[MRI monitoring of autologous hyaline cartilage grafts in the knee joint: a follow-up study over 12 months]. / MRT-Monitoring autologer Chondrozytentransplantate im Kniegelenk: Eine Verlaufsstudie über 12 Monate.

PURPOSE: To evaluate the suitability of different MR sequences for monitoring the stage of maturation of hyaline cartilage grafts in the knee joint and the early detection of complications like hypertrophy. In addition, it was analyzed whether indirect MR arthrography can indicate debonding of the graft. MATERIALS AND METHODS: MRI examinations were performed in 19 patients, aged 17 - 48 years, with autologous transplantation of a hyaline cartilage tissue graft after knee trauma. Examination dates were prior to transplantation to localize the defect, and 6 weeks, 3, 6 and 12 months after transplantation to control morphology and maturation of the autologous graft. Standard T2- and proton-density-weighted turbo spin echo (TSE) sequences and T1-weighted spin echo (SE) sequences were used, as well as gradient echo (GRE) sequences with and without magnetization transfer (MT) prepulses. In some cases, indirect MR arthrography was performed. RESULTS: Cartilage defect and the hyaline cartilage graft could be detected in all 19 patients. Hypertrophy of the graft could be found early in 3 patients and debonding in 1 patient. For depicting the graft a short time after surgery, T2-weighted TSE-sequences showed the best results. Six and 12 months after transplantation, spoiled 3D-GRE-sequences like FLASH3D (fast low angle shot) showed reduced artifacts due to magnetic residues from the surgery. Difference images from GRE-sequences with and without MT pulse provided high contrast between cartilage and surrounding tissue. The quantification of the MT effect showed an assimilation of the graft to the original cartilage within 12 months. Indirect MR arthrography showed subchondral contrast medium even 12 months after transplantation in 3 patients. CONCLUSION: MRI allows a reliable depiction of the hyaline graft and provides very early detection of complications like hypertrophy. The MT effect seems to be correlated with maturation of the graft and allows selective depiction of normal cartilage and engrafted cartilage.

[Hemangiomas and vascular malformations in the area of the head and neck]. / Hämangiome und vaskuläre Malformationen im Kopf- und Halsbereich. Differenzialdiagnostik, Klassifikation und Therapie.

The treatment of paediatric patients with extended vascular anomalies in the head and neck requires a multidisciplinary approach involving paediatricians, maxillofacial surgeons, dermatologists and radiologists. Therapeutic strategies are based on an internationally accepted classification of vascular anomalies, which distinguishes haemangiomas and vascular malformations. Whereas haemangiomas are endothelial proliferations, vascular malformations are considered to be developmental anomalies which are classified into high-flow or low-flow lesions and, according to their vascular channels, into capillary, lymphatic or venous malformations. In this review we present guidelines for the diagnostic assessment of paediatric patients with vascular anomalies in the head and neck region. The indications for treatment are discussed and therapeutic options are outlined.

Giant cavernoma of the brain stem: value of delayed MR imaging after contrast injection.

Cavernous angiomas are vascular malformations composed of slowly perfused, sinusoidal vessels which can be located in any part of the central nervous system. Whereas diagnosis is mostly straightforward in typical cases, some lesions may present in unusual locations or with unusual imaging characteristics. Because of the slow perfusion, contrast enhancement is not regarded as a characteristic imaging feature of cavernomas. We report a large brain stem cavernoma with signs of recent bleeding, in which the differential diagnosis against other mass lesions was facilitated by the demonstration of slow, but intense, contrast enhancement on MRI 1 h after contrast injection. We conclude that contrast enhancement in delayed images may contribute to a safe diagnosis of cavernous haemangiomas and should be performed in atypical cases.

Giant cavernoma of the brain stem: value of delayed MR imaging after contrast injection.

Cavernous angiomas are vascular malformations composed of slowly perfused, sinusoidal vessels which can be located in any part of the central nervous system. Whereas diagnosis is mostly straightforward in typical cases, some lesions may present in unusual locations or with unusual imaging characteristics. Because of the slow perfusion, contrast enhancement is not regarded as a characteristic imaging feature of cavernomas. We report a large brain stem cavernoma with signs of recent bleeding, in which the differential diagnosis against other mass lesions was facilitated by the demonstration of slow, but intense, contrast enhancement on MRI 1 h after contrast injection. We conclude that contrast enhancement in delayed images may contribute to a safe diagnosis of cavernous haemangiomas and should be performed in atypical cases.

Ocular manifestation of primary nervous system lymphoma: what can be expected from imaging?

Primary ocular lymphoma, which affects the posterior parts of the eye, is an ocular manifestation of primary central nervous system lymphoma (PCNSL). It used to be the ocular disease with the shortest time of survival, even worse than ocular melanoma. Death ensues by CNS dissemination. Unfortunately, ocular lymphoma may be the initial manifestation of PCNSL and diagnosis is frequently difficult, even if vitreal biopsy is performed. Therefore, it should be determined whether cross sectional imaging may be helpful in detection and differential diagnosis of ocular lymphoma. MRI of seven patients (female = 6, male = 1, median age 62 years) with biopsy proven ocular lymphoma were retrieved from the files of our hospital and of a multicenter PCNSL study. In four patients, ocular lymphoma was the first manifestation of PCNSL, in three a cerebral lesion had occurred in the first place. Progression to cerebral lymphoma was seen in three of the four patients with initial eye manifestation. Imaging was performed using a dedicated thin section protocol in four patients. An intraocular abnormality was found in four cases, always in T1-weighted images after contrast injection. Differential diagnosis from uveitis or ocular melanoma was not possible by imaging alone. The examination was falsely negative in the remaining three patients.Hence, imaging has a low sensitivity for ocular lymphoma and does not facilitate differential diagnosis against uveitis or ocular melanoma.

Role of hydrodynamic processes in the pathogenesis of peritumoral brain edema in meningiomas.

OBJECT: In a prospective study, 28 patients with 32 intracranial meningiomas were examined to determine the role of hydrodynamic interaction between tumor and surrounding brain tissue in the pathogenesis of peritumoral brain edema. METHODS: Gadolinium-diethylenetriamine pentaacetic acid (Gd-DPTA), an extracellular contrast agent used for routine clinical imaging, remains strictly extracellular without crossing an intact blood-brain barrier. Therefore, it is well suited for investigations of hydrodynamic extracellular mechanisms in the development of brain edema. Spin-echo T1-weighted magnetic resonance images were acquired before and after intravenous administration of 0.2 mmol/kg Gd-DPTA. Additional T1-weighted imaging was performed 0.6, 3.5, and 6.5 hours later. No significant Gd-DPTA diffused from tumor into peritumoral brain tissue in 12 meningiomas without surrounding brain edema. In contrast, in 17 of 20 meningiomas with surrounding edema, contrast agent in peritumoral brain tissue was detectable after 3.5 hours and 6.5 hours. In three of 20 meningiomas with minimum surrounding edema (<5 cm3), contrast agent effusion was absent. After 3.5 hours and 6.5 hours strong correlations of edema volume and the maximum distance of contrast spread from the tumor margin into adjacent brain parenchyma (r = 0.84 and r = 0.87, respectively, p < 0.0001) indicated faster effusion in larger areas of edema. CONCLUSIONS: The results of this study show that significant contrast agent effusion from the extracellular space of the tumor into the interstitium of the peritumoral brain tissue is only found in meningiomas with surrounding edema. This supports the hypothesis that hydrodynamic processes play an essential role in the pathogenesis of peritumoral brain edema in meningiomas.

In vitro evaluation of teratogenic effects by time-varying MR gradient fields on fetal human fibroblasts.

The purpose of this study was to evaluate the influence on fetal cell growth in vitro of rapidly changing magnetic gradient fields such as those produced by the gradient coils of a typical magnetic resonance (MR) imager. The static magnetic field and the radiofrequency pulses were disabled during all measurements. Human fetal fibroblasts were placed within a specially designed MR-compatible incubation system inside the magnet. Trapezoid-shaped waveforms of 500 and 75 Hz base frequency and an amplitude of 2 mT were applied for 2-24 hours. Proliferation of the cells was monitored for 3 weeks after exposure. Cell cycle analysis was performed until 24 hours after exposure to detect alterations in cell division. Tests were performed under two different conditions of growth to detect increased as well as decreased proliferation effects. None of these tests showed differences in proliferation and cell cycle distribution between exposed and nonexposed cells.

Human fetal lung fibroblasts: in vitro study of repetitive magnetic field exposure at 0.2, 1.0, and 1.5 T.

PURPOSE: To evaluate whether repetitive exposure to magnetic fields of 0.2, 1.0, and 1.5 T affect the growth of human fetal lung fibroblasts (HFLFs). MATERIALS AND METHODS: Cultured HFLFs were exposed to static magnetic fields of 0.2, 1.0, and 1.5 T for 1 h/d for 5 consecutive days. Control groups were kept under identical environmental conditions, apart from the magnetic field, during the experiments. Cell cycle analysis for synchronously and nonsynchronously growing cells was performed. Population doublings (PDs) were calculated. To rule out midterm effects, proliferation kinetics of the cells were analyzed for 21 days. RESULTS: Cell cycle analysis of synchronized and nonsynchronized cells did not reveal statistically significant differences between the exposed and control cells. The PDs did not indicate any growth modulation during exposure. Proliferation kinetics did not provide any hint of midterm growth modulation effects of repetitive magnetic field exposure. CONCLUSION: Repetitive magnetic field exposure does not exert any growth-modulating effect on overall cell growth and cell cycle distribution of cultured HFLFs. Midterm effects due to magnetic field exposure were not found.

[Stability of iodinated contrast media in UV-laser irradiation and toxicity of the photoproducts]. / Stabilität jodhaltiger Röntgenkontrastmittel unter UV-Laser-Bestrahlung und Toxizität der Photoprodukte.

PURPOSE: In XeCl-Excimer laser angioplasty, unintended and possibly harmful interaction of the UV-laser light and the contrast media may occur due to the high concentration of contrast medium proximal to the occlusion or subtotal stenosis. METHODS: One ml of three nonionic monomeric contrast agents (iopromide, iomeprol, iopamidol), one nonionic dimeric (jotrolane), and one ionic monomeric (amidotrizoate) X-ray contrast agent were irradiated with a XeCl excimer laser (lambda = 308 nm, pulse duration 120 ns, 50 Hz) using a 9 French multifiber catheter (12 sectors). Up to 20,000 pulses (106 J) were applied. Using high performance liquid chromatography the amount of liberated iodide as well as the fraction of unchanged contrast media were measured. Cytotoxicity of the photoproducts was tested in a colony formation assay of human skin fibroblasts. The contrast agents were irradiated with 2000 pulses/ml (5.3 mJ/pulse; 10.6 J) and then added to the cell cultures for a period of three hours in a concentration of 10%. RESULTS: Excimer laser irradiation induced iodide liberation of up to 3.3 mg iodide/ml. Up to 19% of the contrast agents changed their original molecular structure. Incubation of irradiated contrast agents resulted in a significantly decreased potential for colony formation (p values ranging from 0.0044 to 0.0102) with significantly higher toxicity of amidotrizoate and iomeprol in comparison to iopromide, iotrolan, and iopamidol. DISCUSSION: Due to the cytotoxic photoproducts and the high level of liberated iodide, it is recommended to flush the artery with physiological saline solution before applying a pulsed excimer laser in human arterial obstructions in order to reduce the contrast agent concentration at the site of irradiation.

MR imaging of the liver with Resovist: safety, efficacy, and pharmacodynamic properties.

PURPOSE: To evaluate the safety, efficacy, and pharmacodynamic properties of a new superparamagnetic parenteral iron oxide contrast agent for magnetic resonance (MR) imaging. MATERIALS AND METHODS: Thirty-six patients with liver lesions received a bolus injection of Resovist (SH U 555 A; Schering, Berlin, Germany) at a dose of 4, 8, or 16 micromol iron per kilogram body weight (micromol Fe/kg). Fast low-angle shot, spin-echo, and turbo gradient spin-echo MR images were obtained before and 10, 40, and 70 minutes after injection. Blood samples were obtained, vital signs were monitored, and adverse events were recorded. Lesion detection was assessed by two independent, blinded readers. RESULTS: No drug-related adverse events occurred. Serum iron and ferritin levels were increased at all dose levels. Partial thromboplastin time increased and factor XI level decreased 4 hours after injection of 16 micromol Fe/kg. Lesion detection and diagnostic confidence were increased in patients who received 4 or 8 micromol Fe/kg, with no further increase with a 16-micromol dose. CONCLUSION: Resovist is safe and effective. The best MR imaging results were obtained 40 minutes after injection of 8 micromol Fe/kg.

The value of hyoscine butylbromide in abdominal MR imaging with and without oral magnetic particles.

PURPOSE: The purpose of this article was to assess the impact of intravenous (IV) anticholinergic hyoscine butylbromide in abdominal magnetic resonance (MR) imaging with oral magnetic particles (OMP) [ABDOS-CAN, Ferristene (USAN), Nycomed Imaging AS, Oslo, Norway]. MATERIALS AND METHODS: In 31 patients with abdominal tumors, T1-weighted spin-echo (SE) images (SE 600/ 15; 1.5 T) were obtained without and with IV hyoscine butylbromide (20 mg) before and after administration of 800 ml of OMP. Two blinded readers assessed motion artifacts, bowel-wall visualization, and lesion delineation on the four sets of T1-weighted images. The two-tailed Wilcoxon paired sample test was used for statistical analysis (p < .05). RESULTS: Hyoscine butylbromide reduced motion artifacts and improved bowel-wall visualization on precontrast and OMP-enhanced images at a statistically significant level (p = 0.0006-0.037). The lowest degree of artifacts was recorded on OMP images with hyoscine butylbromide. OMP with hyoscine butylbromide significantly improved lesion delineation compared to studies without antiperistaltic drug before (p = 0.019) and after OMP administration (p = 0.01). CONCLUSIONS: The authors conclude that the use of IV hyoscine butylbromide is recommended for OMP-enhanced abdominal MR imaging with T1-weighted SE pulse sequences at 1.5 T.

Pneumatosis cystoides intestinalis with pneumoperitoneum and pneumoretroperitoneum following chemotherapy.

Pneumatosis cystoides intestinalis (PCI) is a relatively rare, mostly benign, condition. We report a case of chemotherapy-induced PCI with free retro- and intraperitoneal gas in a 17-year-old man with acute lymphoblastic leukemia. Chest radiography and upright abdominal radiography showed free intra- and retroperitoneal gas; computed tomography demonstrated subserosal gas collections. Conservative treatment with oxygen, metronidazol, and parenteral alimentation was performed, and PCI resolved within 2 weeks.

Superparamagnetic iron oxide: detection of focal liver lesions at high-field-strength MR imaging.

AMI-25 was evaluated at 1.5 T as a superparamagnetic iron oxide contrast agent for the liver. Sixteen patients with up to five suspected focal liver lesions were examined with T1-, proton-density-, and T2-weighted spin-echo sequences before and after intravenous administration of AMI-25 (15 mumol/kg iron). The contrast-to-noise ratio (C/N) increased from 1.8 to 3.5 on 600/15 (TR msec/TE msec) images and from 1.7 to 7.9 on 2,500/15 images after AMI-25 administration (P < .01). C/N did not change significantly on 2,500/90 images. Two blinded readers counted the number of lesions visible on unenhanced and contrast-enhanced images, with the 32 sets of images of the 16 patients presented in random order. Both readers identified more lesions on AMI-25-enhanced images, but the difference was not statistically significant (P > .05). Two patients reported minor side effects (flushing, sensation of heat, lower back pain). On the basis of the results obtained in a limited number of patients, the authors conclude that at 1.5 T, AMI-25 does not significantly improve the detection of focal liver lesions on conventional spin-echo images.

[The MR tomography of focal liver lesions with the superparamagnetic contrast agent AMI-25 at 1.5 tesla]. / MR-Tomographie fokaler Leberläsionen mit dem superparamagnetischen Kontrastmittel AMI-25 bei 1,5 Tesla.

Superparamagnetic iron oxide particles (AMI-25) were evaluated as a liver contrast agent in high-field MR imaging (1.5 T). 16 patients with up to 5 presumed focal liver lesions (liver metastases n = 8, HCC n = 5, Klatskin tumours n = 2, FNH n = 1) received 15 mumol Fe/kg BW intravenously and were examined via standard T1- and T2-weighted spin-echo sequences. Quantitative image analysis showed a post-contrast increase of the contrast-to-noise ratio (C/N) from 1.6 to 7.4 on SE 2,500/15 images (p < .05). However, C/N was in the same range on plain SE 2,500/90 scans. Blind evaluation by two independent readers revealed that AMI-25-enhanced images did not provide a significantly increased number of lesions. Two patients reported minor, self-limited side-effects (flush, back pain). We conclude that in contrast to reports at mid-field MR imagers, the use of AMI-25 at 1.5 T does not significantly improve the detection of focal liver lesions on conventional SE images.

Mn-DPDP-enhanced MR imaging of malignant liver lesions: efficacy and safety in 20 patients.

Twenty patients with malignant liver lesions underwent magnetic resonance (MR) imaging with manganese (II) DPDP [N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis(phosphate)] to evaluate the safety and efficacy of the contrast agent. In two groups of 10 patients each, 5 mumol/kg Mn-DPDP was administered intravenously (3 mL/min) at a concentration of either 50 or 10 mumol/mL. T1- and T2-weighted images were obtained with a 1.5-T imager. Six patients reported a total of eight instances of side effects (flush, feeling of warmth, metallic taste) of which seven occurred at the 50 mumol/mL concentration. A significant decrease in alkaline phosphatase levels 2 hours after injection was recorded. On T1-weighted images, the 10 mumol/mL formulation yielded significantly greater increases in contrast-to-noise ratio (79.8%-137.5%) than the 50 mumol/mL formulation (46.2%-86.6%). In a blinded reader study of 10 patients with one to five lesions each, no lesion was missed on Mn-DPDP--enhanced T1-weighted images; however, four false-positive foci were identified. The authors conclude that slow administration of 5 mumol/kg Mn-DPDP at a concentration of 10 mumol/mL is safe and efficient enough to proceed to further clinical trials.

[Manganese DPDP as a contrast medium for MR tomography of focal liver lesions. Tolerance and image quality in 20 patients]. / Mangan-DPDP als Kontrastmittel für die MR-Tomographie fokaler Leberläsionen. Verträglichkeit und Bildgebung bei 20 Patienten.

Twenty patients with focal liver lesions (18 metastases, 1 hepatocellular carcinoma, 1 cholangiocarcinoma) were given manganese DPDP as part of a multicentric phase II study of paramagnetic hepatobiliary MR contrast media. 5 mumol/kg manganese DPDP were injected into 10 patients in a concentration of 50 mumol/ml or 10 mumol/ml (3 ml/min). Blood pressure, pulse rate, ECG, respiratory rate, body temperature, blood and serum parameters and the patients' subjective feelings were recorded. MRI was performed with 1.5 T using T1- and T2-weighted sequences. 6 patients reported 8 side effects (flushing, feeling of warmth, metallic taste); 7 of these were produced by the 50 mumol concentration. Two hours after injection there was a significant reduction in alkaline phosphatase which was no longer present after 24 hours. On T1-weighted images manganese DPDP resulted in marked improvement in the contrast difference between the lesions and the liver parenchyma which resulted in a marked increase in the signal to noise ratio. Comparing the two concentrations, better results were obtained by the lower concentration. Extrahepatic uptake was found in the gallbladder, duodenum, pancreas, kidneys, gastric mucosa and myocardium. Manganese DPDP in a concentration of 10 mumol/ml and a dose of 5 mumol/kg is a well tolerated contrast medium which improves the demonstration of focal liver lesions in view of its distribution and uptake. The mechanisms for the transitory side effects require further studies.