Showing papers in "European Radiology in 2004"

Self-expanding nitinol stents: material and design considerations

Abstract: Nitinol (nickel–titanium) alloys exhibit a combination of properties which make these alloys particularly suited for self-expanding stents. Some of these properties cannot be found in engineering materials used for stents presently. This article explains the fundamental mechanism of shape memory and superelasticity, and how they relate to the characteristic performance of self-expanding stents. Nitinol stents are manufactured to a size slightly larger than the target vessel size and delivered constrained in a delivery system. After deployment, they position themselves against the vessel wall with a low, "chronic" outward force. They resist outside forces with a significantly higher radial resistive force. Despite the high nickel content of Nitinol, its corrosion resistance and biocompatibility is equal to that of other implant materials. The most common Nitinol stents are listed and described.

Volumetric measurements of pulmonary nodules at multi-row detector CT: in vivo reproducibility.

Abstract: The aim of this study was to assess the in vivo measurement precision of a software tool for volumetric analysis of pulmonary nodules from two consecutive low-dose multi-row detector CT scans. A total of 151 pulmonary nodules (diameter 2.2-20.5 mm, mean diameter 7.4+/-4.5 mm) in ten subjects with pulmonary metastases were examined with low-dose four-detector-row CT (120 kVp, 20 mAs (effective), collimation 4x1 mm, normalized pitch 1.75, slice thickness 1.25 mm, reconstruction increment 0.8 mm; Somatom VolumeZoom, Siemens). Two consecutive low-dose scans covering the whole lung were performed within 10 min. Nodule volume was determined for all pulmonary nodules visually detected in both scans using the volumetry tool included in the Siemens LungCare software. The 95% limits of agreement between nodule volume measurements on different scans were calculated using the Bland and Altman method for assessing measurement agreement. Intra- and interobserver agreement of volume measurement were determined using repetitive measurements of 50 randomly selected nodules at the same scan by the same and different observers. Taking into account all 151 nodules, 95% limits of agreement were -20.4 to 21.9% (standard error 1.5%); they were -19.3 to 20.4% (standard error 1.7%) for 105 nodules <10 mm. Limits of agreement were -3.9 to 5.7% for intraobserver and -5.5 to 6.6% for interobserver agreement. Precision of in vivo volumetric analysis of nodules with an automatic volumetry software tool was sufficiently high to allow for detection of clinically relevant growth in small pulmonary nodules.

Hepatobiliary contrast agents for contrast-enhanced MRI of the liver: properties, clinical development and applications

Abstract: Hepatobiliary contrast agents with uptake into hepatocytes followed by variable biliary excretion represent a unique class of cell-specific MR contrast agents Two hepatobiliary contrast agents, mangafodipir trisodium and gadobenate dimeglumine, are already clinically approved A third hepatobiliary contrast agent, Gd-EOB-DTPA, is under consideration The purpose of this review is to provide an overview on the properties, clinical development and application of these three hepatobiliary contrast agents Bolus injectable paramagnetic hepatobiliary contrast agents combine established features of extracellular agents with the advantages of hepatocyte specificity The detection and characterisation of focal liver disease appears to be improved compared to unenhanced MRI, MRI with unspecific contrast agents and contrast-enhanced CT To decrease the total time spent by a patient in the MR scanner, it is advisable to administer the agent immediately after acquisition of unenhanced T1-w MRI After infusion or bolus injection (with dynamic FS-T1-w 2D or 3D GRE) of the contrast agent, moderately and heavily T2w images are acquired Post-contrast T1-w MRI is started upon completion of T2-w MRI for mangafodipir trisodium and Gd-EOB-DTPA as early as 20 min following injection, while gadobenate dimeglumine scans are obtained >60 min following injection Post-contrast acquisition techniques with near isotropic 3D pulse sequences with fat saturation parallel the technical progress made by MSCT combined with an unparalleled improvement in tumour-liver contrast The individual decision that hepatobiliary contrast agent one uses is partly based on personal preferences No comparative studies have been conducted comparing the advantages or disadvantages of all three agents directly against each other

Technology overview: SonoVue (Bracco, Milan).

Abstract: Ultrasound contrast agents introduced to sonography the possibility to demonstrate microvascular organization and parenchymal perfusion. In combination with modern contrast-specific imaging modalities, contrast agent signals can be separated from tissue-derived signals, allowing the detection of extremely small quantities of contrast agent. The following article describes the physical principles for the creation of contrast-specific signals, the particular physicochemical characteristics of SonoVue, a second-generation ultrasound contrast agent, and the resulting possibilities for the assessment of physiological functions.

Capacity of human monocytes to phagocytose approved iron oxide MR contrast agents in vitro.

Abstract: To evaluate the capacity of human monocytes to phagocytose various approved iron oxide based magnetic resonance (MR) contrast agents and to optimize in vitro labeling of these cells. Human monocytes were incubated with two superparamagnetic iron oxide particles (SPIO) as well as two ultrasmall SPIO (USPIO) at varying iron oxide concentrations and incubation times. Iron uptake in monocytes was proven by histology, quantified by atomic emission absorption spectrometry and depicted with T2* weighted fast field echo (FFE) MR images at 1.5 T. Additionally, induction of apoptosis in iron oxide labeled monocytes was determined by YO-PRO-1 staining. Cellular iron uptake was significantly (P<0.01) higher after incubation with SPIO compared with USPIO. For SPIO, the iron oxide uptake was significantly (P<0.01) higher after incubation with the ionic Ferucarbotran as compared with the non-ionic Ferumoxides. Efficient cell labeling was achieved after incubation with Ferucarbotran at concentrations ≧500 μg Fe/ml and incubation times ≧1 h, resulting in a maximal iron oxide uptake of up to 50 pg Fe/cell without impairment of cell viability. In vitro labeling of human monocytes for MR imaging is most effectively obtained with the approved SPIO Ferucarbotran. Potential subsequent in vivo cell tracking applications comprise, e.g. specific targeting of inflammatory processes.

The influence of preoperative MRI of the breasts on recurrence rate in patients with breast cancer

Abstract: Preoperative MRI of the breasts has been proven to be the most sensitive imaging modality in the detection of multifocal or multicentric tumor manifestations as well as simultaneous contralateral breast cancer. The aim of the presented retrospective study was to evaluate the benefit of preoperative MRI for patients with breast cancer. Preoperative MRI performed in 121 patients (group A) were compared to 225 patients without preoperative MRI (group B). Patients of group A underwent contrast-enhanced MR imaging of the breast using a 2D FLASH sequence technique (TR/TE/FA 336 ms/5 ms/90°; 32 slices of 4-mm thickness, time of acquisition 1:27 min, contrast agent dosage 0.1 mmol Gd-DTPA/kg bw). All patients had histologically verified breast cancer and follow-up for more than 20 months (mean time group A: 40.3 months, group B: 41 months). Both groups received the same types of systemic treatment after breast conserving surgery. The in-breast tumor recurrence rate in group A was 1/86 (1.2%) compared to 9/133 (6.8%) in group B. Contralateral carcinoma were detected within follow-up in 2/121 (1.7%) in group A vs. 9/225 (4%) in group B. All results were statistically significant (P<0.001). Based on these results, preoperative MRI of the breasts is recommended in patients with histopathologically verified breast cancer for local staging.

Locally advanced breast cancer: comparison of mammography, sonography and MR imaging in evaluation of residual disease in women receiving neoadjuvant chemotherapy

Abstract: The accuracy of mammography, sonography and magnetic resonance imaging (MRI) in identifying residual disease after neoadjuvant chemotherapy is evaluated and imaging findings are correlated with pathologic findings. Fifteen patients enrolled in an experimental protocol of preoperative neoadjuvant chemotherapy underwent clinical examination, mammography, sonography and dynamic MRI, performed in this order, before and respectively after 2 and 4 cycles of neoadjuvant chemotherapy. Four radiologists, two for mammography, one for sonography and one for MR, examined the images, blinded to the results of the other examinations. All patients underwent radical or conservative surgery, and imaging findings were compared with pathologic findings. MRI identified 2/15 (13.3.%) clinically complete response (CR), 9/15 (60%) partial response (PR), 3/15 (20%) stable disease (SD) and 1/15 (6.7%) progressive disease. Mammography identified 1/15 (6.7%) clinically CR, 8/15 (53.3%) PR and 4/15 (27%) SD, and was not able to evaluate the disease in 2/15 (13%) cases. Sonography presented the same results as MRI. Therefore, MRI and sonography compared to mammography correctly identified residual disease in 100 vs. 86%. MRI resulted in two false-negative results because of the presence of microfoci of in situ ductal carcinoma (DCIS) and invasive lobular carcinoma (LCI). MRI was superior to mammography in cases of multifocal or multicentric disease (83 vs. 33%). Sonography performed after MRI improves the accuracy in evaluation of uncertain foci of multifocal disease seen on MR images with an increase of diagnostic accuracy from 73 to 84.5%. MRI assesses response to neoadjuvant chemotherapy better than traditional methods of physical examination and mammography.

A pragmatic approach to metal artifact reduction in CT: merging of metal artifact reduced images.

Abstract: The purpose of this study was to improve metal artifact reduction (MAR) in X-ray computed tomography (CT) by the combination of two artifact reduction methods. The presented method constitutes an image-based weighted superposition of images processed with two known methods for MAR: linear interpolation of reprojected metal traces (LI) and multi-dimensional adaptive filtering of the raw data (MAF). Two weighting concepts were realized that take into account mean distances of image points from metal objects or additional directional components. Artifact reduction on patient data from the jaw and the hip region shows that although the application of only one of the MAR algorithms can already improve image quality, these methods have specific drawbacks. While MAF does not correct corrupted CT values, LI often introduces secondary artifacts. The corrective impact of the merging algorithm is almost always superior to the application of only one of the methods. The results obtained with directional weighting are equal to or in many cases better than those of the distance weighting scheme. Merging combines the advantages of two fundamentally different approaches to artifact reduction and can improve the quality of images that are affected by metal artifacts.

Current trends in treatment of osteoid osteoma with an emphasis on radiofrequency ablation

Abstract: This article reviews current trends in the treatment of osteoid osteoma with an emphasis on the evolving use of radiofrequency thermoablation as a primary definitive treatment and for recurrent and residual lesions. In so doing, the article reviews merits and relative disadvantages of both surgical and non-surgical imaging-guided techniques in treatment. Radiofrequency ablation of osteoid osteoma is a highly effective, efficient, minimally invasive and safe method of treating osteoid osteoma. Clinical success range from 76 to 100%. Surgery remains the standard treatment in cases where histology of the lesion is in doubt, neurovascular structures are within 1.5 cm or in repeated failure of any other minimally invasive ablative technique or percutaneous resection. Clinical success of surgery ranges from 88 to 100%. Laser interstitial thermal therapy shares many of the advantages and much of the success of radiofrequency thermoablation but has not been as available. Clinical success ranges from 87 to 100%. Cryotherapy, ethanol therapy and imaging-guided excision remain second-line therapies. Clinical success ranges from 77 to 100% for imaging-guided resection and 100% for ethanol therapy.

Assessment of ventricular function and mass by cardiac magnetic resonance imaging

Abstract: Cardiac magnetic resonance imaging is currently the technique of choice for precise measurements of ventricular volumes, function and left ventricular (LV) mass. The technique is 3D and hence independent of geometrical assumptions; this, along with its excellent definition of endocardial and epicardial borders, makes it highly accurate and reproducible. Cardiac magnetic resonance (CMR) is particularly useful in research, as it is highly sensitive to small changes in ejection fraction and mass, and only a small number of subjects are required for a study. The excellent reproducibility makes temporal follow-up of any individual patient in the clinical setting a realistic possibility. This review examines the merits of CMR and describes the techniques used.

Fixed-flexion radiography of the knee provides reproducible joint space width measurements in osteoarthritis.

Abstract: The validity of a non-fluoroscopic fixed-flexion radiographic acquisition and analysis protocol for measurement of joint space width (JSW) in knee osteoarthritis is determined. A cross-sectional study of 165 patients with documented knee osteoarthritis participating in a multicenter, prospective study of chondroprotective agents was performed. All patients had posteroanterior, weight-bearing, fixed-flexion radiography with 10° caudal beam angulation. A specially designed frame (SynaFlexer) was used to standardize the positioning. Minimum medial and lateral JSW were measured manually and twice by an automated analysis system to determine inter-technique and intra-reader concordance and reliability. A random subsample of 30 patients had repeat knee radiographs 2 weeks apart to estimate short-term reproducibility using automated analysis. Concordance between manual and automated medial JSW measurements was high (ICC=0.90); lateral compartment measurements showed somewhat less concordance (ICC=0.72). There was excellent concordance between repeated automated JSW measurements performed 6 months apart for the medial (ICC=0.94) and lateral (ICC=0.86) compartments. Short-term reproducibility for the subsample of 30 cases with repeat acquisitions demonstrated an average SD of 0.14 mm for medial JSW (CV=4.3%) and 0.23 mm for lateral JSW (CV=4.0%). Fixed-flexion radiography of the knee using a positioning device provides consistent, reliable and reproducible measurement of minimum JSW in knee osteoarthritis without the need for concurrent fluoroscopic guidance.

Contrast-agent detection and quantification.

Abstract: The Cadence contrast pulse sequencing (CPS) technology offers improved clinical information and workflow efficiency during contrast agent examinations The technology harnesses unique non-linear microbubble energy discovered within the same fundamental frequency band as the transmitted pulses of sound and thus offers improved sensitivity and penetration An auto tracking contrast quantification (ACQ) technology further complements the CPS detection technology with automatic image alignment during quantification with features such as on-line multiple time intensity curves (TIC) The regional image analysis holds promise of alleviating workflow inefficiency associated with manual alignment of image frames

Evaluation of hepatocellular carcinoma using SonoVue, a second generation ultrasound contrast agent: correlation with cellular differentiation

Abstract: The appearance of hepatocellular carcinoma (HCC) with contrast-enhanced ultrasound (CEUS) in the vascular phase is described and evaluated as to whether the enhancement pattern correlates with the degree of cellular differentiation. One hundred four HCCs were prospectively evaluated with CEUS using coherent-contrast imaging (CCI) and SonoVue with a low mechanical index ( 95% of HCCs, with a few well-differentiated cases not being diagnosed due to the absence of enhancement. Echogenicity in the portal and late phases correlated with cellular differentiation.

Multislice CT imaging of anomalous coronary arteries.

Abstract: The purpose of the present study was to evaluate the role of 16 multislice computed tomography (MSCT) to identify the origin of anomalous coronary arteries and to confirm their anatomic course in relation to the great vessels. Accuracy of coronary artery disease (CAD) detection was a secondary aim and was tested with conventional angiograms (CA) serving as standard of reference. Two hundred and forty-two consecutive patients referred for noninvasive coronary CT imaging were reviewed for the study. Sixteen patients (6.6%) with anomalous coronary arteries were detected and included as the study group. MSCT and CA images were analyzed in a blinded fashion for accuracy of anomalous artery origin and path detection. Results were compared in a secondary consensus evaluation. Accuracy ratios to detect CAD with MSCT in all vessels were calculated. Coronary anomalies for all 16 patients were correctly displayed on MSCT. CA alone achieved correct identification of the abnormality in only 53% (P=0.016). Sensitivity and specificity of MSCT to detect significantly stenosed vessels was 90 and 92%. 16-MSCT is accurate to delineate abnormally branching coronary arteries and allows sufficiently accurate detection of obstructive coronary artery disease in distal branches. It should therefore be considered as a prime non-invasive imaging tool for suspected coronary anomalies.

Longitudinal study of vertebral type-1 end-plate changes on MR of the lumbar spine

Abstract: The purpose of this study was to investigate the temporal evolution of type-1 end-plate changes on MRI in patients with degenerative disease of the lumbar spine and to evaluate whether any correlation exists between such evolution and the change in patients' symptoms. Forty-four patients with 48 Modic type-1 end-plate changes (low TI signal and high T2 signal) were studied. All patients had an initial and a follow-up non-contrast lumbar MRI with variable intervals between the studies (12-72 months). Severity of the end-plate changes was assessed by eyeball estimation. Correlation with patients' symptoms was studied with the help of the Visual Analogue Score (VAS), Oswestry Questionnaire Score (OQS) and patients' subjective assessment. Of the 48 disc levels with type-1 changes, 18 (37.5%) converted fully to type 2 (high T1 signal and intermediate to high T2 signal), 7 (14.6%) partially converted to type 2, 19 (39.6%) became worse (i.e. type 1 changes became more extensive) and 4 (8.3%) showed no change. Higher average VAS (5.7) and OQS (42.3) scores were noted in patients where there was worsening type-1 change and lower scores (3.8 and 27, respectively) were seen in those where there was conversion to type-2 change. These trends, however, did not reach statistical significance (P values 0.16 and 0.09 for VAS and OQS, respectively). The statistical relationship was stronger after exclusion of patients with confounding factors (i.e. changes in lumbar MRI other than end-plate changes that could independently explain the evolution of patients' symptoms) with P-values of 0.08 and 0.07 for VAS and OQS, respectively. Type-1 end-plate change represents a dynamic process and in a large majority of cases either converts to type-2 change or becomes more extensive. The evolution of type-1 change relates to change in patient's symptoms, but not to a statistically significant level.

Effect of iodinated contrast media on thyroid function in adults

Abstract: 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 (eg, 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

Diffusion-weighted MRI of soft tissue tumours.

Abstract: The purpose of this study was to evaluate the clinical utility of a multi-shot spin-echo echo-planar (SE-EPI) diffusion-weighted sequence in the diagnostic work-up of soft tissue tumours. There were 29 patients, 16 with a benign lesion and 13 with a sarcoma. Four of the sarcomas were examined both before and after radiation therapy. Diffusion-weighted imaging was performed with a multi-shot SE-EPI sequence. The b values were 0 and 600 s/mm(2). Phase navigation and pulse trigging were applied. The apparent diffusion constant (ADC) value of a large region of interest (ROI) representing the lesion was measured and compared to diagnosis and treatment. The ADC values of the benign lesions (mean 1.8 x 10(-3) mm(2)/s) overlapped with non-treated sarcomas (mean 1.7 x 10(-3) mm(2)/s). The ADC value increased in all radiated sarcomas. A multi-shot SE-EPI diffusion imaging sequence of less than 2-min duration is technically feasible in soft tissue tumours of the extremities and the trunk. The ADC values of benign soft tissue tumours and sarcomas overlapped and could not be used to differentiate between the bulk of benign and malignant tumours. However, the increase in ADC values of soft tissue sarcomas after radiotherapy warrants further studies of diffusion imaging for evaluating therapy response.

Assessment of Crohn's disease activity in the small bowel with MR and conventional enteroclysis: preliminary results.

Abstract: Every single imaging finding that can be disclosed on conventional and MR enteroclysis was correlated with the Crohn’s disease activity index (CDAI). Nineteen consecutive patients with Crohn’s disease underwent colon endoscopy and both conventional and MR enteroclysis examinations. Seventeen MR imaging findings and seven conventional enteroclysis findings were ranked on a four-point grading scale and correlated with CDAI, with a value of 150 considered as the threshold for disease activity. Six patients had active disease in the colon according to colon endoscopy. In the remaining 13 patients, the presence of deep ulcers (P=0.002), small bowel wall thickening (P=0.022) and gadolinium enhancement of mesenteric lymph nodes (P=0.014) identified on MR enteroclysis images were strongly correlated to disease activity. The product of deep ulcers and enhancement of lymph node ranks identified on MR enteroclysis were the optimum combination for discriminating active from non-active disease (F-test: 55.95, P<0.001). Additionally, the ranking of deep ulcers on conventional enteroclysis provided statistically significant differences between active and non-active patients (F-test: 14.12, P=0.004). Abnormalities strongly suggestive of active Crohn’s disease can be disclosed on MR enteroclysis examinations and may provide pictorial information for local inflammatory activity.

MR mammography in the pre-operative staging of breast cancer in patients with dense breast tissue: comparison with mammography and ultrasound.

Abstract: The aim of this study was to determine whether pre-operative MR mammography could predict the extent of breast cancer in patients with dense breasts or whether dense parenchyma will lead to false-positive or inconclusive examinations. Sixty-seven patients with dense breasts with a malignant breast tumor planned for conservative surgery were reviewed. Detection rates of mammography, ultrasound, and MR mammography were studied, and the diameters of the lesions were measured and compared with pathological examination. Pathology revealed breast cancer in 65 patients. Sensitivity for detection of index lesions was 83% for mammography, 70.8% for ultrasound, and 98% for MR mammography. Mammography underestimated tumor extent in 37%, ultrasound in 40%, and MR in 12.5%. Of the 20 patients (31%) with multifocal or multicentric carcinoma, mammography detected the lesions in 35%, ultrasound in 30%, and MR in 100%, with a false-positive rate of 12.5, 14, and 23%. The MR mammography is more accurate in assessing tumor extent and multifocality in patients with dense breasts, but benign changes may lead to false-positive examinations.

Screening for early lung cancer with low-dose spiral computed tomography: results of annual follow-up examinations in asymptomatic smokers

Abstract: The aim of this study was analysis of incidence results in a prospective one-arm feasibility study of lung cancer screening with low-radiation-dose spiral computed tomography in heavy smokers. Eight hundred seventeen smokers (≥40 years, ≥20 pack years of smoking history) underwent baseline low-dose CT. Biopsy was recommended in nodules >10 mm with CT morphology suggesting malignancy. In all other lesions follow-up with low-dose CT was recommended. Annual repeat CT was offered to all study participants. Six hundred sixty-eight (81.8%) of the 817 subjects underwent annual repeat CT with a total of 1735 follow-up years. Follow-up of non-calcified nodules present at baseline CT demonstrated growth in 11 of 792 subjects. Biopsy was performed in 8 of 11 growing nodules 7 of which represented lung cancer. Of 174 new nodules, 3 represented lung cancer. The 10 screen-detected lung cancers were all non-small cell cancer (6 stage IA, 1 stage IB, 1 stage IIIA, 2 stage IV). Five symptom-diagnosed cancers (2 small cell lung cancer: 1 limited disease, 1 extensive disease, 3 central/endobronchial non-small cell lung cancer, 2 stage IIIA, 1 stage IIIB) were diagnosed because of symptoms in the 12-month interval between two annual CT scans. Incidence of lung cancer was lower than prevalence, screen-detected cancers were smaller, and stage I was found in 70% (7 of 10) of screen-detected tumors. Only 27% (4 of 15) of invasive procedures was performed for benign lesions; however, 33% (5 of 15) of all cancers diagnosed in the population were symptom-diagnosed cancers (3 central NSCLC, all stage III, 2 SCLC) demonstrating the limitations of CT screening.

Can pre-operative contrast-enhanced dynamic MR imaging for prostate cancer predict microvessel density in prostatectomy specimens?

Abstract: The aim of this study was to correlate quantitative dynamic contrast-enhanced MRI (DCE MRI) parameters with microvessel density (MVD) in prostate carcinoma. Twenty-eight patients with biopsy-proven prostate carcinoma were examined by endorectal MRI including multiplanar T2- and T1-weighted spin-echo and dynamic T1-weighted turbo-FLASH MRI during and after intravenous Gd-DTPA administration. Microvessels were stained on surgical specimens using a CD31 monoclonal antibody. The MVD was quantified in hot spots by counting (MVC) and determining the area fraction by morphometry (MVAF). The DCE MRI data were analyzed using an open pharmacokinetic two-compartment model. In corresponding anatomic locations the time shift (Δt) between the beginning of signal enhancement of cancer and adjacent normal prostatic tissue, the degree of contrast enhancement and the contrast exchange rate constant (k21) were calculated. The MVC and MVAF were elevated in carcinoma (p<0.001 and p=0.002, respectively) and correlated to k21 (r=0.62, p<0.001 and r=0.80, p<0.001, respectively). k21-values of carcinoma were significantly higher compared with normal peripheral but not central zone tissue. Δt was longer in high compared with low-grade tumors (p=0.025). The DCE MRI can provide important information about individual MVD in prostate cancer, which may be helpful for guiding biopsy and assessing individual prognosis.

Suspected ureteral colic: plain film and sonography vs unenhanced helical CT. A prospective study in 66 patients.

Abstract: The aim of this study was to compare the sensitivity and specificity of plain abdominal films plus ultrasound, vs nonenhanced CT for the diagnosis of ureteral colic in patients with acute flank pain. During a 4-month period, 66 patients (mean age 48 years) with acute flank pain were prospectively studied by means of plain abdominal film, US, and unenhanced CT. The presence of lithiasis and of obstructive uropathy signs were determined. The plain film was only used as a guide for the US exam. Clinical follow-up of all patients was obtained. Ureteral lithiasis was confirmed in 56 patients. The CT had a greater sensitivity (93 vs 79%) and negative predictive value (71 vs 46%) for the detection of lithiasis. The combination of lithiasis plus obstructive signs showed a sensitivity and a specificity of 100% for CT and of 100 and 90%, respectively, for US. The 11 lithiasis not detected by US were passed spontaneously (10 were <5 mm). Both techniques showed similar extraurinary pathology. Computed tomography is the most accurate technique for the detection of ureteral lithiasis; however, the combination of plain film and US is an alternative to nonenhanced CT with a lower sensitivity and radiation dose that has a good practical value.

Radio-frequency ablation of colorectal liver metastases in 167 patients.

Abstract: The objective of this paper is to report our results from a prospective study of 167 patients with colorectal liver metastases treated with radio-frequency ablation (RFA). Three hundred fifty-four treatments were performed in 167 patients, 99 males, mean age 57 years (34–87). The mean number of metastases was 4.1 (1–27). The mean maximum diameter was 3.9 cm (1–12). Fifty-one (31%) had stable/treated extra-hepatic disease. Treatments were performed under general anaesthesia using US and CT guidance and single or cluster water-cooled electrodes (Valleylab, Boulder, CO). All patients had been rejected for or had refused surgical resection. Eighty percent received chemotherapy. Survival data were stratified by tumour burden at the time of first RFA. The mean number of RFA treatments was 2.1 (1–7). During a mean follow-up of 17 months (0–89), 72 developed new liver metastases and 71 developed progressive extra-hepatic disease. There were 14/354 (4%) major local complications and 22/354 (6%) minor local complications. For patients with ≤5 metastases, maximum diameter ≤5 cm and no extra-hepatic disease, the 5-year survival from the time of diagnosis was 30% and from the time of first thermal ablation was 26%. Given that the 5-year survival for operable patients is a median of 32%, our 5-year survival of 30% is promising.

Spiral CT and multidetector-row CT diagnosis of perforation of the small intestine caused by ingested foreign bodies.

Abstract: The aim of this retrospective study was to emphasize the performances of spiral CT (HCT) and multidetector-row CT (MDCT) as very effective imaging modalities for the diagnosis of intestinal perforations caused by calcified alimentary foreign bodies. Eight sites of perforations of the ileum by ingested foreign bodies were found in seven patients-one patient presenting with two separate sites of perforation. The diagnosis was successfully made by HCT in four patients and MDCT in the remaining three. Involuntarily and generally unconsciously ingested chicken and fish bones were the implicated calcified foreign bodies. The acute clinical presentations were nonspecific, mimicking more common acute abdominal conditions. A thickened intestinal segment (7/8 sites) with localized pneumoperitoneum (4/8 sites), surrounded by fatty infiltration (4/8 sites) and associated with already present or developing obstruction or sub-obstruction (5/7 patients) were the most common CT signs, but the definite diagnosis was clearly made by the identification of the calcified foreign bodies (7/7 patients). In each patient, this identification was only possible thanks to the scrupulous analysis of very thin overlapping reconstructions obtained not only in the perforation sites (6/8 sites), but also through the entire abdomen (2/8 sites). Our report emphasizes the high performances of CTA and MDCT in identifying intestinal perforation caused by calcified alimentary foreign bodies. Moreover, the high specificity of the CT diagnosis made it possible to avoid surgerical exploration in three patients.

Helical CT evaluation of the chemical composition of urinary tract calculi with a discriminant analysis of CT-attenuation values and density.

Abstract: The aim of this study was to evaluate the efficacy of helical CT using a combination of CT-attenuation values and visual assessment of stone density as well as discriminant linear analysis to predict the chemical composition of urinary calculi. One hundred human urinary calculi were obtained from a stone-analysis laboratory and placed in 20 excised pig kidneys. They were scanned at 80, 120 and 140 kV with 3-mm collimation. Average, highest and lowest CT-attenuation values and CT variability were recorded. The internal calculus structure was assessed using a wide window setting, and visual assessment of stone density was recorded. A stepwise discriminant linear analysis was performed. The following three variables were discriminant: highest CT-attenuation value, visual density, and highest CT-attenuation value/area ratio, all at 80 kV. The probability of correctly classifying stone composition with these three variables was 0.64, ranging from 0.54 for mixed calculi to 0.69 for pure calculi. The probabilities of correctly classifying calculus composition were: 0.91 for calcium oxalate monohydrate and brushite, 0.89 for cystine, 0.85 for uric acid, 0.11 for calcium oxalate dihydrate, 0.10 for hydroxyapatite, and 0.07 for struvite calculi. When the first two ranks of highest probability for the accurate classification of each calculus type were taken into account, 81% of the calculi were correctly classified. Assessment at 80 kV of the highest CT-attenuation value, visual density and the highest CT-attenuation value/area ratio accurately predicts the chemical composition of 64-81% of urinary calculi. When the first two ranks of highest probability for the accurate classification of each calculus type were taken into account, all cystine, calcium oxalate monohydrate and brushite calculi were correctly classified.

Functional magnetic resonance imaging for neurosurgical planning in neurooncology.

Abstract: Functional magnetic resonance imaging (fMRI) is a non-invasive technique that is widely available and can be used to determine the spatial relationships between tumor tissue and eloquent brain areas. Within certain limits, this functional information can be applied in the field of neurosurgery as a pre-operative mapping tool to minimize damage to eloquent brain areas. In this article, we review the literature on the use of fMRI for neurosurgical planning. The issues addressed are: (1) stimulation paradigms, (2) the influence of tumors on the blood oxygenation level-dependent (BOLD) signal, (3) post-processing the fMRI time course, (4) integration of fMRI results into neuronavigation systems, (5) the accuracy of fMRI and (6) fMRI compared to intra-operative mapping (IOM).

CT colonography: effect of experience and training on reader performance

Abstract: The purpose of this paper was to investigate the effect of radiologist experience and increasing exposure to CT colonography on reader performance. Three radiologists of differing general experience (consultant, research fellow, trainee) independently analysed 100 CT colonographic datasets. Readers had no prior experience of CT colonography and received feedback and training after the first 50 cases from an independent experienced radiologist. Diagnostic performance and reporting times were compared for the first and second 50 datasets and compared with the results of a radiologist experienced in CT colonography. Before training only the consultant reader achieved statistical equivalence with the reference standard for detection of larger polyps. After training, detection rates ranged between 25 and 58% for larger polyps. Only the trainee significantly improved after training (P=0.007), with performance of other readers unchanged or even worse. Reporting times following training were reduced significantly for the consultant and fellow (P<0.001 and P=0.03, respectively), but increased for the trainee (P<0.001). In comparison to the consultant reader, the odds of detection of larger polyps was 0.36 (CI 0.16, 0.82) for the fellow and 0.36 (CI 0.14, 0.91) for the trainee. There is considerable variation in the ability to report CT colonography. Prior experience in gastrointestinal radiology is a distinct advantage. Competence cannot be assumed even after directed training via a database of 50 cases.

Imaging of urinary tract infection in the adult.

Abstract: The diagnosis of urinary tract infection (UTI) in the adult is primarily based on typical patient symptomatology and urinary evaluation for the presence of bacteria and white blood cells. Uncomplicated UTI usually does not require radiological evaluation unless it is recurrent. Imaging should, in general, be reserved for those patients in whom conventional treatment has failed or those who have recurrent or unusually severe symptoms. Patients with conditions predisposing to infection, or complications thereof, such as diabetes mellitus or immunocompromised states, may also benefit from early imaging. If pyonephrosis is suspected, early imaging and possible urgent drainage is also warranted. Intravenous urogram and ultrasound have traditionally been used in the assessment of these patients, allowing detection of calculi, obstruction and incomplete bladder emptying. These imaging techniques, while useful, have limitations in the evaluation of renal inflammation and infection in the adult. Computerised tomography has now become accepted as a more sensitive modality for diagnosis and follow-up of complicated renal tract infection. Contrast-enhanced CT allows different phases of excretion to be studied and can define extent of disease and identify significant complications or obstruction. Nuclear medicine has a limited role in the evaluation of urinary tract infection in adults. Its main role is in the assessment of renal function, often prior to surgery. Magnetic resonance imaging has a limited but increasing role. It is particularly useful in those with iodinated contrast allergies, offering an ionising radiation free alternative in the diagnosis of both medical and surgical diseases of the kidney.

Cerebral venous sinus thrombosis

Abstract: A comprehensive synopsis on cerebral venous thrombosis is presented. It emphasizes the various aetiologies, the wide clinical spectrum and the unpredictable outcome. Imaging techniques and pitfalls are reported and the therapeutic options are discussed.

Gadolinium-based contrast media may be nephrotoxic even at approved doses

Abstract: It is generally believed that gadolinium-based contrast media are not nephrotoxic at the approved doses for MR (<0.3 mmol/kg body weight). Recently, a patient with diabetic nephropathy required dialysis because of anuria 6–7 days after MR angiography with 0.14 mmol/kg body weight gadolinium-DTPA-BMA to assess renal artery stenosis. No special precautions (e.g., hydration) had been taken. The serum creatinine levels had been within 200 and 300 μmol/l for the last 3 years with a very slow increase. This case highlights that gadolinium-based contrast media can cause contrast medium-induced nephropathy even at doses below 0.2 mmol/kg body weight in patients with multiple risk factors.