Referral guidelines for medical imaging in children: an ESR-EuroSafe Imaging survey on availability, awareness and use in clinical practice among European radiologists.

OBJECTIVES: Justification of medical exposures from medical imaging is fundamental to radiation protection. Referral guidelines are intended to help physicians decide when an imaging study is justified. For two decades, referral guidelines have been a legally binding requirement for European Union member states. Recently, the European Society of Radiology (ESR) developed iGuide tool, which provides evidence-based referral guidance for imaging inclusive of children. The aim of this survey was to assess the availability, use and familiarity of referral guidelines for medical imaging in children and knowledge about the availability of ESR iGuide among ESR member radiologists. METHODS: Over a 2-month period (15 September-15 November 2019), 33,257 ESR member radiologists were invited to respond to an anonymised web-based questionnaire, which consisted of 12 multiple-choice questions. RESULTS: In total, 2067/33,257 responses (6.3%) were received from 52 countries. A total of 1068 out of 2067 (51.7%) respondents were aware that imaging referral guidelines are a legal requirement. One thousand five (48.6%) of all respondents did not know whether dedicated guidelines for imaging in children were available, and only 653 (31.2%) were aware of the mainstays of the available guidelines. Similarly, just 746 (36.1%) of all respondents were aware of ESR iGuide availability and features. CONCLUSIONS: The information gathered confirms that effective and widespread adoption of imaging referral guidelines is lacking, especially in children. Further work is required to improve uptake and awareness. KEY POINTS: • Justification of medical exposures is fundamental to radiation protection and evidence-based referral guidelines are crucial for practical implementation of this principle. • About half of survey respondents are aware that the availability of imaging referral guidelines is a legal requirement, despite this being mandated since 1997. • The information gathered from this survey confirms that, especially in children, an effective and widespread adoption of imaging referral guidelines is lacking.

European consensus on patient contact shielding.

Patient contact shielding has been in use for many years in radiology departments in order to reduce the effects and risks of ionising radiation on certain organs. New technologies in projection imaging and CT scanning such as digital receptors and automatic exposure control (AEC) systems have reduced doses and improved image consistency. These changes and a greater understanding of both the benefits and the risks from the use of shielding have led to a review of shielding use in radiology. A number of professional bodies have already issued guidance in this regard. This paper represents the current consensus view of the main bodies involved in radiation safety and imaging in Europe: European Federation of Organisations for Medical Physics, European Federation of Radiographer Societies, European Society of Radiology, European Society of Paediatric Radiology, EuroSafe Imaging, European Radiation Dosimetry Group (EURADOS), and European Academy of DentoMaxilloFacial Radiology (EADMFR). It is based on the expert recommendations of the Gonad and Patient Shielding (GAPS) Group formed with the purpose of developing consensus in this area. The recommendations are intended to be clear and easy to use. They are intended as guidance, and they are developed using a multidisciplinary team approach. It is recognised that regulations, custom and practice vary widely on the use of patient shielding in Europe and it is hoped that these recommendations will inform a change management program that will benefit patients and staff.

Cumulative radiation dose after lung transplantation in patients with cystic fibrosis.

PURPOSE: The purpose of this study was first to evaluate the imaging-related cumulative post-transplantation radiation dose in cystic fibrosis (CF) lung transplantation (LT) recipients and second, to identify the occurrence and type of malignancies observed after LT. MATERIALS AND METHODS: A total of 52 patients with CF who underwent LT at our institution between January 2001 and December 2006 with at least 3 years of survival were retrospectively included. There were 27 men and 25 women with a mean age of 24.4±9.2 (SD) years (range: 7.6-52.9 years) at the time of LT. Calculation of cumulative effective and organ doses after LT were based on dosimetry information and acquisition parameters of each examination. Cumulative radiation doses were calculated until June 2016, but stopped at the time of de novomalignancy diagnosis, for patients developing the condition. RESULTS: Patients received a mean cumulative effective dose of 110.0±51.6 (SD) mSv (range: 13-261.3 mSv) over a mean follow-up of 8.1±3.6 (SD) years (range: 0.5-13.5 years), with more than 100mSv in 5 years in 19/52 patients (37%). Chest CT accounted for 73% of the cumulative effective dose. Mean doses to the lung, breast and thyroid were 152.8±61.1 (SD) mGy (range: 21.2-331.6 mGy), 106.5±43.2 (SD) mGy (range: 11.9-221.4 mGy) and 72.7±31.8 (SD) mGy (range: 9.5-165.0 mGy), respectively. Nine out of 52 patients (17%) developed a total of 10 de novo malignancies, all but one attributable to immunosuppression after a mean post-transplantation follow-up period of 11.1±3.5 (SD) years (range: 3.7-16.3 years). Six-month cumulative effective dose was not greater in patients with de novomalignancies than in those without de novomalignancies (28.9±14.5 (SD) mGy (range: 13.0-53.4) vs 25.6±15.3 (range: 5.0-69.7), respectively, P>0.05). CONCLUSION: The cumulative effective dose exceeded 100 mSv in 5 years in 37% of LT recipients, the reason why continuous efforts should be made to optimize chest CT acquisitions accounting for 73% of the radiation dose.

[Imaging of response to treatment in oncology]. / Imagerie de la réponse aux traitements en cancérologie.

Imaging plays a crucial role in oncology to assist in the management of patients and selection of drug regimen. Recent advances in imaging techniques allowing to predict and evaluate response to treatments in oncology will be reviewed. The standard in the evaluation of response to treatment is based on the measurement of lesion size. Functional imaging assesses physiological or molecular processes that may be earlier indicators of early response to treatment. Dynamic imaging of tumor vascularization assesses the biodistribution of a contrast agent within tumoral tissues. Diffusion-weighted MR imaging can differentiate free water from water restricted by tissues, providing an assessment of tumor cellularity. MR spectroscopy assesses the relative quantity of specific chemical components within normal and tumoral tissues. 18 FDG PET imaging provides an assessment of the metabolic activity of tissues. FDG uptake is proportional to cellular proliferation and number of viable cells within a tumor. Results from studies assessing the role of these emerging imaging techniques remain preliminary and the medical community must determine their respective role in the routine evaluation of response to treatment in oncological patients.

In vivo dynamic MRI measurement of the noradrenaline-induced reduction in placental blood flow in mice.

PURPOSE: We developed a new model for in vivo placental perfusion measurements based on dynamic MRI in mice. As noradrenaline has been implicated in the pathogenesis of preeclampsia, we examined whether it reduced placental perfusion in mice, and whether such a reduction could be detected with our MRI model. MATERIALS AND METHODS: Mice at 16 days of gestation were injected intramuscularly with saline or noradrenaline solution. A conventional gadolinium chelate was then injected IV, and a single-slice T1-weighed 2D Fast SPGR sequence was acquired for 200 s. Signal intensity was measured on all the images and converted into contrast agent tissue concentrations in the maternal left ventricle (input function) and placentas. A one-compartment model was developed using compartmental and numerical modeling software. Mean blood flow (F) was calculated from a transfer constant. RESULTS: Twenty-six mice were studied, yielding a total of 55 MRI measurements of placental perfusion (29 in the control group and 26 in the noradrenaline group). Mean placental blood flow (F) was significantly lower in the noradrenaline group (0.72+/-0.84 ml/min/g of placenta) than in the control group (1.26+/-0.54 ml/min/g of placenta). CONCLUSION: Noradrenaline reduces placental perfusion in mice. Our MRI dynamic model might be useful for detecting and investigating abnormal placental blood flow, thereby avoiding the need for invasive procedures and animal sacrifice.

[Treatment response evaluation by functional imaging]. / Evaluation de la réponse au traitement par imagerie fonctionnelle.

Imaging in cancer plays a capital role to guide the clinician in his choice of therapies. We will discuss the new techniques available to predict and evaluate treatment response in oncology. The method of reference to evaluate treatment response is based on the measure of lesion size. Functional imaging doesn't evaluate size, but rather a physiological or molecular feature, which is probably modified earlier in response to treatment. Dynamic contrast-enhanced functional imaging of microcirculation follows the biodistribution of a contrast agent and analyses tumour vascularization. Diffusion-weighted Magnetic Resonance Imaging differentiates free and restrained water molecules in tissues, reflecting tumor cellularity. Nuclear Magnetic Resonance spectroscopy is an application of MRI that yields information on the metabolic content of a tissue. It detects relative quantities of various molecules which differ in tumour compared to normal tissue. Positon-emission tomography using (18)FDG is a nuclear medicine technique which gives information on tissue metabolism. Captation of FDG is proportional to the proliferative activity and the number of viable cells in a tumour. Human studies concerning these techniques are still quite preliminary, and the medical community must determine their potential in clinical practice to evaluate treatment response in oncology.

[Placental functional assessment using MRI: mice today, humans tomorrow?]. / L'IRM fonctionnelle pour l'étude de la fonction placentaire: aujourd'hui chez la souris, demain chez l'homme?

Placental insufficiency, a process due to either poor placental perfusion or permeability, may lead to progressive deterioration in placental function and materno-fetal morbidity. Advances in MR contrast media pharmacokinetic studies of transit through tissues and dynamic MRI allow to characterize organs microcirculation in vivo. Placental function assessment might be achieved using analysis of dynamic contrast enhanced MRI of tracers. A murine model of placental assessment has been constructed. Herein, principles, results and limitations of such techniques are discussed as well as their potential interest and weaknesses in humans.

Superparamagnetic iron oxide-enhanced magnetic resonance imaging of experimental liver tumors after mitomycin C administration.

The influence of mitomycin C chemotherapy on superparamagnetic iron oxide (SPIO) uptake by the liver was studied in rats (n = 70). This commonly used antineoplastic drug induces a decrease in the phagocytic function of the macrophage-phagocytic system (MPS). The plasma clearance of SPIO measured by relaxometry followed a biexponential model. The fast component half-life increased from 2.9 minutes in controls to 4.5 minutes in mitomycin C-treated animals. The slow component half-life increased from 11.3 to 36.7 minutes. Nevertheless, the magnetic resonance imaging (MRI) diagnostic efficacy 2 hours after infusion of the superparamagnetic agent AMI 25 (n = 10) was as satisfactory in the treated group as in the untreated one. These MRI results were consistent with the relaxometric T2* liver measurements, which were identical in both groups.

Hepatocyte targeting with Gd-EOB-DTPA: potential application for gene therapy.

RATIONALE AND OBJECTIVES: To evaluate the suitability of the liver-specific MRI contrast agent Gd-EOB-DTPA as a nonviral vector for gene therapy of hepatocellular carcinoma. METHODS: Specific uptake of Gd-EOB-DTPA was quantified by relaxometry in rat cultured hepatocytes and the hepatoma cells HepG2 and Huh7. Nonviral vectors for gene transfer were synthesized by coupling Gd-EOB-DTPA to polyethyleneimine or polylysine as DNA condensing agents, and their efficiency was studied using beta-galactosidase (lacZ) as the reporter gene. RESULTS: Gd-EOB-DTPA was specifically taken up by rat cultured hepatocytes (4.32 vs. 1.08 mmol/L in nonhepatocyte control cells) but not by the hepatoma cells; this uptake was concentration-dependently inhibited by Bromsulphtalein. Polycation linkages were achieved with yields of 0.9 Gd-EOB-DTPA molecule per polyethyleneimine molecule and 10 Gd-EOB-DTPA molecules per polylysine molecule. Incubating the cells with plasmids containing lacZ reporter gene and polyethyleneimine-Gd-EOB-DTPA resulted in a few blue (transfected) cells, whereas no blue cells were observed on incubation with polylysine-Gd-EOB-DTPA. CONCLUSIONS: Gd-EOB-DTPA is taken up by normal hepatocytes but not by HepG2 and Huh7 cells, probably because of the lack of the organic anion transporter in these hepatoma cells. The Gd-EOB-DTPA polycation conjugates, such as polyethyleneimine-Gd-EOB-DTPA, could serve as transfer vectors of interest for gene targeting imagery at the early stage of hepatocarcinogenesis. However, the transfer efficiency of such conjugates is low and requires improvement.

Canine acute myocardial infarction. In vivo detection by MRI with gradient echo technique and contribution of Gd-DOTA.

This experimental study was designed to evaluate the sensitivity of MRI in the detection of acute myocardial infarction, determine the utility of fast gradient-echo (GE) imaging and study possible improvements in diagnostic efficacy using a paramagnetic contrast agent (gadolinium-DOTA). Myocardial infarcts were induced in 11 dogs by semidistal embolization and imaged using spin-echo and/or GE pulse sequences, short TRs (250 to 450 ms) and cardiac gating. After the dogs died, the heart was imaged under the same conditions as in vivo. Blind comparisons between precontrast, postcontrast (0.1 mM/kg and 0.5 mM/kg), postmortem images and anatomic findings (triphenyl-tetrazolium-chloride staining) were recorded. This study shows that infarcted areas can be detected on plain MRI images in the form of a hypersignal, probably attributable to increased proton density, with better efficiency of GE compared with spin-echo imaging; injection of gadolinium-DOTA allows better delineation of infarcted areas, especially for 10 minutes after administration.

Tolerability of hypertonic and isotonic contrast media injected intravenously. A comparative study in the dog.

We examined the use of isotonic and hypertonic contrast media injected intravenously in the dog from the standpoint of cardiovascular tolerance after right atrial injections performed at 2.56 and 5.12 g I/second. The parameters measured were lead II of the electrocardiograph, heart rate, pulmonary and abdominal arterial pressure, and aortic flow. Three contrast media, ioxitalamate, ioxaglate, and iopamidol (two ionic and one nonionic), were compared, either concentrated (32% iodine) or dilute and isotonic with plasma (ioxaglate 160 mg I/mL and iopamidol 128 mg I/mL). At an injection rate of 5.12 g I/second, iopamidol-128 showed lower electrophysiologic tolerability and caused a higher increase in aortic flow than ioxitalamate 160 or ioxaglate 160. These effects may explain the lower radiographic efficacy observed with iopamidol-128 in previous digital subtraction angiography studies.

Study of isotonic contrast media in intravenous digital subtraction angiography.

Arterial enhancement obtained with isotonic contrast media in intravenous digital subtraction angiography was studied. Ten dogs were injected with ioxaglate, iopamidol, and ioxitalamate at equal iodine concentration and at concentrations corresponding to plasma osmolality. Three variables were studied: osmolality, injection rate, and iodine dose. Provided their iodine concentration is sufficient, isotonic contrast media appear as efficient as the corresponding hypertonic formulation, at equal iodine dose. Moreover, the use of isotonic ioxaglate allows a lower dose of iodine to be administered without significant reduction in peak arterial value.

The aryepiglottic fold as a rare location of adenoid cystic carcinoma.

We report one case of a mass in the aryepiglottic fold seen on CT, which proved to be an adenoid cystic carcinoma. There was nothing specific about the imaging characteristics that would allow it to be confidentially differentiated from squamous cell carcinoma.

Normal laryngeal CT findings after supracricoid partial laryngectomy.

BACKGROUND AND PURPOSE: Supracricoid horizontal partial laryngectomy (SCPL) is increasingly used to treat endolaryngeal carcinoma. However, few radiologic reports of these procedures exist. Our purpose was to evaluate the normal CT appearance of the neolarynx after surgery. METHODS: SCPL includes cricohyoidopexy (CHP), cricohyoidoepiglottopexy (CHEP), and tracheocricohyoidoepiglottopexy (TCHEP). We examined CT scans obtained from 18 patients without local superficial recurrence who underwent SCPL: 10, CHEP; seven, CHP; and one, TCHEP. Three reference sections were used to analyze the main surgical reconstruction: an upper section through the hyoid bone, a lower section through the cricoid cartilage, and a middle section in between. The distance between the hyoid bone and cricoid cartilage was measured. RESULTS: The epiglottis and valleculae were visible in the upper section in seven of 10 patients who underwent CHEP; this finding allowed distinction between CHEP and CHP. The arytenoids were depicted in 13 of 18 cases and reflected neolaryngeal shortening. The lower section showed the empty cricoid lumen lined by a thin mucosa; the anterior arch of the cricoid was amputated at TCHEP. The middle section showed the neovestibule, the lateral boundaries of which were the hypertrophic neoaryepiglottic folds; the anterior limit was the epiglottis for CHEP or the base of the tongue for CHP. The average distance between the hyoid bone and cricoid cartilage was 11 mm. CONCLUSION: Normal CT anatomy of the larynx after SCPL is defined. Three key sections may accurately distinguish the various types of SCPL. CT is a valuable tool for depicting tumor recurrence, especially when the tumor is submucosal.

MR imaging of acute spinal cord injury: results of an experimental study in dogs.

A weight-drop model was used to induce 16 acute lesions of varying severity in the spinal cords of eight mongrel dogs. The subsequent 3- to 7-hr postinjury MR images (0.5 T) were assessed. T1-weighted images contributed little information. Injection of gadolinium tetra-azacyclododecane tetraacetic acid did not result in significant enhancement. T2-weighted sequences offered precise detection and delineation of the lesions, displaying fusiform hyperintense signal abnormalities that corresponded to both edema and hemorrhage. In low-impact injuries, abnormalities were small and centrally located, sparing the periphery of the spinal cord. In these cases hemorrhage was minimal and limited to the center of the lesion. In severe-impact injuries, MR showed widespread longitudinal extension with involvement of the periphery of the spinal cord. In the most severe injuries, a central heterogeneous signal component was frequently observed opposite the site of impact because of important hemorrhage within the cord. Overall, hyperintense areas correlated closely with lesion severity, as demonstrated by pathologic findings. T2-weighted MR images obtained at 0.5 T were found to be reliable in the evaluation of acute spinal cord trauma.

Contrast agents in magnetic resonance imaging of the liver: present and future.

New contrast agents are being developed by drug companies to better image the liver magnetic resonance imaging (MRI). They can be divided into hepatobiliary agents (Gd-EOB-DTPA, Gd-BOPTA, Mangafodipir) and nanoparticulate agents directed to the reticulo-endothelial system (ferumoxides, SHU 555A). After intravenous injection, all these agents concentrate in the liver and induce profound signal changes. Particulate agents induce predominantly a darkening of the liver parenchyma, while hepatobiliary agents induce a brightening. In both cases, liver-lesion conspicuity is enhanced, leading to a better visualization of the lesion. After a description of the principal pharmacokinetic characteristics of the compounds, this review paper summarizes the utility of the agents in the detection and characterization of focal liver diseases.

Liver imaging with ferumoxides (Feridex): fundamentals, controversies, and practical aspects.

Superparamagnetic nanoparticles (Feridex) have been recently made available to the radiological community as a contrast agent for MR imaging of the liver. This article reviews the principal physicochemical characteristics of this new compound, with an emphasis on the explanation of the contrast obtained (either positive or negative enhancement) that depends on the local concentration and the sequence used. The clinical use of Feridex is detailed, both for lesion detection and characterization. Finally, some guidelines for image optimization are given.

Capillary leakage of a macromolecular MRI agent, carboxymethyldextran-Gd-DTPA, in the liver: pharmacokinetics and imaging implications.

Capillary leakage of a macromolecular contrast agent, Carboxymethyl Dextran-Gd-DTPA (CMD-Gd-DTPA) was characterized in a highly permeable system, the liver, to assess its potential as a blood pool marker. Its elimination kinetics in hepatic lymph were compared in nephrectomized rabbits with that of a tracer of extra cellular fluid space, Gd-DOTA. Four parameters were defined: volume of distribution, normalized initial leakage rate (ILRn), maximum ratio of lymph and plasma concentrations (max Cl/Cp), and the time to obtain this maximum ratio. The effect of this leakage was studied on MR images by comparing liver contrast enhancement after injection and after almost total removal of the contrast agent from the blood by exchange transfusion. Capillary leakage of CMD-Gd-DTPA was detected in lymph. Compared to Gd-DOTA, it was slower (ILRn = 0.36 10(-5) l min-1 for CMD-Gd-DTPA and ILRn = 2.6 10(-5) l min-1 for Gd-DOTA), less abundant (max Cl/Cp was 80% for CMD-Gd-DTPA and 100% for Gd-DOTA). Liver enhancement remained stable, which indicated that the leakage did not modify the enhancement induced by the intravascular fraction of the contrast agent. These results obtained in a highly permeable capillary model indicate that this agent can be used as a selective blood pool enhancer.

Liver positive enhancement after injection of superparamagnetic nanoparticles: respective role of circulating and uptaken particles.

Superparamagnetic nanoparticles have both high r1 and r2 relaxivities responsible for positive or negative enhancement properties. The aim of this study was to investigate to what extent perfusion (circulating particles) and uptake (clustered particles) mechanisms contribute to liver positive or negative enhancement using two different particles, superparamagnetic iron oxides (ferumoxides, AMI 25) and ultrasmall superparamagnetic iron oxides (ferumoxtran, AMI-227). Uptake kinetics were studied after intravenous injection of 20 micromol Fe/kg ferumoxtran on a washout liver model. Livers of 82 rats were surgically isolated and washed with saline infusion. Imaging was performed ex vivo at 0.5T with T1- and T2-weighted sequences. Enhancement kinetics of the liver were studied in vivo using MRI up to 180 min post injection of 20 micromol Fe/kg ferumoxtran (time response study) or 10, 20, 40 micromol Fe/kg ferumoxtran and 20 micromol Fe/kg ferumoxides (dose response study.) Particle uptake occurred early and resulted in a negative enhancement of the washed livers 15 min after injection of both T1 and T2 sequences. In vivo, a positive enhancement was only seen during the first five min with the lowest dose of ultrasmall superparamagnetic iron oxides and the T1 sequence. Uptake and clustering of the particles induced a negative liver enhancement. During the first minutes after injection, when uptake has not significantly occurred, perfusion imaging of the liver at a dose of 10 micromol Fe/kg results in a positive enhancement with T1-weighted sequences.