Retroisthmic cleft: a stress fracture of the lamina

The retroisthmic cleft is a rarely diagnosed defect in the lamina of the lumbar spine. It has always been considered a congenital anomaly. This is the first report we are aware of showing radiological changes in a retroisthmic cleft over a period of time. The follow-up of this patient over a period of 6 years, the radiological and scintigraphic appearances and a review of the literature suggests that the retroisthmic cleft is a stress fracture of the lamina.

Hydro-MRI for the visualization of gastric wall motility using RARE magnetic resonance imaging sequences

BACKGROUND

Although different imaging techniques such as conventional X-ray, ultrasonography, and hydro-computed tomography are available for the imaging of the stomach, none can depict this organ in full size without radiation. Therefore, the study of the entire gastric wall motility of the stomach is difficult and in principle only performable with rapid magnetic resonance imaging (MRI) techniques. T1-weighted imaging sequences have been used for the dynamic study of gastric wall motility. This technique was combined with the oral intake of para- or superparamagnetic contrast agents to achieve sufficient intraluminal contrast. The technique described in the present study is based on a different contrast mechanism.

METHODS

The stomach was filled with 500 mL of 10% of aqueous dextrose solution, and a strongly T2-weighted fast rapid acquisition with relaxation enhancement (RARE) type imaging sequence was used for data acquisition. No other contrast agents were applied. An ultrafast RARE imaging sequence with an asymmetric phase-encoding scheme was developed to achieve a high temporal and spatial resolution. The scanning time per image was approximately 1 s.

RESULTS

The stomach was imaged in full size. The concentric constrictor rings moved from the proximal part of the body toward the antrum. The mean duration for one contraction cycle was approximately 17.9 +/- 2.5 s, the mean contractile frequency was 3.4 +/- 0.5 s, and the mean spreading velocity was 65.5 +/- 3.6 cm/min.

CONCLUSIONS

The purpose of this study was to demonstrate a new technical approach for a noninvasive dynamic study of gastric motor function with hydro-MRI. This robust method may have clinical application, e.g., in the diagnosis of gastroparesis, and may be extended to the rest of the gastrointestinal tract.

Selection of patients for carotid thromboendarterectomy: the role of magnetic resonance angiography

It has been shown in clinical trials that patients with high grade symptomatic carotid stenosis benefit from carotid thromboendarterectomy. Because of the invasiveness and the costs of intra-arterial digital subtraction angiography, the current standard of reference for the grading of carotid stenosis, magnetic resonance angiography, has become a technique of utmost interest for evaluation of the carotid arteries. The time-of-flight and the newly developed contrast-enhanced magnetic resonance angiography techniques are discussed. At present, we recommend computer enhanced magnetic resonance angiography for screening procedures and for the post-operative follow-up. For pre-operative evaluation we still recommend intra-arterial digital subtraction angiography.

MR angiography: supra-aortic vessels

Magnetic resonance angiography (MRA) has become an imaging modality which comprises various techniques based on two concepts: methods relying on the natural flow effects, the time-of-flight and phase-contrast technique, either in two- or three-dimensional acquisition mode, and the more recently developed contrast-enhanced (CE) MRA methods. The main indications for evaluation of the supra-aortic vessels are, firstly, the grading of carotid artery stenoses caused by an atherosclerotic process, and secondly, the evaluation of dissections of the cervical arteries because this disease plays an important role as a cause for stroke especially in younger patients. The various MRA techniques in their application to the main pathologies encountered at the supra-aortic vessels are presented, and recent developments in the promising field of CE MRA are discussed.

Effect of combined mouth closure and chin lift on upper airway dimensions during routine magnetic resonance imaging in pediatric patients sedated with propofol

BACKGROUND

In pediatric patients, obstruction of the upper airway is a common problem during general anesthesia. Chin lift is a commonly used technique to improve upper airway patency. However, little is known about the mechanism underlying this technique.

METHODS

The authors studied the effect of the chin lift maneuver on airway dimensions in 10 spontaneously breathing children (aged 2-11 yr) sedated with propofol during routine magnetic resonance imaging. The minimal anteroposterior and corresponding transverse diameters of the pharynx were determined at the levels of the soft palate, dorsum of the tongue, and tip of the epiglottis before and during the chin lift maneuver. Additionally, cross-sectional areas were calculated at these sites, including tracheal areas 2 cm below the glottic level.

RESULTS

Minimal anteroposterior diameter of the pharynx increased significantly during chin lift at all three levels in all patients. The diameters of the soft palate, tongue, and epiglottis increased from 6.7+/-2.8 mm (SD) to 9.9+/-3.6 mm, from 9.6+/-3.6 mm to 16.5+/-3.1 mm, and from 4.6+/-2.5 mm to 13.1+/-2.8 mm, respectively. The corresponding transverse diameter of the pharynx also increased significantly at all three levels in all patients but without significant predominance. The diameters at the levels of the soft palate, tongue, and epiglottis increased from 15.8+/-5.1 mm to 22.8+/-4.5 mm, from 13.5+/-4.9 mm to 18.7+/-5.3 mm, and from 17.2+/-3.9 mm to 21.2+/-3.7 mm, respectively. Cross-sectional pharyngeal areas increased significantly at all levels (soft palate, from 0.88+/-0.58 cm2 to 1.79+/-0.82 cm2; tongue, from 1.15+/-0.45 cm2 to 2.99+/-1.30 cm2; epiglottis, from 1.17+/-0.70 cm2 to 3.04+/-0.99 cm2), including the subglottic level (from 0.44+/-0.15 cm2 to 0.50+/-0.14 cm2).

CONCLUSIONS

This study shows that all children had a preserved upper airway at all measured sites during propofol sedation. Chin lift caused a widening of the entire pharyngeal airway that was most pronounced between the tip of the epiglottis and the posterior pharyngeal wall. In pediatric patients, chin lift may be used as a standard procedure during propofol sedation.

Gene therapy study of cytokine-transfected xenogeneic cells (Vero-interleukin-2) in patients with metastatic solid tumors

On the basis of compelling preclinical data in cats and dogs, we initiated a clinical gene therapy study in nine patients with advanced solid tumors using xenogeneic fibroblasts secreting human interleukin (IL)-2 (Vero-IL-2 cells). Cohorts of three successive patients with tumors accessible to computed tomography- or ultrasound-guided injection were treated repeatedly with 5 x 10(5), 5 x 10(6), or 5 x 10(7) Vero-IL-2 cells. The endpoints of the study were feasibility, toxicity, and the clinical and biological effects of this novel approach to immunotherapy of cancer. Histopathological, immunological, and molecular analyses were performed on biopsy specimens of tumors and blood samples before, during, and after treatment. Treatment was well tolerated, and toxicity consisted of transient fever in one patient and short-lived, mild itching and erythema in two others. One patient with soft-tissue sarcoma showed a reduction of >90% and >50% of the volume of two distant, noninjected metastases, lasting for 29+ and 26 months, respectively. Four other patients showed stabilization of their disease for 3-9 months; of these patients, one with melanoma developed marked vitiligo. We conclude that repeated injections of < or =5 x 10(7) Vero-IL-2 cells are feasible and safe in heavily pretreated patients with advanced solid tumors. An additional evaluation of an intratumoral application of Vero-IL-2 seems warranted.

Detection of pulmonary nodules with overlapping vs non-overlapping image reconstruction at spiral CT

The aim of this study was to analyze whether overlapping image reconstruction increases numbers of pulmonary nodules detected at helical CT. Forty-eight helical CT scans (21 with a slice thickness of 10 mm; 27 with a slice thickness of 5 mm) of patients with known pulmonary nodules were reconstructed both with overlapping and non-overlapping image reconstruction. Two readers recorded number and size of pulmonary nodules as well as diagnostic confidence. With overlapping image reconstruction each reader diagnosed more pulmonary nodules (slice thickness 10 mm: +24.0 and +26.7%, both p < 0.01; slice thickness 5 mm: +9.5 and +11.9%, both not significant) and more "definite" nodules (slice thickness 10 mm: +20.3%, p < 0.05, and +30.8%, p < 0.005; slice thickness 5 mm: +18.0 and +17.0%, both p < 0.05). Nodules diagnosed with overlapping image reconstruction only were almost exclusively smaller than the slice thickness. The increase in number of nodules detected was not associated with a decrease in diagnostic confidence. Overlapping image reconstruction improves detection of pulmonary nodules smaller than the slice thickness at spiral CT.

CT-guided intratumoral gene therapy in non-small-cell lung cancer

The objective of this study was to prove the principle of CT-guided gene therapy by intratumoral injection of a tumor suppressor gene as an alternative treatment approach of incurable non-small-cell lung cancer. In a prospective clinical phase I trial six patients with non-small-cell lung cancer and a mutation of the tumor suppressor gene p53 were treated by CT-guided intratumoral gene therapy. Ten milliliters of a vector solution (replication-defective adenovirus with complete wild-type p53 cDNA) were injected under CT guidance. In four cases the vector solution was completely applied to the tumor center, whereas in two cases 2 ml aliquots were injected into different tumor areas. For the procedure the scan room had been approved as a biosafety cabinet. Gene transfer was assessed by reverse transcription and polymerase chain reaction in biopsy specimens obtained under CT guidance 24-48 h after therapy. Potential therapeutic efficacy was evaluated on day 28 after treatment using spiral CT. The CT-guided gene therapy was easily performed in all six patients without intervention-related complications. Besides flu-like symptoms, no significant adverse effects of gene therapy were noted. Three of the four patients with central injection exhibited gene transfer in the posttreatment biopsy. Gene transfer could not be proven in the two patients with multiple 2 ml injections. After 28 days, four of the six patients showed stable disease at the treated tumor site, whereas other tumor manifestations progressed. Computed tomography-guided injections are an adequate and easy-to-perform procedure for intratumoral gene therapy.

[Pathological deglutition pattern after tumor surgery of the oro- and hypopharynx. Analysis by differentiated deglutition]

Dysphagia is a common complaint following surgical intervention in the oral cavity and hypopharynx, often leading to prolonged postoperative recovery. Videofluoroscopy allows detailed visualization of deglutition, demonstrating the morphology as well as the functional aspects. Therefore, videofluoroscopy provides the basis for further therapeutic management. We discuss the pathology of deglutition in 19 patients recovering from tumor surgery of the oro- and hypopharynx. In most cases the results demonstrated severe impairment of both the oral and pharyngeal phase of deglutition. Our data emphasize the importance of the oral phase of deglutition for preparation and initiation of the following phases.

Gene therapy with cytokine-transfected xenogeneic cells in metastatic tumors

On the basis of compelling preclinical data in cats and dogs we initiated a clinical gene therapy study in nine patients with advanced solid tumors using xenogeneic fibroblasts secreting human IL-2 (Vero-IL-2 cells). Cohorts of three successive patients with tumors accessible to CT- or ultrasound-guided injection were treated repeatedly with 5 x 10(5), 5 x 10(6), or 5 x 10(7) Vero-IL-2 cells. Endpoints of the study were feasibility, toxicity, and clinical and biological effects of this novel approach to immunotherapy of cancer. Histopathological, immunological and molecular analyses were performed on biopsy specimens of tumors and blood samples from before, during and after treatment. Low levels of serum antibodies to Vero cells developed in 2/9 patients. Analysis of tumor biopsies showed increased expression of CD3 mRNA and enhanced tumor infiltration with varying lymphocyte subpopulations after treatment. In addition, monoclonal alterations of the TCR repertoire of blood and tumor lymphocytes were observed. Treatment was well tolerated and toxicity consisted of transient fever in one patient and short-lived, mild itching and erythema in two others. One patient with soft tissue sarcoma showed a more than 90% and more than 50% reduction of the volume of two distant, non-injected metastases, respectively, lasting for 22+ months. Four other patients showed stabilization of their disease for three to nine months, among whom was a patient with melanoma who developed marked vitiligo. We conclude that repeated injection of up to 5 x 10(7) Vero-IL-2 cells was safe and showed biological and clinical activity in heavily pretreated patients with advanced solid tumors. Further evaluation of intratumoral application of Vero-IL-2 seems warranted.

Helical CT of pulmonary nodules in patients with extrathoracic malignancy: CT-surgical correlation

OBJECTIVE

Our aim was to assess the sensitivity of helical CT for revealing pulmonary nodules. Thoracotomy with palpation of the deflated lung, resection, and histologic examination of palpable nodules was used as the gold standard.

SUBJECTS AND METHODS

Thirteen patients underwent helical CT (slice thickness, 5 mm; reconstruction intervals, 3 mm and 5 mm; interpreted by two independent observers). Subsequently, patients underwent unilateral (n = 6) or bilateral (n = 7) surgical exploration, and CT-surgical correlation of 20 lungs was performed.

RESULTS

Ninety nodules were resected (61 were smaller than 6 mm; 13 were 6-10 mm; 11 were larger than 10 mm; in five nodules, the size was not recorded at surgery). Sixty-nine nodules were located in the pulmonary parenchyma and 21 in the visceral pleura. Of the 90 lesions, 43 (48%) were found on histology to represent metastases. For lesions detected by at least one observer, the sensitivity of helical CT was 69% for intrapulmonary nodules smaller than 6 mm, 95% for intrapulmonary nodules larger than or equal to 6 mm, and 100% for histologically proven intrapulmonary metastases larger than or equal to 6 mm. For lesions smaller than or equal to 10 mm, sensitivity was better using a reconstruction interval of 3 mm rather than of 5 mm.

CONCLUSION

In this study, the sensitivity of helical CT exceeded the sensitivity of conventional CT in previous reports. However, because of limitations in the detection of intrapulmonary nodules smaller than 6 mm and of pleural lesions, complete surgical exploration should remain the procedure of choice in patients undergoing pulmonary metastasectomy. Preoperative helical CT should be used to guide the surgeon to lesions that are difficult to palpate.

Anterior neopharyngeal pseudodiverticulum. A possible cause of dysphagia in laryngectomized patients

Anterior neopharyngeal pseudodiverticula are out-pouchings of the neopharyngeal lumen in laryngectomized patients which can cause postoperative dysphagia. In this study 20 laryngectomized patients were examined endoscopically and with barium swallow to determine the frequency of pseudodiverticulum formation, the correlation with clinical symptoms, and to evaluate the best modality for diagnosis. In 12 patients an anterior neopharyngeal pseudodiverticulum was present. Of these patients eight complained of dysphagia. The barium swallow showed more clearly the pseudodiverticula than laryngoscopy and gave additional information on functional implications. All symptomatic patients were successfully operated on with endoscopic laser therapy.

Diameter of the common bile duct in the elderly patient: measurement by ultrasound

We wanted to assess the width of the common bile duct (CBD) in an asymptomatic elderly (> 75 years) population, since no previous report has particularly considered the important age-related increase in CBD diameter for this patient group. CBD width of 92 asymptomatic people over 75 years of age (mean 84.7 years, range 75-96 years) without clinical or laboratory evidence for biliary, hepatocellular or pancreatic disease was measured by real-time high-resolution ultrasound of the upper abdomen. All examinations were performed by one experienced radiologist. Mean values were calculated for three groups: patients with and without cholecystolithiasis and after cholecystectomy. Statistical analysis was carried out by analysis of variance. Considering the measurements of all patients, the mean width (+/- SD) of the CBD was calculated as 6.5 +/- 2.5 mm. The difference between patients without cholecystolithiasis (6.2 +/- 2.3 mm) and patients after cholecystectomy (8.7 +/- 2.9 mm) was statistically significant (P < 0.0001). Cholecystolithiasis (6.0 +/- 1.6 mm) proves not to be an additional factor for CBD widening in comparison with patients without stone disease. The CBD of these very elderly subjects shows a considerable increase in comparison with the recommended borderline values in the ultrasound literature. An upper limit of 10 mm seems reasonable for patients with and without cholecystolithiasis. A significant increase in CBD width after cholecystectomy was found and measurements up to 14 mm may occur. Measurements have to be correlated with clinical and laboratory findings.

MR angiography in internal carotid artery dissection: improvement of diagnosis by selective demonstration of the intramural haematoma

We studied eight consecutive patients with clinical and intra-arterial angiographic (DSA) diagnosis of internal carotid artery (ICA) dissection to analyse the accuracy of MRA in dissections, using a new technique with presaturation pulses. Spin-echo images of the head were followed by three-dimensional time-of-flight (TOF) MRA at the site of the dissection, with and without a special caudal saturation pulse in addition to the cranial one. The accuracy of MRA was assessed in 64 segments of 16 ICA, all examined with DSA and MRA. High-signal intramural haematoma in the ICA at the level of the dissection was observed in all patients either on the maximal-intensity projection (MIP) reconstructions or on the partitions with this presaturation pulse technique. MRA had a sensitivity to detect dissected vessels of 100%. Specificity for vessels correctly identified as not having a lesion was also 100%. There was good correlation between DSA and MRA in demonstrating the site of the dissected ICA segment and the degree of stenosis. In only two cases was there overestimation of the degree of stenosis on the MIP reconstructions of the 3-D MRA.

Pulmonary circulation

Evaluation of the pulmonary vasculature is mainly indicated in patients with suspected pulmonary thromboembolism. The routine procedure so far is ventilation-perfusion scintigraphy alone or in combination with diagnostic assessment of the legs to rule out deep venous thrombosis. The results are still not reliable for the majority of patients. In the case of equivocal diagnosis, invasive conventional angiography is considered the gold standard. With steady improvements in tomographic imaging techniques, such as computed tomography (CT) or magnetic resonance imaging (MRI), non-invasive alternatives to the routine diagnostic work-up are given. Helical CT and CTA techniques are already in clinical use and estimated to sufficiently serve the demands for detection/exclusion of pulmonary thromboembolism. The disadvantages mainly concern peripheral disease and reconstruction artifacts. MRI and MR angiography have been implemented in the diagnosis of pulmonary vascular disease since the introduction of contrast-enhanced MRA. In breath-hold techniques, the entire lung vascularization can be delineated and thromboemboli can be detected. The clinical experience in this field is limited, but MRI has the potential to demonstrate its superiority over CT due to its improved delineation of the vascular periphery and the more comprehensive three-dimensional reconstruction.

[Pathologic swallowing pattern after tumor surgery of oro- and hypopharynx. Analysis with differentiated deglutition imaging]

Dysphagia is a common complaint following surgical intervention in the oral cavity and hypopharynx, often leading to prolonged postoperative recovery. Videofluoroscopy allows detailed visualization of deglutition, demonstrating the morphology as well as the functional aspects. Therefore, videofluoroscopy provides the basis for further therapeutic management. We discuss the pathology of deglutition in 19 patients recovering from tumor surgery of the oro- and hypopharynx. In most cases the results demonstrated severe impairment of both the oral and pharyngeal phase of deglutition. Our data emphasize the importance of the oral phase of deglutition for preparation and initiation of the following phases.

Massive pulmonary embolism: treatment with thrombus fragmentation and local fibrinolysis with recombinant human-tissue plasminogen activator

PURPOSE

To report the results of thrombus fragmentation in combination with local fibrinolysis using recombinant human-tissue plasminogen activator (rtPA) in patients with massive pulmonary embolism.

METHODS

Five patients with massive pulmonary embolism were treated with thrombus fragmentation followed by intrapulmonary injection of rtPA. Clot fragmentation was performed with a guidewire, angiographic catheter, and balloon catheter. Three patients had undergone recent surgery; one of them received a reduced dosage of rtPA.

RESULTS

All patients survived and showed clinical improvement with a resultant significant (p < 0.05) decrease in the pulmonary blood pressure (mean systolic pulmonary blood pressure before treatment, 49 mmHg; 4 hr after treatment, 28 mmHg). Angiographic follow-up in three patients revealed a decrease in thrombus material and an increase in pulmonary perfusion. Two patients developed retroperitoneal hematomas requiring transfusion.

CONCLUSION

Clot fragmentation and local fibrinolysis with rtPA was an effective therapy for massive pulmonary embolism. Bleeding at the puncture site was a frequent complication.

Noninvasive stress testing of myocardial ischemia: comparison of GRE-MRI perfusion and wall motion analysis to 99 mTc-MIBI-SPECT, relation to coronary angiography

In the evaluation of ischemic heart disease only MR imaging seems to have the potential to assess myocardial perfusion, function, and coronary morphology on a single instrument. The aim of this study was to assess the feasibility of a stress test with dipyridamole (0. 56 mg/kg) to analyze myocardial perfusion by Gd first-pass enhancement in ultrafast gradient-recalled-echo MRI (perf-MRI), and wall motion by cine gradient-recalled-echo MRI (Cine-MRI) in one imaging session. Twelve patients underwent complete rest and stress studies; satisfactory MR images were acquired in 10 patients. By 99 mTc-MIBI-SPECT sensitivities to detect ischemic segments were 66.7 % with Perf-MRI, 80.0 % with WM-MRI and 86.7 % for Perf-WM-MRI (Perf-MRI vs Perf-WM-MRI; p = 0.03). Scar was equally detected with a sensitivity of 91.6 % with either MRI technique. Thus, Perf-Cine-MRI provides complementary information for the management of ischemic heart disease and has a higher sensitivity than Perf-MRI alone.

[MR angiography of thoracic blood vessels]

Through the introduction of newly invented high-performance gradient systems to MRI, which enable for echoplanar imaging (EPI), also magnetic resonance angiography (MRA) has gained an entirely new field of applications and techniques. Ultrafast imaging techniques in MRA allow the investigation of larger vascular areas within a single breath-hold-period. Artifacts like motion induced signal misregistrations, dephasing or saturation of the vascular signal are minimized by extremely short echo times. The technique thus requires the intravenous application of a contrast media bolus, usually a gadolinium compound, which is in standard clinical use. Coordination of the bolus injection and the timing of the data acquisition is crucial for optimal results. The first pass evaluation of the contrast media resembles CTA to a certain extend. Due to the fast measurement and the high contrast in contrast-enhanced MRA (CE-MRA) new applications and indications are developed like MRA of the pulmonary vessels. The paper offers considerations and trials for optimization of thoracical CE-MRA. Besides parameter constellation also bolus-optimization is described with respect to the dedicated anatomical premises. Investigations on volunteers and on patients build a basis for suggestions of optimized CE-MRA procedures. To date, a final estimation of the clinical value of the new technique cannot be given since ongoing improvements change the optimal protocol frequently and the potential of further developments is high.

[Conventional magnetic resonance angiography and contrast enhanced magnetic resonance angiography of extracranial blood vessel segments]

The introduction of fast gradient systems allows a reliable visualization of the extracranial carotid vessels by the magnetic resonance angiography (MRA) which meanwhile is implemented into clinical routine. By the mainly applied time-of-flight (TOF) technique, vessels can be imaged without contrast agent (CA). Due to the application of ultra-fast gradient-echo-sequences, the first-pass evaluation of an intravenous bolus-injection of Gadolinium in the carotids from the aortic arch up to the skull base can be performed in less than 30 s. In this study. Advantages and disadvantages of both techniques are discussed. For a qualitatively optimal contrast enhanced MRA (CE-MRA) timing parameters like injection delay, flow rate and the adjustment of sequence parameters have to be considered in relation to the fast venous return from the sinus to the jugular veins. First, the optimal time point of the data acquisition have been determined at a model and with a computer simulation in reference to the presence of CA in the arteries. As a result, 90% of the contrast contribution is defined by 16% of the symmetrically acquired central k-space lines. A measuring protocol for clinical use was obtained by a gradual variation of spacial resolution, measuring time and CA-injection parameters and was proved in normal volunteers and patients. An exact determination of the bolus-arrival-time by means of a test-bolus injection was acquired. The best qualitative results were achieved by a double-dose- injection at 2 ml/s injection rate. The temporal reserves of ultra-fast sequences should be invested in the improvement of the spatial resolution. To date, further investigations related to the problem of optimal CA-application may improve the potentials of CE-MRA procedures.

Anatomic evaluation of the circle of Willis: MR angiography versus intraarterial digital subtraction angiography

PURPOSE

To evaluate the reliability of source images and maximum intensity projection images of MR angiography in showing the arterial segments of the circle of Willis.

METHODS

In 62 patients, 526 arterial segments of the circle of Willis were determined to be present, partially present, or absent by blinded observers evaluating MR angiographic source images and maximum intensity projection images. Vessel diameter was measured on source images. These results were then compared with the results from intraarterial digital subtraction angiography.

RESULTS

MR angiographic maximum intensity projection images had a sensitivity of 87% and a specificity of 88% and MR angiographic source images had a sensitivity of 89% and a specificity of 63% in depicting the presence of a vessel segment. The positive predictive value of an arterial segment with a diameter of at least 1 mm was 99%.

CONCLUSION

MR angiography is a sensitive technique for detecting the anatomy of the circle of Willis. Maximum intensity projection images are more specific than source images. An arterial segment with a diameter of at least 1 mm on the source image is almost always present and patent.

Is there a hazard to health by mercury exposure from amalgam due to MRI?

The local magnetic fields from computer monitors are well known. Recently a hypothesis was published that these magnetic fields may lead to a 400% increase of mercury dissolution from dental amalgam fillings. In MRI the exposure to the magnetic field exceeds by far the exposure from computer monitors. Therefore, this study examined the amalgam-related mercury release for typical MRI conditions, separated for both the static and the variable magnetic fields in a 1.5 T MR-unit. First, 20 dental cavities were filled with a non-gamma-2 amalgam, and the mercury release was measured for 14 days in a non-magnetic environment. Second, one half of the specimens were exposed to a static magnetic field for 24 hours (group A), while the other specimens were exposed to a repetitive gradient echo sequence for 60 minutes (group B). In both experiments there was no significant increase in mercury release due to MRI. This in vitro study demonstrated no evidence of an elevated mercury dissolution from a non-gamma-2 amalgam during magnetic field exposure by MRI; therefore, there is no increased risk to health.

[In vitro validation of intravascular ultrasound, computerized and magnetic resonance tomography in diagnosis of atherosclerotic vascular segments in comparison with direct magnification radiography]

The depiction of atherosclerotic vessel abnormalities is a prerequisite for percutaneous interventional therapy and long-term observations of peripheral artery disease. The aim of this in-vitro study was to determine the potentials and limitations of 12.5 and 20 MHz intravascular ultrasound, computed tomography and magnetic resonance (MR) imaging in comparison to direct magnification radiography for the localization and quantification of peripheral vessel wall calcifications. Forty-three postmortem, human iliac segments were examined by intravascular ultrasound (12.5 and 20 MHz), computed tomography and magnetic resonance tomography (gradient echo-and spin echo-technique). For comparative analysis, each segment was divided into eight sectors of 45 degrees each; using all five methods, the presence of calcified wall areas was examined in each sector, and luminal area (42 segments) and plaque area (32 isolated plaques) were quantitatively estimated. In the sonograms, the circumferential extension of the boundary between intima and media was measured. 122 of 344 sectors showed regional vessel wall calcifications. Sensitivity of 20 MHz intravascular ultrasound was 73% versus 59% with the 12.5 probe, specificity was 97% with 20 MHz, 96% with 12.5 MHz. Sensitivity of both 12.5 and 20 MHz intravascular ultrasound was higher with increased thickness of the calcified structures. 20 MHz ultrasound identified the intima-media boundary averaging 146.8 degrees of the vessel circumference; the corresponding value of 131.8 degree with 12.5 MHz did not differ significantly. Computed tomography detected calcifications with a sensitivity of 88%, specificity was 88%. With MR imaging, sensitivity of the gradient echo-technique was 94% versus a sensitivity of 86% with spin echo-technique. Quantification of luminal and plaque areas showed that luminal area was precisely estimated only by 20 MHz ultrasound (no significant difference to direct magnification radiography), whereas all other techniques showed significant overestimation. Plaque areas were markedly overestimated by computed tomography and MR imaging, too. In an in vitro set-up, intravascular ultrasound, MR tomography and computed tomography do not allow an authentic depiction of peripheral vessel wall architecture. Limited resolution, subintimal shadowing and and distortion are the main limitations of these new techniques so that details of regional vessel wall calcifications cannot be presented thoroughly. Relevant over-estimation of luminal and plaque areas must be considered.

The significance of three-dimensional MR-defined neurovascular compression for the pathogenesis of trigeminal neuralgia

Three-dimensional MR tomography was used to examine the relationship between symptoms of trigeminal neuralgia and neurovascular compression of the nerve in 18 patients. The intensity of neurovascular interaction was classified according to neuroradiological criteria. We found that a radiologically defined compression or dislocation of the nerve by an artery was always associated with symptoms of trigeminal neuralgia. A simple contact between vessel and nerve, however, was also observed on the asymptomatic sides of 10 out of 18 patients. In 6 of 18 patients, in contrast, trigeminal neuralgia was present in spite of the absence of neurovascular contact. In accordance with a cited study based on autopsy and intraoperative findings, our findings indicate that, in a certain proportion of cases, trigeminal neuralgia may be caused by neurovascular compression alone, whereas in other cases, other pathogenetic factors may be involved to a varying degree or be even exclusively responsible for the development of trigeminal neuralgia. The possible significance of the method for a preoperative estimation of the success of microvascular decompression of the trigeminal nerve is discussed.

Initial feasibility studies using single-shot EPI for the detection of focal liver lesions

Echo planar MR imaging (EPI) has been developed to completely eliminate motion artifacts and is currently being prepared for implementation into clinical MR systems. Thus, the purpose of this study was to evaluate the clinical utility of EPI in the detection of focal liver lesions and to compare EPI with in the detection of focal liver lesions and to compare EPI with contrast-enhanced CT. EPI studies were performed on an experimental 1.0 Tesla whole body system using fat-suppressed single-shot spin echo (SE) and inversion recovery (IR) pulse sequences. A total of 26 liver tumors in 12 patients scheduled for liver resection were prospectively examined and correlated with intraoperative ultrasound, surgery, and pathology as the gold standard. Quantitative analysis of EPI was performed by means of liver signal-to-noise and tumor-liver contrast-to-noise calculations. Diagnostic performance compared with contrast-enhanced CT was assessed by means of ROC analysis. Lesion-liver contrast was highest with EPI SE at a TE-time of 70 ms and this technique showed best lesion detectability as measured by area under curve (AUC) values. Among EPI techniques, the IR sequence with an inversion time of 300 ms to null the liver signal showed high lesion-liver contrast but all four reviewers reported problems assessing liver anatomy. Improved EPI techniques may prove useful for screening of focal liver lesions.

[MRI in soft tissue tumors]

MRI has been shown to be very useful in the diagnostic work-up of soft tissue masses. Because of its multiplanar capability and excellent contrast resolution, MRI is the method of choice for identification of tumour extent and follow-up examinations of soft tissue lesions. Due to the unspecific appearance of most soft tissue tumours, MRI cannot replace biopsy for definitive determinations of the nature of the lesion (benign vs malignant) in the majority of cases.

[Magnetic resonance angiography of supra-aortic arteries]

MR angiography of the carotid system was found to be readily applicable due to the laminar and fast flow conditions in the supra-aortic arteries. Time-of-flight methods are superior to phase-contrast measurements for the investigation of atherosclerotic lesions. Recent developments in sequence design enable improvement of the MR angiographic results with respect to correct staging of stenotic alterations. Two-dimensional acquisitions are preferred in slow flow conditions with the disadvantage of decreased resolution, in-plane saturation effects, and poststenotic signal voids. In 3D MR angiography, the major advantage is improved resolution, although the saturation effects within the measurement volume must be compensated for either by sequential acquisition of multiple thin volumes or by the application of asymmetric excitation pulses. In a prospective trial with 50 patients, the advantages of a new type of rf-pulse (TONE) are demonstrated.

[Localization dependent patterns of findings in chondroblastoma]

In a retrospective study the radiographs of 48 chondroblastomas from the files of the Bone Tumour Registry of Westphalia were evaluated. The purpose of the study was to investigate whether chondroblastomas display localisation-dependent radiographic patterns. All radiographs were analysed using the Lodwick criteria. All chondroblastomas (mean age: 18 y., m:f = 1.25:1) showed a geographic pattern of bone destruction. 32 lesions affected long bones, 10 short bones, and 6 flat bones. Chondroblastomas localised in flat bones (Lodwick IA: 0%, IB: 33%, IC: 67%) demonstrated more aggressive patterns of bone destruction compared to lesions affecting long bones (Lodwick IA: 56%, IB: 31%, IC: 13%) or short bones (Lodwick IA: 40%, IB: 50%, IC: 10%). There was no difference between the three bone types in other radiographic patterns (periostitis, calcification, trabeculation).

Polycystic disease of the kidneys complicating the diagnosis of myocardial echinococcosis

The case of a 30-year-old woman with polycystic disease of the kidneys and a large cyst in the interventricular septum is presented. The hypothesis of an echinococcal disease or of a cardiac manifestation of a polycystic disease was raised. The patient's history, serologic data, and the morphological aspect of the cyst did not give evidence for echinococcal disease before surgery. However, the postoperative pathological evaluation confirmed the diagnosis of a single echinococcal cyst. The presented case shows that even in cases without proven diagnosis of echinococcal disease and preexisting hereditary cysts in other organ systems, care should be taken during surgery to avoid anaphylaxis and preoperative spread of the parasite throughout the body.

[Magnetic resonance tomography of soft tissue tumors]

Soft tissue tumors are relatively often seen on MR tomography, although they make up a fairly small proportion of malignant lesions. To date, most soft tissue tumors have been investigated by MRI because of its unique soft tissue contrasts and its flexibility in slice orientation. But is MRI really adequate for staging and defining soft tissue tumors, or what role does it have pre-therapeutic work-up? Most malignant soft tissue tumors give rise to somewhat similar MRI findings and may not be sufficiently well characterized. On the other hand, some benign lesions can be clearly identified and staged. The goal of this paper is a critical discussion of the ability of MRI to define a lesion's degree of malignancy, to evaluate diagnostic criteria, and to describe requirements in the set-up of the investigation.

[Magnetic resonance tomography of the ankle joint]

To define the clinical role of MRI of the ankle joint, a total of 88 patients was investigated. In the evaluation of ligamentous injury, MRI was inferior to established imaging methods. By contrast, it provided additional therapy-relevant information in the assessment of hemophilic arthropathy, osteochondritis dissecans, and inflammatory and neoplastic diseases of the ankle joint. In the latter conditions, MRI may make other more conventional methods of examining the ankle joint unnecessary.

[The diagnostic reliability of the occipitomental radiograph of the paranasal sinuses. Correlation with magnetic resonance tomography]

100 conventional occipitomental radiographs of the paranasal sinuses were studied independently by five radiologists. Predictive values were determined, based on MRI as the gold standard. Sensitivity and specificity for detection of mucosal thickening in the sinuses were: maxillary sinus: 0.73/0.76, frontal sinus: 0.20/0.85, ethmoid sinus: 0.38/0.87, sphenoid sinus: 0.14/0.96. In the maxillary sinus polypoid thickening was demonstrated with a significantly higher sensitivity than that of diffuse mucosal thickening (0.82 versus 0.65, Chi-square-test, p less than 0.01). Because of the low predictive values the occipitomental view is insufficient to assessing mucosal thickening in the paranasal sinuses, with the exception of polypoid mucosal thickening in the maxillary sinus.

Detection of hepatic masses in patients with carcinoma: comparative sensitivities of sonography, CT, and MR imaging

To evaluate the sensitivity of sonography, CT, and MR imaging in the detection of hepatic masses in carcinoma patients, we conducted a prospective study of 75 consecutive patients with gastrointestinal tumors who were admitted for surgical resection of the primary tumor. Sonography was performed with convex transducers of 3.5 and 5.0 MHz. Three noninvasive CT techniques were used: unenhanced CT scans, the incremental bolus dynamic scanning technique, and delayed scanning 4-6 hr after bolus injection of 60 g of iodine. MR images (1.5 T) were acquired as presaturated T1- and T2-weighted spin-echo sequences and as breath-holding fast low-angle shot (FLASH) 60 degrees and FLASH 15 degrees sequences. As it is difficult to distinguish benign from malignant masses solely on the basis of morphologic criteria, the techniques for each imaging method were designed to detect and not to characterize hepatic lesions. Each examination was interpreted blindly, and the results were compared with surgical findings, intraoperative sonography, and biopsy of the liver as the gold standard. All focal hepatic masses verified at surgery, malignant or benign, were included in the analysis. Sixty-five (68%) of 95 focal hepatic masses were detected by CT, 60 lesions (63%) by MR, and 50 lesions (53%) by sonography. Although lesions 1-2 cm were shown almost equally well by CT and MR (74% and 77%, respectively), the detection rate of smaller lesions (less than 1.0 cm) decreased more drastically with MR (31%) than with CT (49%). Sonography had a sensitivity of only 20% with the smaller lesions. All imaging techniques had a sensitivity of 100% for focal hepatic masses larger than 2.0 cm. Our results show that CT has a higher overall sensitivity (68%) than MR and sonography for the detection of focal hepatic masses. When the results of the three procedures are combined, the overall sensitivity is 77%. This is unsatisfactorily low, as CT and MR have a size threshold of about 1.0 cm and are relatively unreliable for the detection of smaller lesions.

[Hallervorden-Spatz syndrome. Indicative findings in cranial computerized and magnetic resonance tomography for intra vitam diagnosis]

We report the case of a female patient with a progressive therapy-resistant extrapyramidal movement disorder. Cranial computed tomography showed symetrical hyperdensities in the globus pallidus. The same areas are of decreased signal intensity in magnetic resonance imaging. These findings suggest an increased iron accumulation. The clinical symptoms and the radiological findings of the cerebrum are highly indicative for a Hallervorden-Spatz disease.

[Radiologic findings following supraglottic and total laryngectomy]

The treatment of carcinoma of the larynx has recently been greatly improved with the development of supraglottic and total laryngectomy. This has also led to a high five year survival rate. The normal postoperative radiological appearances are presented together with the spectrum of relevant radiological investigations and their indications. The most frequently seen postoperative complications and findings in patients with dysphagia are described with special reference to pharyngograms and cineradiography. The morphology of the vibrating segment after laryngectomy in patients who do not develop effective alaryngeal speech is demonstrated.

[Asymptomatic Moyamoya syndrome. Diagnosis by EEG and magnetic resonance angiography]

Alternating hemiplegias in children suggest the possibility of a Moyamoya syndrome. In the absence of clinical symptoms it is the EEG which will offer the decisive clue in childhood Moyamoya syndrome. The pertinent finding, which consists in progressive frequency decrease and amplitude activation after hyperventilation, has only been described in pediatric patients. It has been termed re-build-up phenomenon. Magnet resonance imaging and magnet resonance angiography (MR angiography) are able to confirm the tentative diagnosis of a Moyamoya syndrome based on the EEG.

[MRT of the hypophysis: spin echo 2D or gradient echo 3D?]

Diagnostic efficacy of T1-weighted 3D gradient-echo and 2D spin-echo pulse sequences in the detection of adenomas were evaluated in a ROC study of 50 patients. Sensitivity, specificity and accuracy did not differ significantly, but in direct comparison gradient-echo received a clear lower rating due to susceptibility artifacts, lower signal-to-noise ratio, and inferior periglandular contrasts. Additional lesions could not be reliably detected in gradient-echo imaging at 1 mm slice thickness. A substitution of 2D spin-echo imaging by gradient-echo sequences cannot be recommended at present.

[The place of diagnostic imaging in xanthogranulomatous pyelonephritis]

The urographic, angiographic, sonographic and computed tomographic findings in 4 cases of xanthogranulomatous pyelonephritis are presented along with correlation with the pathological specimens. The parenchyma of the kidney was replaced by multiple, rounded, low-density respectively hypoechogenic areas on CT and sonography that corresponded to dilated calices and/or inflammatory tissue. For diagnosing the characteristic extrarenal extension of the disease sonography was not as accurate as CT.

[The place of magnetic resonance tomography in the diagnosis of diseases of the shoulder joint]

In a prospective study 43 patients with shoulder pain were examined by sonography and MRI. The findings were controlled by plain radiography, arthrography, and CT arthrography. Joint effusions and humeral head defects were equally identified by MR and sonography. In the diagnosis of labrum lesions, rotator cuff lesions, subacromial spurs, and synovial inflammatory disease sonography was not as accurate as MR. A special MR scoring system improved the diagnosis of an impingement syndrome.

[The use of rapid sequences in craniocerebral MR diagnosis]

MRI of the head is routinely performed with spin-echo sequences whereas gradient-echo sequences are still uncommon. Certain features of fast imaging sequences make them a promising tool for clinical investigations. The relative high signal-to-noise ratio/unit time demonstrates the usefulness of GE imaging as localising images. The extremely high contrast-flexibility is sometimes superior to SE imaging and may help to characterise structures and lesions. Flow dynamics are more clearly depicted than with SE sequences and lead to the dynamic evaluation of intracranial motion (CSF flow, blood flow). This information may be used in a special mode to achieve MR angiograms. Due to the very short repetition times, GE sequences are excellently suited to 3D application. This enables to reduce slice thickness to less than 1 mm with optional reconstructions in any virtual direction. In view of present developments in MR, GE imaging will be accepted in clinical diagnostic imaging in the near future.

[The MR tomographic findings in cranial manifestations of neurofibromatosis]

Twelve patients with central neurofibromatosis underwent MR examination of the head. Among these, chiasma glioma was the most common CNS tumour (6/12). Seven patients had multifocal areas of increased T2-signal without mass effect predominantly involving the region of the basal ganglia. No corresponding CT abnormalities were present. These lesions may represent multifocal dysplasia and seem to be characteristic of central neurofibromatosis.

Musculoskeletal neoplasms: fast low-angle shot MR imaging with and without Gd-DTPA

In 121 patients, image contrast and contrast-to-noise ratios (C/Ns) obtained with gadolinium diethylene-triaminepentaacetic acid (DTPA)-enhanced and nonenhanced fast low-angle shot (FLASH) sequences were compared with those achieved with spin-echo (SE) sequences. Among FLASH sequences, contrast between neoplasms and muscle was sufficient with a flip angle of 90 degrees following administration of Gd-DTPA but was 61% lower than that with the T2-weighted SE sequence. High contrast levels were obtained between tumors and bone marrow or fat in sclerotic, calcified, and fibrotic lesions with the use of a flip angle of 90 degrees and in lytic lesions with a flip angle of 10 degrees, reaching 66% of the contrast level obtained with the T1-weighted SE sequence. C/N between tumor and surrounding tissue was always significantly lower with FLASH sequences than with the ideal SE sequences usually used for tumor delineation. Thus, a replacement of the T2-weighted SE sequences by FLASH sequences cannot be recommended. A replacement of the T1-weighted SE sequences by FLASH sequences seems possible but does not significantly reduce examination time.