Field strength dependence of MRI contrast enhancement: phantom measurements and application to dynamic breast imaging.

Differences in MRI-measured contrast enhancement have been used for tissue characterization, particularly for the characterization of mammary tumours. T1 weighted spoiled gradient echo sequences have usually been acquired for this purpose and relative signal intensity increase (Srel) has been determined to quantify contrast uptake. The field strength dependence of this technique is evaluated in this paper by phantom measurements. Srel is compared with the recently introduced "enhancement factor" (EF) and "contrast uptake equivalent" (CE) as a quantitative assessment parameter for contrast uptake. Enhancing tissues were simulated with water phantoms doped with increasing concentrations of Gd-DTPA. Spoiled gradients echo images (FLASH-2D) were obtained on a 0.2 T and 1.5 T MR system. Srel, EF and CE were determined and the results of the phantom measurements were applied to typical types of breast tissues. Srel showed a strong dependence on the magnetic field strength and was greater at higher field strengths. This is because Srel correlates positively with the native T1 which is longer at higher field strengths. Conversely, the EF and CE almost eliminated the distorting influences of the magnetic field strength. CE provided a good approximation of the actual contrast uptake. In practice, the dependence of Srel on the magnetic field strength might cause malignant lesions to be misclassified as benign at low field strengths. Either Srel criteria should be adjusted to magnetic field strength or EF and CE should be used instead of Srel for tissue characterization with dynamic contrast-enhanced MRI.

Magnetic resonance imaging of absent pulmonary valve syndrome.

A neonate with absent pulmonary valve syndrome was examined by means of echocardiography and magnetic resonance imaging (MRI). MRI provided an excellent evaluation of the intracardial morphology, vessel anatomy, mediastinal structures, and shunt flow; and it was superior to echocardiography for detection of aortopulmonary collaterals and vessel abnormalities. This case report of an uncommon cardiac abnormality confirms that MRI is a useful complementary modality to echocardiography in neonates and is recommended for problems with central pulmonary vessels and their relation to tracheobronchial structures.

Preoperative staging of osteosarcoma: efficacy of MR imaging in detecting joint involvement.

OBJECTIVE: Selecting the appropriate surgical procedure for treatment of patients with osteosarcoma requires accurate preoperative evaluation of tumor extent. Establishing the presence or absence of joint involvement is particularly important. Accordingly, we studied the efficacy of MR imaging for detecting joint involvement in 46 patients with osteosarcoma around joint spaces. SUBJECTS AND METHODS: Preoperative MR examinations were performed in 46 consecutive patients with osteosarcoma whose tumors were located around the knee (n = 33), the hip (n = 8), or the shoulder (n = 5). T2-weighted and unenhanced and contrast-enhanced T1-weighted spin-echo MR images were obtained for all patients. We assessed the presence or absence of tumor invasion of the intracapsular-intrasynovial joint space, either by disruption of the joint capsule or by intraarticular destruction of the cortical bone and articular cartilage or the intracapsular-extrasynovial cruciate ligaments of the knee. All patients subsequently had surgery. The MR findings were correlated with findings from macroscopic and microscopic pathologic examinations. RESULTS: All 10 patients who subsequently proved to have tumor involvement of the joint were correctly identified (sensitivity, 100%). The tumor involved the knee joint in seven patients, the hip joint in two, and the shoulder joint in one. However, the MR diagnosis was false-positive in another 11 patients who did not have joint involvement at surgery (specificity, 69%). In the knee, MR imaging was more accurate in identifying tumor extension to the cruciate ligaments than to the intrasynovial joint space. Post-contrast T1-weighted images were most useful in detecting joint involvement. CONCLUSION: MR imaging is highly sensitive for detecting joint invasion of osteosarcoma. However, false-positive diagnoses may lead to overstaging of tumor and result in unnecessarily radical surgical procedures.

Postcontrast MR arthrography in assessment of cartilage lesions.

OBJECTIVE: Although MR has been proven effective in evaluating many components of the musculoskeletal system, including ligaments, fibrocartilage, muscle, and bone marrow, its role in the evaluation of articular cartilage remains controversial. Recent studies have demonstrated that intraarticular injection of Gd-DTPA [MR arthrography (MRA)] improves the detection of cartilage abnormalities in cadaveric specimens. The aim of this study was to determine the efficacy of MRA for the detection of naturally occurring cartilage lesions in a clinical population. MATERIALS AND METHODS: Sixty knees of 58 patients were studied with a three-dimensional (3D) T2*-weighted GE sequence (FISP) both before and after and a T1-weighted (T1W) SE sequence after the intraarticular injection of a 2 mmol/L Gd-DTPA solution. All knees subsequently underwent arthroscopy or arthrotomy. RESULTS: The MRA sequences performed significantly better (kappa = 0.85) than the routine FISP sequences (kappa = 0.39) in both the detection and the staging of cartilage abnormalities. The MRA FISP sequence (kappa = 0.91) performed slightly better than the MRA T1W sequence (kappa = 0.85), but there was no statistically significant difference between the two sequences. No complications from the intraarticular injection of contrast material occurred. CONCLUSION: Therefore, MRA appears to be an effective and safe method for the evaluation of articular cartilage abnormalities.

The diagnostic value of magnetic resonance imaging for the detection of tumor recurrence in patients with carcinoma of the ovaries.

Disease status during follow-up evaluation of patients with carcinoma of the ovaries is the main criterion for the selection of appropriate management. A cohort analysis was performed to investigate if magnetic resonance imaging (MRI) could improve noninvasive assessment of disease status in patients with carcinoma of the ovaries during follow-up examination. Twenty-four women with carcinoma of the ovaries after primary surgical treatment with subsequent platinum containing chemotherapy were entered into the study. MRI was performed in addition to sonography and computed tomography (CT). Patients without evidence of disease underwent restaging laparotomy. Sensitivity of sonography, CT and MRI was 50, 63 and 75 percent, respectively. Combination of CT and MRI revealed a 75 percent sensitivity rate. Specificity for sonography, CT and MRI was 100, 94 and 94 percent, respectively, and for the combination of CT and MRI, 88 percent. Positive and negative predictive value and accuracy of these methods were 100, 80 and 83 percent for sonography; 83, 83 and 83 percent for CT; 86, 88 and 88 percent for MRI, and 75, 88 and 83 percent for the combination of CT and MRI. In one instance of false-negative sonographic and CT results, MRI detected recurrence located in postoperative scar tissue. In one instance, MRI did not add essential information to the other imaging methods. Therefore, MRI as a time- and cost-intensive procedure should be reserved for instances in which there are doubtful findings arising with other diagnostic tools, rather than as an indispensable routine procedure in the follow-up evaluation of patients with carcinoma of the ovaries.

Polymyositis: MRI-appearance at 1.5 T and correlation to clinical findings.

The thigh regions of 10 patients suffering from polymyositis were examined by magnetic resonance imaging (MRI) at 1.5 T; follow-up examinations were performed in all patients. MRI findings were correlated with findings at physical examination and serological parameters. In four patients focal areas of hyperintensity on T2-weighted (T2W) spin echo (SE) images were found within muscles. They were not detectable on T1-weighted (T1W) images. In three of these cases enhancement within the musculature was seen following i.v. administration of Gd-DTPA on T1W images. In another five patients there was varied replacement of muscle by fatty tissue. In one patient the muscle appeared completely normal. On follow-up three patients showed definite changes in imaging findings; two correlated well with clinical and biochemical findings while the third exhibited massive deterioration clinically with mild improvement on imaging. Seven patients exhibited no change on MRI; four of these had shown a significant clinical change in the course of the disease, whilst three were clinically stable. In our small series MRI using SE technique (T1W and T2W) and contrast enhancement to date seems to be of limited value for the assessment of muscular changes during therapy. The i.v. use of Gd-DTPA did not add to MRI's diagnostic value in this series.

CT and MR accuracy in the detection of tumor recurrence in patients treated for ovarian cancer.

OBJECTIVE: The aim of this prospective study was to evaluate the accuracy of clinical examinations (palpation/determination of serum tumor-associated antigen CA125 level), CT, and MRI in the detection of tumor recurrence in patients with treated ovarian cancer. MATERIALS AND METHODS: Twenty-four patients who had been treated for ovarian carcinoma were prospectively examined by clinical means (palpation/serum tumor-associated antigen CA125 level), CT, and MRI to assess their accuracy in detecting recurrent disease; results were correlated with surgical/bioptic/pathoanatomic findings. Nine patients had relapse; 15 women were disease-free. RESULTS: Examinations were true-negative in 14 patients (on palpation/CA125, CT, and MRI) and true-positive in 9 on palpation/CA125, in 6 on CT, and in 7 patients on MRI. False-positive examinations occurred in one patient on palpation/CA125, CT, and MRI and false-negative in zero on palpation/CA125, in three on CT, and in two on MRI, a sensitivity of 100% for palpation/CA125, 66.6% for CT, and 77.7% for MRI and a specificity of 93.3% for palpation/CA125, CT, and MRI. Accuracy of palpation/CA125 examinations was 95.8% in comparison with 83.3% for CT and 87.5% for MRI. CONCLUSION: Our results suggest that in the follow-up of ovarian cancer patients, assessment of serum tumor-associated antigen CA125 level is accurate in the determination of patients with tumor recurrence. Computed tomography is the primary imaging modality to prove macroscopic disease recurrence and can spare these patients from invasive restaging second-look laparotomy; MRI should be performed in women with questionable macroscopic recurrent tumor and negative CT examination. Neither CT nor MRI can confidently exclude microscopic disease.

Superparamagnetic particles as oral contrast medium in magnetic resonance imaging of patients with treated ovarian cancer--comparison with plain MRI.

In 23 patients with treated ovarian cancer, 24 magnetic resonance (MR) examinations of the abdomen and pelvis were performed before and after administration of an oral superparamagnetic contrast medium. Depiction of bowel loops was judged sufficient in 47% with plain scans and in 85% with enhanced scans. Minor artefacts attributed to the agent were noted in 32% of examinations and were classified as disturbing in 8%. The diagnostic information obtained after contrast enhancement was estimated to be superior to that from plain MRI in 20% of patients. The use of oral contrast medium did not alter the MR diagnosis of "tumour recurrence" or "disease-free" in any patient. Our results suggest that superparamagnetic iron oxide is an effective and reliable approach to negative bowel contrast enhancement, increasing the confidence level when distinguishing intestines from solid structures.

[Chondromatous tumors of the larynx based on three case reports with special reference to magnetic resonance tomography]. / Chondromatöse Tumore des Larynx anhand dreier Kasuistiken unter besonderer Berücksichtigung der Magnetresonanztomographie.

Cartilaginous tumours of the larynx are rare, altogether about 250 cases being reported in the literature. These tumours typically grow slowly and malignant types usually show only local infiltrative growth. Distant metastases are rarely observed. Up until the present CT has been the main diagnostic tool due to its excellent demonstration of intra-tumoral calcifications. In the German literature Grevers et al. reported on MRI in cases of laryngeal tumours. Since we do not know of any reports discussing the special situation of cartilaginous tumours in this location, we present three cases of cartilaginous tumours outlining the effectiveness of MRI.

[The importance of magnetic field strength in the MR diagnosis of multiple sclerosis: a comparison of 0.5 and 1.5 T]. / Bedeutung der Magnetfeldstärke in der MR-Diagnostik der multiplen Sklerose: Ein Vergleich von 0.5 und 1.5T.

The value of magnetic resonance (MR) to establish the diagnosis of multiple sclerosis (MS) is well known. This study was undertaken to compare MR imaging of the brain of MS patients at high (1.5T) and mid (0.5T) field strength. 25 patients with MS underwent two consecutive MR studies within one hour, each consisting of axial proton density and T2-weighted spin-echo images. Lesions in the supratentorial white matter and corpus callosum and those in the brain stem and cerebellum were separately counted. At 1.5T significantly more lesions were seen than at 0.5T (p < 0.05). Although T2-weighted images at 1.5T added significant information compared to images obtained at 0.5T, in none of our 25 patients the diagnosis was missed at 0.5T. However, at 1.5T dissemination in space was better demonstrated, suggesting MR scanning with high field-units to be favourable in patients with clinically suspected MS.

[MRI of the temporomandibular joint. Demonstrability and significance of the retro-articular vascular plexus]. / MRT des Kiefergelenks. Darstellbarkeit und Bedeutung des retroartikulären vaskulären Plexus.

The retro-articular vascular plexus of the temporomandibular joint (TMJ) is of great importance for the function of this joint. Aim of this study was to determine the amount of increase of signal intensity in the retro-articular vascular plexus after intravenous injection of contrast medium and to figure out potential advantages of this procedure. The posterior band of the articular disc--a landmark in the diagnosis of disc dislocations--becomes prominent after injection of contrast medium. Forty-five temporomandibular joints were studied before, and after intravenous injection of contrast medium with magnetic resonance imaging (MRI) using T1-weighted images in parasagittal plane. In all cases a measurable increase of signal intensity was demonstrable in healthy volunteers as well as in patients with normal or pathological TMJ findings. In 53.3% of cases the posterior band was better differentiable after administration of contrast medium. In patients with suspicion of pathological features in series without contrast medium, in 27.3% of those cases administration of contrast medium led to a more precise--"diagnostic"--evaluation of disc location. The study emphasizes the use of contrasts medium for evaluations of disc dislocation with MRI in cases of pathological or unclear findings in precontrast MRI series.

[High-resolution computed tomography of the lung in young patients with cystic fibrosis]. / Hochauflösende Computertomographie der Lunge bei jungen Patienten mit zystischer Fibrose.

In a prospective study we proved the value of high-resolution computed tomography (HRCT) and the CT scoring system developed by Stiglbauer et al. on 47 young patients suffering from cystic fibrosis (CF) (median age: 10.1 years). The most frequent pulmonary finding was bronchial wall thickening (BWT) in 43 patients (94.6%), followed by bronchiectasis (BE) in 36 patients (79.2%). A less frequent finding was ill-defined patchy consolidation (39.6%). We found an almost even distribution of BWT and BE in the upper and lower lobes of the lung. These two findings were scored according to their severity and extent. The maximum possible score for BWT and BE was 72 in a single patient. For both the overall score was 19.9 +/- 11.1. A statistically significant correlation of the CT scoring system with the lung function tests FEV1/FVC (P = 0.03) and MEF50 (P = 0.02) was found. The results of HRCT and the CT scoring system were shown to be valuable methods in the assessment of pulmonary changes, in young patients suffering from CF.

[Chondromatous tumors in MRT: clinical picture in relation to localization and histopathology]. / Chondromatöse Tumoren in der MRT: Erscheinungsbild in Abhängigkeit von Lokalisation und Histopathologie.

19 patients with histologically verified cartilaginous tumours (chondromas, chondrosarcomas) were examined with magnetic resonance imaging (MRI) in order to assess differences regarding the MR appearance of these tumours which would provide information on the biological behaviour of these lesions. MR findings were then correlated with histopathology. With regard to the signal behaviour of cartilaginous tumours a good correlation with histopathology could be established insofar as the relatively hypocellular tumours composed of hyaline cartilage exhibited a high signal level on T2-weighted images. There were no significant differences regarding signal characteristics of cartilaginous tumours in various anatomical locations. However, lesions located in the pelvis and the long bones showed predominantly peripheral enhancement whereas tumours of the skull base and larynx exhibited diffuse enhancement patterns in the majority of cases. 10 tumours (6 benign, 4 malignant) exhibited a lobular appearance. No relevant information in respect of tumour grading could be obtained.

[Stenosis of the extracranial carotid artery]. / Stenose der extrakraniellen Arteria carotis.

Magnetic resonance angiography (MRA) as well as intraarterial digital subtraction angiography (DSA) were performed in 45 patients suffering from cerebrovascular disease, both procedures within one week of each other. MRA und DSA were evaluated separately for every patient retrospectively by two experienced radiologists on consensus basis. The results were then compared using catheter angiography as gold standard. Evaluation was confined to the common and internal carotid arteries (CCA, ICA) in the neck subdivided into 5 grades of stenosis. A comparative assessment was impossible in 9% cases due to motion artifacts and patient malposition. Out of 18 verified CCA stenoses 13 were demonstrated by MRA and 39 out of 44 ICA stenoses were assessed by MRA. There was a highly significant correlation between degree of stenosis detected by the two methods. Spearman Rank correlation coefficients of 0.824 and 0.913 were found for CCA and ICA, respectively.

Haemorrhage in intracerebral arteriovenous malformations: detection with MRI and comparison with clinical history.

Fifty-one patients with 59 angiographically proven cerebral arteriovenous malformations (AVMs) were examined by high-field MRI to detect blood breakdown products. Results were correlated with the history of intracranial bleeding. Evidence of previous episodes of haemorrhage was seen in 10 of 12 patients (83.3%) with verified bleeding, in 4 of 9 patients (44.4%) with symptoms which could suggest bleeding and in 6 of 30 patients (20%) with negative histories. Because of the known rebleeding rate and the increased risk of associated complications, identification of the subgroup who had had haemorrhage and should therefore be considered for surgery may be beneficial. MRI can make a contribution to management by demonstrating prior haemorrhage in patients with an inadequate clinical history.

Pituitary adenomas: findings of postoperative MR imaging.

Preoperative and postoperative magnetic resonance (MR) images obtained in 25 patients with pituitary macroadenomas (1.1-5.2 cm in diameter) were evaluated to determine normal (physiologic) and abnormal findings after transsphenoidal or subfrontal surgery. With a 1.5-T unit, T1-weighted sagittal and coronal images were obtained before and after administration of gadopentetate dimeglumine. The physiologic changes after surgery included resorption of packing material and sphenoid sinus opacifications, reexpansion of the pituitary gland, and lowering of the optic chiasm. Implanted gelatin foam appeared as an endosellar, circularly enhancing mass that was seen on follow-up studies to have decreased in size. Muscle-and-fat implants appeared as areas of high signal intensity. In 14 patients, residual tumors were found in the suprasellar (n = 4), retrosellar (n = 3), parasellar (n = 8), and/or endosellar (n = 3) space. Residual tumors were differentiated from implant materials by means of location, characteristic signal intensity, and enhancing pattern, which were identical to those of the corresponding preoperative adenoma in 13 cases (93%). Preoperative studies and clinical information are helpful in the evaluation of postoperative MR imaging examinations.

High resolution CT in children with cystic fibrosis.

High resolution CT (HRCT) was performed in 24 children (median age 57.9 months) suffering from cystic fibrosis (CF). In 23 patients (one examination unacceptable because of motion artifacts) the most frequent finding was bronchial wall thickening, shown in 21 patients (91%), followed by bronchiectasis in 15 patients (65%). Less frequent findings were mucus plugging and patchy consolidations, which could be demonstrated in 11 patients each (48%). Findings were classified using a CT scoring system and including only irreversible pulmonary changes; a statistically significant correlation with lung function tests (FEV1/FVC; MEF50) could be established. HRCT to date seems to be the most valuable method to determine extent and severity of lung involvement in children with CF and should therefore be routinely used for the staging of this disease.

MRI of spondylitis.

MRI of proven spondylitis was performed in 39 patients. Acute spondylitis appeared hypointense on T1-weighted and hyperintense on T2-weighted images. Following intravenous administration of Gd-DTPA, enhancement of the marrow and disc was seen. With progressive healing an increasing signal was seen on T1-weighted images. This was caused by the presence of focal fat marrow representing the first sign of therapy response. As healing progressed, the T1-signal increased due to fatty marrow, while the T2-signal decreased as well as the enhancement following Gd-DTPA administration. Therefore, MR imaging can be recommended as the method of choice for early diagnosis of spondylitis and assessment of therapy response.

MRI of cartilaginous tumours of the larynx.

Cartilaginous lesions of the larynx are uncommon, approximately 250 cases being documented in the literature. In general, these tumours grow slowly, exhibiting only local aggressiveness. Distant metastases are rare. Up until now CT has been the best diagnostic tool for the evaluation of these tumours because it demonstrates intratumoral calcification so well. To the best of our knowledge there are no reports of the use of MRI for these lesions. Three cases of cartilaginous laryngeal tumours are presented, emphasizing the MRI features.