Trends in contrast media research the last 100 years.

This review focuses on the trends in contrast media (CM) research published in Acta Radiologica during the last 100 years, since the first edition in 1921. The main topics covered are the developments of iodine- and gadolinium-based CM. Other topics include manganese-based CM for magnetic resonance imaging (MRI) and barium for the investigation of the alimentary tract. From a historic point of view, special CM for use in cholegraphy and myelography are addressed in the review. Today, these imaging procedures are obsolete due to the development of computed tomography, MRI, and ultrasound. The historical use of radioactive thorium-based CM for angiography is also addressed. Furthermore, publications on adverse reactions to CM are reviewed.

Contrast-enhanced peripheral MRA: technique and contrast agents.

In the last decade contrast-enhanced magnetic resonance angiography (CE-MRA) has gained wide acceptance as a valuable tool in the diagnostic work-up of patients with peripheral arterial disease. This review presents current concepts in peripheral CE-MRA with emphasis on MRI technique and contrast agents. Peripheral CE-MRA is defined as an MR angiogram of the arteries from the aortic bifurcation to the feet. Advantages of CE-MRA include minimal invasiveness and lack of ionizing radiation. The basic technique employed for peripheral CE-MRA is the bolus-chase method. With this method a paramagnetic MRI contrast agent is injected intravenously and T1-weighted images are acquired in the subsequent arterial first-pass phase. In order to achieve high quality MR angiograms without interfering venous contamination or artifacts, a number of factors need to be taken into account. This includes magnetic field strength of the MRI system, receiver coil configuration, use of parallel imaging, contrast bolus timing technique, and k-space filling strategies. Furthermore, it is possible to optimize peripheral CE-MRA using venous compression techniques, hybrid scan protocols, time-resolved imaging, and steady-state MRA. Gadolinium(Gd)-based contrast agents are used for CE-MRA of the peripheral arteries. Extracellular Gd agents have a pharmacokinetic profile similar to iodinated contrast media. Accordingly, these agents are employed for first-pass MRA. Blood-pool Gd-based agents are characterized by prolonged intravascular stay, due to macromolecular structure or protein binding. These agents can be used for first-pass, as well as steady-state MRA. Some Gd-based contrast agents with low thermodynamic stability have been linked to development of nephrogenic systemic fibrosis in patients with severe renal insufficiency. Using optimized technique and a stable MRI contrast agent, peripheral CE-MRA is a safe procedure with diagnostic accuracy close to that of conventional catheter X-ray angiography.

Artificial Intelligence based detection of pneumoperitoneum on CT scans in patients presenting with acute abdominal pain: A clinical diagnostic test accuracy study.

PURPOSE: The primary aim was to investigate the diagnostic performance of an Artificial Intelligence (AI) algorithm for pneumoperitoneum detection in patients with acute abdominal pain who underwent an abdominal CT scan. METHOD: This retrospective diagnostic test accuracy study used a consecutive patient cohort from the Acute High-risk Abdominal patient population at Herlev and Gentofte Hospital, Denmark between January 1, 2019 and September 25, 2019. As reference standard, all studies were rated for pneumoperitoneum (subgroups: none, small, medium, and large amounts) by a gastrointestinal radiology consultant. The index test was a novel AI algorithm based on a sliding window approach with a deep recurrent neural network at its core. The primary outcome was the area under the curve (AUC) of the receiver operating characteristic (ROC). RESULTS: Of 331 included patients (median age 68 years (Range 19-100; 180 women)) 31 patients (9%) had pneumoperitoneum (large: 16, moderate: 7, small: 8). The AUC was 0.77 (95% CI 0.66-0.87). At a specificity of 99% (297/300, 95% CI: 97-100%), sensitivity was 52% (16/31, 95% CI 29-65%), and positive likelihood ratio was 52 (95% CI 16-165). When excluding cases with smaller amounts of free air (<0.25 mL) the AUC increased to 0.96 (95% CI 0.89-1.0). At 99% specificity, sensitivity was 81% (13/16) and positive likelihood ratio was 82 (95% CI 27 - 254). CONCLUSIONS: An AI algorithm identified pneumoperitoneum on CT scans in a clinical setting with low sensitivity but very high specificity, supporting its role for ruling in pneumoperitoneum.

Unenhanced MR Imaging in adults with clinically suspected acute appendicitis.

PURPOSE: The purpose of the study was to evaluate unenhanced Magnetic Resonance Imaging (MRI) for the diagnosis of appendicitis or another surgery-requiring condition in an adult population scheduled for emergency appendectomy based on a clinical diagnosis of suspected acute appendicitis. MATERIALS AND METHODS: The prospective study included 48 consecutive patients (29 female, 19 male, 18-70 years old, mean age=37.1 years). MRI examination was designed to be comfortable and fast; no contrast was administered. The sequences were performed during quiet respiration. The MRI findings were reviewed by two radiologists and one surgeon independent of each other and compared with surgical and pathological records. RESULTS: According to the surgical and histopathological findings 30 of 48 patients (63%) had acute appendicitis. Of the remaining 18 patients, 4 patients had no reasons for the clinical symptoms and 14 patients had other pathology. For the three reviewers the performance of MRI in the diagnosis of acute appendicitis showed the following sensitivity, specificity and accuracy ranges: 83-93%, 50-83% and 77-83%. Moderate (κ=0.51) and fair (κ=0.31) interobserver agreements in the MR diagnosis of acute appendicitis were found between the reviewers. Sensitivity, specificity and accuracy values for overall performance of MRI in detecting pelvic abnormalities were 100%, 75% (3 of 4 healthy patients were identified by MRI) and 98%, respectively. CONCLUSION: Unenhanced fast MRI is feasible as an additional fast screening before the appendectomy. It may prevent unnecessary surgeries. The fast MRI examination can be adequately performed on an MRI unit of broad range of field strengths.

Whole-body magnetic resonance angiography with additional steady-state acquisition of the infragenicular arteries in patients with peripheral arterial disease.

The purpose of this investigation was to determine if addition of infragenicular steady-state (SS) magnetic resonance angiography (MRA) to first-pass imaging improves diagnostic performance compared with first-pass imaging alone in patients with peripheral arterial disease (PAD) undergoing whole-body (WB) MRA. Twenty consecutive patients with PAD referred to digital-subtraction angiography (DSA) underwent WB-MRA. Using a bolus-chase technique, first-pass WB-MRA was performed from the supra-aortic vessels to the ankles. The blood-pool contrast agent gadofosveset trisodium was used at a dose of 0.03 mmol/kg body weight. Ten minutes after injection of the contrast agent, high-resolution (0.7-mm isotropic voxels) SS-MRA of the infragenicular arteries was performed. Using DSA as the "gold standard," sensitivities and specificities for detecting significant arterial stenoses (>/=50% luminal narrowing) with first-pass WB-MRA, SS-MRA, and combined first-pass and SS-MRA were calculated. Kappa statistics were used to determine intermodality agreement between MRA and DSA. Overall sensitivity and specificity for detecting significant arterial stenoses with first-pass WB-MRA was 0.70 (95% confidence interval 0.61 to 0.78) and 0.97 (0.94 to 0.99), respectively. In first-pass WB-MRA, the lowest sensitivity was in the infragenicular region, with a value of 0.42 (0.23 to 0.63). Combined analysis of first-pass WB-MRA and SS-MRA increased sensitivity to 0.81 (0.60 to 0.93) in the infragenicular region, with specificity of 0.94 (0.88 to 0.97). Sensitivity and specificity for detecting significant arterial stenoses with isolated infragenicular SS-MRA was 0.47 (0.27 to 0.69) and 0.86 (0.78 to 0.91), respectively. Intermodality agreement between MRA and DSA in the infragenicular region was moderate for first-pass WB-MRA (kappa = 0.49), fair for SS-MRA (kappa = 0.31), and good for combined first-pass/SS-MRA (kappa = 0.71). Addition of infragenicular SS-MRA to first-pass WB MRA improves diagnostic performance.

Whole-body magnetic resonance angiography at 3 tesla using a hybrid protocol in patients with peripheral arterial disease.

The purpose of this study was to determine the diagnostic performance of 3T whole-body magnetic resonance angiography (WB-MRA) using a hybrid protocol in comparison with a standard protocol in patients with peripheral arterial disease (PAD). In 26 consecutive patients with PAD two different protocols were used for WB-MRA: a standard sequential protocol (n = 13) and a hybrid protocol (n = 13). WB-MRA was performed using a gradient echo sequence, body coil for signal reception, and gadoterate meglumine as contrast agent (0.3 mmol/kg body weight). Two blinded observers evaluated all WB-MRA examinations with regard to presence of stenoses, as well as diagnostic quality and degree of venous contamination in each of the four stations used in WB-MRA. Digital subtraction angiography served as the method of reference. Sensitivity for detecting significant arterial disease (luminal narrowing > or = 50%) using standard-protocol WB-MRA for the two observers was 0.63 (95%CI: 0.51-0.73) and 0.66 (0.58-0.78). Specificities were 0.94 (0.91-0.97) and 0.96 (0.92-0.98), respectively. In the hybrid protocol WB-MRA sensitivities were 0.75 (0.64-0.84) and 0.70 (0.58-0.8), respectively. Specificities were 0.93 (0.88-0.96) and 0.95 (0.91-0.97). Interobserver agreement was good using both the standard and the hybrid protocol, with kappa = 0.62 (0.44-0.67) and kappa = 0.70 (0.59-0.79), respectively. WB-MRA quality scores were significantly higher in the lower leg using the hybrid protocol compared to standard protocol (p = 0.003 and p = 0.03, observers 1 and 2). Distal venous contamination scores were significantly lower with the hybrid protocol (p = 0.02 and p = 0.01, observers 1 and 2). In conclusion, hybrid-protocol WB-MRA shows a better diagnostic performance than standard protocol WB-MRA at 3 T in patients with PAD.

Whole-body MR angiography with body coil acquisition at 3 T in patients with peripheral arterial disease using the contrast agent gadofosveset trisodium.

RATIONALE AND OBJECTIVES: Whole-body magnetic resonance angiography (WB-MRA) at 3 T with body coil acquisition has not previously been investigated. In this study, WB-MRA was performed in this manner using the blood pool contrast agent gadofosveset trisodium. MATERIALS AND METHODS: Eleven consecutive patients (five men, six women) with symptomatic peripheral arterial disease (two with critical limb ischemia, nine with claudication) were examined. Conventional digital subtraction angiography (DSA) of the aorta and the inflow and runoff arteries was used as the reference method. WB-MRA was performed using four slightly overlapping stations covering the arteries from the neck to the ankles. The arterial system was divided into 42 segments that were analyzed for the presence of significant arterial disease (> or =50% luminal narrowing or occlusion) by two blinded observers. RESULTS: Sensitivities for detecting a significant arterial lesion with WB-MRA using gadofosveset as the contrast agent were 0.66 (95% confidence interval [CI], 0.49-0.79) and 0.68 (95% CI, 0.52-0.81) for the two observers. Specificities were 0.82 (95% CI, 0.74-0.88) and 0.93 (95% CI, 0.87-0.96), respectively. Intermodality agreement between WB-MRA and DSA was moderate to good, with overall kappa values of 0.44 (95% CI, 0.29-0.59) and 0.63 (95% CI, 0.5-0.77) for the two observers. Interobserver agreement for WB-MRA was good, at kappa = 0.60 (95% CI, 0.50-0.71). CONCLUSION: WB-MRA at 3 T with body coil acquisition in patients with peripheral arterial disease showed good reproducibility but only moderate to good agreement with DSA. Further assessment of the method's clinical application is warranted.