Ultrashort echo time MRI of the lung in children and adolescents: comparison with non-enhanced computed tomography and standard post-contrast T1w MRI sequences.

OBJECTIVES: To compare the diagnostic value of ultrashort echo time (UTE) magnetic resonance imaging (MRI) for the lung versus the gold standard computed tomography (CT) and two T1-weighted MRI sequences in children. METHODS: Twenty-three patients with proven oncologic disease (14 male, 9 female; mean age 9.0 + / - 5.4 years) received 35 low-dose CT and MRI examinations of the lung. The MRI protocol (1.5-T) included the following post-contrast sequences: two-dimensional (2D) incoherent gradient echo (GRE; acquisition with breath-hold), 3D volume interpolated GRE (breath-hold), and 3D high-resolution radial UTE sequences (performed during free-breathing). Images were evaluated by considering image quality as well as distinct diagnosis of pulmonary nodules and parenchymal areal opacities with consideration of sizes and characterisations. RESULTS: The UTE technique showed significantly higher overall image quality, better sharpness, and fewer artefacts than both other sequences. On CT, 110 pulmonary nodules with a mean diameter of 4.9 + / - 2.9 mm were detected. UTE imaging resulted in a significantly higher detection rate compared to both other sequences (p < 0.01): 76.4% (84 of 110 nodules) for UTE versus 60.9% (67 of 110) for incoherent GRE and 62.7% (69 of 110) for volume interpolated GRE sequences. The detection of parenchymal areal opacities by the UTE technique was also significantly higher with a rate of 93.3% (42 of 45 opacities) versus 77.8% (35 of 45) for 2D GRE and 80.0% (36 of 45) for 3D GRE sequences (p < 0.05). CONCLUSION: The UTE technique for lung MRI is favourable in children with generally high diagnostic performance compared to standard T1-weighted sequences as well as CT. Key Points • Due to the possible acquisition during free-breathing of the patients, the UTE MRI sequence for the lung is favourable in children. • The UTE technique reaches higher overall image quality, better sharpness, and lower artefacts, but not higher contrast compared to standard post-contrast T1-weighted sequences. • In comparison to the gold standard chest CT, the detection rate of small pulmonary nodules small nodules ≤ 4 mm and subtle parenchymal areal opacities is higher with the UTE imaging than standard T1-weighted sequences.

Hyperthermia affects collagen fiber architecture and induces apoptosis in pancreatic and fibroblast tumor hetero-spheroids in vitro.

Desmoplasia, an aberrant production of extracellular matrix (ECM), is considered as one predictive marker of malignancy of pancreatic cancer. In this paper, we study the effect of mild hyperthermia on fibrillary collagen architecture in murine Achilles tendons and in a pancreatic cancer model, in vitro, i.e. 3D hetero-type tumor spheroids, consisting of pancreatic cancer (Panc-1) cells and fibroblasts (WI-38), producing collagen fibers. We clearly demonstrate that i) mild hyperthermia (40 °C, 42 °C) damages the collagen architecture in murine Achilles tendons. ii) Mild extrinsic (hot air) and iron oxide nanoparticle based magnetic hyperthermia reduce the level of collagen fiber architecture in the generated hetero-type tumor spheroids. iii) Mild magnetic hyperthermia reduces cell vitality mainly through apoptotic and necrotic processes in the generated tumor spheroids. In conclusion, hetero-type 3D tumor spheroids are suitable for studying the effect of hyperthermia on collagen fibers, in vitro.

The role of gadolinium in magnetic resonance imaging for early prostate cancer diagnosis: A diagnostic accuracy study.

OBJECTIVE: Prostate lesions detected with multiparametric magnetic resonance imaging (mpMRI) are classified for their malignant potential according to the Prostate Imaging-Reporting And Data System (PI-RADS™2). In this study, we evaluate the diagnostic accuracy of the mpMRI with and without gadolinium, with emphasis on the added diagnostic value of the dynamic contrast enhancement (DCE). MATERIALS AND METHODS: The study was retrospective for 286 prostate lesions / 213 eligible patients, n = 116/170, and 49/59% malignant for the peripheral (Pz) and transitional zone (Tz), respectively. A stereotactic MRI-guided prostate biopsy served as the histological ground truth. All patients received a mpMRI with DCE. The influence of DCE in the prediction of malignancy was analyzed by blinded assessment of the imaging protocol without DCE and the DCE separately. RESULTS: Significant (CSPca) and insignificant (IPca) prostate cancers were evaluated separately to enhance the potential effects of the DCE in the detection of CSPca. The Receiver Operating Characteristics Area Under Curve (ROC-AUC), sensitivity (Se) and specificity (Spe) of PIRADS-without-DCE in the Pz was 0.70/0.47/0.86 for all cancers (IPca and CSPca merged) and 0.73/0.54/0.82 for CSPca. PIRADS-with-DCE for the same patients showed ROC-AUC/Se/Spe of 0.70/0.49/0.86 for all Pz cancers and 0.69/0.54/0.81 for CSPca in the Pz, respectively, p>0.05 chi-squared test. Similar results for the Tz, AUC/Se/Spe for PIRADS-without-DCE was 0.75/0.61/0.79 all cancers and 0.67/0.54/0.71 for CSPca, not influenced by DCE (0.66/0.47/0.81 for all Tz cancers and 0.61/0.39/0.75 for CSPca in Tz). The added Se and Spe of DCE for the detection of CSPca was 88/34% and 78/33% in the Pz and Tz, respectively. CONCLUSION: DCE showed no significant added diagnostic value and lower specificity for the prediction of CSPca compared to the non-enhanced sequences. Our results support that gadolinium might be omitted without mitigating the diagnostic accuracy of the mpMRI for prostate cancer.

Dataset on the role of endoglin expression on melanin production in murine melanoma and on the influence of melanin on optical imaging.

The underlying data demonstrates that the expression of endoglin in murine melanoma cells influences melanin production in the cells. Also, the data shows that melanin production is further increased when the cells are subcutaneously implanted in mice models and that the high melanin production prevents detection of the cells by fluorescence imaging. The processed data presented herein is related to a research article by Tansi et al. (2018) entitled "Endoglin based in vivo near-infrared fluorescence imaging of tumor models in mice using activatable liposomes".

Endoglin based in vivo near-infrared fluorescence imaging of tumor models in mice using activatable liposomes.

BACKGROUND: Endoglin (CD105) is overexpressed on tumor cells and tumor vasculatures, making it a potential target for diagnostic imaging and therapy of different neoplasms. Therefore, studies on nanocarrier systems designed for endoglin-directed diagnostic and drug delivery purposes would expose the feasibility of targeting endoglin with therapeutics. METHODS: Liposomes carrying high concentrations of a near-infrared fluorescent dye in the aqueous interior were prepared by the lipid film hydration and extrusion procedure, then conjugated to single chain antibody fragments either selective for murine endoglin (termed mEnd-IL) or directed towards human endoglin (termed hEnd-IL). A combination of Dynamic Light Scattering, electron microscopy, cell binding and uptake assays, confocal microscopy and in vivo fluorescence imaging of mice bearing xenografted human breast cancer and human fibrosarcoma models were implemented to elucidate the potentials of the liposomes. RESULTS: The mEnd-IL and hEnd-IL were highly selective for the respective murine- and human endoglin expressing cells in vitro and in vivo. Hence, the hEnd-IL bound distinctly to the tumor cells and enabled suitable fluorescence imaging of the tumors, whereas the mEnd-IL bound the tumor vasculature, but also to the liver, kidney and lung vasculature of mice. CONCLUSIONS: The work highlights key differences between targeting vascular (murine) and neoplastic (human) endoglin in animal studies, and suggests that the hEnd-IL can serve as a delivery system that targets human endoglin overexpressed in pathological conditions. GENERAL SIGNIFICANCE: The endoglin-targeting liposomes presented herewith represent strategic tools for the future implementation of endoglin-directed neoplastic and anti-angiogenic therapies.

Activatable bispecific liposomes bearing fibroblast activation protein directed single chain fragment/Trastuzumab deliver encapsulated cargo into the nuclei of tumor cells and the tumor microenvironment simultaneously.

Molecular targeting plays a significant role in cancer diagnosis and therapy. However, the heterogeneity of tumors is a limiting obstacle for molecular targeting. Consequently, clinically approved drug delivery systems such as liposomes still rely on passive targeting to tumors, which does not address tumor heterogeneity. In this work, we therefore designed and elucidated the potentials of activatable bispecific targeted liposomes for simultaneous detection of fibroblast activation protein (FAP) and the human epidermal growth factor receptor 2 (HER2). The bispecific liposomes were encapsulated with fluorescence-quenched concentrations of the near-infrared fluorescent dye, DY-676-COOH, making them detectable solely post processing within target cells. The liposomes were endowed with a combination of single chain antibody fragments specific for FAP and HER2 respectively, or with the FAP single chain antibody fragment in combination with Trastuzumab, which is specific for HER2. The Trastuzumab based bispecific formulation, termed Bi-FAP/Tras-IL revealed delivery of the encapsulated dye into the nuclei of HER2 expressing cancer cells and caused cell death at significantly higher rates than the free Trastuzumab. Furthermore, fluorescence imaging and live microscopy of tumor models in mice substantiated the delivery of the encapsulated cargo into the nuclei of target tumor cells and tumor stromal fibroblasts. Hence, they convey potentials to address tumor plasticity, to improve targeted cancer therapy and reduce Trastuzumab resistance in the future. STATEMENT OF SIGNIFICANCE: This work demonstrates the design of activatable bispecific liposomes aimed to target HER2, a poor prognosis tumor marker in many tumor types, and fibroblast activation protein (FAP), a universal tumor marker overexpressed on tumor fibroblasts and pericytes of almost all solid tumors. Encapsulating liposomes with a quenched concentration of a NIRF dye which only fluoresced after cellular degradation and activation enabled reliable visualization of the destination of the cargo in cells and animal studies. Conjugating single chain antibody fragments directed to FAP, together with Trastuzumab, a humanized monoclonal antibody for HER2 resulted in the activatable bispecific liposomes. In animal models of xenografted human breast tumors, the remarkable ability of the bispecific probes to simultaneously deliver the encapsulated dye into the nuclei of target tumor cells and tumor fibroblasts could be demonstrated. Hence, the bispecific probes represent model tools with high significance to address tumor heterogeneity and manage Trastuzumab resistance in the future.

Computer-aided Detection Fidelity of Pulmonary Nodules in Chest Radiograph.

AIM: The most ubiquitous chest diagnostic method is the chest radiograph. A common radiographic finding, quite often incidental, is the nodular pulmonary lesion. The detection of small lesions out of complex parenchymal structure is a daily clinical challenge. In this study, we investigate the efficacy of the computer-aided detection (CAD) software package SoftView™ 2.4A for bone suppression and OnGuard™ 5.2 (Riverain Technologies, Miamisburg, OH, USA) for automated detection of pulmonary nodules in chest radiographs. SUBJECTS AND METHODS: We retrospectively evaluated a dataset of 100 posteroanterior chest radiographs with pulmonary nodular lesions ranging from 5 to 85 mm. All nodules were confirmed with a consecutive computed tomography scan and histologically classified as 75% malignant. The number of detected lesions by observation in unprocessed images was compared to the number and dignity of CAD-detected lesions in bone-suppressed images (BSIs). RESULTS: SoftView™ BSI does not affect the objective lesion-to-background contrast. OnGuard™ has a stand-alone sensitivity of 62% and specificity of 58% for nodular lesion detection in chest radiographs. The false positive rate is 0.88/image and the false negative (FN) rate is 0.35/image. From the true positive lesions, 20% were proven benign and 80% were malignant. FN lesions were 47% benign and 53% malignant. CONCLUSION: We conclude that CAD does not qualify for a stand-alone standard of diagnosis. The use of CAD accompanied with a critical radiological assessment of the software suggested pattern appears more realistic. Accordingly, it is essential to focus on studies assessing the quality-time-cost profile of real-time (as opposed to retrospective) CAD implementation in clinical diagnostics.

Nanoparticle-based hyperthermia distinctly impacts production of ROS, expression of Ki-67, TOP2A, and TPX2, and induction of apoptosis in pancreatic cancer.

So far, the therapeutic outcome of hyperthermia has shown heterogeneous responses depending on how thermal stress is applied. We studied whether extrinsic heating (EH, hot air) and intrinsic heating (magnetic heating [MH] mediated by nanoparticles) induce distinct effects on pancreatic cancer cells (PANC-1 and BxPC-3 cells). The impact of MH (100 µg magnetic nanoparticles [MNP]/mL; H=23.9 kA/m; f=410 kHz) was always superior to that of EH. The thermal effects were confirmed by the following observations: 1) decreased number of vital cells, 2) altered expression of pro-caspases, and 3) production of reactive oxygen species, and 4) altered mRNA expression of Ki-67, TOP2A, and TPX2. The MH treatment of tumor xenografts significantly (P≤0.05) reduced tumor volumes. This means that different therapeutic outcomes of hyperthermia are related to the different responses cells exert to thermal stress. In particular, intratumoral MH is a valuable tool for the treatment of pancreatic cancers.

A fast and effective determination of the biodistribution and subcellular localization of fluorescent immunoliposomes in freshly excised animal organs.

BACKGROUND: Preclinical research implementing fluorescence-based approaches is inevitable for drug discovery and technology. For example, a variety of contrast agents developed for biomedical imaging are usually evaluated in cell systems and animal models based on their conjugation to fluorescent dyes. Biodistribution studies of excised organs are often performed by macroscopic imaging, whereas the subcellular localization though vital, is often neglected or further validated by histological procedures. Available systems used to define the subcellular biodistribution of contrast agents such as intravital microscopes or ex vivo histological analysis are expensive and not affordable by the majority of researchers, or encompass tedious and time consuming steps that may modify the contrast agents and falsify the results. Thus, affordable and more reliable approaches to study the biodistribution of contrast agents are required. We developed fluorescent immunoliposomes specific for human fibroblast activation protein and murine endoglin, and used macroscopic fluorescence imaging and confocal microscopy to determine their biodistribution and subcellular localization in freshly excised mice organs at different time points post intravenous injection. RESULTS: Near infrared fluorescence macroscopic imaging revealed key differences in the biodistribution of the respective immunoliposomes at different time points post injection, which correlated to the first-pass effect as well as the binding of the probes to molecular targets within the mice organs. Thus, a higher accumulation and longer retention of the murine endoglin immunoliposomes was seen in the lungs, liver and kidneys than the FAP specific immunoliposomes. Confocal microscopy showed that tissue autofluorescence enables detection of organ morphology and cellular components within freshly excised, non-processed organs, and that fluorescent probes with absorption and emission maxima beyond the tissue autofluorescence range can be easily distinguished. Hence, the endoglin targeting immunoliposomes retained in some organs could be detected in the vascular endothelia cells of the organs. CONCLUSIONS: The underlying work represents a quick, effective and more reliable setup to validate the macroscopic and subcellular biodistribution of contrast agents in freshly excised animal organs. The approach will be highly beneficial to many researchers involved in nanodrug design or in fluorescence-based studies on disease pathogenesis.

Dataset on FAP-induced emergence of spontaneous metastases and on the preparation of activatable FAP-targeting immunoliposomes to detect the metastases.

The underlying data demonstrates that fibroblast activation protein (FAP) paves the way for fibrosarcoma cells, which require the proteolysis of the extracellular matrix (ECM) and basement membranes to intravasate from implanted subcutaneous primary tumors into blood vessels, be transported to distant organs where they extravasate from the blood vessels, reattach and proliferate to metastases. The data additionally shows that FAP, when overexpressed on fibrosarcoma cells induces their invasion and formation of spontaneous metastases in multiple organs, particularly after subcutaneous co-implantation of the FAP-expressing and wildtype fibrosarcoma. The raw and processed data presented herein is related to a research article entitled "Potential of activatable FAP-targeting immunoliposomes in intraoperative imaging of spontaneous metastases" (F.L. Tansi, R. Rüger, C. Böhm, R.E. Kontermann, U.K. Teichgraeber, A. Fahr, I. Hilger, 2016) [1]. Furthermore, evidence for the detection of FAP-expressing tumor cells and cells of the tumor stroma by activatable FAP-targeting liposomes is presented in this dataset.

Lowering photosensitizer doses and increasing fluences induce apoptosis in tumor bearing mice.

The objective of this study was to determine an optimal dose of photodynamic therapy (PDT) for inducing apoptotic tumor cells in vivo. In this context, mice bearing human tongue-squamous epithelium carcinomas were treated with various photosensitizer concentrations and fluences. Tumor apoptosis was imaged after 2 days via a self-designed DY-734-annexin V probe using near-infrared fluorescence (NIRF) optical imaging. Apoptosis was verified ex vivo via TUNEL staining. Apoptotic tumor cells were detected in vivo at a dose of 40 µg photosensitizer and a fluency of 100 J/cm(2). This is the lowest photosensitizer dose reported so far.

Assessment of PI-RADS v2 for the Detection of Prostate Cancer.

PURPOSE: To evaluate the diagnostic performance and inter-reader reliability of the multiparametric magnetic resonance imaging (mpMRI) based prostate imaging reporting and data system (PI-RADS) version 1 and version 2 for the assessment of prostate cancer. MATERIAL AND METHODS: A cohort of 82 patients underwent endorectal mpMRI at 1.5T. Patients had at least one lesion with a PI-RADS v1 assessment category of ≥3 and were selected for targeted in-bore MR-guided biopsy in a subsequent session. The results of the histopathological workup were used as reference standard. All lesions were retrospectively evaluated according to PI-RADS v2 by an experienced and unexperienced blinded reader. Diagnostic performance was compared by analyzing the area under the Receiver Operating Characteristics Curve (AUC). The weighted kappa method was used to calculate inter-reader reliability. RESULTS: Targeted MR-guided biopsy was performed in 136 lesions and revealed 39 malignant lesions in 31 patients. AUC values increased for the experienced reader (PI-RADS v1 0.79; PI-RADS v2 0.83) and unexperienced reader (PI-RADS v1 0.70; PI-RADS v2 0.83). When excluding the cases of low grade cancer (Gleason score=3+3), AUC values increased further for the experienced reader (PI-RADS v1 0.88; PI-RADS v2 0.91) and unexperienced reader (PI-RADS v1 0.78; PI-RADS v2 0.90). Specificity at the selected threshold of a PI-RADS v1/v2 assessment category ≥4 improved for both readers. Inter-reader agreement increased from κ=0.55 in PI-RADS v1 to κ=0.68 in v2. CONCLUSION: PI-RADS v2 improved diagnostic performance for the assessment of suspicious intraprostatic lesions identified in PI-RADS v1 for both readers and led to higher inter-reader reliability. These results suggest that PI-RADS v2 is a reliable and replicable reporting system for the assessment of prostate cancer.

Potential of activatable FAP-targeting immunoliposomes in intraoperative imaging of spontaneous metastases.

Despite intensive research and medical advances met, metastatic disease remains the most common cause of death in cancer patients. This results from late diagnosis, poor therapeutic response and undetected micrometastases and tumor margins during surgery. One approach to overcome these challenges involves fluorescence imaging, which exploits the properties of fluorescent probes for diagnostic detection of molecular structures at the onset of transformation and for intraoperative detection of metastases and tumor margins in real time. Considering these benefits, many contrast agents suitable for fluorescence imaging have been reported. However, most reports only demonstrate the detection of primary tumors and not the detection of metastases or their application in models of image-guided surgery. In this work, we demonstrate the influence of fibroblast activation protein (FAP) on the metastatic potential of fibrosarcoma cells and elucidate the efficacy of activatable FAP-targeting immunoliposomes (FAP-IL) for image-guided detection of the spontaneous metastases in mice models. Furthermore, we characterized the biodistribution and cellular localization of the liposomal fluorescent components in mice organs and traced their excretion over time in urine and feces. Taken together, activatable FAP-IL enhances intraoperative imaging of metastases. Their high accumulation in metastases, subsequent localization in the bile canaliculi and liver kupffer cells and suitable excretion in feces substantiates their potency as contrast agents for intraoperative imaging.

Evaluation of laparoscopic liver resection with two different Nd:YAG lasers for future use in a high-field open MRI.

OBJECTIVE: Laparoscopic liver surgery is a safe and feasible technique for the treatment of benign and malignant liver tumors and has been well established at many specialized centers. Many different techniques of tissue dissection have been developed. As an alternative various lasers have been applied to conventional liver resections. Laser surgery is potentially beneficial for laparoscopic liver resection, allowing parenchymal dissection and vessel coagulation. A second advantage is the non-ferromagnetic character of this instrument, which facilitates magnetic resonance (MR)-guided interventions. In this study two different Nd:YAG lasers were evaluated for laparoscopic liver resection in a porcine model. In other studies this technique will be transferred into an interventional open MRI for image-guided liver resection. MATERIALS AND METHODS: We used 1064-nm and 1318-nm Nd:YAG lasers for laparoscopic wedge, segmental, and left lateral liver lobe resection. During the intervention blood loss, resection time, and cardiopulmonary parameters were quantified. The resected specimen underwent histomorphometric analysis for thermal tissue effects, including parenchymal carbonization, necrosis, and vessel coagulation. RESULTS: The resected volume showed a positive correlation with intraoperative blood loss, which increased from wedge resection (245 mL, SD +/- 71 mL) and segment resection (325 mL), to left lateral resection (455 mL). Total parenchymal dissection was slightly faster with the 1064-nm Nd:YAG laser (9 min, SD +/- 5 min) compared with the 1318-nm Nd:YAG laser (11 min, SD +/- 4 min). Thermally-induced vessel sealing was shown for liver veins and arteries to a maximum diameter of 2 mm. CONCLUSION: Laparoscopic liver resection with both Nd:YAG lasers is a safe and feasible technique, allowing parenchymal dissection and coagulation. The 1064-nm Nd:YAG laser showed increased tissue damage with more effective coagulation capability than the 1318-nm Nd:YAG laser. Because of its non-ferromagnetic characteristics, laser-based laparoscopic liver resection is potentially useful for image-guided surgery in an open MRI.

The effect of thermotherapy using magnetic nanoparticles on rat malignant glioma.

Thermotherapy using magnetic nanoparticles is a new technique for interstitial hyperthermia and thermoablation based on magnetic field-induced excitation of biocompatible superparamagnetic nanoparticles. To evaluate the potential of this technique for minimally invasive treatment, we carried out a systematic analysis of its effects on experimental glioblastoma multiforme in a rat tumor model. Tumors were induced by implantation of RG-2-cells into the brains of 120 male Fisher rats. Animals were randomly allocated to 10 groups of 12 rats each, including controls. Animals received two thermotherapy treatments following a single intratumoral injection of two different magnetic fluids (dextran- or aminosilane-coated iron-oxide nanoparticles). Treatment was carried out on days four and six after tumor induction using an alternating magnetic field applicator system operating at a frequency of 100 kHz and variable field strength of 0-18 kA/m. The effectiveness of treatment was determined by the survival time of the animals and histopathological examinations of the brain and the tumor.Thermotherapy with aminosilane-coated nanoparticles led up to 4.5-fold prolongation of survival over controls, while the dextran-coated particles did not indicate any advantage. Intratumoral deposition of the aminosilane-coated particles was found to be stable, allowing for serial thermotherapy treatments without repeated injection. Histological and immunohistochemical examinations after treatment revealed large necrotic areas close to particle deposits, a decreased proliferation rate and a reactive astrogliosis adjacent to the tumor.Thus, localized interstitial thermotherapy with magnetic nanoparticles has an antitumoral effect on malignant brain tumors. This method is suitable for clinical use and may be a novel strategy for treating malignant glioma, which cannot be treated successfully today. The optimal treatment schedules and potential combinations with other therapies need to be defined in further studies.

A randomized trial assessing the value of ultrasound-guided puncture of the femoral artery for interventional investigations.

Using a prospectively collected database of patients undergoing diagnostic or therapeutic angiography via transfemoral access, we sought to determine those patients who may benefit from ultrasound-guided puncture of the femoral artery. One-hundred-twelve patients with normal anticoagulation parameters were randomized in two groups. Fifty-six patients received ultrasound-guided puncture of the femoral artery, 56 patients underwent traditional palpation-guided vessel cannulation. Parameters assessed included procedure-time, number of attempts for successful puncture, intensity of the arterial pulse, previous ipsilateral punctures, history and risk factors of arteriosclerosis and leg circumference at the site of puncture. The data was analyzed by using outcome measures according to evidence-based medicine criteria. Only in patients with weak arterial pulse and thoses with a leg circumference of 60 cm or greater ultrasound guidance significantly decreased the number of attempts needed as well as the time for successful arterial puncture. In both patient subgroups, the number needed to treat (NNT) was 2, the absolute benefit increase (ABI) was 50 and 57%, respectively. In contrast, time for vessel cannulation was increased in patients with strong arterial pulse using ultrasound guidance. No significant differences were found with respect to diminished complications neither comparing both patient groups nor comparing risk subgroups. In conclusion ultrasound guidance for femoral artery access is recommended only in patients with a weak or absent arterial pulse and obese patients.