Search for New Physics in Electronic Recoil Data from XENONnT

We report on a blinded analysis of low-energy electronic recoil data from the first science run of the XENONnT dark matter experiment. Novel subsystems and the increased 5.9 ton liquid xenon target reduced the background in the (1, 30) keV search region to (15.8±1.3)  events/(ton×year×keV), the lowest ever achieved in a dark matter detector and ∼5 times lower than in XENON1T. With an exposure of 1.16 ton-years, we observe no excess above background and set stringent new limits on solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter.

Material radiopurity control in the XENONnT experiment

The selection of low-radioactive construction materials is of the utmost importance for rare-event searches and thus critical to the XENONnT experiment. Results of an extensive radioassay program are reported, in which material samples have been screened with gamma-ray spectroscopy, mass spectrometry, and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{222}$$\end{document}222Rn emanation measurements. Furthermore, the cleanliness procedures applied to remove or mitigate surface contamination of detector materials are described. Screening results, used as inputs for a XENONnT Monte Carlo simulation, predict a reduction of materials background (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sim $$\end{document}∼17%) with respect to its predecessor XENON1T. Through radon emanation measurements, the expected \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{222}$$\end{document}222Rn activity concentration in XENONnT is determined to be 4.2 (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{+0.5}_{-0.7}$$\end{document}-0.7+0.5) \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu $$\end{document}μBq/kg, a factor three lower with respect to XENON1T. This radon concentration will be further suppressed by means of the novel radon distillation system.

[FH-deficient renal cell carcinoma expands the spectrum of renal papillary tumors]

Fumarate hydratase (FH)-deficient renal cell carcinoma (RCC) is a distinct entity, which shows a biallelic inactivation of the FH gene that consequently leads to FH protein expression and function loss, respectively. This alteration leads to an accumulation of the oncometabolite fumarate in the citrate cycle and various disorders of the cell balance and DNA processing. FH-deficient RCC often shows a morphologically overlapping spectrum with papillary renal cell carcinoma (type 2), whereby a typical mixture of growth patterns including tubulo-cystic, cribriform, and/or solid differentiation can be observed. A characteristic but non-specific morphological feature is prominent eosinophilic, virus-inclusion body-like nucleoli with perinucleolar halos. Tumoral immunohistochemical loss of FH expression supports the diagnosis but may be preserved in rare cases. Most FH-deficient RCCs show very aggressive biological behavior and are often metastasized at the time of diagnosis. The initial description encompassed RCC in association with the hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome, which also includes cutaneous and uterine leiomyomas. However, current data also show an increasing proportion of sporadic cases, so that a distinction (hereditary vs. sporadic) seems appropriate. So far, few but promising data on effective systemic therapeutic options have been reported. In summary, precise diagnosis is of great importance due to the frequent aggressive biological behavior, potential need to deviate from the therapeutic standard, and the possible indicator of a hereditary disease.

222 Rn emanation measurements for the XENON1T experiment

The selection of low-radioactive construction materials is of utmost importance for the success of low-energy rare event search experiments. Besides radioactive contaminants in the bulk, the emanation of radioactive radon atoms from material surfaces attains increasing relevance in the effort to further reduce the background of such experiments. In this work, we present the 222 Rn emanation measurements performed for the XENON1T dark matter experiment. Together with the bulk impurity screening campaign, the results enabled us to select the radio-purest construction materials, targeting a 222 Rn activity concentration of 10 μ Bq / kg in 3.2 t of xenon. The knowledge of the distribution of the 222 Rn sources allowed us to selectively eliminate problematic components in the course of the experiment. The predictions from the emanation measurements were compared to data of the 222 Rn activity concentration in XENON1T. The final 222 Rn activity concentration of ( 4.5 ± 0.1 ) μ Bq / kg in the target of XENON1T is the lowest ever achieved in a xenon dark matter experiment.

Search for Coherent Elastic Scattering of Solar ^{8}B Neutrinos in the XENON1T Dark Matter Experiment

We report on a search for nuclear recoil signals from solar ^{8}B neutrinos elastically scattering off xenon nuclei in XENON1T data, lowering the energy threshold from 2.6 to 1.6  keV. We develop a variety of novel techniques to limit the resulting increase in backgrounds near the threshold. No significant ^{8}B neutrinolike excess is found in an exposure of 0.6  t×y. For the first time, we use the nondetection of solar neutrinos to constrain the light yield from 1-2 keV nuclear recoils in liquid xenon, as well as nonstandard neutrino-quark interactions. Finally, we improve upon world-leading constraints on dark matter-nucleus interactions for dark matter masses between 3 and 11  GeV c^{-2} by as much as an order of magnitude.

Light Dark Matter Search with Ionization Signals in XENON1T

We report constraints on light dark matter (DM) models using ionization signals in the XENON1T experiment. We mitigate backgrounds with strong event selections, rather than requiring a scintillation signal, leaving an effective exposure of (22±3) tonne day. Above ∼0.4  keV_{ee}, we observe <1  event/(tonne day keV_{ee}), which is more than 1000 times lower than in similar searches with other detectors. Despite observing a higher rate at lower energies, no DM or CEvNS detection may be claimed because we cannot model all of our backgrounds. We thus exclude new regions in the parameter spaces for DM-nucleus scattering for DM masses m_{χ} within 3-6  GeV/c^{2}, DM-electron scattering for m_{χ}>30  MeV/c^{2}, and absorption of dark photons and axionlike particles for m_{χ} within 0.186-1  keV/c^{2}.

Search for Light Dark Matter Interactions Enhanced by the Migdal Effect or Bremsstrahlung in XENON1T

Direct dark matter detection experiments based on a liquid xenon target are leading the search for dark matter particles with masses above ∼5  GeV/c^{2}, but have limited sensitivity to lighter masses because of the small momentum transfer in dark matter-nucleus elastic scattering. However, there is an irreducible contribution from inelastic processes accompanying the elastic scattering, which leads to the excitation and ionization of the recoiling atom (the Migdal effect) or the emission of a bremsstrahlung photon. In this Letter, we report on a probe of low-mass dark matter with masses down to about 85  MeV/c^{2} by looking for electronic recoils induced by the Migdal effect and bremsstrahlung using data from the XENON1T experiment. Besides the approach of detecting both scintillation and ionization signals, we exploit an approach that uses ionization signals only, which allows for a lower detection threshold. This analysis significantly enhances the sensitivity of XENON1T to light dark matter previously beyond its reach.

Constraining the Spin-Dependent WIMP-Nucleon Cross Sections with XENON1T

We report the first experimental results on spin-dependent elastic weakly interacting massive particle (WIMP) nucleon scattering from the XENON1T dark matter search experiment. The analysis uses the full ton year exposure of XENON1T to constrain the spin-dependent proton-only and neutron-only cases. No significant signal excess is observed, and a profile likelihood ratio analysis is used to set exclusion limits on the WIMP-nucleon interactions. This includes the most stringent constraint to date on the WIMP-neutron cross section, with a minimum of 6.3×10^{-42}  cm^{2} at 30  GeV/c^{2} and 90% confidence level. The results are compared with those from collider searches and used to exclude new parameter space in an isoscalar theory with an axial-vector mediator.

First Results on the Scalar WIMP-Pion Coupling, Using the XENON1T Experiment

We present first results on the scalar coupling of weakly interacting massive particles (WIMPs) to pions from 1  t yr of exposure with the XENON1T experiment. This interaction is generated when the WIMP couples to a virtual pion exchanged between the nucleons in a nucleus. In contrast to most nonrelativistic operators, these pion-exchange currents can be coherently enhanced by the total number of nucleons and therefore may dominate in scenarios where spin-independent WIMP-nucleon interactions are suppressed. Moreover, for natural values of the couplings, they dominate over the spin-dependent channel due to their coherence in the nucleus. Using the signal model of this new WIMP-pion channel, no significant excess is found, leading to an upper limit cross section of 6.4×10^{-46}  cm^{2} (90% confidence level) at 30  GeV/c^{2} WIMP mass.

Dark Matter Search Results from a One Ton-Year Exposure of XENON1T

We report on a search for weakly interacting massive particles (WIMPs) using 278.8 days of data collected with the XENON1T experiment at LNGS. XENON1T utilizes a liquid xenon time projection chamber with a fiducial mass of (1.30±0.01)  ton, resulting in a 1.0 ton yr exposure. The energy region of interest, [1.4,10.6]  keV_{ee} ([4.9,40.9] keV_{nr}), exhibits an ultralow electron recoil background rate of [82_{-3}^{+5}(syst)±3(stat)]  events/(ton yr keV_{ee}). No significant excess over background is found, and a profile likelihood analysis parametrized in spatial and energy dimensions excludes new parameter space for the WIMP-nucleon spin-independent elastic scatter cross section for WIMP masses above 6  GeV/c^{2}, with a minimum of 4.1×10^{-47}  cm^{2} at 30  GeV/c^{2} and a 90% confidence level.

First Dark Matter Search Results from the XENON1T Experiment

We report the first dark matter search results from XENON1T, a ∼2000-kg-target-mass dual-phase (liquid-gas) xenon time projection chamber in operation at the Laboratori Nazionali del Gran Sasso in Italy and the first ton-scale detector of this kind. The blinded search used 34.2 live days of data acquired between November 2016 and January 2017. Inside the (1042±12)-kg fiducial mass and in the [5,40]  keV_{nr} energy range of interest for weakly interacting massive particle (WIMP) dark matter searches, the electronic recoil background was (1.93±0.25)×10^{-4}  events/(kg×day×keV_{ee}), the lowest ever achieved in such a dark matter detector. A profile likelihood analysis shows that the data are consistent with the background-only hypothesis. We derive the most stringent exclusion limits on the spin-independent WIMP-nucleon interaction cross section for WIMP masses above 10  GeV/c^{2}, with a minimum of 7.7×10^{-47}  cm^{2} for 35-GeV/c^{2} WIMPs at 90% C.L.

Search for Electronic Recoil Event Rate Modulation with 4 Years of XENON100 Data

We report on a search for electronic recoil event rate modulation signatures in the XENON100 data accumulated over a period of 4 yr, from January 2010 to January 2014. A profile likelihood method, which incorporates the stability of the XENON100 detector and the known electronic recoil background model, is used to quantify the significance of periodicity in the time distribution of events. There is a weak modulation signature at a period of 431_{-14}^{+16} day in the low energy region of (2.0-5.8) keV in the single scatter event sample, with a global significance of 1.9σ; however, no other more significant modulation is observed. The significance of an annual modulation signature drops from 2.8σ, from a previous analysis of a subset of this data, to 1.8σ with all data combined. Single scatter events in the low energy region are thus used to exclude the DAMA/LIBRA annual modulation as being due to dark matter electron interactions via axial vector coupling at 5.7σ.

[The clinical importance of arthrography after lesions of the meniscus and capsular ligament (author's transl)]

Clinical, arthrographic and operative findings of 100 patients were compared and analyzed by a study group with the result, that in questionable lesions of the meniscus, the indication for a double contrast arthrography was markedly reduced when plain films of the knee, an exact case history and a physical examination of the knee joint were performed. Above all, the improved examination technique, with the knowledge of the functional anatomy of the capsular ligament apparatus and the correlation of all stabilizing forces of the knee joint had reduced clinical errors in diagnosis. Clinically clearly analyzed meniscus lesions are therefore no indication for arthrography. In our clinic the indicatin will be reduced to those cases where there are still complaints after meniscectomy. There is a great advantage, if the examinating physician, the radiologist and the orthopedic surgeon cooperate closely together.

Cervical artery dissection: improved diagnosis by B-Flow ultrasound

OBJECTIVE

The objective of this study was to evaluate the efficiency of B-Flow ultrasound in diagnosing supraaortic vessel dissections compared with other ultrasound techniques including B scan, Color-Coded Doppler (CCDS) and Power Doppler (PD).

MATERIALS AND METHODS

Eighty-eight patients with suspected arterial dissection of the neck vessels were included in this prospective trial. All patients were examined using B scan, Color-Coded Doppler sonography and Power Doppler. After documentation of the diagnoses, the patients were additionally examined by B-Flow ultrasound. Contrast-enhanced magnetic resonance angiography (MRA) was used as reference standard in all cases.

RESULTS

Dissections of the carotid artery (n=19) and of the vertebral artery (n=35) were found in 44 patients. B-Flow imaging identified 52 of 54 arterial dissections that were confirmed by MRA. There were no false-positive diagnoses in ultrasound examination. The sensitivity of ultrasound examination using B scan, CCDS and PD in detecting all dissections was 95.9% and 99.1% with additional B-Flow examination. Sensitivity using B-Flow increased from 98.3% to 100% for carotid dissections and from 93.3% to 94.3% for vertebral artery dissections. Due to the lack of overwriting artifacts, B-Flow imaging detected residual flow within the false lumen more precisely. The reduced effect of the ultrasound probe angle facilitated imaging of fissures, membranes and low flow phenomena and improved the identification of low-reflection wall structures. The cine mode of the B-Flow showed undulating membrane movement most clearly. Contrast-enhanced MRA in conjunction with axial T1 and T2 weighted sequences enabled the best visualization of intramural hematomas.

CONCLUSION

B-Flow imaging can significantly increase the sensitivity of ultrasound examination for dissections of the neck vessels. It also improves the visualization of flow within the true and false lumen, of hypoechoic thrombi and of intramural hematoma.

B-flow and B-flow with 3D and SRI postprocessing before intervention and monitoring after stenting of the internal carotid artery

OBJECTIVE

To investigate the extent to which B-flow and B-flow with 3D postprocessing and speckle reduction imaging (SRI) have advantages in appraising the morphology of a high-grade stenosis of the internal carotid artery (ICA) for preinterventional planning and for postinterventional ultrasonographic follow-up.

MATERIALS/METHODS

A comparative appraisal of flow with CCDS, power Doppler, B-flow and 3D B-Flow with SRI were carried out prospectively in 50 patients with >70% stenosis according to NASCET criteria in contrast medium-enhanced MRA before and after the intervention. After stenting of the internal carotid artery (ICA), i.a. digital substraction angiography (DSA) served as an additional reference method.

RESULTS

In >70% ICA stenosis, simultaneous imaging of the pre-stenotic, intra-stenotic and post-stenotic flow was attained with B-flow in 45/90 cases (90%), with power Doppler in 39/50 cases (78%) and with CCDS in only 31/50 cases (62%). After intervention, a complete detection of flow without overwriting or blooming artifacts was achieved in all 50 patients only by B-flow. The intrastenotic flow (p<0.05) could be better demarcated against the lumen and the vessel wall before the intervention, whereas the flow within the stent could be very much better appraised after the intervention (p<0.01) using 3D postprocessing of B-flow with additional SRI. Re-stenoses with hypoechoic vascular wall changes (3/50 patients) were detected at an early stage using B-flow.

CONCLUSIONS

B-flow technique with SRI and 3D postprocessing can facilitate the intrastenotic detection of flow in >70% ICA stenosis with fewer flow artifacts. After stenting, the perfused vascular lumen shows less flow artifacts compared with CCDS and power Doppler. In order to elucidate hemodynamic changes, additional Doppler examinations are still necessary.

Cost analysis in interventional radiology—A tool to optimize management costs

OBJECTIVE

The objective of the study was to analyze the methods to reduce cost in interventional radiology departments by reorganizing procurement.

MATERIALS AND METHODS

All products used in the Department of Interventional Radiology were inventoried. An ABC-analysis was completed and A-products (high-value and high turnover products) underwent a XYZ-analysis which predicted demand on the basis of ordering frequency. Then criteria for a procurement strategy for the different material categories were fixed. The net working capital (NWC) was calculated using an interest rate of 8%/year.

RESULTS

Total annual material turnover was 353,000 euro. The value of all A-products determined by the inventory was 260,000 euro. Changes in the A-product procurement strategy tapped a cost reduction potential of 14,500/year euro. The resulting total saving was 17,200 euro. Improved stores management added another 37,500 euro. The total cost cut of 52,000 euro is equivalent to 14.7% of annual expenses.

CONCLUSION

A flexible procurement strategy helps to reduce the storage and capital tie-up costs of A-products in interventional radiology without affecting the quality of service provided to patients.

Diagnostics and characterisation of preocclusive stenoses and occlusions of the internal carotid artery with B-flow

The purpose was to evaluate whether B-flow can improve the ultrasonographic diagnosis of preocclusive stenosis and occlusion of the internal carotid artery (ICA) compared with colour-coded Doppler and power Doppler. Ninety patients with occlusions or preocclusive stenoses of the ICA suspected by Doppler sonography were examined with B-flow in comparison with colour-coded Doppler sonography (CCDS), power Doppler (PD) and intra-arterial digital subtraction angiography (DSA). Intrastenotic flow detection and lengths of stenoses were the main criteria. Ulcerated plaques found by surgery in 42/90 patients were compared by ultrasonography (US). Diagnosis of ICA occlusion with CCDS, PD and B-flow was correct in all 42 cases. A preocclusive ICA stenosis in DSA was detected correctly in all 48/48 cases (100%) for B-flow, in 44/48 (92%) for PD and in 39/48 (81%) for CCDS. Surgical findings showed in 17/42 cases ulcerated plaques; 15/17 (89%) of these cases were detected with B-flow, 12/17 (71%) with PD, 10/17 (59%) with CCDS, and 8/17 (47%) with DSA. With B-flow the extent of stenosis was appraised more precisely than with PD and CCDS (P<0.0001). In conclusion, B-flow is a reliable method for preocclusive stenosis of the ICA with less intrastenotic flow artefacts. B-flow facilitates the characterization of plaque morphologies.

Improved diagnosis of vascular dissection by ultrasound B-flow: a comparison with color-coded Doppler and power Doppler sonography

The purpose was to evaluate the diagnostic results of different ultrasound techniques: color-coded Doppler (CCD), power Doppler (PD) and B-flow in the diagnosis of vascular dissection. Findings from 68 patients with arterial dissection proven either by vascular ultrasound (US) or by magnetic resonance angiography (MRA), computed tomographic angiography (CTA) or intra-arterial digital subtraction angiography (DSA) were reviewed in retrospect. The study compared results from three different modes of ultrasound, i.e., CCD, PD and B-flow, in dissections of the carotid artery (n=11), of the vertebral artery (n=9), of the abdominal aorta (n=13), of the iliac artery (n=12) and of the femoral artery (n=23). MRA, CTA and DSA were considered as reference standard. The sensitivity of CCD for detecting all dissections was 78%, 84% for the PD and 98% for B-flow. For carotid artery dissection, the sensitivity of CCD, PD and B-flow was 82, 91 and 98%, for the vertebral artery 67, 78 and 98%, for the abdominal aorta 85, 85 and 98%, for the iliac artery 67, 75 and 98%, for the femoral artery 83, 87 and 98%, respectively. Intima flaps, fissures of membranes and residual flow within the true and false lumen were better detected by B-flow than by CCD and PD. The lack of angle dependence of the US probe in B-flow made the examination procedure easier. In the cine mode of B-flow, the pulse synchronic movement of the membrane was more apparent than in any other imaging method. With B-flow, accuracy for the diagnosis of arterial dissection is improved compared to CCD and PD. Flow within the true and false lumen, low-echo thrombi, intramural hematoma and even movements of the dissection membrane are clearly distinguished.

Tissue Harmonic Imaging (THI) und Contrast Harmonic Imaging (CHI) zur sonographisch gezielten Vakuumstanzbiopsie mammographisch okkulter Brusttumoren

PURPOSE

To assess the guidance of tissue harmonic imaging (THI) and contrast harmonic imaging (CHI) for vacuum assisted biopsies of suspicious breast lesions compared to fundamental B-mode ultrasound-guided biopsies.

MATERIAL AND METHODS

In 550 patients, ultrasound examinations of the breast were performed prospectively using fundamental B-scan, THI, and CHI. Focal lesions were documented in comparable projections for all three ultrasound modes. As contrast agent, a dose of 0.5 milliliters of Perflutren Protein-Type A microspheres ( Optison) was injected. An ultrasound-guided biopsy was performed in 38 focal lesions. Three radiologists experienced in breast imaging retrospectively assessed the lesions on the ultrasound images.

RESULTS

Thirty-eight suspicious focal lesions [size 4 - 15 mm; median 8 mm] were detected by ultrasound. Of these, 29 were detected by fundamental B-scan images, 34 by THI, and 38 by CHI. Ultrasound-guided biopsy was performed on all of these lesions. No complications related to the biopsy were observed. In 25/38 cases, invasive carcinomas were found; in 6/38 ductal carcinomas in situ; in 3 cases metastases of already known invasive ductal carcinomas; and in 4 cases fibroadenomas. The size of the lesion was best identified using THI, smaller lesions (< 10 mm) using CHI.

CONCLUSION

THI and CHI can help to detect focal lesions in dense breasts. Both modes can make it easier to perform ultrasound-guided biopsies of focal breast lesions.

Materialverwaltung in der interventionellen Radiologie - erste Erfahrungen mit einem computergestützten Programm

PURPOSE

To perform a cost analysis for assessing options of reorganizing material supplies and reducing costs of the radiology division through the introduction of a materials management system.

MATERIALS AND METHODS

A materials management system (Piranha, Boston Scientific) was installed on an existing computer system. All consumables were inventoried and entered into the system. An ABC analysis determined further action. On the basis of order frequencies and availability requirements for emergencies, safety levels were agreed with physicians and other medical staff. Inventory costs were computed using these data. The interest rate for the capital tied up in the inventory was 8 % per year.

RESULTS

The inventory showed that the capital tied up in stocks was euro 260,000 in 2001 and euro 190,000 in 2002. A change in supply strategy reduced inventory cost in 2001 and 2002. Annual interest expense was lowered by euro 18,420. Another saving of euro 2,700 was achieved by a reduction in storage cost. Annual inventory turnover totaled euro 298,000. The total cost cut through improved inventory management was euro 21,120 per year, which is equivalent to 7 % of the annual expenses. Adding the decline in the cost of shelf time overruns equal to 5 % of the annual expenses, the saving was approximately 12 % of total interventional radiology cost in 2001 and some 11 % in 2002.

CONCLUSION

Flexible supply strategies and the introduction of a materials management program can help to reduce inventory costs in interventional radiology divisions without any impact on service levels.

[Contrast-enhanced ultrasound with Optison in percutaneous thermoablation of liver tumors]

PURPOSE

To detect vascularization of liver tumors by ultrasound enhanced with Optison and to determine whether increasing necrosis during a percutaneous thermal ablation can be visualized by this method.

MATERIALS AND METHODS

Twenty-two patients with non-resectable malignant liver tumors (9 patients with HCC, 13 patients with metastases) and a total number of 34 lesions underwent percutaneous radiofrequency thermoablation using a needle applicator perfused with a 0.9 % NaCl solution (Electrotome HiTT 106, Berchtold). The tumor size ranged from 2 to 8 cm with an average size of 3.6 cm. While intermittent energy was supplied during thermoablation, multi-slice CT (Volume-Zoom, Siemens) and ultrasound were obtained. Ultrasound was performed with a multi-frequency transducer (3 - 7 MHz, LOGIQ 700, GE) and 0.5 to 1 ml of Optison as contrast agent. If necessary, the injection of the contrast agent was repeated after about 30 min. The mechanical index (MI) was set low (0.2 - 0.3) to prevent bubble destruction. Ultrasound power Doppler (PD), contrast harmonic imaging (CHI) and coded harmonic angiography (CHA) as subtraction mode of harmonic imaging were applied intermittently.

RESULTS

Only 21 of the 34 lesions showed increased intratumoral perfusion when the conventional B-Mode with PD was used. Similar to spiral CT, the tumor vascularization in the early arterial phase was only reliably visible with CHA after application of contrast agent. CHI with PD was best to detect increasing hypoperfusion of the tumors. When the energy supply was continued, hyperechoic border zones became visible around the central hypoechoic defects. The contrast between remaining tumor and surrounding liver tissue improved in CHI for up to 30 min after the bolus injection of contrast medium, considerably facilitating the evaluation of perfusion. Metal artifacts and the limited amount of contrast agent that can be safely administered interfered with monitoring the thermal ablation with spiral-CT. After an administered energy of maximal 100.000 watts, no more tumor vascularization was seen in 28 of 34 cases. Follow-up spiral-CT showed a complete necrosis in these cases.

CONCLUSION

Evaluating perfusion with contrast-enhanced ultrasound may be helpful in monitoring the evolving necrosis during thermoablation of liver tumors. The more reliable assessment of the tumor necrosis enables a more targeted therapy.

[B-flow and color-coded B-flow in sonographic diagnosis of filiform stenosis of the internal carotid artery]

PURPOSE

To evaluate B-flow ultrasound in filiform (> 90 %) stenosis or occlusion of the internal carotid artery (ICA) and to compare it with other imaging modalities.

METHODS AND MATERIALS

Fifty patients with suspected occlusion or filiform stenosis of the internal carotid artery (ICA) on Doppler ultrasound were examined using B-flow ultrasound in either color-coded or brightness mode. The pre-, intra- and poststenotic flow phenomena were compared with color-coded duplex (CCD) and power Doppler (PD) ultrasound. A contrast agent (Optison) was injected in 15 cases. The results were compared with those of selective intraarterial DSA and in 15 cases also with those of MR-angiography (MRA). Twenty-two patients came to surgical intervention.

RESULTS

Diagnosis of ICA occlusion was correct in all 22 cases using CCD, PD and B-flow ultrasound. A filiform ICA-stenosis was correctly seen in all 28 cases when using brightness-modulated or color-coded B-flow or contrast-enhanced power Doppler, but only in 15 cases when using CCD. All 9 ulcerated plaques with appositional thrombi were detected with B-flow, but only 4 cases with CCD. Pre-, intra- and poststenotic flow phenomena in the longitudinal scan were demonstrated simultaneously using color-coded B-flow in 27 out of 28 cases, but only in 17 cases using CCD and in 22 cases using PD. In the 15 cases given contrast agent, B-flow showed no superimposed vessel walls (reverberation artefacts) in the intra- and poststenotic area. In the longitudinal scan, true extend and degree of the distal stenosis of ICA carotid artery stenosis were more precisely measured with B-flow than with PD and CCD.

CONCLUSIONS

The ultrasound diagnosis of filiform stenosis of the ICA is more reliable with B-flow ultrasound than with other ultrasound modalities. B-flow ultrasound has flow phenomena that are less angle-dependent and that are better demarcated against the vessel walls. It is free of superimposed vessel walls and offers better simultaneous intra- and poststenotic flow detection. The improved delineation of the plaque morphology by B-flow ultrasound enables a better evaluation of ulcerations and possible thrombi.

[Improved evaluation of stenoses of hemodialysis fistulas by B-flow ultrasound]

PURPOSE

To evaluate the new technique of B-flow ultrasound in assessing stenoses of hemodialysis fistulas.

MATERIALS AND METHODS

50 patients (mean age 58 years) with Brescia-Cimino-Shunts (27 shunts of the radial and 23 of the cubital artery) were prospectively assessed with intraarterial DSA and vascular ultrasound by independent examiners. Eligibility for the study was a shunt-volume of less than 400 ml/min and an angiographically suspected hemodynamically significant stenosis of the anastomosis or of shunt veins. Sonography was performed with a multifrequency ultrasound probe (5 to 10 MHz, Logic 700, GE) using B-mode, color coded Doppler sonography (CCDS) and B-flow technique.

RESULTS

Anastomotic stenosis and stenosis of the shunt veins were equally distributed, found in 25 patients each. The measurements of the residual lumen of the 25 anastomotic stenoses were 1.47 to 3.43 mm (average: 2.3 mm) for intraarterial DSA, 1.57 to 3.73 mm (average: 2.6 mm) for B-mode ultrasound, 1.97 to 4.17 mm (average: 2.9 mm) for CCDS, 1.43 to 3.47 mm (average: 2.3 mm) for B-flow technique in the brightness mode and 1.6 to 3.47 mm (average: 2.4 mm) for B-flow technique in the B-mode. The brightness mode of the B-flow correlated best with intraarterial DSA (r=0.994), with a significantly lower correlation between CCDS and intraarterial DSA. B-flow displays less vascular distortion within the stenosis and fewer flow artifacts. Even in angulated stenoses, the detected intra- and poststenotic flow was markedly less angle-dependent in comparison with CCDS. B-flow clearly facilitates the visualization of hypoechoic plaques and intima proliferation. Furthermore, eccentric cicatricial stenoses, intima flaps or hypoechoic thrombi, which were not seen with DSA or B-mode, showed improved visualization in comparison with CCDS.

CONCLUSION

Ultrasound B-flow makes it easier to assess the morphology and the local degree of stenotic hemodialysis fistulas. Flow detection is achieved with fewer artifacts and reduced angle dependence. This opens the way for better planning of interventional therapy.

[Examination of the constancy of the medium optical density of conventional chest radiographs]

PURPOSE

To determine whether the medium optical density of conventional chest radiographs is constant.

MATERIALS AND METHODS

47 PA chest radiographs were digitized to measure the optical density and its dynamic range of normal and pathologically altered lungs.

RESULTS

For constant exposure factors and a correctly positioned region of interest, the medium optical density deviates only minimal despite differences in AP chest diameter, entry dose and dynamic range, and is largely independent of the pathologic pulmonary findings.

CONCLUSION

Digitization of the radiograph enables the determination of the physical parameters used to operate the imaging system, such as medium optical density, image contrast, image latitude and density distribution, in accordance to the guidelines of the German Medical Association. If the region of interest encompasses the clinically relevant region of the lung, the measured value of the optical density corresponds with only minor variation to the average value of the entire lung region.

[Preoperative wire localisation of breast lesions by tissue harmonic imaging (THI) sonography]

PURPOSE

To obtain a fast and reliable preoperative wire localisation of occult lesions in dense breast tissue by tissue harmonic imaging (THI) sonography when localisation by mammography is not reliable enough.

MATERIAL AND METHODS

In addition to biplane mammography for breast screening or for follow-up examination after breast-saving therapy, ultrasound was performed by two independent radiologists in 350 patients with mastopathic or fibrotic breast tissue. Using a multifrequency probe (5 - 10 MHz), lesions were documented by conventional B-mode and by THI in similar projections. In 25 lesions not precisely identified in mammography sonographically guided puncture with wire localisation was performed.

RESULTS

In 22 of 350 patients 25 circumscribed suspicious lesions with an average diameter of 8 mm were identified, regarded suspicious by ultrasound but not by mammography. Nineteen of 25 lesions found by M-Mode and THI, an additional 6 only by THI. Guided puncture and wire localisation was achieved in 10 minutes on the average. In B-mode, the course of needle and wire was reliably seen in 16 of 25 cases, in THI in all cases. After surgical removal of tissue, histopathology revealed a ductal or lobular carcinoma in 19 cases, metastasis in three cases and benign complicated cysts with fibrotic tissue in the remaining three cases.

CONCLUSION

THI is superior to B-mode ultrasound in differentiating suspicious lesions in dense glandular breast tissue. If tumor signs in mammography are not reliable enough or if a precise localisation is not possible, sonographically guided puncture by THI can give reliable results and, furthermore, is faster and more comfortable for the patient than localisation by mammography.

[B-flow and contrast medium-enhanced power Doppler (Optison(R))--preoperative diagnosis of high-grade stenosis of the internal carotid artery]

PURPOSE

To improve sonographic diagnosis of high-grade stenosis of the internal carotid artery (ICA) by vascular sonography in "B-flow"-mode and in contrast medium (Optison(R))-enhanced power Doppler (PD).

MATERIAL AND METHODS

88 patients suspected of a high-grade stenosis of the extracranial ICA were examined by independent examiners with color-coded Doppler (CCD), B-flow and PD to compare the methods for morphology and degree of stenosis. In 21 cases contrast medium was used in PD. Sonographic results of all 88 patients were compared with selective angiography (DSA), in 53 cases with operative findings.

RESULTS

A complete occlusion was found in 9 patients and a 50 - 70 % degree non-exulcerated stenosis in 26 cases. 53 of 88 patients presented findings in both sonography and DSA leading to operation of the ICA. Among these 47 had a stenosis > 70 % and 6 a stenosis of 60 - 70 % with exulcerated plaques. Even a small dose of contrast medium (0.3 ml) gave a significant signal increase in PD improving flow detection even in extensive vascular calcification. In both the early phase (up to the first minute p. i.) flow contrast was optimal and without significant artifacts. Thus, the extent and the morphology of the stenosis was better appreciated. Hypoechogenic plaques, ulcerations and thrombi are as easily recognized by B-flow as flow in preocclusive stenosis, free of vibration and blooming artifacts. This gave a better correlation with DSA and a higher diagnostic accuracy in grading a stenosis than CCD and PD. Circular calcifications or vessel kinking made diagnosis of flow more difficult.

CONCLUSION

B-flow allows a reliable diagnosis of the degree of stenosis of ICA and a better appreciation of plaque morphology than CCD. In some cases with extensive calcifications contrast medium-enhanced PD is able to detect better intrastenotic flow. Only small quantities of contrast medium (Optison(R)) are required.

[B-Flow: sonographic assessment and therapy for femoral artery pseudoaneurysm]

PURPOSE

To evaluate the diagnostic accuracy of femoral artery pseudoaneurysm by B-flow, a new ultrasound method and the outcome of compression treatment.

MATERIAL AND METHODS

700 patients with radiological interventions (300 DSA, 355 PTA, 45 thrombolysis) have been examined by vascular ultrasound for possible bleeding at the puncture site to rule out pseudoaneurysms. The new B-flow ultrasound with a multi-frequency probe was used besides color-coded Doppler (CCD) and power Doppler (PD).

RESULTS

No pseudoaneurysm was found in patients with diagnostic angiography and thrombolysis. In 25 of 355 patients a pseudoaneurysm was detected after PTA in 8 of them in the common and in 17 in the superficial femoral artery. The diameters were 1.5 to 4.5 cm, 3 cm on average. By ultrasound compression treatment of 20 minutes on the average 23 out of 25 pseudoaneurysms were occluded without any further complication. In B-flow the lesion of the vessel wall, the flow in the fistula and in the sack of the pseudoaneurysm were better demonstrated and without artifacts compared to both other methods. This makes treatment by compression much easier, first of all because remaining flow phenomena and the progression of intracavitary thrombosis can be controlled.

CONCLUSION

The newly developed B-flow detects both slow and fast flow phenomena. Visualisation of the fistula canal and the aneurysm sack is more reliable and examiner-independent than other Doppler methods such as CCD and PD. This allows better compression treatment of the fistula canal.

[Low-dose thrombolysis using rt-Pa in extensive peripheral vascular occlusion]

PURPOSE

To evaluate the efficacy of intra-arterial thrombolysis by rt-PA in acute and subacute extensive peripheral vascular occlusion.

MATERIAL AND METHODS

100 patients with acute and subacute occlusion of peripheral arteries were treated by catheter thrombolysis using 20 mg of rt-PA over a period of 20-24 hours. In all cases the occlusion extended to more than 20 cm and two stages of the extremity were involved. In 80 patients the original vessels (69/80 by thrombosis, 11/80 by embolization) and in 20 cases the femoro-popliteal bypass vessel was occluded. A catheter was inserted into the thrombus into which rt-PA and heparin were separately infused by two injectors. Heparin was given in a dose of 800-1000 U/h depending on the continuously monitored PTT levels. A control angiography was performed after 10 mg of rt-PA. After successful thrombolysis either PTA or aspiration thrombectomy was performed, if necessary, to reestablish a nearly normal vascular lumen. Open arteries of the thigh and at least one main vessel of lower leg was considered as success.

RESULTS

Recanalization of the original vessels was successfully by thrombolysis, PTA or aspiration thrombectomy in 68/80 [85%] cases. Thrombolysis and PTA reestablished a normal lumen of the bypass vessel in 11/20 [65%] and in 6 more cases a recanalization with minor stenosis. In 13/15 patients with critical ischemia, thrombolysis probably helped to avoid amputation by reopening smaller collateral arteries. Bleeding at the puncture site, as a complication of thrombolysis, was the reason for stopping therapy in three cases. There was no retroperitoneal or cerebral bleeding. After successful thrombolysis, reocclusion occurred in 15 patients within one year, only in five cases amputation was necessary.

CONCLUSION

Extensive occlusion of peripheral arteries or of a femoro-cural bypass can be successfully treated by low dose rt-PA thrombolysis with a low complication rate. Even partial reopening may prevent amputation.

[Diagnosis of pre-occlusive stenosis of the internal carotid artery by power mode ultrasound]

PURPOSE

To evaluate the accuracy of power mode (PM) vascular ultrasound in preocclusive (> 90%) stenosis of the extracranial internal carotid artery (ICA) compared to other diagnostic methods and to operative findings.

MATERIAL AND METHODS

50 patients with preocclusive stenosis have been examined in a prospective study by power mode and color flow duplex ultrasound, by triplane aortic arch and four plane selective DSA. In 11 cases a MR angiography (time-of-flight) was available. Diagnostic findings were compared to operative results.

RESULTS

There was an agreement in findings in 50/50 patients (100%) for selective DSA, in 47/50 (94%) for power mode ultrasound, in 38/50 (76%) for aortic arch DSA, in 31/50 (62%) for color flow duplex ultrasound, and in 5/11 for MR angiography. In contrast to all other methods, ultrasound showed best the true extent of non-calcified atheromatous plaques. In extended vascular calcifications or kinking, however, only parts of the lumen of the vessel could be demonstrated.

CONCLUSION

Power mode ultrasound shows preocclusive stenosis of the ICA in a faster and more simple way than color flow duplex ultrasound and has diagnostic results near to those of selective DSA. It improves preoperative diagnostic screening.