Combined PET/MRI: Global Warming-Summary Report of the 6th International Workshop on PET/MRI, March 27-29, 2017, Tübingen, Germany

The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both clinically and as a research tool, and attempted to chart future directions. The meeting addressed the use of PET/MRI and workflows in oncology, neurosciences, infection, inflammation and chronic pain syndromes, as well as deeper discussions about how best to characterise the tumour microenvironment, optimise the complementary information available from PET and MRI, and how advanced data mining and bioinformatics, as well as information from liquid biomarkers (circulating tumour cells and nucleic acids) and pathology, can be integrated to give a more complete characterisation of disease phenotype. Some issues that have dominated previous meetings, such as the accuracy of MR-based attenuation correction (AC) of the PET scan, were finally put to rest as having been adequately addressed for the majority of clinical situations. Likewise, the ability to standardise PET systems for use in multicentre trials was confirmed, thus removing a perceived barrier to larger clinical imaging trials. The meeting openly questioned whether PET/MRI should, in all cases, be used as a whole-body imaging modality or whether in many circumstances it would best be employed to give an in-depth study of previously identified disease in a single organ or region. The meeting concluded that there is still much work to be done in the integration of data from different fields and in developing a common language for all stakeholders involved. In addition, the participants advocated joint training and education for individuals who engage in routine PET/MRI. It was agreed that PET/MRI can enhance our understanding of normal and disrupted biology, and we are in a position to describe the in vivo nature of disease processes, metabolism, evolution of cancer and the monitoring of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care.

Synthetic MRI for Clinical Neuroimaging: Results of the Magnetic Resonance Image Compilation (MAGiC) Prospective, Multicenter, Multireader Trial

BACKGROUND AND PURPOSE

Synthetic MR imaging enables reconstruction of various image contrasts from 1 scan, reducing scan times and potentially providing novel information. This study is the first large, prospective comparison of synthetic-versus-conventional MR imaging for routine neuroimaging.

MATERIALS AND METHODS

A prospective multireader, multicase noninferiority trial of 1526 images read by 7 blinded neuroradiologists was performed with prospectively acquired synthetic and conventional brain MR imaging case-control pairs from 109 subjects (mean, 53.0 ± 18.5 years of age; range, 19-89 years of age) with neuroimaging indications. Each case included conventional T1- and T2-weighted, T1 and T2 FLAIR, and STIR and/or proton density and synthetic reconstructions from multiple-dynamic multiple-echo imaging. Images were randomized and independently assessed for diagnostic quality, morphologic legibility, radiologic findings indicative of diagnosis, and artifacts.

RESULTS

Clinical MR imaging studies revealed 46 healthy and 63 pathologic cases. Overall diagnostic quality of synthetic MR images was noninferior to conventional imaging on a 5-level Likert scale (P < .001; mean synthetic-conventional, -0.335 ± 0.352; Δ = 0.5; lower limit of the 95% CI, -0.402). Legibility of synthetic and conventional morphology agreed in >95%, except in the posterior limb of the internal capsule for T1, T1 FLAIR, and proton-density views (all, >80%). Synthetic T2 FLAIR had more pronounced artifacts, including +24.1% of cases with flow artifacts and +17.6% cases with white noise artifacts.

CONCLUSIONS

Overall synthetic MR imaging quality was similar to that of conventional proton-density, STIR, and T1- and T2-weighted contrast views across neurologic conditions. While artifacts were more common in synthetic T2 FLAIR, these were readily recognizable and did not mimic pathology but could necessitate additional conventional T2 FLAIR to confirm the diagnosis.

[Whole body MRI--diagnostic strategy of the future?]

Whole body magnetic resonance imaging (MRI) opens new opportunities in diagnostic radiology as systemic disease entities can be examined with high sensitivity. This can lead to a change of paradigm, so that not only organ-related but rather disease-specific MRI examination protocols can be applied which focus on the underlying pathophysiology of the disease. Whole body MRI has already been successfully used for several oncological and non-oncological indications. In addition, whole body MRI has broadened the discussion regarding its use for secondary prevention. Compared to computed tomography, MRI does not use radiation. Although whole body MRI is still in an early stage, the enormous medical and economical potential can be envisioned.

[Diagnostic performance of contrast-enhanced MR angiography of the aortoiliac arteries with the blood pool agent Vasovist: initial results in comparison to intra-arterial DSA]

PURPOSE

To prospectively assess the accuracy of contrast-enhanced MR angiography of the aortoiliac arteries using the blood pool agent Vasovist compared to unenhanced time-of-flight MRA. Conventional digital subtraction angiography served as the standard of reference.

MATERIALS AND METHODS

Twenty-nine patients with suspected or known peripheral arterial occlusive disease (PAOD) were examined by means of contrast-enhanced aortoiliac MR angiography using a dosage of 0.03 mmol/kg bodyweight Vasovist. Unenhanced two-dimensional time-of-flight (TOF) MRA of the same anatomic region was performed immediately prior to injection of the contrast agent. This study was approved by the local Institutional Review Board and informed consent was obtained from all subjects. Both contrast-enhanced and unenhanced MRA images were compared to conventional angiography with respect to the presence of vascular stenosis. Three independent, blinded readers evaluated vessel stenosis and occlusion on the basis of DSA and MR angiographic image readings. Sensitivity, specificity, accuracy, and the area under the receiver operating characteristic curve were analyzed. Correlations between readers of conventional angiograms were calculated and compared to the MR results.

RESULTS

In the case of pooled readings, unenhanced TOF MR angiography had a sensitivity of 42.6 %, a specificity of 78.4 % and an accuracy of 74.9 % for detection of clinically significant (>50 %) stenosis. Vasovist-enhanced MRA showed significant improvement in sensitivity (83.3 %), specificity (88.8 %) and accuracy (88.3 %) compared to TOF MRA (p<0.01). The areas under the receiver operating characteristic curve for quantitative measurements increased significantly (p<0.01) in the case of Vasovist-enhanced MRA compared to TOF MRA. All readers found fewer images uninterpretable with Vasovist enhancement and the agreement regarding stenosis location and degree of stenosis between MR angiography and DSA improved substantially after Vasovist administration compared to the noncontrast examination.

CONCLUSION

MR angiography using the blood pool agent Vasovist is a feasible and minimally invasive alternative to DSA and provides angiograms of the aortoiliac region with high sensitivity, specificity, and diagnostic accuracy.

Dark lumen MR colonography: can high spatial resolution VIBE imaging improve the detection of colorectal masses?

PURPOSE

To assess whether the detection of colorectal lesions can be improved using high spatial resolution VIBE imaging.

MATERIALS AND METHODS

48 patients underwent same-day dark lumen MR colonography (MRC) and conventional colonoscopy (CC) as the standard for the detection of colorectal masses. MRC was performed using contrast-enhanced standard and high spatial resolution T1-weighted 3D VIBE sequences. The findings and the image quality of the standard and high spatial resolution VIBE sequences were compared qualitatively and quantitatively. The findings of both sequences regarding colorectal lesions were compared to those of a subsequently performed colonoscopy.

RESULTS

The high spatial resolution VIBE sequence significantly improved the quantitative image quality (CNR 54.0 vs. 36.8). However, high spatial resolution VIBE imaging did not detect more colorectal lesions than the standard VIBE sequence. In addition, none of the sequences employed was able to detect lesions with a diameter of less than 5 mm (CC 40 lesions). However, 13 colorectal lesions with a diameter of greater than 5 mm were detected by both sequences (CC 15).

CONCLUSION

High spatial resolution VIBE imaging did not improve the detection of colorectal masses and MRC fails to detect colorectal lesions with a diameter of less than 5 mm.

[Cardiovascular whole-body MRI: possibilities and limitations in prevention]

Cardiovascular disease is a major challenge to the healthcare with increasing prevalence in western societies. Hence, early detection of cardiovascular pathologies and preventative strategies will experience growing relevance in the future. Magnetic resonance imaging (MRI) nowadays allows a comprehensive analysis of the cardiovascular system. By combining separate examinations of brain, arterial vasculature, and heart the technique permits early detection of pathological changes with high diagnostic accuracy void of adverse events. Such a protocol has been proven feasible and technically robust and can be performed within 45 min. Inherent limitations are low spatial resolution of whole-body MR angiography and lack of functional stress testing of the heart. However, while being suitable as a fast and comprehensive imaging technique for cardiovascular screening purposes, medical consequences and socioeconomic relevance must further be elucidated.

Measuring tongue volumes and visualizing the chewing and swallowing process using real-time TrueFISP imaging--initial clinical experience in healthy volunteers and patients with acromegaly

This study assessed both two-dimensional (2D) TrueFISP imaging for quantifying tongue volume and real-time TrueFISP imaging for evaluating chewing and swallowing in healthy volunteers and patients with acromegaly. In 50 healthy volunteers, tongue volumes were measured using a 2D TrueFISP sequence. Chewing and swallowing were visualized using a real-time TrueFISP sequence. Ten patients with acromegaly were examined twice with the same magnetic resonance imaging protocol: once prior to therapy and a second time 6 months after therapy. Prior to therapy, healthy volunteers had an average tongue volume of 140 ml for men and 90 ml for women, and patients with acromegaly had an average tongue volume of 180 ml for men and 145 ml for women. However, 6 months after therapy the mean tongue volumes in patients with acromegaly had decreased to 154 ml in the men and to 125 ml in the women. The chewing and swallowing process was normal in all volunteers. Prior to therapy, just two patients showed a chewing and swallowing pathology, which disappeared after therapy. Patients with acromegaly had larger tongue volumes than healthy volunteers, and TrueFISP imaging proved feasible for visualizing chewing and swallowing in real time and is capable of detecting possible pathologies. Furthermore, TrueFISP imaging can be used to monitor therapeutic approaches in patients with acromegaly.

[New techniques in computed tomography. Significance for urology]

Computed tomographic (CT) imaging has become the modality of choice for the assessment of patients with urological malignancies. Recently, multi-slice CT imaging was introduced, providing faster acquisition times and higher resolution leading to improved image quality. Several studies show that thin-slice, high-resolution acquisition strategies lead to an improved accuracy for T-staging, especially of renal cell carcinomas. Three-dimensional post-processing techniques for the visualization of the vascular supply as well as the ureter (CT-angiography and CT-urography) are helpful for surgical planning. Compared to conventional imaging strategies unenhanced CT images render higher sensitivities and specificities for detecting stone disease in patients with acute flank pain. In the USA unenhanced CT imaging has almost replaced conventional urography, as no contrast agent is administered and the examination time is shorter. PET/CT examinations provide information on the morphology and function of tumors in one examination. However, there are only few data available for the assessment of urologic tumors.

Gadobenate dimeglumine (MultiHance®) for magnetic resonance angiography: review of literature

Although limited in number, reports describing the use of Gd-BOPTA for 3D CE-MRA reveal that this agent is safe, well tolerated and effective for CE-MRA at doses up to 0.3 mmol/kg bodyweight. The use of Gd-BOPTA leads to additional diagnostically relevant information comparable to that attainable with conventional DSA and superior to that on non-enhanced MRA in most arterial territories. In studies in which Gd-BOPTA is compared at equal dose with other gadolinium-based MR contrast agents, Gd-BOPTA has consistently shown significantly better quantitative and qualitative performance. Thus, Gd-BOPTA can be considered to have a very favorable risk/benefit ratio for MRA. In summary, it is likely the documented superiority of Gd-BOPTA for MR angiography will lead to its broad usage for this indication wherever the agent becomes available.

Value of transesophageal echocardiography, esophago-gastroduodenoscopy and retinoscopy prior to intra-arterial fibrinolytic therapy in patients with peripheral arterial disease

BACKGROUND

We prospectively investigated the need for esophagogastroduodenoscopy (EGD), transesophageal echocardiography (TEE) and retinoscopy for pre-interventional screening in patients with peripheral arterial occlusive disease (PAD) prior to intraarterial fibrinolytic therapy.

PATIENTS AND METHODS

212 consecutive patients suffering from PAD (164 male and 48 female, mean age: 64 +/- 11 years, 161 patients stage II of Fontaine's classification, 10 patients at stage III and 41 patients at stage IV) referred for interventional treatment were included. 173 EGDs, 169 TEEs and 188 retinoscopies were performed within one week prior to fibrinolysis. 114 patients had all three examinations.

RESULTS

Pathologic findings were detected in 56 (49%) of the 114 patients: 23 erosions, 12 ulcers, 2 esophagites, 1 gastric carcinomata, 3 intracardiac thrombi, 5 aortic thrombi, 11 diabetic and 5 hypertensive retinopathies and 1 with retinal aneurysms. 30 patients (25%) received fibrinolytic therapy, despite a contraindication: The one patient with ventricular thrombus was treated as an ultimate therapy, and amputation was prevented. Two patients showing plaques covered by large thrombi in the descending thoracic aorta were treated because cranial embolism should not occur. Four diabetic patients with multilevel disease, severe claudication and prior retinal bleeding were treated. Fibrinolytic therapy was started on 23 patients after complete healing of the mucosal lesions.

CONCLUSION

TEE revealed potential sources of embolization in 4% of the patients and is justified to reduce the individual risk. Retinoscopy should be done in patients with diabetes mellitus and hypertension, and if prior bleeding is present fibrinolysis should be done only if other treatment-regimes are not available.

Recurrent exercise induced subclavian vein thrombosis in a conductor

We present a case of a young male patient with recurrent subclavian vein thrombosis due to conducting after prior successful thrombolytic therapy. Musculoskeletal problems are common among musicians. A thoracic outlet syndrome associated to a profession induced thrombosis in a musician has not been described before. Surgical removal of the first rip can prevent recurrent thrombotic occlusion of the subclavian vein, but was not performed in this patient. Considering the specific situation of a young musician there is no information whether surgical or conservative treatment is suitable to allow a successful career as an active musician.

[Prevention without radiation--a strategy for comprehensive early detection using magnetic resonance tomography]

Recent advances in hardware technology, noninvasiveness, lack of radiation and high diagnostic accuracy combine to allow the usage of magnetic resonance imaging (MRI) for disease screening in asymptomatic people. 175 volunteers were examined by means of a comprehensive 60-minute MR-screening-protocol covering four organ systems: the brain, the arterial vasculature, the heart and the colon. In 28% of the cases vascular pathology (cerebral, peripheral or cardiovascular) was detected. In up to 17% of the single examination parts relevant incidental findings were seen. The outlined comprehensive MR-protocol is an accurate and patient-friendly imaging tool for the detection of vascular pathology as well as colonic polyps. The socio-economic relevance of this screening exam has to be further investigated in larger patient cohorts.

[MR Angiography: First choice for diagnosis of the arterial vascular system]

Contrast medium-enhanced, 3D MR angiography enables an extensive and diagnostically accurate evaluation of arterial vessels in the neck, thorax, abdomen, and limbs. Advances in the field of MR apparatus technology and the introduction of contrast-medium enhanced MR angiographic techniques have made this development possible. Contrast medium-enhanced MR angiography combines the intravenous bolus administration of a paramagnetic contrast medium with the rapid acquisition of 3D datasets. The possibilities for obtaining data in the thorax and abdomen within one breath-hold, the resulting high contrast between vessel lumen and surrounding soft tissue as well as the inherent 3D nature of the images allow for diagnostically relevant image quality. In many centers contrast-enhanced 3D MR angiography has widely replaced the conventional digital subtraction roentgenography for the clarification of pathologies in arterial vessels. This review presents a survey of the technical background of contrast medium eýnhanced 3D MRA. In addition, the spectrum of indications is given and discussed on the basis of clinical examples.

0.5 M Gd chelate (Magnevist) versus 1.0 M Gd chelate (Gadovist): dose-independent effect on image quality of pelvic three-dimensional MR-angiography

To compare the effect on image quality of a 1.0 M gadolinium (Gd) chelate to that of a conventional 0.5 M Gd chelate, five healthy volunteers and seven patients with angiographically documented aorto-iliac disease underwent a mono-station three-dimensional magnetic resonance angiography (MRA) exam (Siemens SONATA, Erlangen, Germany) twice, once using Gadovist 1.0 and the other time using Magnevist as the contrast agent. All subjects received a fixed volume of Gadovist 1.0, corresponding to a dose between 0.1 and 0.15 mmol/kg body weight followed by a saline flush. For the Magnevist exam, the contrast agent volumes and flow rates were doubled. For both quantitative and qualitative analysis of the angiographic data sets, the arterial tree was divided into nine segments. 1 M Gadovist 1.0-enhanced three-dimensional MRA data sets were characterized by significantly higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values compared to 0.5 M Magnevist-enhanced images. The data revealed mean SNR/CNR increases exceeding 70% (P < 0.01). Although there was no statistically significant difference in the rating of image quality (P > 0.05), the Gadovist 1.0 exam led to better delineation of the arterial morphology, especially of small vessels.

Peripheral magnetic resonance angiography

Peripheral vascular disease (PVD) is a common disorder in western society. Reflecting on the risks and costs of contrast arteriography, magnetic resonance angiography is a powerful noninvasive imaging modality for the diagnostic workup of patients with peripheral vascular disease. This article reviews the current state of the art of magnetic resonance angiography of the peripheral vasculature.

[Modern diagnostic concepts in dissection and aortic occlusion]

For the diagnostic work-up of the aorta, non-invasive cross-sectional imaging techniques have almost replaced invasive catheter angiography. CT- and MR-angiography are supplemented by sonography which is used predominantly for the assessment of abdominal aortic aneurysm and dissections of the thoracic aorta. This review deals with the diagnostic approach to two disease entities involving the aorta: aortic dissection and aortic occlusion. Transoesophageal echocardiography (TEE), CT- and MR-angiography (MRA) are used in the assessment of aortic dissection. Published sensitivity and specificity values regarding the detection and classification of dissections into Stanford A and Stanford B range between 96-100% for all three modalities. Results for multislice CTA have not yet been reported, but can be expected to be at least as good. The ability to delineate additional information regarding the precise morphology of true and false lumen, entry and reentry-sites, the development of thrombus or paraaortic hematomas, as well as the assessment of aortic regurgitation or involvement of coronary arteries depend on the chosen technique. Reflecting the ability to collect functional imaging data, both TEE and MRA are superior to CTA in the assessment of aortic valve involvement, while TEE is the modality of choice for evaluation of coronary arteries. Sonography is of limited use in the assessment of abdominal dissections. For the evaluation of patients with suspected aortic occlusion both CTA and MRA represent the imaging modalities of choice. Both provide for a comprehensive and precise depiction of the underlying aortic morphology, the extent of collateral flow as well as delineation of distal run-off vessels. MRA should be employed in patients with impaired renal function as paramagnetic contrast agents are not nephrotoxic.

Whole-body MR imaging in 30 seconds with real-time true FISP and a continuously rolling table platform: feasibility study

A technique for whole-body magnetic resonance (MR) imaging in only 30 seconds was developed on the basis of a rolling table platform with integrated surface coils and real-time true fast imaging with steady-state precession. In five patients, all hepatic and pulmonary lesions with a diameter exceeding 8 mm were detected by using thoracic and abdominal helical computed tomography as the reference method. Whole-body MR imaging with real-time true fast imaging with steady-state precession is feasible and may be suitable for tumor screening and staging.

Rapid magnetic resonance angiography for detection of atherosclerosis

BACKGROUND

Choice of treatment for atherosclerosis depends on various clinical factors and radiological techniques. We aimed to assess the diagnostic accuracy of a new three-dimensional magnetic resonance angiography (3D MRA) strategy for the display of arterial vasculature from supra-aortic arteries to distal runoff vessels in 72 s.

METHODS

We examined five healthy volunteers and six patients over 6 weeks. Conventional digital subtraction angiography (DSA) was available as reference standard in all six patients. Magnetic resonance imaging was done on a commercially available 1.5 Tesla scanner. The imaging technique was based on the acquisition of five 3D data sets in rapid succession with an optimum single injection protocol.

FINDINGS

Compared with conventional catheter angiography, according to the findings of two independent and masked readers, whole-body MRA had overall sensitivities of 91% (95% CI 0.76-0.98) and 94% (0.8-0.99), and specificities of 93% (0.85-0.97) and 90% (0.82-0.96) for the detection of substantial vascular disease (luminal narrowing >50%), interobserver agreement for assessment of whole-body magnetic angiograms was very good (kappa=0.94; 95% CI 0.9-0.98).

INTERPRETATION

The technique provides a comprehensive non-invasive approach for morphological screening assessment of the arterial vasculature from supra-aortic arteries to the distal runoff arteries.

MR evaluation of ventricular function: true fast imaging with steady-state precession versus fast low-angle shot cine MR imaging: feasibility study

Short- and long-axis cine magnetic resonance (MR) images were obtained with a standard fast low-angle shot, or FLASH, sequence and a first-generation true fast imaging with steady-state precession (FISP) sequence on a 1.5-T MR imager. Contrast-to-noise ratios and volumetric left ventricular measurements were compared for manual and automatic segmentation. True FISP images were associated with significantly (P<.01) higher contrast-to-noise ratios and allowed better detection of the endocardial border. True FISP images were provided with short acquisition times and excellent contrast between the myocardium and the ventricular lumen.

Kontrastmittelverstärkte 3D-MR-Venographie der oberen Thoraxapertur: Erste Erfahrungen

PURPOSE

To evaluate the usefulness of three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) venography for evaluation of thoracic central veins.

MATERIALS AND METHODS

Over a 4-month period, 14 patients with suspected central venous abnormalities were examined on a 1.5 T scanner (Magnetom Sonata, SIEMENS, Germany) by means of MR venography. A FLASH-3D sequence using the following parameters was employed: TR 1.6 ms, TE 0.6 ms, TA 3.74 s, flip: 15 degrees, slab thickness 110 mm, effective slice thickness: 2.75 mm, 40 partitions, FOV 360 mm, matrix 140 x 256. 10 s prior to imaging 20 ml of Gd-DOPTA (Multihance, BRACCO, Italy) were automatically injected (MEDRAD, Pittsburgh, USA) flushed by 20 ml of normal saline (flow 4 ml/s). Six 3D data sets were acquired in immediate succession in under 24 s. Results were corroborated with findings from duplex sonography.

RESULTS

MR venograms were of diagnostic quality for all 14 patients. Compared to duplex sonography thromboses, post-thrombotic changes as well as functional compressions were reliably detected. Unsuspected findings were found in two patients.

CONCLUSION

The outlined strategy allows for dynamic diagnostic imaging of central thoracic veins. Gadolinium-enhanced breath-hold 3D MR venography is easy to perform, well tolerated and highly accurate in assessing central venous pathology.

Dynamic 3D MR angiography of the pulmonary arteries in under four seconds

Although 3D MRA has been shown to provide excellent depiction of the pulmonary arterial tree, its clinical use has been limited due to lengthy breath-holding requirements. Employing the newest gradient generation (1.5 T MR system, amplitude of 40 mT/m and a slew rate of 200 mT/m/msec), we evaluated a technique permitting the dynamic acquisition of 3D data sets of the entire pulmonary tree in under 4 seconds. Coronal image sets were collected using a repetition time of 1.64 msec and an echo time of 0.6 msec, resulting in an acquisition time of 3.74 seconds. Three volunteers and eight dyspneic patients with known or suspected pulmonary embolism underwent MRI of the pulmonary arteries. The pulmonary arterial tree was visible to a subsegmental level in all examined subjects. Regarding the presence of pulmonary emboli in four patients, there was complete concordance between MR angiographic findings and those of corroborative studies. We conclude that diagnostic MRA of the pulmonary vasculature can be obtained even in patients with severe respiratory distress.

Improved multi-station peripheral MR angiography with a dedicated vascular coil

Delineation of small branch vessels can be crucial for assessing the peripheral arterial system of patients requiring surgical grafting. Thus signal-to-noise needs to be maximized. We evaluated the performance of a dedicated peripheral vascular coil in four subjects by comparing it to the body coil using DSA as the standard of reference. SNR and CNR values of the dedicated peripheral coil exceeded those obtained with the body coil by a mean of 398%, thus permitting improved delineation of the infrapopliteal arterial morphology.

Pulmonary arteriovenous malformation: Characterization with time-resolved ultrafast 3D MR angiography

To avoid potentially deadly consequences from paradoxical emboli, early detection and accurate characterization of pulmonary arteriovenous malformations (AVMs) is highly desirable. We report on a patient with a suspected pulmonary AVM who underwent ultrafast time-resolved 3D MR angiography of the pulmonary arteries. The case documents the suitability of the MRA technique as a noninvasive alternative to computed tomographic angiography and digital subtraction angiography for accurate pre-therapeutic characterization of pulmonary AVMs.

Risk factors in young patients with peripheral atherosclerosis

BACKGROUND

Risk factors and especially the combination of multiple risk factors are associated with the development of atherosclerosis. Therefore, patients with an early manifestation of atherosclerotic disease are likely to show an extraordinary risk profile. We analysed the frequencies and severity of risk factors in young patients with manifest peripheral arterial occlusive disease as compared to old patients.

METHODS

We analysed the risk profiles in 303 patients who were sent for interventional treatment of a symptomatic peripheral arterial occlusive disease. The risk profiles were described for different age groups (54 patients under 50 years of age, 194 patients from 51 to 74 years, 55 patients over 75 years). Multiple linear regression analysis and analysis of variance were performed to look for age-dependent effects.

RESULTS

Elevated total cholesterol, and triglyceride levels and nicotine abuse were more frequent in patients younger than 50 years. Diabetes mellitus and hypertension were more frequent in patients older than 75 years. The different frequencies for smoking, diabetes mellitus and hypertension were age-related (p<0.05). Concerning laboratory parameters such as HDL- and LDL-cholesterol, fibrinogen, lipoprotein(a) and homocysteine there were no relevant age-related differences in frequency nor in absolute values with the exception of the hematocrit and uric acid. The coincidence with clinically manifest myocardial infarction was 11.15% in the patients under 50 years compared to 20.6% in those aged 51-74 years and 16.4% in those over 75 years, for cerebral stroke it was 5.6%, 17.5% and 14.5%, respectively. Patients under 50 years with peripheral arterial occlusive disease and a history of myocardial infarction were characterised by high levels of total cholesterol, triglyceride and lipoprotein(a). Excluding patients with prior myocardial infarction patients did not show any difference in risk profile between the three age groups.

CONCLUSIONS

In a population suffering from manifest peripheral arterial occlusive disease the risk profile in patients under 50 years is not different from that in older patients. In contrast an additional myocardial infarction in such a population is associated with pathological lipid profiles.

[Whole-body MRA on a rolling table platform (AngioSURF)]

PURPOSE

Development of a technique for whole-body MR angiography based on a rolling table platform and integration of a surface coil.

MATERIAL AND METHODS

The developed rolling table platform AngioSURF (System for Unlimited Rolling Field-of-view) with integrated surface coil can be mounted on top of the original patient table of a Siemens Symphony System. Data acquisition was performed with a standard body array surface coil. The system was tested on three volunteers and one patient with angiographically documented vascular pathology. Data acquisition was performed with a 3D-FLASH-sequence (TR/TE 2.1/0.7 ms, flip angle: 20 degrees, FOV 40 x 40 cm, 80 partitions, matrix 512 x 420 with zero interpolation). Five data sets were collected in immediate succession during continuous injection of a paramagnetic contrast agent. Time of acquisition per data set was 10 seconds. Table repositioning was performed manually within 3 seconds. Thus the total acquisition time amounted to 72 seconds.

RESULTS

No problems with handling occurred in any of the four cases. The excellent image quality enables detailed assessment of the displayed vascular territories.

CONCLUSIONS

The rolling table platform with integrated surface coil (AngioSURF) allows diagnostic display of the arterial vascular system from supraaortic vessels to the distal trifurcation arteries in only 72 seconds.

The pelvic digit--a rare developmental anomaly. A case report with CT correlation and review of the literature

Radiography of the pelvis may incidentally reveal a rare congenital anomaly called "pelvic digit" and it is important to be aware of its existence in order to differentiate it from acquired abnormalities due to trauma. A case of a pelvic digit with CT correlation is presented and the literature is reviewed.

MR-angiography: the role of contrast agents

Contrast-enhanced 3D MR angiography (MRA) permits comprehensive assessment of the supraaortic arteries as well as the arterial system in the chest, abdomen and lower extremities. 3D MRA combines intravenous injection of a non-nephrotoxic, paramagnetic, extracellular contrast agent that increases the signal intensity of blood by shortening its T1 value with the acquisition of a fast 3D data set. High contrast between the vascular lumen and surrounding tissues, inherent three-dimensionality and the ability to collect image data in the chest and abdomen under apnea conditions all contribute to excellent image quality. This review provides clinical applications of 3D MRA in the chest, abdomen and lower extremities based upon the available literature and several clinical examples.

Improved peripheral MRA using multi-velocity-encoding phase contrast-enhanced MRA techniques

Phase contrast MR angiography (PC-MRA) depends on phase shifts caused by blood flow. Generally, PC sequences employ one VENC (velocity-encoding) value for each encoded spatial direction to optimize the signal in major vessels during peak systolic flow. We compared a mono-(30) with a multi-(20/30/45) VENC-PC-MRA technique in 10 patients with peripheral arterial occlusive disease. In all patients, the multi-VENC-PC sequence enhanced the vascular signal in vessels with very different flow velocities in one measurement. Large fields-of-view can be measured in a relatively short examination time to obtain an overview of the peripheral arterial system of the patient when contrast-enhanced MRA is not possible.

Intravascular ultrasound angioplasty in peripheral arterial occlusion. Preliminary experience

PURPOSE

To determine if ultrasound angioplasty in a percutaneous approach was capable of recanalizing occluded arteries in acute and subacute peripheral arterial occlusions.

MATERIALS AND METHODS

We applied an ultrasound angioplasty device in a percutaneous approach in 9 patients with peripheral arterial occlusions. All patients suffered from severe leg ischemia due to subacute thrombotic occlusions.

RESULTS

The ultrasound transmitter easily created a channel within the occlusive material. To further reduce the mass of the occlusive material, an aspiration thrombectomy was performed in all cases, leading to a complete recanalization in 7 cases. In 2 cases, a remaining stenosis was successfully dilated.

CONCLUSION

Intravascular ultrasonic devices can be useful for recanalization of occluded peripheral arteries. In particular, if thrombolytic therapy of longer peripheral arterial occlusions fails or is contraindicated, ultrasound angioplasty may be a new approach for recanalization.

[Hypothenar hammer syndrome: causes, sequelae and diagnostic aspects]

PURPOSE

To investigate the reasons and disease course of Hypothenar Hammer Syndrome.

INTRODUCTION

Occlusion of the ulnar artery at the level of the hamate bone due to repetitive trauma to the hypothenar eminence is implicated as the cause of the rarely diagnosed hypothenar hammer syndrome (HHS). The thrombotic occlusion and the formation of an aneurysm of the ulnar artery and the superficial palmar arch with possible peripheral embolism of the digital arteries are a direct cause of the chronic damage to the vessel wall. Generally, HHS is diagnosed too late for recanalization to be a viable therapeutic option.

METHODS

From 1996 to 1998 the diagnosis of an HHS was made in 8 patients at our hospital. Etiology, clinical settings and disease course were assessed.

RESULTS

Our analysis suggests that HHS may be caused by a single severe trauma in addition to repetitive injuries. The pathogenesis of the syndrome is dependent on the vascular anatomy of the individual hand. Interindividual variations in the arterial supply of the affected hand influences the clinical symptomatology with possible masking of arterial occlusions.

CONCLUSION

An exact investigation concerning the pathogenesis of HHS is a precondition for treating the disease and may help to establish HHS as an occupational disease. MR-angiography may be a new approach for assessing HHS.

Interventional therapy of vascular complications caused by the hemostatic puncture closure device angio-seal

The hemostatic puncture closure device Angio-Seal is a quick, safe, and easy-to-use system, allowing rapid sealing of the vascular access site following coronary angiography and interventional procedures. It is advantageous for patients in whom early mobilization is desired and may therefore decrease hospital costs. Despite the documented low complication rate, there are some specific problems. Reporting on five cases, we describe problems in diagnosis and possible interventional therapy of Angio-Seal-associated complications such as stenosis, occlusion, or peripheral embolism. Our experience led to the concept of precise diagnosis in any patient with leg symptoms and early interventional treatment with the aim of complete removal of the intra-arterial parts of the Angio-Seal device. Any delay in diagnosis and treatment increases the risk of additional thrombotic occlusion. Spontaneous dissolution of the Angio-Seal sponge limits interventional possibilities of complete removal. Cathet. Cardiovasc. Intervent. 49:142-147, 2000.

[Therapeutic ultrasound for the recanalization of peripheral vascular occlusions]

Since the development of percutaneous transluminal angioplasty several techniques such as laser or atherectomy devices have been developed for recanalization of peripheral arterial occlusions. In a first clinical study we investigated if also the application of intravascular ultrasound can be useful for recanalization of occluded peripheral arteries. We applied an ultrasound angioplasty device (ACOLYSIS, ANGIOSONICS, USA) in a percutaneous approach in 8 patients with peripheral arterial occlusions (7 femoro-popliteal segments, 1 external iliac artery-occlusion). All patients suffered from severe leg ischemia due to subacute thrombotic occlusions. The ultrasound transmitter was introduced and advanced under fluoroscopic guidance to the site of the lesion. After activation the ultrasound transmitter was slowly advanced into the occlusion easily creating a channel within the occlusive material. Depending on the length of the occlusion (5-16 cm) treatment times ranged from 120-480 s. To further reduce the mass of the occlusive material an aspiration thrombectomy was performed in all cases leading to a complete recanalization in 6 cases. In 2 cases a remaining stenosis was successfully dilated. Intra-vascular ultrasonic devices can be useful for recanalization of occluded peripheral arteries. With the use of high-energy ultrasound a selective injury of the occlusive material can be induced without damaging the surrounding arterial wall. This selectivity is based on the differences in elasticity between the atherosclerotic plaque and the media layers. Especially if thrombolytic therapy of longer peripheral arterial occlusions fails or is contraindicated ultrasound angioplasty may be a new approach for recanalization.

Stenosis-jet can cause a dissection of the superficial femoral artery

A dissection of the superficial femoral artery mainly occurs due to trauma or manipulation of the artery by means of interventional procedures. In contrast to dissections of the carotid arteries which are known to occur spontaneously we present the case of a stenosis of the superficial femoral artery that led to a dissection caused by the stenosis-jet. The dissection on the other hand caused an appositional thrombus which led to the embolic occlusion of the pedal-arteries. In case of peripheral embolisms in patients with or without history of peripheral arterial occlusion disease it is important to look for a causing arterial pathology preferably by duplex sonography.

[Difficulties in the detection of heparin-induced thrombocytopenia type II]

We report about a 29 year old female who developed right-sided leg vein thrombosis over three levels. Thrombectomy was attempted followed by intravenous anticoagulation with heparin. The platelet count dropped acutely from 176,000/microliter to 11,000/microliter after the sixth day. A lung perfusion-ventilation-scintigraphy suggested recent pulmonary embolism by lateral, predominantly right-sided perfusion deficits. ACT scan of the pelvic region showed rethrombosis of the right common iliac vein. The clinical suspicion of heparin-induced thrombocytopenia (HIT) type II was confirmed by a positive heparin-induced platelet aggregation test and the detection of antibodies by heparin-platelet factor 4-ELISA. The patient was treated with lepirudin at body-weight-adapted dose. After recovery of the platelet count to 102,000/microliter within seven days the treatment was changed to Orgaran after exclusion of immunologic cross reactivity. An overlapping oral anticoagulation with Marcoumar was initiated. Although HIT type II usually develops over a few days, acute thrombopenia can also occur. There is therefore no safe diagnostic interval permitting a timely detection.

[Vascular imaging with magnetic resonance angiography (MRA)]

Magnetic resonance angiography (MRA) has become firmly established within the scope of diagnostic imaging procedures for assessing many pathological conditions and, depending on the questions posed, is often used on its own or as a supplementary method. MRA allows the (non)-invasive visualization of the vasculature by using the effects of moving spins on the magnetic resonance signal. MRA techniques can be classified into two different techniques depending on how the contrast is achieved: Time-of-flight (TOF) and phase contrast (PC) methods. Both methods have advantages and limitations as an imaging technique. This article outlines the basic understanding of MRA as well as the recent rapid expansion in MRA acquisition and processing techniques.

[The anxious patient during magnetic resonance tomography (MRI) examination. Health care economic aspects of patient education]

Due to the increasing debate of limiting costs in the public health system, the use of magnetic resonance imaging (MRI) has been under discussion for several times. Diagnostic imaging by means of MRI is an expensive but informative and safe method. Instead of looking on cost-benefit analysis, it is shown how the efficiency of MRI can be increased by improving patient information about this imaging method. Because of the technical conditions, up to 40% of the patients show anxiety-related-reactions. These reactions include slight discomfort up to claustrophobic reactions and panic attacks. Therefore, correct and complete informing of patients prior to MRI examinations by the physicians is very important. The given information should include technical aspects about MRI and in addition, the physician has a chance to evaluate the patients' disposition to anxiety-related-reactions. To prepare risk patients for successful MRI technics like music, prone positioning, sedatives and relaxation exercises are available. By taking patients' anxiety into consideration and using the techniques mentioned above, unnecessary costs for unsuccessful or repeated MRI examinations can be avoided and the overall costs for clinical diagnostics will be reduced.