Conception and Interpretation of Interdisciplinarity in Research Practice: Findings from Group Discussions in the Emerging Field of Digital Transformation

In recent years, we have been observing the phenomenon of an emerging scientific field: digital transformation research (DTR). Due to the diversity and complexity of its object of research digital, transformation is not effectively researchable if confined to the boundaries of individual disciplines. In the light of Scientific/Intellectual Movement theory (Frickel and Gross 2005), we wonder how interdisciplinarity could and should be mobilized to further advance the development of the field of DTR. To answer this question, we (a) need to understand how interdisciplinarity is conceived and (b) how it is considered in research practice by researchers in the emerging field. This is important, as scientists' application of interdisciplinarity will highly influence an emerging field, shape its growth, consolidation as well as its academic establishment. We conducted six group discussions with 26 researchers from different disciplines and career levels (PhD students, postdocs, professors). The discussions were studied with a structuring qualitative content analysis. The results reflect the vagueness of the concept of interdisciplinarity. Interdisciplinarity is largely conceived as multidisciplinarity. Further, the interviewees mentioned more challenges than opportunities when it comes to interdisciplinary DTR. The present study widens the scientific understanding about how researchers of different career levels perceive, learn, and practice interdisciplinarity in DTR. It further provides valuable indications of how interdisciplinary research in an emerging field can be profitably shaped for practice.

gagCEST imaging at 3 T MRI in patients with articular cartilage lesions of the knee and intraoperative validation

OBJECTIVE

The aim of this study was to compare glycosaminoglycan chemical exchange saturation transfer (gagCEST) of knee cartilage with intraoperative results for the assessment of early osteoarthritis (OA) and to define gagCEST values for the differentiation between healthy and degenerated cartilage.

DESIGN

Twenty-one patients with cartilage lesions or moderate OA were examined using 3 T Magnetic Resonance Imaging (MRI). In this prospective study, regions of interest (ROIs) were examined by a sagittal gagCEST analysis and a morphological high-resolution three-dimensional, fat-saturated proton-density space sequence. Cartilage lesions were identified arthroscopically, graded by the International Cartilage Repair Society (ICRS) score in 42 defined ROIs per patient and consecutively compared with mean gagCEST values using analysis of variance and Spearman's rank correlation test. Receiver operating characteristics (ROC) curves were applied to identify gagCEST threshold values to differentiate between the ICRS grades.

RESULTS

A total of 882 ROIs were examined and graduated in ICRS score 0 (67.3%), 1 (25.2%), 2 (6.2%) and the merged ICRS 3 and 4 (1.0%). gagCEST values decreased with increasing grade of cartilage damage with a negative correlation between gagCEST values and ICRS scores. A gagCEST value threshold of 3.55% was identified to differentiate between ICRS score 0 (normal) and all other grades.

CONCLUSIONS

gagCEST reflects the content of glycosaminoglycan and might provide a diagnostic tool for the detection of early knee-joint cartilage damage and for the non-invasive subtle differentiation between ICRS grades by MRI even at early stages in clinical practice.

[EUROCRINE®: adrenal surgery 2015-2019- surprising initial results]

Hintergrund

Seit 2015 erfolgt in Europa mithilfe des EUROCRINE®-Registers eine systematische Dokumentation endokrin-chirurgischer Operationen. Ziel dieser ersten Auswertung war eine Darstellung der Versorgungsrealität für Nebenniereneingriffe in einem homogenen Versorgungsumfeld, entsprechend des deutschsprachigen Raums – bzw. des Präsenzgebiets der Chirurgischen Arbeitsgemeinschaft Endokrinologie (CAEK) der Deutschen Gesellschaft für Allgemein- und Viszeralchirurgie (DGAV) – einschließlich einer Analyse der Adhärenz zu geltenden Therapieempfehlungen.

Methodik

Es erfolgte eine deskriptive Analyse der präoperativen Diagnostik, der angewandten Operationstechniken sowie der zugrunde liegenden histologischen Entitäten der zwischen den Jahren 2015 und 2019 über EUROCRINE® in Deutschland, Österreich und der Schweiz dokumentierten Nebennierenoperationen.

Ergebnisse

In den insgesamt 21 teilnehmenden Kliniken des deutschsprachigen EUROCRINE®-Gebiets wurden 658 Operationen an Nebennieren durchgeführt. In 90 % erfolgten unilaterale, in 3 % bilaterale Adrenalektomien und in 7 % andere Resektionsverfahren. Die in 41 % der Operationen dokumentierte histologische Hauptdiagnose war das adrenokortikale Adenom. In 15 % lagen maligne Befunde zugrunde (einschließlich 6 % Nebennierenrindenkarzinome (ACC) und 8 % Nebennierenmetastasen). 23 % der Operationen erfolgten bei Phäochromozytomen. Diese wurden zu 82 % minimal-invasiv operiert, Nebennierenrindenkarzinome lediglich zu 28 % und Nebennierenmetastasen zu 66 %.

Schlussfolgerung

Überraschenderweise wurden nach Nebennierenadenomen und Phäochromozytomen an dritthäufigster Stelle Nebennierenmetastasen unterschiedlicher Primärtumoren reseziert. 28 % der ACC waren für minimal-invasive Techniken vorgesehen, wobei 20 % dieser Fälle eine Konversion zur offenen Operation erforderten. Die aktuelle Analyse deckte Diskrepanzen zwischen Versorgungsrealität und Leitlinienempfehlungen auf, aus denen sich zahlreiche Fragestellungen ergeben, welche nun in ein überarbeitetes EUROCRINE®-Modul zur Dokumentation von Nebennierenoperationen einfließen werden.

Intraoperative validation of quantitative T2 mapping in patients with articular cartilage lesions of the knee

OBJECTIVE

The aim of this study was to compare T2 relaxation times of knee cartilage with intraoperative results for the assessment of early osteoarthritis (OA) and to define T2 values for the differentiation between healthy and degenerated cartilage.

DESIGN

Twenty-one patients with cartilage lesions or moderate OA were examined using 3T magnetic resonance imaging (MRI). In this prospective study, a total of 882 regions of interest (ROIs) were examined by a sagittal, multi-echo, spin-echo T2 sequence and a morphological high-resolution three-dimensional, fat-saturated proton-density space sequence. Cartilage lesions were identified arthroscopically, graded by the International Cartilage Repair Society (ICRS) score in 42 defined ROIs per patient and consecutively compared with mean T2 values using analysis of variance and Spearman's rank correlation test. Receiver operating characteristics (ROC) curves were developed to identify threshold T2 values to differentiate between the ICRS grades.

RESULTS

A total of 882 ROIs were examined and graduated in ICRS score 0 (67.3%), 1 (25.2%), 2 (6.2%) and the merged ICRS 3 and 4 (1.0%). T2 values increased with increasing grade of cartilage damage with a statistically significant positive correlation between T2 values and ICRS scores. A T2 value threshold of 47.6 ms was identified to differentiate between ICRS score 0 (normal) and all other grades (ROC curve analysis).

CONCLUSION

T2 mapping might provide a diagnostic tool for the detection of early knee-joint cartilage damage and for the non-invasive differentiation between ICRS grades by MRI in clinical practice.

[The utilization of MRI by orthopaedic surgeons: requirements and limitations]

BACKGROUND

The tendency in surgical fields to subspecialize continues. Diagnostic possibilities and surgical indications are becoming more and more sophisticated. As a consequence, surgeons in Germany have the possibility to acquire qualifications in magnetic resonance imaging (MRI) and are allowed to employ MRI scanners without consulting radiologists.

AIMS

This article aims to describe the requirements to achieve this special qualification and to give a summary on the legal issues in this matter.

Hole dynamics in noble metals

Hole dynamics in noble metals (Cu and Au) is investigated by means of first-principles many-body calculations. While holes in a free-electron gas are known to live shorter than electrons with the same excitation energy, our results indicate that d holes in noble metals exhibit longer inelastic lifetimes than excited sp electrons, in agreement with experiment. The density of states available for d-hole decay is larger than that for the decay of excited electrons; however, the small overlap between d and sp states below the Fermi level increases the d-hole lifetime. The impact of d-hole dynamics on electron-hole correlation effects is also addressed.

Decay times of surface plasmon excitation in metal nanoparticles by persistent spectral hole burning

We describe a new technique to determine the homogeneous linewidths of surface plasmon resonances of metal nanoparticles and thus measure the decay time of this collective electron excitation. The method is based on spectral hole burning and has been applied to supported oblate Ag particles with radii of 7.5 nm. From the experimental results and a theoretical model of hole burning the linewidth of 260 meV corresponding to a decay time of 4.8 fs was extracted. This value is shorter than expected for damping by bulk electron scattering. We conclude that additional damping mechanisms have been observed and reflect confinement of the electrons in nanoparticles with sizes below 10 nm.

The stachydrine catabolism region in Sinorhizobium meliloti encodes a multi-enzyme complex similar to the xenobiotic degrading systems in other bacteria

Stachydrine (proline betaine) can be used by Sinorhizobium meliloti as a source of carbon and nitrogen. Catabolism depends on an initial N-demethylation, after which the resultant N-methyl proline enters general metabolism. Deletion and insertion mutagenesis demonstrated that the information necessary for catabolism is carried on the symbiotic plasmid (pSym) distal to nodD2 and the nod-nif cluster. Sequencing of an 8.5kb fragment spanning this region revealed four open reading frames with functional homology to known proteins, including a putative monooxygenase and a putative NADPH-FMN-reductase, which were shown by insertional and frame-shift mutagenesis to be necessary for stachydrine catabolism. Other open reading frames, encoding a putative flavoprotein and a repressor, were judged not to be required for stachydrine catabolism, since they were not included in a fragment capable of complementing a deletion of the entire stc region. Sequence and mutagenesis data suggest that stachydrine is demethylated by an iron-sulfur monooxygenase of the Rieske type with a requirement for a specific reductase. The stc catabolic cluster, therefore, resembles xenobiotic degradation in other bacteria and recalls rhizopine catabolism in S. meliloti. Stachydrine appears to have multiple roles in osmoprotection, nutrition and nodulation. Genes involved in stachydrine catabolism are also necessary for carnitine degradation; thus, they could be important in the catabolism of a variety of root exudates and mediate other relationships.

Prevention of heterotopic ossification about the hip: final results of two randomized trials in 410 patients using either preoperative or postoperative radiation therapy

PURPOSE

Experimental and clinical data support effectiveness of perioperative radiotherapy to prevent heterotopic ossification after hip surgery or trauma. Since 1987, two prospectively randomized trials were performed in patients with high-risk factors to develop heterotopic ossification: the first (HOP 1) to assess the prophylactic efficacy of postoperative low vs. medium dose radiotherapy, and the second (HOP 2) to assess the prophylactic efficacy of pre vs. postoperative radiotherapy.

METHODS AND MATERIAL

410 patients with high risk to develop heterotopic ossifications about the hip following hip surgery were recruited. Between June 1987 and June 1992, 249 patients were randomized in HOP 1 to postoperative "low dose" (5 x 2 Gy; total: 10 Gy) or "medium dose" (5 x 3.5 Gy; total: 17.5 Gy) radiotherapy. Between July 1992 and December 1995, 161 patients were randomized in HOP 2 to either 1 x 7 Gy preoperatively (< or = 4 h before surgery) or 5 x 3.5 Gy (total: 17.5 Gy) postoperatively (< or = 96 h after surgery). With exception of age and type of implant (cemented vs. uncemented prosthesis) all confounding patient variables (gender, prior surgery) and predisposing risk factors were similarly distributed between both trials and treatment arms. Portals encompassed the periacetabular and intertrochanteric soft tissues. Radiographs were obtained prior and immediately after surgery and at least 6 months after surgery to assess the extent of ectopic bone formation about the hip. Modified Brooker grading was used to score the extent of heterotopic ossification. Harris scoring was applied to evaluate the functional hip status. If the scores decreased from immediate post or preoperative status, respectively, to the last follow-up, radiological or functional failures were assumed.

RESULTS

Effective prophylaxis was achieved in 227 (91%) hips of HOP 1 and in 142 (88%) of HOP 2. In HOP 1, 15 (11%) radiological failures were observed in the low-dose group compared to 7 (6%) in the medium dose group (p > 0.05). In HOP 2, 4 (5%) radiological failures were observed in the postoperative and 11 (19%) in the preoperative group (p < 0.05). Subgroup analysis of the preoperative group revealed that the highest failure rate occurred in patients with prophylactic radiotherapy prior to removal of ipsilateral Brooker Grade III and IV ossification (39%) (p < 0.001), while all other patients in the preoperative group had a failure rate that was comparable to postoperative treatment groups. In multivariate logistic regression analysis the number of high-risk factors for development of heterotopic ossification (p = 0.03) and the time to RT initiation (p = 0.05) were independent prognostic factors in the HOP 1 study. For the HOP 2 study, the multivariate logistic regression analysis revealed the number of high-risk factors for development of heterotopic ossification (p = 0.003), the preoperative HO grade (p = 0.001) and the RT dose concept (p = 0.05) as independent prognostic factors. Other factors including type of implant (cemented vs. uncemented) did not affect the prophylactic efficacy of radiotherapy. There were no increased intra- and postoperative complications seen in the preoperative group, and no long-term complications were observed in both HOP studies. For functional failures (decrease of Harris score) no statistically prognostic factors were found. There were less functional failures in HOP 1 (18 = 7%) than in HOP 2 (23 = 14%, but this difference was not statistically significant. Only patients with high Brooker Grade III and IV at last FU achieved a lower Harris score than those with low Brooker Grade 0, I and II (p < 0.05).

CONCLUSION

With the exception of a small subgroup of patients with ipsilateral high Brooker Grade III and IV, pre- and postoperative radiotherapy are equally effective to prevent heterotopic ossification about the hip after hip surgery and total hip arthroplasty. Fractionated medium dose radiotherapy resulted in the low

Biological activities of the nortropane alkaloid, calystegine B2, and analogs: structure-function relationships

Calystegines, polyhydroxy nortropane alkaloids, are a recently discovered group of plant secondary metabolites believed to influence rhizosphere ecology as nutritional sources for soil microorganisms and as glycosidase inhibitors. Evidence is presented that calystegines mediate nutritional relationships under natural conditions and that their biological activities are closely correlated with their chemical structures and stereochemistry. Assays using synthetic (+)- and (-)-enantiomers of calystegine B2 established that catabolism by Rhizobium meliloti, glycosidase inhibition, and allelopathic activities were uniquely associated with the natural, (+)-enantiomer. Furthermore, the N-methyl derivative of calystegine B2 was not catabolized by R. meliloti, and it inhibited alpha-galactosidase, but not beta-glucosidase, whereas the parent alkaloid inhibits both enzymes. This N-methyl analog therefore could serve to construct a cellular or animal model for Fabry's disease, which is caused by a lack of alpha-galactosidase activity.

Tissue characterisation of atherosclerotic carotid plaques by MRI

Carotid artery plaques with intraplaque haemorrhage or atheromatous debris have been found to be associated with an increased risk of embolic stroke. Other methods have failed to detect plaque morphology, and it is not clear whether MRI allows differentiation between prognostically and therapeutically relevant plaque types. We examined 17 carotid bifurcation plaques which had been removed in toto by MRI. For quantifying MR signal intensities (I) the contrast-to-noise ratio (CNR) was used: (ITissue-IRef)/SDRef, with normal saline (0.9%) as reference (Ref) and the standard deviation (SD) of the noise. Measurements were correlated with the histopathological appearance of "simple plaques", consisting of fibrous intimal thickening, lipid deposits and/or atheromatous tissue with cholesterol crystals, largely calcified plaques, and "complicated plaques", containing recent intramural haemorrhage or friable atheromatous debris. Significantly different mean CNR could be measured in the three plaque types on T1- and T2-weighted sequences (p < 0.00001) and using the FLASH pulse sequence with a flip angle of 15 degrees (p < 0.001). With the T1-weighted sequence simple plaques showed a CNR of 4.4 +/- 2.3, calcified plaques -4.8 +/- 2.6 and complicated plaques 15.1 +/- 4.3. Using this technique, each single plaque could be correctly classified, an unalterable prerequisite for a clinical application. To date, motion artefacts due to patient movement or insufficiently triggerable vessel pulsation in combination with relative long acquisition times (6-7 min) have limited in vivo investigations. If these problems could be overcome, MRI might become a valuable technique for studying carotid plaque morphology.

Endoscopic fenestration of the 3rd ventricular floor in aqueductal stenosis

Six endoscopic fenestrations of the 3rd ventricular floor have been performed in patients with stenosis (SAS) of the aqueduct of Sylvius in our institute during the last two years. The endoscopic intraventricular landmarks were the Monro's foramen followed by the mamillary bodies. The fenestration instrument was a monopolar coagulation wire, the dilatation instrument was a balloon catheter. The patients included two newborns and four adults. The two newborns developed a recurrent hydrocephalus after 2 months. The four adults remained well after the operation. The only complication was edema (SIADH syndrome) in one case for 24 hours. Flow sensitised phase MRI showed a mirroring in the prestenotic CSF pulsation curve preoperatively. This, in combination with an increased intraventricular pulsation, is a sign of reduced capacity of the subarachnoid space at the cerebral surface. The postoperative patency of the fenestration with diminished intraventricular pulsation can be demonstrated with ECG retrogated phase MRI. There was a slow and incomplete decrease of the preoperative enlarged ventricular size. This operative method is a low-risk, minimal invasive alternative method to shunt implantation in adults with SAS.

Stereotactic and ultrasound guided minimal invasive surgery of subcortical cavernomas

The experience of 7 operated patients with cavernous haemangiomas (CHa) and of 2 conservatively treated older patients is reported. There was no further postoperative neurological deficit, although 6 of the 7 patients had the CHa in an eloquent cerebral region. Two of the operated patients (22%) had several bleedings before surgery. In these cases seizures and visual field deficits remained. The relatively low rate of complications in our patient group was possible because an exact preoperative localisation helped to avoid a large traumatisation. This is possible with a stereotactic system or directly by CT guided skin marking. Intraoperative ultrasound was necessary in all cases because there was no landmark at the cerebral surface. The CHa was removed by a transsulcal microsurgical operation. A complete removal of the surrounding haemosiderin rim around the angioma seems necessary to avoid further seizures. The used technique has proved to be a simple and safe minimal invasive method.

[The postoperative MR tomographic findings following the removal of a hypophyseal adenoma]

36 patients with pituitary adenomas were examined via MRI to describe physiological changes and to visualise a residual tumour. Pre- and postoperative examinations included T1- and T2-weighted SE sequences. T1-weighted images were obtained in sagittal and coronal orientation pre- and post-Gd-DTPA application and T2-weighted images in coronal orientation. In 12 cases a residual tumour was found. Its signal intensity and contrast enhancement were similar to those of the primary tumour. Implanted material could be distinguished by localisation, decrease in volume and different signal intensity. The behaviour of contrast enhancement was helpful, since implanted material showed a rim enhancement. In our experience a sensitive imaging protocol in the follow-up of operated pituitary adenomas would be an early examination three months postoperatively followed by a control examination after one year. Information on the size and localisation of the primary tumour and the performed operative procedure is essential.

Differentiation between hemangiomas and cysts of the liver with nonenhanced MR imaging: efficacy of T2 values at 1.5 T

The authors studied the utility of non-contrast-agent-enhanced magnetic resonance (MR) imaging for differentiating cysts and cavernous hemangiomas of the liver. Nineteen patients with hemangiomas (51 lesions) and 16 with cysts (30 lesions) were studied with a 1.5-T MR imager. T2 values were calculated with the two-point method to evaluate the efficacy of T2 values in the differentiation between hemangiomas and cysts of the liver. For lesions larger than 1 cm, the mean T2 value of cysts (306 msec +/- 156) was significantly longer than that of hemangiomas (113 msec +/- 15) (P < .0001); there was no overlap of the ranges for T2 values of hemangiomas and cysts. All cysts larger than 1 cm could be differentiated from hemangiomas by using a threshold T2 value of 140 msec. This study suggests that calculated T2 values permit differentiation between hemangiomas and cysts larger than 1 cm at 1.5 T.

Calystegins, a novel class of alkaloid glycosidase inhibitors

The alkaloid extract from roots of naturally growing Convolvulus arvensis, purified by ion-exchange chromatography, showed significant inhibitory activity toward beta-glucosidase and alpha-galactosidase. The demonstrated occurrence of polyhydroxy-nortropane alkaloids, the calystegins, in C. arvensis and their structural similarity to known polyhydroxy alkaloid glycosidase inhibitors, suggested that these might be responsible for the observed activity. Pure calystegins, isolated from transformed root cultures of the related plant species Calystegia sepium, were tested for glycosidase inhibitory activity. The purity of the alkaloids was established by gas chromatography and their identity confirmed by their mass spectrometric fragmentation patterns. The trihydroxy alkaloid, calystegin A3, was a moderately good inhibitor of beta-glucosidase (Ki = 4.3 x 10(-5) M) and a weak inhibitor of alpha-galactosidase (Ki = 1.9 x 10(-4) M). An increased level of hydroxylation, as in the tetrahydroxy calystegins B, consisting of 27% calystegin B1 and 73% calystegin B2, resulted in greatly enhanced inhibitory activity. The calystegins B were potent inhibitors of beta-glucosidase (Ki = 3 x 10(-6) M) and alpha-galactosidase (Ki = 7 x 10(-6) M). These levels of activity are comparable with those of the polyhydroxy indolizidine alkaloids castanospermine and swainsonine toward alpha-glucosidase and alpha-mannosidase, respectively, and of the polyhydroxy pyrrolizidine alkaloid australine toward alpha-glucosidase. The calystegins therefore compose a new structural class of polyhydroxy alkaloids, the nortropanes, possessing potent glycosidase inhibitory properties.

[MR tomography and MR angiography of an extensive glomus jugulare tumor]

The diagnosis of a glomus jugulare tumour was established by MR tomography and MR angiography. MR tomography demarcated the tumour from the surrounding tissue and MR angiography showed the vascularity of the glomus tumour.

[MR-myelography of the lumbar spine using a PSIF sequence: first experiences]

A rapid gradient-echo acquisition (PSIF) was used to delineate the lumber spine. Because this sequence is heavily T2 weighted the cerebrospinal fluid shows a bright signal, the myelon has a poor signal. 5 healthy volunteers and 5 patients with suspected lumbar disc herniation were examined by this technique. All MR myelograms were compared with spin-echo sequences (sagittal and transversal slices). All lumbar disc herniations which were recognized by MRI were also delineated by MR myelography.

[Magnetic resonance tomographic imaging of pulsatile CSF movement in communicating hydrocephalus before and after shunt placement]

16 patients with hydrocephalus communicans and 5 healthy volunteers were examined to demonstrate the pattern of the pulsatile CSF flow. After implantation of a CSF shunt system the same patients were examined again to show the influence of the shunt on the CSF pulsations. We used a flow-sensitised, cardiac-gated 2D FLASH sequence and analysed the phase and magnitude images. It could be shown that most patients (n = 12) had a hyperdynamic pulsatile flow preoperatively. After shunt implantation the pulsatile CSF motion and the clinical symptoms were improved in 8 of these patients. MRI of pulsatile CSF flow movement seems to be a helpful noninvasive tool to estimate the prognosis of a shunt implantation in patients with hydrocephalus communicans.

[Stent-supported percutaneous therapy of iliac vein stenosis following operative thrombectomy and placement of a shunt]

Among 15 patients with acute thrombotic disease of pelvic veins who had been submitted to operative thrombectomy and creation of arteriovenous fistula in the groin, 12 presented with stenotic lesions 3 months later. These stenoses were submitted to percutaneous angioplasty. If angioplasty failed, percutaneous placement of a vascular stent (wall stent) was performed immediately (n = 7). Stenting in cross-over-technique proved practicable in all cases. Secondary stenotic disease in the exclusively dilated area was observed in 3/5 cases and was also treated with a wall stent. In one patient with recurrent stenoses who refused stenting, extended thrombosis occurred after occlusion of the AV-fistula. At mid-term PTA was successful in only two cases. Intimal hyperplasia was observed in only one wall stent treated patient. Percutaneous treatment of iliacal stenoses in patients with postthrombotic syndrome may be performed safely under the protective effect of the fistula. With the presented technique, patency of pelvic veins could be restored in 11/12 patients with postoperative significant venous stenoses.

[Potentialities and limitations of MR angiography in the imaging of intracranial aneurysms]

The potential value of MR angiography in imaging of intracranial aneurysms was analyzed in seven patients. Six cases were confirmed by angiography or computed tomography. In one patient MR angiography was not useful in distinguishing bleeding from an aneurysm. Five aneurysms were imaged by 3D angiography, one was diagnosed by 2D angiography. The extent of thrombosis was evaluated by selective presaturation. MR angiography was a useful non-invasive method in imaging of intracranial aneurysms. However, for complete work-up angiography is mandatory.

MR angiography of the liver

Recently, several versatile techniques have been developed for performing magnetic resonance (MR) angiography in the body. Relative to MR angiography in the head and neck, these methods require more interactive involvement by a physician to derive their full benefit, but they show great promise in the clinical workup of several vascular problems relating to the liver. This article outlines practical clinical applications for MR angiography of the liver, based on the experience of the authors and others working in the field.

Improved time-of-flight MR angiography of the brain with magnetization transfer contrast

The authors hypothesized that magnetization transfer contrast (MTC) could be used to improve flow contrast in time-of-flight (TOF) magnetic resonance (MR) angiography. Two- and three-dimensional flow-compensated gradient-echo images were obtained with and without MTC. MTC images were obtained by applying low-power radio-frequency (RF) radiation with a frequency offset from the bulk "free" water resonance frequency before the excitation RF pulse. The signal intensity of stationary tissue decreased as the power applied for the MTC pulse was increased. A smaller decrease occurred in venous signal intensity as measured in the superior sagittal sinus, and less change was seen in the arterial signal intensity as measured in the middle cerebral artery. Cerebrospinal fluid showed no MTC effect. The use of MTC improved small-vessel depiction on maximum-intensity projection images. The authors conclude that use of MTC can substantially enhance the quality of TOF MR angiography of the brain.

[Magnetic resonance tomography of the liver with TurboFLASH and segmented acquisition. Fast imaging with flexible image contrast]

The value of a fast imaging sequence in diagnosing focal liver lesions was assessed in 43 patients. The sequence (TurboFLASH with segmented acquisition) allows the acquisition of T1- and T2-weighted images within a breath-hold interval. Lesion-liver contrast was compared with T2-weighted spin-echo, T1-weighted gradient-echo, and single shot TurboFLASH sequences. All lesions that were seen with the latter sequences were also visible on the segmented TurboFLASH images. Contrast on the segmented TurboFLASH images was similar to that of T2-weighted spin-echo sequences and superior to T1-weighted gradient-echo sequences. Signal of fat could be nulled at an inversion time of 10 ms, signal from liver tissue could be nulled at an inversion time of 300 ms. By minimising the liver signal, the lesions could be "highlighted". This was not possible with the other imaging sequences. The segmented TurboFLASH technique allows breath-hold imaging of the liver with arbitrary image contrast. The lesion-liver contrast is comparable to time-consuming T2-weighted spin-echo sequences.

High-speed black blood imaging of vessel stenosis in the presence of pulsatile flow

Stenosis phantoms were created to study the ability of "black blood" methods to image a vessel stenosis in the presence of pulsatile flow. Black blood images were acquired with a modified TurboFLASH (fast low-angle shot) method that eliminates flow signal by applying a set of prepulses before segmented data acquisition. With this high-speed approach, imaging can be completed within 16 seconds. This technique was compared with conventional spin-echo black blood, gradient-echo black blood, and gradient-echo bright blood methods. Loss of flow signal, which extended beyond the site of the stenosis, was seen on the gradient-echo bright blood images. The pattern of signal loss varied with the type of stenosis. Flow voids were achieved with spin-echo black blood imaging; however, substantial ghosting artifacts were seen. With gradient-echo black blood imaging, it was difficult to eliminate all flow signal, particularly for in-plane flow. The modified TurboFLASH method produced high-quality black blood images in a fraction of the time needed for spin-echo imaging. It showed no ghosting artifacts even in the presence of pulsatile flow.

Plesiomonas shigelloides sepsis and meningoencephalitis in a neonate

A newborn infant is described who presented with septicaemia and meningoencephalitis caused by Plesiomonas shigelloides, a Gram-negative rod belonging to the family Vibrionaceae. The patient in this case, the first to be documented in Europe, developed multilocular lysis of the brain despite immediate treatment with antibiotics active in vitro. A cranial CT revealed garland-like calcifications and a large amount of medullary necrosis was seen on MRI.

Image artifacts in fast magnetic resonance imaging

Image artifacts are unwanted, spurious signal intensities that interfere with clinical diagnosis. This article gives an overview of image artifacts in magnetic resonance imaging. We discuss the causes of these artifacts, provide clinical examples, and offer solutions to avoid them.

[Computed tomographic aspects of intestinal intussusception]

This article describes typical CT findings of intestinal intussusception of different genesis and localisation. It is shown that a characteristic image resembling a target is obtained both in case of an invaginated Meckel's diverticulum, an idiopathic ileocolic intussusception in an infant, and in colorectal invagination in condition after resection of a polyp of the sigmoid. Compared with the conventional imaging methods such as sonography, colon contrast enema or contrast imaging of the small intestine, CT enables not only unequivocal diagnosis of intestinal invagination but frequently also the identification or exclusion of underlying causes that trigger the phenomenon.