Renal Sympathetic Denervation by Image-Guided Percutaneous Ethanol Injection - Histopathologic Characteristics, Efficacy and Safety.

PURPOSE: Evaluation of the efficacy and safety of chemical renal denervation by image-guided periarterial ethanol injection in pigs with emphasis on histopathological characteristics. MATERIALS AND METHODS: Unilateral renal periarterial ethanol injection under general anesthesia was performed in 16 animals with the contralateral kidney serving as the control. All interventions were performed in an open MRI system under real-time multiplanar guidance. In 10 pigs an ethanol-carbostesin contrast agent mixture was injected with amounts of 5 ml (6 animals, group I) and 10 ml (4 animals, group II). 6 pigs (group III) were treated with 10 ml of an ethanol-polyacrylic (2 %) mixture. Four weeks after treatment, all animals underwent MRI including MRA. After euthanasia, macroscopic and histologic examination of the kidneys, renal arteries and periarterial tissue was performed to assess nerve injury and potential side effects. Furthermore, the norepinephrine concentration (RTNEC) in the renal tissue was determined as a surrogate parameter of efficacy. RESULTS: Histologic signs of nerval degeneration with various degrees of severity and circumferential distribution were found in all groups. Injury depths ranged up to 7.6 mm. In groups II and III the nerve count was significantly lower on the treated side. Renal artery stenosis was not observed in any pig. In all pigs of group II treatment resulted in neural degeneration with a mean RTNEC reduction of 53 % (p < 0.02). In groups I and III significant changes in RTNEC were not observed. CONCLUSION: Image-guided percutaneous periarterial ethanol injection was efficient and safe for renal denervation. The detected variations in histologic outcome underlined the importance of the preclinical optimization of the technique in order to maximize treatment effects in humans. KEY POINTS: · Renal denervation by percutaneous periarterial ethanol injection is an effective and potentially safe procedure.. · The percutaneous approach is less prone to anatomical and procedural limitations compared to catheter-based procedures.. · The achievable nerve injury depth lies beyond those of current RFA-probes.. · Efficacy depends on amount, concentration, viscosity and periarterial distribution of the ethanol-mixture.. · Establishing an optimal balance between these parameters is mandatory for a maximum treatment effect at minimum risk for sensitive adjacent structures.. CITATION FORMAT: · Freyhardt P, Haage P, Walter A et al. Renal Sympathetic Denervation by Image-Guided Percutaneous Ethanol Injection - Histopathologic Characteristics, Efficacy and Safety. Fortschr Röntgenstr 2020; 192: 549 - 560.

Radiological journals in the online world: should we think Open? A response.

This discussion on developments within publishing presents further thought on green, gold and hybrid models of open access. It also discusses some of the advantages and disadvantages which may be encountered by researchers, authors, institutions, scientific organisations and publishers.

Dual-source CT assessment of ventricular function in healthy and infarcted myocardium: an animal study.

PURPOSE: To assess global and regional ventricular function in the presence of myocardial infarction (MI) using cardiac dual-source computed tomography (DSCT) in comparison to magnetic resonance (MR) imaging. MATERIALS AND METHODS: Fourteen pigs (58.6 ± 8.9 kg) were included in this study. In seven animals acute MI was induced by temporary balloon occlusion of the left circumflex artery. Thereafter, DSCT and MR imaging were performed with standardized examination protocols. Left (LV) and right ventricular (RV) volumes, ejection fraction (EF), peak filling rate (PFR), and peak ejection rate (PER) as well as LV myocardial mass were calculated. LV wall motion was visually assessed from cine loops. Data was analyzed using Bland-Altman plots, Lin's concordance-correlation coefficient (ρ(c)) and weighted kappa statistics. RESULTS: Ventricular volumes and mass as determined by DSCT correlated well with MR imaging. Mean LV-EF was 49.4 ± 16.5% on DSCT and 50.0 ± 16.1% on MR imaging (ρ(c) = 0.9928). The corresponding mean RV-EF results were 45.9 ± 10.6% and 45.8 ± 10.6% (ρ(c) = 0.9969), respectively. Bland-Altman plots revealed no systematic errors, but PER and PFR showed a relevant scattering. Regional wall motion scores agreed in 216/224 myocardial segments (κ = 0.925). CONCLUSION: DSCT permits the reliable assessment of global and regional function in healthy and infarcted myocardium, but is not yet suited for the assessment of dynamic functional parameters like PER and PFR.

Evaluation of an active vena cava filter for MR imaging in a swine model.

PURPOSE: To evaluate the feasibility of magnetic resonance (MR) imaging-guided placement of an active vena cava filter (AVCF) in a swine model, the effectiveness of the system in filtering thrombi, and the detection of thrombi with MR imaging. MATERIALS AND METHODS: This study was approved by the government committee on animal investigations. An AVCF tuned to the Larmor frequency of a 1.5-T MR unit was placed in the inferior vena cava (IVC) of seven pigs under real-time MR imaging guidance. Steady-state free precession sequences with four different flip angles (90°, 40°, 25°, and 15°), T1-weighted turbo spin-echo sequences with two flip angles (90° and 15°), and black-blood proton-density-weighted sequences with a flip angle of 90° were performed before and after filter placement. In six cases, extracorporeally produced thrombi were injected through the femoral access to test filter function. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were assessed before and after filter deployment and compared by using the signed-rank test. RESULTS: All AVCFs were successfully deployed. Significant differences (P < .05) in the SNR and CNR of the IVC were found before and after AVCF placement and between sequences with different flip angles. Intravenous thrombi were caught in all cases and clearly depicted with MR imaging. On black-blood proton-density-weighted images, high-signal-intensity thrombi inside the filter were clearly detectable without any overlaying artifacts. CONCLUSION: MR imaging-guided deployment and monitoring of an AVCF is feasible. The AVCF enhances the SNR and CNR, resulting in clear depiction of thrombi inside the filter without the need for contrast material. Design modifications for improved intracaval fixation and retrieval of the prototype AVCF will be required.

Assessment of myocardial edema by computed tomography in myocardial infarction.

OBJECTIVES: The aim of this study was to analyze whether cardiac computed tomography (CT) permits the assessment of myocardial edema in acute myocardial infarction (MI). BACKGROUND: Several studies proved the value of detecting myocardial edema from T2-weighted cardiac magnetic resonance (CMR) for differentiating acute from chronic MI. Computed tomography is suited for depicting MI, but there are no data on CT imaging of myocardial edema. We hypothesized that areas of reduced attenuation in acute MI may correspond to edema. METHODS: In 7 pigs (55.2 +/- 7.3 kg), acute MI was induced using a closed chest model. Animals underwent unenhanced arterial and late-phase dual source computed tomography (DSCT) followed by T2-weighted and delayed contrast-enhanced CMR. Animals were sacrificed, and the excised hearts were stained with 2,3,5-triphenyltetrazolin chloride (TTC). Size of MI, contrast-to-noise ratio, and percent signal difference were compared among the different imaging techniques with concordance-correlation coefficients (rho(c)), Bland-Altman plots, and analysis of variance for repeated measures. RESULTS: Infarction was transmural on all slices. On unenhanced, arterial, and late-phase DSCT, mean sizes of MI were 27.2 +/- 8.5%, 20.1 +/- 6.9%, and 23.1 +/- 8.2%, respectively. Corresponding values on T2-weighted and delayed enhanced CMR were 28.5 +/- 7.8% and 22.2 +/- 7.7%. Size of MI on TTC staining was 22.6 +/- 7.8%. Best agreement was observed when comparing late-phase CT (rho(c) = 0.9356) and delayed enhanced CMR (rho(c) = 0.9248) with TTC staining. There was substantial agreement between unenhanced DSCT and T2-weighted CMR (rho(c) = 0.8629). Unenhanced DSCT presented with the lowest percent signal difference (46.0 +/- 18.3) and the lowest contrast-to-noise ratio (4.7 +/- 2.0) between infarcted and healthy myocardium. CONCLUSIONS: Unenhanced DSCT permits the detection of myocardial edema in large acute MI. Further studies including smaller MI in different coronary artery territories and techniques for improving the contrast-to-noise ratio are needed.

Time-resolved 3D MR angiography of the foot at 3 T in patients with peripheral arterial disease.

OBJECTIVE: The objective of our study was to prove the feasibility and clinical relevance of fast contrast-enhanced time-resolved 3D MR angiography (MRA) with submillimeter spatial resolution at a high magnetic field strength. SUBJECTS AND METHODS: Twenty-one patients (five women, 16 men; mean age +/- SD, 65 +/- 14 years) were examined on a 3-T whole-body MR system with an 8-element phasedarray coil for preoperative evaluation of the pedal arterial system and assessment of the visualized vessels to serve as a graft touch-down site in pedal bypass surgery. Time-resolved 3D MRA of the foot was performed after automatic injection of 0.2 mmol/kg of gadobenate dimeglumine using a sagittal gradient-echo T1-weighted sequence (TR/TE, 4.2/1.6; flip angle, 30 degrees ; field of view, 290 mm; matrix, 352; 120 slices; slice thickness, 0.8 mm) with a spatial resolution of 0.8 x 0.8 x 1.6 mm reconstructed to 0.6 x 0.6 x 0.8 mm and a temporal resolution of 3.9 seconds using keyhole and sensitivity-encoding (SENSE) technology (SENSE factors: 4 in anteroposterior direction and 2 in right-left direction). Dynamic subtractions and rotating maximum intensity projections were calculated. The original image data sets were transferred to a dedicated workstation for objective signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) analysis of the arteries. Subjective image analysis regarding image quality and diagnostic findings was performed by two radiologists in consensus. RESULTS: In all patients, images of diagnostic quality were obtained. Despite the known limitations regarding signal intensity measurements in images acquired with the use of parallel imaging technique, SNR and CNR proved to be excellent, with mean +/- SD values of 294 +/- 158 and 248 +/- 144, respectively. Although most of the patients had diabetic foot syndrome with arteriovenous shunting, the arteries and the potential vessel for bypassing could be clearly separated from the veins in each case due to the temporal information given by our study. The ability to reliably discriminate arteries from veins is of high clinical relevance in planning pedal bypass surgery. CONCLUSION: Fast contrast-enhanced time-resolved 3D MRA of the foot at 3 T is feasible and of high clinical value for the preoperative evaluation of the arterial supply of the foot.

Dual-source computed tomography for assessing cardiac function: a phantom study.

PURPOSE: To investigate the influence of heart rate and temporal resolution on the assessment of global ventricular function with dual-source computed tomography (DSCT). MATERIALS AND METHODS: A dynamic cardiac phantom was repeatedly scanned with a DSCT scanner applying a standardized scan protocol at different heart rates, ranging from 40 to 140 bpm. Images were reconstructed with monosegmental and bisegmental algorithms using data from a single source and from both sources. Ventricular volumes and ejection fraction (EF) were computed by semiautomated analysis. Results were compared with the phantom's real volumes. Interscan, intraobserver, and interobserver variability were calculated. RESULTS: For single-source data reconstruction temporal resolution was fixed to 165 milliseconds, whereas dual-source image reconstructions resulted in a temporal resolution of 83 milliseconds (monosegmental) and 67.7+/-14.2 milliseconds (bisegmental), respectively. In general, deviation from the phantom's real volumes was less with dual-source data reconstruction when compared with single-source data reconstruction. Comparing dual-source data reconstruction with single-source data reconstruction, the percent deviation from the phantom's real volumes for EF was 0.7% (monosegmental), 0.7% (bisegmental), and 4.3% (single source), respectively. There was no correlation between heart rate and EF for dual-source data reconstruction (r=-0.168; r=-0.157), whereas a relevant correlation was observed for single-source data reconstruction (r=-0.844). Interscan, intraobserver, and interobserver variability for EF were 1.4%, 0.9%, and 0.3%, respectively. CONCLUSIONS: DSCT allows reliable quantification of global ventricular function independent of the heart rate. Multisegmental image reconstruction is not needed for DSCT assessment of global ventricular function.

Evaluation of catheter loops in central venous port systems.

OBJECTIVES: We sought to evaluate the cause for catheter loops of central venous ports. MATERIAL AND METHODS: A total of 241 patients who received a central venous port via subclavian vein access were included in this retrospective study. Eighty of these patients had undergone a computed tomography of the chest, allowing retrospective evaluation of the course of central venous catheters. Complications were evaluated by review of the clinical data charts. RESULTS: In 49 patients, the catheter penetrated only the major pectoralis muscle. Only one of these patients (2.0%) showed a loop. In 31 cases, the catheter went through both the major and minor pectoralis muscle, and in 26 of these patients (83.9%), a loop was seen. Complications after port implantation were catheter occlusion (n = 2), pneumothorax (n = 2), thrombosis (n = 2), infection (n = 1), and catheter dislocation (n = 1). CONCLUSIONS: The loop of catheter of central venous ports is caused by catheter penetration through pectoralis major and minor.

In vivo safe catheter visualization and slice tracking using an optically detunable resonant marker.

The purpose of this study was to test the in vivo feasibility of safe automatic catheter tracking based on an optically detunable resonant marker installed on the catheter tip, and also to test the compatibility of this approach with guidewire materials. The design of the resonant marker and the integration into the real-time MR environment is described. The catheter was used for real-time MR-guided catheterization of the aorta, left ventricle, and carotid in two swine. For in-plane visualization, the marker was repeatedly detuned. For automatic slice tracking, a projection difference measurement including detuning was interleaved with the imaging sequence. In vitro experiments were conducted to investigate the RF-safety of the marker and the effect of the guidewires on the signal intensity. For all orientations the marker provided excellent in vivo contrast using a radial steady-state free-precession sequence. Flashing of the marker by repetitive tuning/detuning further improved the in-plane visualization. Automatic slice tracking during real-time imaging was successfully performed. The plastic guidewires did not interfere with the marker, and detuning by guidewires containing nitinol could be compensated. In conclusion, automatic slice tracking as well as excellent in-plane visualization can be achieved with this approach and it is safe with respect to RF transmission.

Phase-inversion tissue harmonic imaging compared with conventional B-mode ultrasound in the evaluation of pancreatic lesions.

The aim of this study was to compare the diagnostic sensitivity, specificity, and image quality of conventional B-mode US (BM) and phase-inversion tissue harmonic imaging (PTHI) regarding pancreatic pathology. In a prospective study, 107 patients, aged between 28 and 85 years, underwent US examinations of the pancreas with both BM and PTHI in a randomly chosen order. As diagnostic reference, either contrast-enhanced CT or MRI examinations of the upper abdomen were obtained in all patients. Sensitivity and specificity were evaluated using the Student's t test. Differences in overall image quality, lesion conspicuity, fluid-solid differentiation, and delineation of the pancreatic tail were analyzed using Wilcoxon's signed ranks test and Bowker's symmetry test. Sixteen of 107 examined patients (15%) were non-diagnostic and excluded due to technical limitations such as abdominal gas. A total of 60 pancreatic lesions (cysts, acute pancreatitis, dilatation of the pancreatic duct, calcifications, and solid tumors) were diagnosed by CT or MRI. Phase-inversion tissue harmonic imaging had a higher sensitivity of 70% (14 of 20) than BM (60%; 24 of 40) for the detection of pancreatic lesions; however, the difference was not statistically significant ( p=0.46). In the assessment of lesions <1 cm of size, PTHI had a sensitivity of 70% and BM 46.7%, whereby the difference again was not statistically significant. Phase-inversion tissue harmonic imaging proved to be superior to BM regarding overall image quality ( p<0.0001), lesion conspicuity ( p=0.0045), and fluid-solid differentiation ( p=0.0002), as well as the delineation of the pancreatic tail ( p<0.0001). These differences were statistically significant. The statistically significant improvement of image quality with regards to lesion conspicuity, fluid-solid differentiation, and delineation of the pancreatic tail favors the use of PTHI when evaluating the pancreas with US. Sensitivity for pancreatic lesions is increased with PTHI in comparison with conventional sonography (BM), especially in lesions <1 cm in diameter, although the difference was not statistically significant.

Respiratory motion artifact suppression in diffusion-weighted MR imaging of the spine.

Diffusion-weighted spin-echo imaging of the spine has been successfully implemented for differentiation of benign fracture edema and tumor infiltration of the vertebral body. Nevertheless, this technique still suffers from insufficient image quality in numerous patients due to motion artifacts. The aim of this study was to investigate the impact of variable respiratory motion artifact suppression techniques on image quality in diffusion-weighted spin-echo imaging of the spine. In addition to phase-encoding reordering, a newly implemented right hemi-diaphragmaitc navigator for respiratory gating was used. Subjective and objective image quality parameters were compared. Respiratory motion artifact suppression has a major impact on image quality in diffusion-weighted imaging of the spine. Phase-encoding reordering does not enhance image quality while right hemi-diaphragmatic respiratory navigator gating significantly improves image quality at the cost of data acquisition time. Navigator gating should be used if standard spin-echo diffusion-weighted imaging demonstrates insufficient image quality.

Simultaneous real-time visualization of the catheter tip and vascular anatomy for MR-guided PTA of iliac arteries in an animal model.

PURPOSE: To examine the feasibility of simultaneous MR real-time active tip tracking and near real-time depiction of the vascular anatomy for percutaneous angioplasty of iliac arteries under MR guidance. MATERIALS AND METHODS: Nine surgically created stenoses of external iliac arteries in pigs were dilated with MR-compatible balloon catheters (Cordis, Roden, The Netherlands). These catheters were equipped with a microcoil for active tracking of the catheter tip with an in-plane update rate of 10 positions per second. The procedures were performed on an interventional 1.5 T Gyroscan ACS-NT scanner (Philips, Best, The Netherlands). Real-time calculation of images acquired by radial k-space filling was performed on a specially designed backprojector exploiting the sliding window reconstruction technique (Philips Research Laboratories, Hamburg, Germany). The image update rate was 20 frames per second using a radial gradient-echo technique (TR = 12 msec, TE = 3.3 msec, 300 radials). MR angiography and X-ray digital subtraction angiography on the X-ray system positioned in-line next to the interventional MR system served as control for the angioplasty results. RESULTS: Real-time guidance and positioning of the balloon catheters was possible. The actual position of the catheter tip was indicated in the MR images without any time delay for the reconstruction of the anatomical MR images, which were updated with a rate of 20 frames per second. This yielded a combination of a roadmap and fluoroscopy image, in which the catheter position and the anatomical background image both were continuously updated in real time. Six out of nine stenoses were successfully dilated. The effects of the angioplasty could be visualized by the real-time MR technique, as was proven by X-ray digital subtraction angiography. CONCLUSION: Active tip tracking simultaneous with MRI of the vascular anatomy-both in real time-is possible with the applied technique, enabling MR-guided percutaneous dilatation (PTA) of iliac arteries.