European Society of Urogenital Radiology guidelines on contrast media application

PURPOSE OF REVIEW

The present review covers the European Society of Urogenital Radiology guidelines for safe use of contrast media of importance for referring urologists.

RECENT FINDINGS

During the recent years contrast medium-induced nephropathy has become a hot topic. It is of importance to reduce its incidence. First of all, the patients at risk should be identified prior to the administration of a contrast medium, so that appropriate measures can be taken. Before intravenous administration of an iodinated agent but not before gadolinium-based and ultrasound agents, all patients should be questioned about the potential renal dysfunction at the time of referral, and only those who answer affirmative to at least one question should have their serum creatinine level determined. Before intraarterial injection, the serum creatinine should always be measured. In case of an abnormal level, another imaging procedure should be considered. If impossible, hydration should be instituted and administration of nephrotoxic drugs should be stopped. After administration, delayed reactions such as nephrogenic systemic fibrosis, thyreotoxicosis, skin rash, etc. may be seen. Interaction with isotope studies and biochemical analysis occurs too.

SUMMARY

The awareness regarding the potential adverse reactions due to contrast media and the necessary precautions to be taken are of utmost importance both for radiologists and referring physicians. This is the only way to reduce their incidence.

Arterial contamination: a useful indirect sign of cerebral sino-venous thrombosis

BACKGROUND

Various imaging findings of cerebral sino-venous thrombosis (CSVT) have been described on magnetic resonance venography (MRV).

OBJECTIVE

The purpose of this study was to evaluate the significance of visualization of the arterial system on cerebral MRV, also described as arterial contamination, as an indirect sign of CSVT.

METHODS

Forty patients with a clinical suspicion of venous sinus thrombosis underwent MR imaging of the brain, followed by MRV sequence, based on 2D time of flight technique in the coronal oblique plane. Patient's clinical symptoms and signs were noted with particular interest for papilloedema. Twenty-seven patients were diagnosed to have cerebral venous thrombosis on MRV, and of these, arterial contamination was visualized in 16 patients. In the remaining 13 cases, in which there was no evidence of venous sinus thrombosis, arterial contamination was absent. The sensitivity of this finding was 59.25% (n = 16/27), specificity was 100%, positive predictive value was 100% and negative predictive value was 54.2%. Of these 16 patients with arterial contamination, 12 patients had evidence of increased intracranial pressure in the form of papilloedema.

CONCLUSION

Visualization of the arterial system is a useful indirect sign of CSVT, and may be an indicator of increased intracranial pressure in these patients.

Using the Magnetic Resonance Three-Dimensional Volume Rendering for Tissues Technique in the Planning of Craniotomy Flaps with Linear Scalp Incision

Preoperative three-dimensional images with surface venous anatomy may be used in the planning of a linear scalp incision and the opening site of the dura mater for protection of surface veins during surgical dissection, and to find the splitting site of the brain according to the lesion. In 45 patients who had a brain tumor, linear scalp incision planning was done by regarding the three-dimensional images derived from post-contrast time-of-flight (TOF) sequence raw data. The findings of correspondence and the quality of routine contrast-enhanced magnetic resonance imaging (MRI) and three-dimensional volume rendering for tissues (VRT) images were analyzed separately with the surgical findings according to a visual grading system. Our experience revealed that the surgical findings correlated well with the three-dimensional VRT images. According to a visual surgical grading system, a grade III correlation was found in 20 (45%), grade II in 15 (33%), grade I in 7 (15%), and grade 0 in 3 (7%) patients in our study population. At the end of our research we conclude that this method is useful in terms of the preoperative determination of brain surface anatomy and may be used in the determination of the site of a linear scalp incision according to the localization of an intracranial lesion.

CT arteriography for orbital tumors: diagnostic and surgical value

The aim of this study is to investigate the efficacy of dynamic computed tomography (CT) during selective angiography (CT-arteriography) of orbital tumors in the evaluation of intratumoral vascular anatomy, feeding artery territory, and histological diagnosis. Among 35 consecutive cases with various orbital lesions, those cases showing tumor staining or pooling of the contrast medium on digital subtraction angiography (DSA) were evaluated by CT-arteriography (n = 14). The information obtained by CT-arteriography was compared with that provided by enhanced MRI (n = 31) and dynamic MRI (n = 21), in which the contrast medium was injected intravenously. In addition to the visualization of fine vascular anatomy, CT-arteriography emphasized areas of nodular enhancement and non-enhancing cystic/necrotic components as well as the intratumoral feeding arteries. Patterns of CT-arteriography were categorized into three subgroups: homogeneous enhancement (benign lymphoid lesion), partial enhancement (schwannomas and carcinomas), and patchy multinodular enhancement (specific for cavernous angiomas). In addition, CT-arteriography with selective arterial catheterization clearly delineated the feeding artery territories. CT-arteriography, with a minimal dose of contrast medium, can offer significant advantages over intravenously injected dynamic neuroimaging, and provides additional valuable preoperative information about the orbital tumor under investigation.

ESUR guidelines on contrast media

Since 1996 the Contrast Media Safety Committee of the European Society of Urogenital Radiology has released 15 guidelines regarding safety in relation to the use of radiographic, ultrasonographic, and magnetic resonance contrast media. The guidelines have been well received by the radiologic community in Europe and all over the world and comprise current standards for good practice at many institutions. The present report is an overview of the work accomplished by the European Society of Urogenital Radiology over the past 8 years. The committee has covered renal and nonrenal adverse events and other aspects of contrast media.

Contrast-enhanced transcranial Doppler ultrasound for diagnosis of patent foramen ovale

The suspected cause of clinical manifestations of patent foramen ovale (PFO) is a transient or a permanent right-to-left shunt (RLS). Contrast-enhanced transcranial Doppler ultrasound (c-TCD) is a reliable alternative to transesophageal echocardiography (TEE) for diagnosis of PFO, and enables also the detection of extracardiac RLS. The air-containing echo contrast agents are injected intravenously and do not pass the pulmonary circulation. In the presence of RLS, the contrast agents bypass the pulmonary circulation and cause microembolic signals (MES) in the basal cerebral arteries, which are detected by TCD. The two main echo contrast agents in use are agitated saline and D-galactose microparticle solutions. At least one middle cerebral artery (MCA) is insonated, and the ultrasound probe is fixed with a headframe. The monitored Doppler spectra are stored for offline analysis (e.g., videotape) of the time of occurrence and number of MES, which are used to assess the size and functional relevance of the RLS. The examination is more sensitive, if both MCAs are investigated. In the case of negative testing, the examination is repeated using the Valsalva maneuver. Compared to TEE, c-TCD is more comfortable for the patient, enables an easier assessment of the size and functional relevance of the RLS, and allows also the detection of extracardiac RLS. However, c-TCD cannot localize the site of the RLS. Therefore, TEE and TCD are complementary methods and should be applied jointly in order to increase the diagnostic accuracy for detecting PFO and other types of RLS.

Technology Insight: imaging amyloid plaques in the living brain with positron emission tomography and MRI

Alois Alzheimer first imaged amyloid plaques in 1906 by examining dead tissue under the microscope, but their clinical significance has remained undetermined. Now, nearly a century later, investigators are beginning to image amyloid plaques in living brains using both positron emission tomography and MRI. In this article, we review the studies that report on these recent technical advances, and discuss their potential importance in clarifying the diagnostic and pathogenic relevance of amyloid plaques to Alzheimer's disease.

Regulatory compliance associated with contrast media

A basic understanding of the role of regulatory agencies in governing the healthcare environment and their influence over contrast media use is required of radiographers and imaging administrators to meet the many standards of compliance. In addition, radiology management teams must consider cost effectiveness, departmental efficiency, workplace safety, and compliance in choosing to implement new products. Regulatory agencies may be classified into 2 groups, voluntary and involuntary. Involuntary agencies are governmental agencies mandating regulatory compliance by local, state, or federal laws. Voluntary agencies are precisely that, those agencies an institution voluntarily chooses to participate with, to demonstrate the quality of care they provide. Failure to follow involuntary regulatory guidelines or to participate in voluntary best practice standards jeopardizes patient safety and the quality of care provided, and exposes the institution and the individual to liability risks. Severe penalties may result from a failure to maintain regulatory compliance, including the possibility of large fines, criminal indictments, and loss of third-party reimbursement. Achieving regulatory compliance is never an easy venture with the number of regulatory agencies and standards needing to be addressed. Combining regulatory compliance with the effects of doing business provides quite a challenge for today's imaging departments. A solid knowledge base in regulatory standards along with continuous investigation of new standards will allow departments to evaluate their own processes involved in providing patient care. Recognition of areas of high risk/high volume, including contrast media use, will assist in directing the departments' focus appropriately. A thorough evaluation of the products used and their respective handing and administration, in regard to patient and workplace safety, and appropriate documentation of workplace injuries due to contrast media packaging, will assist in maintaining a high level of compliance.

Assessment of CE-MRA for the rapid detection of supra-aortic vascular disease

BACKGROUND

Contrast-enhanced MR angiography (CE-MRA) using a combined head and neck coil permits non-invasive imaging of the vasculature from the aortic arch through to the Circle of Willis in less than 2 minutes.

OBJECTIVE

To determine the accuracy of CE-MRA for the detection of vascular pathology, in particular vascular stenoses, using digital subtraction angiography (DSA) as the gold standard.

METHODS

In a prospective study of 81 patients referred for DSA, CE-MRA and DSA studies were performed within 72 hours of each other. CE-MRA was performed on a 1.5 Tesla clinical MRI scanner using a five-channel neurovascular array (head and neck coil), with dynamic tracking of the IV gadolinium bolus. CE-MRAs and DSA films were read by two interventional neuroradiologists blinded to the clinical presentation of the patient.

RESULTS

On DSA, there were 77 vascular stenoses > or =50% identified, 51 extracranial and 26 intracranial. The overall sensitivity of CE-MRA using the neurovascular array for the detection of vascular stenoses > or =50% was 57% (95% CI: 46 to 68%) with a specificity of 98% (97 to 99%). The sensitivity for the detection of extracranial vascular stenoses > or =50% was 82% (72 to 93%) with a specificity of 97% (96 to 98%). However, the sensitivity for the detection of intracranial vascular stenoses > or =50% was only 8% (0 to 18%), with a specificity of 99% (98 to 100%).

CONCLUSIONS

At this stage Contrast-enhanced MR angiography using a neurovascular coil shows promise as a rapid, specific, and noninvasive screening method for extracranial vascular disease, but not for intracranial vascular disease.

Contrast enhanced harmonic ultrasound for differentiating breast tumors - first results

PURPOSE

To investigate the extent to which indeterminate lesions of the breast can be differentiated in the early and late phase after bolus injection of the ultrasound contrast medium Optison.

MATERIALS AND METHODS

Fifty female patients (mean age: 49 years) with a altogether 53 preoperatively impalpable indeterminate breast tumors, 20 fibroadenomas and 33 carcinomas, were examined by B-mode imaging and contrast medium-enhanced ultrasound with power Doppler (three patients had multifocal carcinomas). The tumors had a diameter of 5-15 mm (mean diameter: 9 mm). Histological confirmation was performed in all lesions by vacuum biopsies and/or surgical preparation. All examinations were performed with a multifrequency linear array probe (5-10 MHz, Logiq9 and Logiq 7, GE). Power Doppler (PD) and B-mode imaging as well as tissue harmonic imaging (THI) were employed. A bolus of 0.5 ml Optison was injected intravenously and spreading of the contrast enhancement and washout in the tumors were followed for at least 20 minutes. A low mechanical index was chosen to avoid early destruction of the microbubbles. Maximum tumor size was measured and tumors vessels were evaluated in digital cine ultrasound sequences.

RESULTS

Without CM administration, 14 of 19 tumor lesions smaller than 10 mm could be distinguished better from the surrounding tissue with THI compared to fundamental B-mode imaging. Both benign (17/20) and malignant (30/33) tumors exhibited increased tumor marginal vessels or intratumoral vessels in the early phase after CM injection. A diffuse contrast medium accumulation was observed in the late phase (8-18 min, mean: 12 min) in 30 of 33 malignant tumors, but in none of the benign tumors. The diagnostic confirmation for this late enhancement was there with 90% for the malignant tumors.

CONCLUSION

After intravenous bolus administration of Optison, breast carcinomas appear to have a prolonged diffuse enhancement of central tumor vasularity in the late phase compared to an earlier marginal vascularity of fibroadenomas.

A standard for radiopacity of root-end (retrograde) filling materials is urgently needed

AIM

To assess the radiopacity of materials used, or recommended for use, as apical root-end (retrograde) fillings.

METHODOLOGY

The radiopacity of 14 materials falling into the category of root-end filling materials was measured in equivalent millimetres of aluminium (mm Al) using a new computerized method. These included temporary or intermediate sealing materials; composite, compomer and GIC filling materials; EBA-derived cements; amalgam, etc. Gutta-percha cone material was added as a control. Samples of 1 mm thickness were radiographed on periapical film alongside an aluminium step wedge calibrated in millimetres, and the opacity of the materials, in greyscale or pseudo-colour, was compared with the equivalent step.

RESULTS

The radiopacity ranged from 1.75 mm Al to >10 mm Al. The lower range appears insufficient for routine clinical detection when it is compared with the minimal requirement for intracanal fillings.

CONCLUSIONS

Because of the proliferation of root-end filling materials with a broad range of radiopacity, an international standard stipulating the required minimal radiopacity, as well as other properties, is needed urgently. It should be based on in vitro results and on large-scale clinical radiographic surveys.

Methylcellulose gel is a superior contrast agent for ultrasound examination of the cervix in obstetric patients

OBJECTIVE

To determine the superior contrast agent for cervical sonography: water-soluble methylcellulose gel vs. normal saline.

METHODS

Women with an indication for cervical sonography underwent placement of 10 mL water-soluble methylcellulose gel or normal saline. Assessment of cervical dimensions and contour was performed via transperineal sonography prior to and after contrast placement.

RESULTS

Twenty-five patients with similar demographic characteristics and indications for ultrasonography were enrolled into each group. Administration of contrast improved the ability to visualize the external os or vaginal fornices in 18 women in the gel group vs. six in the saline group (P = 0.002). In the gel group, 17 patients had easier identification of the external os and visualization of the fornices was enhanced in 13 patients. The assessment of cervical length prior to and after contrast administration was not statistically different with the use of either of these agents.

CONCLUSION

Intravaginal soluble gel is superior to normal saline as a cervical contrast agent. Intravaginal contrast may allow for easier identification of cervical anatomy during ultrasonographic examination in selected patients.

Dialysis and contrast media

In a previous survey we revealed uncertainty among responders about (a) whether or not to perform hemodialysis in patients with severely reduced renal function who had received contrast medium; and (b) when to perform hemodialysis in patients on regular treatment with hemodialysis or continuous ambulatory dialysis who received contrast medium. Therefore, the Contrast Media Safety Committee of The European Society of Urogenital Radiology decided to review the literature and to issue guidelines. The committee performed a Medline search. Based on this, a report and guidelines were prepared. The report was discussed at the Ninth European Symposium on Urogenital Radiology in Genoa, Italy. Hemodialysis and peritoneal dialysis safely remove both iodinated and gadolinium-based contrast media. The effectiveness of hemodialysis depends on many factors including blood and dialysate flow rate, permeability of dialysis membrane, duration of hemodialysis and molecular size, protein binding, hydrophilicity, and electrical charge of the contrast medium. Generally, several hemodialysis sessions are needed to removal all contrast medium, whereas it takes 3 weeks for continuous ambulatory dialysis to remove the agent completely. There is no need to schedule the dialysis in relation to the injection of iodinated or MR contrast media or the injection of contrast agent in relation to the dialysis program. Hemodialysis does not protect poorly functioning kidneys against contrast-medium-induced nephrotoxicity. Simple guidelines are given.

Comparison between GdDTPA and two gadolinium polyoxometalates as potential MRI contrast agents

Two gadolinium polyoxometalates, Gd(2)P(2)W(18)O(62) and K(15)[(GdO)(3)(PW(9)O(34))(2)], have been evaluated by in vivo as well as in vitro experiments as the candidates of tissue-specific magnetic resonance imaging (MRI) contrast agents. T(1)-relaxivities of 28.4 mM(-1).s(-1) for Gd(2)P(2)W(18)O(62) and 11.2 mM(-1).s(-1) for K(15)[(GdO)(3)(PW(9)O(34))(2)] (400 MHz, 25 degrees C) were higher than that of the commercial MRI contrast agent (GdDTPA). Their relaxivities in bovine serum albumin and human serum transferrin were also reported. The favorable liver-specific contrast enhancement and renal excretion capability in in vivo MRI with Sprague-Dawley rats after i.v. administration of K(15)[(GdO)(3)(PW(9)O(34))(2)] was demonstrated. In vivo and in vitro assay showed that K(15)[(GdO)(3)(PW(9)O(34))(2)] is a promising liver-specific MRI contrast agent. However, Gd(2)P(2)W(18)O(62) did not show the favorable quality in vivo as expected from its high relaxivity in vitro, which was attributed to low bioavailability, indicating that it is of limited value as tissue-specific MRI contrast agent.

Differential conjugation of tat peptide to superparamagnetic nanoparticles and its effect on cellular uptake

Surface modification of superparamagnetic contrast agents with HIV-1 tat peptide has emerged as a promising means for intracellular magnetic labeling and noninvasive tracking of a large number of cell types with MRI. To achieve efficient intracellular delivery of the nanoparticles, we investigated the effect on cellular uptake of superparamagnetic iron oxide particles by varying the number of attached tat peptides. First, we report here a modified P2T method in measuring the numbers of surface attachments per particle through disulfide linkage. The method was shown to have desirable simplicity and reproducibility. With the P2T method as a tool, conjugates with progressively higher ratios of peptide-to-particle were synthesized. We were able to demonstrate that higher numbers of tat peptide facilitate the cellular uptake of iron oxide nanoparticles in a nonlinear fashion. Cells labeled with these optimized preparations were readily detectable by MR imaging. The increase in sensitivity could allow in vivo tracking of 100-fold lower cell concentration than currently described.

The value of contrast-enhanced color Doppler ultrasound in the detection of vascularization of finger joints in patients with rheumatoid arthritis

OBJECTIVE

A prospective study was performed to assess the usefulness of contrast-enhanced color Doppler ultrasound (CDUS) in the evaluation of intraarticular vascularization of finger joints in patients with rheumatoid arthritis (RA).

METHODS

We investigated 198 finger joints in 46 patients with RA, and 80 finger joints in 10 healthy volunteers. Joints with varying levels of clinical activity of inflammation were classified as being active, moderately active, or inactive. CDUS was performed with a high-frequency multi-D linear array transducer. A microbubble-based ultrasound (US) contrast agent (Levovist; Schering, Berlin, Germany) was intravenously infused. Doppler findings were rated on the basis of both unenhanced and contrast-enhanced CDUS images.

RESULTS

Healthy joints showed no intraarticular vascularization on either unenhanced or contrast-enhanced CDUS. Unenhanced CDUS detected intraarticular vascularization in 7 (8%) of 83 inactive joints, in 31 (52%) of 60 moderately active joints, and in 32 (58%) of 55 active joints. Contrast-enhanced CDUS detected intraarticular vascularization in 41 (49%) of 83 joints with inactive RA, in 59 (98%) of 60 joints with moderately active RA, and in all 55 joints with active RA. Detection of intraarticular vascularization was improved by administration of the microbubble-based US contrast agent (P < 0.001). Contrast-enhanced CDUS demonstrated differences in intraarticular vascularization between joints with inactive RA and those with active RA (P < 0.001), between joints with inactive RA and those with moderately active RA (P < 0.001), and between joints with moderately active RA and those with active RA (P < 0.001).

CONCLUSION

The use of a microbubble-based US contrast agent significantly improved the detection of intraarticular vascularization in the finger joints of patients with RA. This technique seems to be a useful adjunct in the assessment of disease activity.