Aart J. van der Molen

CT urography: definition, indications and techniques. A guideline for clinical practice

The aim was to develop clinical guidelines for multidetector computed tomography urography (CTU) by a group of experts from the European Society of Urogenital Radiology (ESUR). Peer-reviewed papers and reviews were systematically scrutinized. A summary document was produced and discussed at the ESUR 2006 and ECR 2007 meetings with the goal to reach consensus. True evidence-based guidelines could not be formulated, but expert guidelines on indications and CTU examination technique were produced. CTU is justified as a first-line test for patients with macroscopic haematuria, at high-risk for urothelial cancer. Otherwise, CTU may be used as a problem-solving examination. A differential approach using a one-, two- or three-phase protocol is proposed, whereby the clinical indication and the patient population will determine which CTU protocol is employed. Either a combined nephrographic-excretory phase following a split-bolus intravenous injection of contrast medium, or separate nephrographic and excretory phases following a single-bolus injection can be used. Lower dose (CTDIvol 5–6 mGy) is used for benign conditions and normal dose (CTDIvol 9–12 mGy) for potential malignant disease. A low-dose (CTDIvol 2–3 mGy) unenhanced series can be added on indication. The expert-based CTU guidelines provide recommendations to optimize techniques and to unify the radiologist’s approach to CTU.

Extracellular gadolinium-based contrast media: An overview

Increasing use is made of extracellular MRI contrast agents that alter the image contrast following intravenous administration; they predominantly shorten the T1 relaxation time of tissues. The degree and location of these changes provide substantial diagnostic information. However gadolinium-based contrast agents (Gd-CA) are not inert drugs. They may cause acute non-renal adverse reactions (e.g. anaphylactoid reactions), acute renal adverse reactions (e.g. contrast induced nephropathy), delayed adverse reactions (nephrogenic systemic fibrosis) and problems at the site of injection (e.g. local necrosis). This review describes the current status of Gd-CA, their mechanism of action, chemical structure, pharmacokinetics, dosage, elimination, nephrotoxicity and adverse events.

Effect of iodinated contrast media on thyroid function in adults

Excess free iodide in the blood (ingested or injected) may cause thyrotoxicosis in patients at risk. Iodinated contrast medium solutions contain small amounts of free iodide and may be of significance for patients at risk. The free iodide may also interfere with nuclear medicine diagnostic studies and treatment. Therefore the Contrast Media Safety Committee of the European Society of Urogenital Radiology reviewed the literature on this subject in order to prepare guidelines. A report and guidelines were prepared based on an extensive Medline search. The report was discussed with the participants attending the Tenth European Symposium on Urogenital Radiology, Uppsala, Sweden, September 2003. Contrast medium induced thyrotoxicosis is rare. Contrast medium injection does not affect thyroid function tests (e.g., T3, T4, TSH) in patients with a normal thyroid. Routine monitoring of thyroid function tests before contrast medium injection in patients with a normal thyroid is not indicated even in areas where there is dietary iodine deficiency. Patients at risk of developing thyrotoxicosis after contrast medium injection are patients with Graves’ disease and patients with multinodular goiter with thyroid autonomy, especially elderly patients and patients living in areas of iodine deficiency. Patients at high-risk should be carefully monitored by endocrinologists after contrast medium examinations. Prophylaxis in these groups is not generally recommended, although it may offer some protection in selected high-risk individuals. The free iodide load of contrast media injections interferes with iodide uptake in the thyroid and therefore compromises diagnostic thyroid scintigraphy and radio-iodine treatment of thyroid malignancies for 2 months after administration of contrast media. Simple guidelines on the subject are proposed.

Development and validation of segmentation and interpolation techniques in sinograms for metal artifact suppression in CT.

PURPOSE Metal prostheses cause artifacts in computed tomography (CT) images. The purpose of this work was to design an efficient and accurate metal segmentation in raw data to achieve artifact suppression and to improve CT image quality for patients with metal hip or shoulder prostheses. METHODS The artifact suppression technique incorporates two steps: metal object segmentation in raw data and replacement of the segmented region by new values using an interpolation scheme, followed by addition of the scaled metal signal intensity. Segmentation of metal is performed directly in sinograms, making it efficient and different from current methods that perform segmentation in reconstructed images in combination with Radon transformations. Metal signal segmentation is achieved by using a Markov random field model (MRF). Three interpolation methods are applied and investigated. To provide a proof of concept, CT data of five patients with metal implants were included in the study, as well as CT data of a PMMA phantom with Teflon, PVC, and titanium inserts. Accuracy was determined quantitatively by comparing mean Hounsfield (HU) values and standard deviation (SD) as a measure of distortion in phantom images with titanium (original and suppressed) and without titanium insert. Qualitative improvement was assessed by comparing uncorrected clinical images with artifact suppressed images. RESULTS Artifacts in CT data of a phantom and five patients were automatically suppressed. The general visibility of structures clearly improved. In phantom images, the technique showed reduced SD close to the SD for the case where titanium was not inserted, indicating improved image quality. HU values in corrected images were different from expected values for all interpolation methods. Subtle differences between interpolation methods were found. CONCLUSIONS The new artifact suppression design is efficient, for instance, in terms of preserving spatial resolution, as it is applied directly to original raw data. It successfully reduced artifacts in CT images of five patients and in phantom images. Sophisticated interpolation methods are needed to obtain reliable HU values close to the prosthesis.

Magnetic resonance imaging of knee cartilage using a water selective balanced steady-state free precession sequence†

To compare an optimized water selective balanced steady‐state free precession sequence (WS‐bSSFP) with conventional magnetic resonance (MR) sequences in imaging cartilage of osteoarthritic knees.

Transepicondylar axis accuracy in computer assisted knee surgery: A comparison of the CT-based measured axis versus the CAS-determined axis

Rotational malalignment is recognized as one of the major reasons for knee pain after total knee arthroplasty (TKA). Although Computer Assisted Orthopaedic Surgery (CAOS) systems have been developed to enable more accurate and consistent alignment of implants, it is still unknown whether they significantly improve the accuracy of femoral rotational alignment as compared to conventional techniques. We evaluated the accuracy of the intraoperatively determined transepicondylar axis (TEA) with that obtained from postoperative CT-based measurement in 20 navigated TKA procedures. The intraoperatively determined axis was marked with tantalum (RSA) markers. Two observers measured the posterior condylar angle (PCA) on postoperative CT scans. The PCA measured using the intraoperatively determined axis showed an inter-observer correlation of 0.93. The intra-observer correlation, 0.96, was slightly better than when using the CT-based angle. The PCA had a range of −6° (internal rotation) to 8° (external rotation) with a mean of 3.6° for observer 1 (SD = 4.02°) and 2.8° for observer 2 (SD = 3.42°). The maximum difference between the two observers was 4°. All knees had a patellar component inserted with good patellar tracking and no anterior knee pain. The mean postoperative flexion was 113° (SD = 12.9°). The mean difference between the two epicondylar line angles was 3.1° (SD = 5.37°), with the CT-based PCA being larger. During CT-free navigation in TKA, a systematic error of 3° arose when determining the TEA. It is emphasized that the intraoperative epicondylar axis is different from the actual CT-based epicondylar axis.

Hematuria: A Problem-Based Imaging Algorithm Illustrating the Recent Dutch Guidelines on Hematuria

OBJECTIVE To present a problem-based algorithm in the work-up of patients with Hematuria. Since the 2010 Dutch Guideline on Hematuria was problem-based, this served as an illustration for such an approach.. CONCLUSION The work-up of hematuria should be individualized and risk-based. Given the a priori low likelihood of cancer in hematuria, risk categories should be established and imaging algorithms should be tailored to populations at low-risk, medium-risk and high-risk for developing urothelial cancer.

A randomized comparison of 1-h sodium bicarbonate hydration versus standard peri-procedural saline hydration in patients with chronic kidney disease undergoing intravenous contrast-enhanced computerized tomography

BACKGROUND Guidelines recommend saline hydration for prophylaxis of contrast-induced acute kidney injury (CI-AKI) in patients with chronic kidney disease (CKD) undergoing intravenous contrast media-enhanced CT (CE-CT). The safety and efficacy of a brief hydration protocol using sodium bicarbonate in this population is unknown. We analysed whether 1-h sodium bicarbonate hydration prior to CE-CT is non-inferior to saline hydration prior to and after CE-CT in CKD patients. METHODS We performed an open-label multicentre randomized trial. Patients were randomized to 250 mL of 1.4% sodium bicarbonate hydration prior to CE-CT or 1000 mL of 0.9% saline hydration prior to and, once again, after CE-CT. Primary outcome was the relative increase in serum creatinine 48-96 h post-CE-CT. Secondary outcomes were incidence of CI-AKI [serum creatinine increase >25%/>44 µmol/L (0.5 mg/dL)], recovery of renal function, the need for dialysis and 2-month hospital costs. RESULTS Five hundred and seventy adult CKD patients undergoing CE-CT were randomized between 2010 and 2012, of whom 548 were included in the intention-to-treat population. Mean relative serum creatinine increase was 1.2% for sodium bicarbonate and 1.5% for saline (mean difference -0.3%; 95% confidence interval -2.7 to 2.1, P-value for non-inferiority <0.0001). CI-AKI occurred in 22 patients (4.1%); 8 (3.0%) randomized to sodium bicarbonate versus 14 (5.1%) to saline (P = 0.23). Renal function recovered in 75 and 69% of CI-AKI patients, respectively (P = 0.81). No patients developed a need for dialysis. Mean hydration costs per patient were €224 for the sodium bicarbonate and €683 for the saline regime (P < 0.001). Other healthcare costs were similar. CONCLUSIONS Short hydration with sodium bicarbonate prior to CE-CT was non-inferior to peri-procedural saline hydration with respect to renal safety and may result in healthcare savings. [Netherlands Trial Register (http://www.trialregister.nl/trialreg/index.asp), Nr 2149, date of registration 23 December 2009.].

Reducing the risk of iodine-based and MRI contrast media administration: Recommendation for a questionnaire at the time of booking

This paper presents a practical questionnaire to be used when a contrast medium examination is requested. The questionnaire is based on the guidelines from the European Society of Urogenital Radiology. Its aim is to identify patients at increased risk of clinically relevant renal and non-renal adverse reactions to iodine-based and MRI contrast agents. The questionnaire should be completed by the referring physician when the examination is requested.

How Much Dose Can Be Saved in Three-Phase CT Urography? A Combination of Normal-Dose Corticomedullary Phase With Low-Dose Unenhanced and Excretory Phases

OBJECTIVE The purpose of this study was to investigate the degree to which the total radiation dose for CT urography can be lowered by selective reduction of the dose in the unenhanced and excretory phases when images in these phases are systematically evaluated alongside normal-dose corticomedullary phase images. SUBJECTS AND METHODS Twenty-seven patients (mean age, 74±9 years) underwent single-bolus CT urography with acquisition in the unenhanced, corticomedullary, and 5-minute excretory phases. The scanning parameters for normal-dose CT urography were as follows: 16×0.75 mm, 120 kV, and automatic exposure control technique reference tube loads of 100, 120, and 100 effective mAs (mAseff). The patients also underwent low-dose unenhanced and excretory phase scanning, in which the dose was escalated stepwise from a volume CT dose index (CTDIvol) of 1.7 to 6.6 mGy (reference 20-40-60-80 mAseff). Images were analyzed for quality and diagnostic confidence. If low-dose scans of three patients were inadequate, the study continued to the next dose level. When 20 patients were successfully included in the unenhanced and excretory phase groups, the study ended. Doses were calculated with a CT patient dosimetry calculator. RESULTS Combined with the normal dose for corticomedullary phase scanning, doses of CTDIvol 1.5 mGy for the unenhanced phase and CTDIvol 2.7 mGy for the excretory phase were sufficient. The effective dose for three-phase CT urography was lowered from 16.2 to 9.4 mSv, a decrease of 42%. Diagnostic confidence in low-dose images was equal to that in normal-dose images when low-dose unenhanced and excretory phase images were read along-side normal-dose corticomedullary phase images. CONCLUSION With a three-phase CT urographic protocol, significant dose reductions in the unenhanced and excretory phases can be achieved when these phases are combined with a normal-dose corticomedullary phase.