Magnetic resonance imaging]

During the last ten years substantial improvement of hardware and software used for the construction of MRI scanners has made available MRI sequences with high temporal and spatial image resolution. Therefore, MR imaging has become an excellent tool and in certain cases the gold standard for the evaluation of cardiovascular diseases. Primary indications for cardiovascular MRI include the assessment of aortic diseases, the arrhythmogenic right ventricle, surgically corrected congenital heart diseases, pericardial disease, intra- and paracardiac tumors and quantification of ventricular function and volumes and myocardial mass. Secondary indications include hypertrophic and dilative cardiomyopathies, valvular and ischemic heart disease. MRI is a totally noninvasive diagnostic technique which is safe and without known harmful potential to biological tissue. The wide diagnostic spectrum providing anatomical, geometrical functional and biochemical information cannot be accomplished by any other diagnostic method.     

Magnetic resonance imaging in optic neuropathy

Magnetic resonance imaging has revolutionised the ability to investigate intrinsic disease of the anterior optic pathways. We review the data accumulated from this technique not only in the conditions, such as neoplasia, which have traditionally been the domain of neuroimaging, but also in inflammatory, metabolic and degenerative diseases.     

Magnetic resonance imaging in acute pyelonephritis

The diagnosis of acute pyelonephritis in children remains a clinical challenge. We assessed the feasibility of magnetic resonance imaging (MRI) detection of pyelonephritis in four pediatric patients and compared the results with renal cortical scintigraphy. MRI revealed areas of high signal intensity in the kidney that coincided with photon-deficient regions in the radionuclide scans in two children with acute pyelonephritis. These findings confirm work in experimental animals and indicate that MRI can accurately detect acute pyelonephritis in children.     

Magnetic resonance imaging in pseudotumor cerebri

Post-transplantation lymphoproliferative disorders (PTLD) are a complication of immunosuppressed transplant recipients, and their incidence is reported to be 20-120 times greater than the rate in the general population. After kidney transplantation, PTLD more likely arise within the renal transplant fossa. Radiological patterns of these forms are presented and discussed, according to a review of the literature, and illustrated by cases from our institution. Ultrasound plays an essential role in the early diagnosis of PTLD by detecting a urinary obstruction associated with adenopathy or an ill-defined mass not previously seen. However, in the case of an inconclusive US examination, CT or MRI should be performed to confirm the presence of a mass. Both techniques are useful in evaluating the extension of the process within the transplantation fossa; MRI seems more accurate and can be used for the follow-up, especially after reduction in immunosuppressive therapy without transplant removal.     

Magnetic resonance imaging in vascular dementia

This case report presents a patient who developed right shoulder pain following strenuous upper-extremity exercise. Approximately 6 weeks later his pain resolved, he noticed persistent right upper-extremity weakness. He was referred to physical therapy for evaluation and treatment. Physical therapy evaluation revealed isolated serratus anterior muscle paralysis. A long thoracic neuropathy was subsequently confirmed by electromyographic testing. The etiology, pathophysiology, and pathokinesiology of serratus anterior muscle paralysis are reviewed. A case is presented, illustrating how the clinical decision making is based on the pathokinesiology and pathophysiology. The patient was followed over the course of 17 months and has recovered full right shoulder active range of motion. His serratus anterior muscle strength has increased to Good minus, and he reports significantly improved functional use of the upper extremity.     

Magnetic resonance imaging in coccidioidal arthritis

Aortic pseudoaneurysm starts as small disruption of the aortic wall with an extravasation of blood into the mediastinum, contained only by fibrous tissue and by parietal pericardium. The most common cause of this condition is dehiscence or inflammatory processes of suture stitches after surgical interventions on aortic value or ascending sorts. Pseudoaneurysm represents about 40% of complications of cardiac surgery involving the ascending sorts. This complication occurs in about 1% of cases of aortic valve or ascending tract replacement. In this study, we evaluated, with different diagnostic techniques, 4 patients (all males, mean age 48 +/- 23 years, range 17-74) affected by aortic pseudoaneurysm occurring at different times after surgical intervention on the sorts. Clinically only 1 of the 4 patients referred chest pain. Repeated chest radiography and cardiac magnetic resonance were performed in every patient; 3 subjects were evaluated by transthoracic and transesophageal echocardiography; contrast-enhanced computed tomography was performed in 1 patients. Pseudoaneurysm diagnosis obtained by non invasive methods was later confirmed and better described by angiography. Our study demonstrated that transesophageal echocardiography and magnetic resonance are useful and reliable methods in the diagnosis of aortic pseudoaneurysm. However, in case of mediastinal he or pericardial effusion (suggestive of aortic pseudoaneurysm) by transesophageal echocardiography or magnetic resonance, angiography is necessary and may show the exact rupture site on the aortic wall. This diagnostic approach yields enough information for both diagnosis and surgical correction of this rare but high-risk pathological condition.     

Magnetic resonance imaging in lactic acidosis

Mitochondrial defects, defects in gluconeogenesis, and biotin-responsive multiple carboxylase deficiency are disorders characterized by primary lactic acidosis. In this review, characteristic findings in magnetic resonance imaging (MRI) of the brain, as related to histopathological abnormalities, are described for the different disorders and the diagnostic value of the MRI findings is discussed. Inborn errors of metabolism with primary lactic acidosis should be considered in particular when MRI shows lesions similar to or reminiscent of effects of focal or generalized hypoxia-ischaemia, or when MRI shows signs of chronic neurodegeneration, but rarely in cases with predominantly white-matter changes.     

Disappearing enhancing brain lesion in a child with neurofibromatosis type I

Neurofibromatosis type 1 (NF1) in children can produce a variety of parenchymal signal abnormalities on cranial MR. Areas of abnormal signal in these patients may represent regions of disordered myelination, "hamartomatous" change or frank neoplasia. The presence of contrast enhancement in intracranial lesions in patients with NF1 is usually strongly suggestive of tumor. We report the case of a child with NF1 and a focal enhancing brain parenchymal lesion which spontaneously resolved without specific therapy.     

Magnetic resonance imaging in breast cancer staging

For many solid carcinomas, high-resolution cross-sectional imaging has changed cancer staging, the evaluation of therapeutic response, the detection of recurrence, and even how therapy is selected and performed. Such imaging has not yet had similar effects on breast cancer. Evaluations of therapeutic response in breast carcinomas have been impeded by the current limited methods of evaluating breast tumor size and extent: clinical palpation, ultrasonography, and mammography. The use of magnetic resonance imaging (MRI) of the breast in the evaluation of breast tumors brings the advantages of high-resolution cross-sectional imaging to breast cancer staging and treatment evaluation and is likely to greatly enhance research efforts in this complex disease. MRI of the breast has evolved to be the most accurate noninvasive technique for local staging of breast cancer. MRI is most accurate in measuring tumor size and detecting multicentric disease. These staging characteristics affect the selection of therapy and initial determination of prognosis; therefore, MRI of the breast can change the assessment of fundamental parameters on which treatment is selected. Because clinical trials of new cancer treatments are predicated on proper and accurate characterization of the tumor, MRI also should affect how clinical trials are performed and evaluated.     

Magnetic resonance imaging in macromelia and macrodactyly

We report five cases presenting with soft tissue and bone overgrowth that demonstrate the ability of MRI to establish a diagnosis in the absence of specific clinical features. Disorders included macrodystrophia lipomatosa, angiolipomatosis, Klippel-Trenaunay-Weber syndrome, blue rubber bleb naevus syndrome and one case of segmental limited hypertrophy. The MRI appearances, and other radiological features of these conditions are discussed. MRI is recommended in all cases of macrodystrophy when the clinical features and plain film findings are indeterminate.     

NF1 (neurofibromatosis type 1)

Several distinct Ras GTPase activating proteins (GAPs) from mammals, including Ras GAP of 120 kDa (GAP1) and NF1, stimulate the intrinsic GTPase activity of normal Ras, but not oncogenic Ras mutants (Trahey and McCormick, 1987). That is the reason why normal Ras remains predominantly in the inactive GDP-bound form (D-Ras), whereas oncogenic Ras remains constitutively in the active GTP-bound form (T-Ras). NF1 is a tumor suppressor of 2818 amino acids whose disruption or deletion causes brain tumors called neurofibromatosis type 1 by elevating the T-Ras level. T-Ras activates several distinct oncogenic effectors, including Ser/Thr kinase Raf, GAP1, P1-3 kinase, PKC-zeta and Ra1 GDS. Interestingly, the binding of T-Ras to either GAPs or these oncogenic effectors requires the same effector domain I (residues 32-40) of T-Ras molecule. In other words, these GAPs and effectors compete for binding to T-Ras. Using a series of N- and C-terminal deletion mutants of NF1, we identified a 78 amino acid fragment (NF78, residues 1441-1518) as the minimum GAP domain, and a 56 amino acid fragment (NF 56, residues 1441-1496) as the minimum Ras-binding domain. Furthermore, we identified the Raf fragment of 81 amino acids (Raf81, residues, 51-131) as the minimum Ras-binding domain with a high affinity. We found that (i) these NF1 fragments and Raf81 compete for binding to T-Ras, and that (ii) over-expression of these NF1 or Raf fragments strongly suppresses the malignant transformation caused by oncogenic Ras mutants. Thus, these agents offer a unique opportunity to control the proliferation of T-Ras-associated tumors that represent more than 30% of all human carcinomas including neurofibromatosis type 1.     

Magnetic resonance imaging of the shoulder

MRI has rapidly become a commonly used technique for evaluation of the shoulder. It provides a wealth of information regarding the entire shoulder girdle, and it is the most accurate noninvasive method available for imaging the rotator cuff. There have been numerous technical improvements in MRI in the relatively short time that clinical MRI has been in existence. Further refinements in design, new imaging sequences, and additional clinical experience should help to increase the accuracy and flexibility of this imaging modality.     

Magnetic resonance imaging of seronegative sacroiliitis

A total of 27 patients with advanced previously untreated non-small-cell lung cancer were treated with paclitaxel and ifosfamide. The starting dose of paclitaxel was 175 mg/m2 given for 3 h by intravenous infusion on day 1. Ifosfamide 4 g/m2 was given for 4 h by intravenous infusion on day 2. Dosage of the two drugs was modified according to nadir white blood count after each cycle. Involved in the treatment were 17 males and 10 female patients. The median age was 61 years (range 47-71 years) and the median Karnofsky performance status was 70% (range 60-90%), 13 cases were stage IIIb and 14 cases were stage IV. One case was not evaluable due to lost follow-up after a single dose of chemotherapy. There were five cases not determined due to a timing error. Of 21 evaluable cases, eight achieved partial response (PR 38%, confidence interval 18.1-61.5%), seven achieved stable disease, two had a minor response. The median survival time of the whole group was 255 days (range from 38 to 567 days). The major toxicities were myalgia; arthralgia and neuropathies. Throughout the study, only three cases (15%) were treated at dose level 0. After the first cycle, 18 cases were treated at dose level 1, after a second cycle, 13 cases were treated at dose level 2. Three cases with grade 3 leukopenia were seen at dose level 0. At dose level 1, two cases had grade 3 leukopenia. At dose level 2, four episodes of grade 3 leukopenia were noted. It is concluded that paclitaxel can be combined safely with ifosfamide at these dosage levels. The response rates were comparable to the other chemotherapy combination in advanced non-small-cell lung cancer. The survival results were acceptable and comparable to the cisplatin-containing regimen. This study indicates that combinations of paclitaxel and/or ifosfamide with other agents, such as gemcitabine and vinorelbine, should be explored.     

Magnetic resonance imaging of brain death

The db/db mutant mouse is a rodent model of genetic diabetes that develops renal glomerular lesions with striking mesangial matrix accumulation by the age of 16 weeks, after 8-10 weeks of sustained hyperglycemia. However, abnormalities in renal function that antedate or accompany the appearance of these pathologic changes, which resemble those found in human diabetes, have not been delineated. We therefore examined renal function in young db/ db mice and their nondiabetic db/m littermates from the age of 8 through 15 weeks. Serum creatinine and blood urea nitrogen concentrations at the onset of diabetes in db/db mice did not differ significantly from mean concentrations in db/m controls. An elevated creatinine clearance, due in large part to increased body weight, and increased urinary albumin excretion were observed in db/db compared with db/m mice soon after establishment of sustained hyperglycemia. A relative reduction in creatinine clearance was demonstrable in db/db mice at the age of 15 weeks, coincident with the appearance of overt compromise in renal function manifested by frank increases in the serum creatinine and blood urea nitrogen. The findings indicate that the well-documented glomerular pathology in db/db mice is accompanied by definable alterations in renal function, which are similar in chronology and nature to those found in human diabetes.     

Magnetic resonance imaging of disseminated sclerosis

Multiple sclerosis is a chronic demyelinating disease. Paraclinical examinations may contribute to the diagnosis of multiple sclerosis. Magnetic resonance imaging (MRI) has a very high sensitivity concerning multiple sclerosis, and has made it possible to visualize multiple sclerosis plaques in vivo, to follow each plaque over the course of time and in this way to obtain information about the pathogenesis. MRI has shown that the size of plaques may vary considerably, and that plaques are dynamic structures with the ability to change in size over few weeks. By using MRI and the contrast agent Gadolinium-DTPA, it is possible to distinguish a newly developed plaque from an older one. Therefore, MRI has become an important examination in therapeutic trials. Just now, MRI with Gadolinium-DTPA is being used to evaluate the efficacy of plasmapheresis and immunoglobulin treatment in a joint study between Rigshospitalet and Hvidovre Hospital.     

Magnetic resonance imaging of primary cardiomyopathies

Cardiomyopathies are diseases of the myocardium of unknown etiology associated with cardiac dysfunction. On the grounds of their morphology and pathophysiology, primary or idiopathic cardiomyopathies may be classified into a number of disorders; namely, hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy, and restrictive cardiomyopathy. The term "secondary cardiomyopathies" is reserved to specific heart muscle diseases clinically very similar to primary cardiomyopathies. Cardiac magnetic resonance imaging has long been used to study cardiac morphology and, more recently, to assess blood flow, perfusion, and contractile function. The emerging role of magnetic resonance imaging for the understanding and treatment of primary cardiomyopathies cannot be underestimated. From a clinical point of view, an examination based on a single, efficient, and noninvasive MR study focusing on the clinically relevant features of cardiomyopathies is an objective and reproducible means for diagnosing and monitoring hypertrophic, arrhythmogenic, dilated, and restrictive cardiomyopathies.