IsoDAR injection system, an RFQ buncher with 32.8 MHz of operation frequency provides 70 keV acceleration and strong bunching of the H2+ beam. The RFQ will be installed halfway inside the iron yoke of the cyclotron to be very close to the median plane. Because the beam starts diverging after the RFQ in both transverse and longitudinal direction, a re-buncher is employed in the end transition cell to re-focus the beam longitudinally. In this paper, we describe in detail the beam dynamics study and RF analysis of the IsoDAR RFQ for direct injection into a compact cyclotron
Thoraco-abdominal high-pitch dual-source CT angiography: Experimental evaluation of injection protocols with an anatomical human vascular phantom
No full textOBJECTIVE: To experimentally evaluate three different contrast injection protocols at thoraco-abdominal high-pitch dual-source computed tomography angiography (CTA), with regard to level and homogeneity of vascular enhancement at different cardiac outputs. MATERIALS AND METHODS: A uniphasic, a biphasic as well as an individually tailored contrast protocol were tested using a human vascular phantom. Each protocol was scanned at 5 different cardiac outputs (3-5L/min, steps of 0.5L/min) using an extracorporeal cardiac pump. Vascular enhancement of the thoraco-abdominal aorta was measured every 5cm. Overall mean enhancement of each protocol and mean enhancement for each cardiac output within each protocol were calculated. Enhancement homogeneity along the z-axis was evaluated for each cardiac output and protocol. RESULTS: Overall mean enhancement was significantly higher in the uniphasic than in the other two protocols (all p<.05), whereas the difference between the biphasic and tailored protocol was not significant (p=.76). Mean enhancement among each of the 5 cardiac outputs within each protocol was significantly different (all p<.05). Only within the tailored protocol mean enhancement differed not significantly at cardiac outputs of 3.5L/min vs. 5L/min (484±25HU vs. 476±19HU, p=.14) and 4 vs. 5L/min (443±49HU vs. 476±19HU, p=.05). Both, uniphasic and tailored protocol yielded homogenous enhancement at all cardiac outputs, whereas the biphasic protocol failed to achieve homogenous enhancement. CONCLUSION: This phantom study suggests that diagnostic and homogenous enhancement at thoraco-abdominal high-pitch dual-source CTA is feasible with either a uniphasic or an individually tailored contrast protocol
Association of the Timing and Type of Acute Symptomatic Seizures With Poststroke Epilepsy and Mortality
No full textBACKGROUND: Acute symptomatic seizures (ASyS) increase the risk of epilepsy and mortality after a stroke. The impact of the timing and type of ASyS remains unclear. METHODS: This multicenter cohort study included data from 9 centers between 2002 and 2018, with a final analysis in February 2024. The study included 4552 adults (2005 female; median age, 73 years) with ischemic stroke and no seizure history. Seizures were classified using International League Against Epilepsy definitions. We examined ASyS occurring within seven days after stroke. The main outcomes were all-cause mortality and epilepsy. Validation of the updated SeLECT score (SeLECT-ASyS) was performed in 3 independent cohorts (Switzerland, Argentina, and Japan) collected between 2012 and 2024, including 74 adults with ASyS. RESULTS: The 10-year risk of poststroke epilepsy ranged from 41% to 94%, and mortality from 36% to 100%, depending on ASyS type and timing. ASyS on stroke onset day had a higher epilepsy risk (adjusted hazard ratio [aHR], 2.3 [95% CI, 1.3-4.0]; P=0.003) compared with later ASyS. Status epilepticus had the highest epilepsy risk (aHR, 9.6 [95% CI, 3.5-26.7]; P<0.001), followed by focal to bilateral tonic-clonic seizures (aHR, 3.4 [95% CI, 1.9-6.3]; P<0.001). Mortality was higher in those with ASyS presenting as focal to bilateral tonic-clonic seizures on day 0 (aHR, 2.8 [95% CI, 1.4-5.6]; P=0.004) and status epilepticus (aHR, 14.2 [95% CI, 3.5-58.8]; P<0.001). The updated SeLECT-ASyS model, available as an application, outperformed a previous model in the derivation cohort (concordance statistics, 0.68 versus 0.58; P=0.02) and in the validation cohort (0.70 versus 0.50; P=0.18). CONCLUSIONS: ASyS timing and type significantly affect epilepsy and mortality risk after stroke, improving epilepsy prediction and guiding patient counseling
Humoral immune response to SARS-CoV-2 third vaccination in patients with multiple sclerosis and healthy controls: A prospective multicenter study
No full textBACKGROUND: Third vaccination against SARS-CoV-2 is recommended for patients with multiple sclerosis (pwMS), usually six months after the last vaccination. METHODS: In this prospective multicenter study on 292 pwMS and 46 healthy controls (HC), who had all received two vaccinations prior to study enrollment, SARS-CoV-2 IgG response was measured in the month before and 2–4 months after third vaccination. PwMS were categorized as follows: untreated (N-DMT, n = 32), receiving disease-modifying therapy (DMT) with expected humoral response (er-DMT: interferon-beta preparations, glatiramer acetate, dimethyl fumarate, teriflunomide, natalizumab, cladribine, alemtuzumab; n = 120) or no expected humoral response (nr-DMT: S1PMs, CD20mAb; n = 140). RESULTS: PwMS on nr-DMT had significantly lower median antibody levels before (12.1 U/ml [0.4–2500]) and after third vaccination (305 U/ml [0.4–2500]) in comparison to other groups (p<0.001). We did not find differences in antibody levels after homologous (n = 281; 2500 [0.4–2500]) and heterologous (n = 57; 2500 [0.4–2500]) vaccination regime regardless of the DMT group. The DMT group ([Formula: see text] = –0.60; 95% CI –1195.73, –799.10; p<0.001) was associated with antibody levels after third vaccination, while time to revaccination (6 months [1–13]) was not. After third vaccination, seropositivity was reached in 75.8% and 82.2% of pwMS on anti-CD20 mAbs and S1PMs, respectively. Complete B-cell depletion significantly decreased the probability of seroconversion even after the third vaccination (OR 0.14; p = 0.021), whereas time interval to last DMT intake and time to revaccination did not. Twenty-two patients reported a SARS-CoV-2 infection (3 N-DMT, 9 er-DMT, 10 nr-DMT), one being asymptomatic and the rest having a mild course. CONCLUSION: Humoral response to SARS-CoV-2 third vaccination in pwMS is excellent. While reduced by S1PMs and CD20mAb, protective response is still expected in the majority of patient
Low kilovoltage CT of the neck with 70 kVp: comparison with a standard protocol
No full textBACKGROUND AND PURPOSE: CT protocols should aim for radiation doses being as low as reasonably achievable. The purpose of our study was to assess the image quality and radiation dose of neck CT at a tube potential of 70 kVp.
MATERIALS AND METHODS: Twenty patients (7 female, mean age 51.4 years, age range 19-81 years) underwent contrast-enhanced 64-section CT of the neck at 70 kVp (ATCM, effective tube current-time product 614 eff.mAs, range 467-713 eff.mAs). All 20 patients had a previous neck CT at 120 kVp on the same scanner. Two radiologists assessed image quality and artifacts in the upper, middle, and lower neck. Image noise and attenuation were measured, and the CNR was calculated. Effective radiation dose was calculated.
RESULTS: Interobserver agreement regarding image quality of soft tissue for 70-kVp and 120-kVp scans was good to excellent. At 70 kVp, soft tissues were of diagnostic image quality in all scans, whereas the lower cervical spine was not of diagnostic quality in 3 and 4 scans per both readers. No difference was found among 70-kVp and 120-kVp scans for soft tissue image quality in the upper neck, while image quality was significantly better in the middle at 70 kVp (P < .05) and better in the lower third at 120 kVp (P < .05). CNR was significantly higher at 70 kVp in all levels for both readers (P < .001). Effective radiation dose at 70 kVp was significantly lower (0.88 ± 0.2 mSv) than at 120 kVp (1.33 ± 0.2 mSv, P < .001).
CONCLUSIONS: CT of the cervical soft tissues at 70 kVp is feasible, provides diagnostic image quality with improved CNR, and reduces radiation dose by approximately 34% compared with a standard protocol at 120 kVp. In contrast, low kVp CT of the lower cervical spine suffers from compromised image quality
Low-dose CT of the lung: potential value of iterative reconstructions
No full textObjectives: To prospectively assess the impact of sinogram-affirmed iterative reconstruction (SAFIRE) on image quality of nonenhanced low-dose lung CT as compared to filtered back projection (FBP). Methods: Nonenhanced low-dose chest CT (tube current-time product: 30mAs) was performed on 30 patients at 100kVp and on 30 patients at 80kVp. Images were reconstructed with FBP and SAFIRE. Two blinded, independent readers measured image noise; two readers assessed image quality of normal anatomic lung structures on a five-point scale. Radiation dose parameters were recorded. Results: Image noise in datasets reconstructed with FBP (57.4 ± 15.9) was significantly higher than with SAFIRE (31.7 ± 9.8, P < 0.001). Image quality was significantly superior with SAFIRE than with FBP (P < 0.01), without significant difference between FBP at 100kVp and SAFIRE at 80kVp (P = 0.68). Diagnostic image quality was present with FBP in 96% of images at 100kVp and 88% at 80kVp, and with SAFIRE in 100% at 100kVp and 98% at 80kVp. There were significantly more datasets with diagnostic image quality with SAFIRE than with FBP (P < 0.01). Mean CTDIvol and effective doses were 1.5 ± 0.7mGy·cm and 0.7 ± 0.2mSv at 100kVp, and 1.4 ± 2.8mGy·cm and 0.5 ± 0.2mSv at 80kVp (P < 0.001, both). Conclusions: Use of SAFIRE in low-dose lung CT reduces noise, improves image quality, and renders more studies diagnostic as compared to FBP. Key Points : • Low-dose computed tomography is an important thoracic investigation tool. • Radiation dose can be less than 1mSv with iterative reconstructions. • Iterative reconstructions render more low-dose lung CTs diagnostic compared to conventional reconstruction
Automated attenuation-based kilovoltage selection: preliminary observations in patients after endovascular aneurysm repair of the abdominal aorta
No full textOBJECTIVE: The objective of our study was to assess prospectively the impact of automated attenuation-based kilovoltage selection on image quality and radiation dose in patients undergoing body CT angiography (CTA) after endovascular aneurysm repair (EVAR) of the abdominal aorta.
SUBJECTS AND METHODS: Thirty-five patients (five women, 30 men; mean age ± SD, 69 ± 13 years; mean body mass index ± SD, 27.3 ± 4.5 kg/m(2)) underwent 64-MDCT angiography of the thoracoabdominal aorta using a fixed 120-kVp protocol (scan A: 120 mAs [reference]; rotation time, 0.33 second; pitch, 1.2) and, within a median time interval of 224 days, using a protocol with automated kilovoltage selection (scan B: tube voltage, 80-140 kVp). Subjective image quality (5-point scale: 1 [excellent] to 5 [nondiagnostic]) and objective image quality (aortic attenuation at four locations of the aortoiliac system, noise, contrast-to-noise ratio [CNR]) were assessed independently by two blinded radiologists. The volume CT dose index (CTDI(vol)) was compared between scans A and B.
RESULTS: The subjective image quality of scans A and B was similar (median score for both, 1; range, 1-4; p = 0.74), with all datasets being of diagnostic quality. Automated attenuation-based kilovoltage selection led to a reduction to 80 kVp in one patient (2.9%) and 100 kVp in 18 patients (51.4%). Fifteen of 35 patients (42.9%) were scanned at 120 kVp, whereas in one patient (2.9%) the kilovoltage setting increased to 140 kVp. Image noise (scan A vs scan B: mean ± SD, 12.8 ± 2.3 vs 13.7 ± 2.9 HU, respectively) was significantly (p < 0.05) higher in scan B than in scan A, whereas CNR was similar among scans (A vs B: mean ± SD, 15.7 ± 7.0 vs 16.9 ± 9.7; p = 0.43). The CTDI(vol) was significantly lower in scan B (mean ± SD, 8.9 ± 2.9 mGy; scan A, 10.6 ± 1.5 mGy; average reduction, 16%; p = 0.002) despite a higher tube current-exposure time product (B vs A: mean ± SD, 152 ± 27 vs 141 ± 29 mAs; p = 0.01).
CONCLUSION: In patients undergoing follow-up after EVAR of the abdominal aorta, body CTA using automated attenuation-based kilovoltage selection yields similar subjective image quality and CNR at a significantly reduced dose compared with a protocol that uses 120 kVp
