Whole-body MR-DWIBS vs. [18F]-FDG-PET/CT in the study of malignant tumors: a retrospective study.

PURPOSE: Our aim was to assess the overall diagnostic accuracy of magnetic resonance diffusion-weighted whole-body imaging with background signal suppression (MR-DWIBS) compared with ([(18)F]-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT), considered the reference standard of whole-body tumour imaging modalities, in a series of consecutive patients with malignant tumour. MATERIALS AND METHODS: Thirty-eight patients diagnosed with a malignant tumour over a 4-month period were enrolled in this retrospective, observational study. PET/CT and MR-DWIBS images were reviewed in double-blind manner by a nuclear medicine physician and radiologists with 4 years experience. Lesion size, standard uptake value (SUV) and apparent diffusion coefficient (ADC) were measured and calculated for each lesion. RESULTS: The qualitative analysis of MR-DWIBS and [(18)F]-FDG-PET/CT showed that two patients were negative at both techniques. MR-DWIBS was positive in 36 patients, 34 of whom were positive and two negative at [(18)F]-FDG-PET/CT, respectively. Two hundred and fifty-five lesions were identified by MR-DWIBS and 184 by [(18)F]-FDG-PET/CT, which was a significative discordance. Correlation between SUV and ADC of lesions positive at both techniques was not statistically significant. The mean difference between lesion size in [(18)F]-FDG-PET/CT and MR-DWIBS was not statistically significant. No correlation was found between glucose metabolism and water motion. CONCLUSIONS: MR-DWIBS may be used to evaluate localisation of parenchymal neoplasms but is less efficacious in characterising lymph-node and skeletal lesions. [(18)F]-FDG-PET/CT remains the best whole-body technique to identify lymph-node and skeletal lesions, but its limitation is identifying tumours with low glucose metabolism as in mucinous neoplasms. MR-DWIBS evaluation must be integrated with morphological images to increase MR diagnostic accuracy.

Evaluation of magnetic resonance signal modification induced by hyaluronic acid therapy in chondromalacia patellae: a preliminary study.

Hyaluronic Acid (HA) is an alternative method for the treatment of osteoarthritis (OA), which acts on pain through a double action: anti-inflammatory and synovial fluid (SF) visco-supplementation. Magnetic Resonance Imaging (MRI), utilizing specific sequences, is a valid method for studying the initial phase of chondral damage. The analysis of the data, obtained through the intensity of values taken by positioning Region of Interest (ROIs) within the lesion, determining the differences before and after treatment with HA injected into the knee. The results obtained after six months and one year from the injection were statistically different in respect to those taken before, immediately and after three months of treatment. MRI represents a valid tool to evaluate the grade of chondromalacia patellae and also to follow the cartilage modification induced by HA therapy.

Role of perfusion-weighted imaging at 3 Tesla in the assessment of malignancy of cerebral gliomas.

PURPOSE: This study was performed to clarify the role of perfusion-weighted imaging (PWI) at 3 Tesla in the characterisation of haemodynamic heterogeneity within gliomas and surrounding tissues and in the differentiation of high-grade from low-grade gliomas. MATERIALS AND METHODS: We examined 36 patients with histologically verified gliomas (25 with high-grade and 11 with low-grade gliomas). PWI was performed by first-pass gadopentetate dimeglumine T2*-weighted echo-planar images, and cerebral blood volume (CBV) maps were computed with a nondiffusible tracer model. Relative CBV (rCBV) was calculated by dividing CBV in pathological areas by that in contralateral white matter. RESULTS: In high-grade gliomas, rCBV were markedly increased in mass [mean+/-standard deviation (SD), 4.3+/-1.2] and margins (4.0+/-1.1) and reduced in necrotic areas (0.3+/-0.3). Oedematous-appearing areas were divided in two groups according to signal intensity on T2-weighted images: tumour with lower (nearly isointense to grey matter) and oedema with higher (scarcely isointense to cerebrospinal fluid) signal intensity. Tumour showed significantly higher rCBV than did oedema (1.8+/-0.5 vs. 0.5+/-0.2; p<0.001) areas. In low-grade gliomas, mass (2.0+/-1.5) and margin (2.2+/-1.2) rCBV were significantly lower than in high-grade gliomas (p<0.001). CONCLUSIONS: Three-Tesla PWI helps to distinguish necrosis from tumour mass, infiltrating tumour from oedema and high-grade from low-grade gliomas. It enhances the magnetic resonance (MR) assessment of cerebral gliomas and provides useful information for planning surgical and radiation treatment.

3.0-T functional brain imaging: a 5-year experience.

The aim of this paper is to illustrate the technical, methodological and diagnostic features of functional imaging (comprising spectroscopy, diffusion, perfusion and cortical activation techniques) and its principal neuroradiological applications on the basis of the experience gained by the authors in the 5 years since the installation of a high-field magnetic resonance (MR) magnet. These MR techniques are particularly effective at 3.0 Tesla (T) owing to their high signal, resolution and sensitivity, reduced scanning times and overall improved diagnostic ability. In particular, the high-field strength enhances spectroscopic analysis due to a greater signal-to-noise ratio (SNR) and improved spectral, space and time resolution, resulting in the ability to obtain high-resolution spectroscopic studies not only of the more common metabolites, but also--and especially--of those which, due to their smaller concentrations, are difficult to detect using 1.5-T systems. All of these advantages can be obtained with reduced acquisition times. In diffusion studies, the high-field strength results in greater SNR, because 3.0-T magnets enable increased spatial resolution, which enhances accuracy. They also allow exploration in greater detail of more complex phenomena (such as diffusion tensor and tractography), which are not clearly depicted on 1.5-T systems. The most common perfusion study (with intravenous injection of a contrast agent) benefits from the greater SNR and higher magnetic susceptibility by achieving dramatically improved signal changes, and thus greater reliability, using smaller doses of contrast agent. Functional MR imaging (fMRI) is without doubt the modality in which high-field strength has had the greatest impact. Images acquired with the blood-oxygen-level-dependent (BOLD) technique benefit from the greater SNR afforded by 3.0-T magnets and from their stronger magnetic susceptibility effects, providing higher signal and spatial resolution. This enhances reliability of the localisation of brain functions, making it possible to map additional areas, even in the millimetre and submillimetre scale. The data presented and results obtained to date show that 3.0-T morphofunctional imaging can become the standard for high-resolution investigation of brain disease.

3.0-T morphological and angiographic brain imaging: a 5-years experience.

Ever since the introduction of magnetic resonance (MR), imaging with 1.5 Tesla (T) has been considered the gold standard for the study of all areas of the body. Until not long ago, higher-field MR equipment was exclusively employed for research, not for clinical use. More recently, the introduction of 3.0-T MR machines for new and more sophisticated clinical applications has resulted in important benefits, especially in neuroradiology. Indeed, their high gradient power and field intensity (3.0 T) allow adjunctive and more advanced diagnostic methodologies to be performed with excellent resolution in a fraction of the acquisition time required with earlier machines. The purpose of this paper is to illustrate the distinctive semeiological characteristics of 3.0-T morphological and angiographic brain imaging compared with lower-field systems and highlight the respective advantages and drawbacks based on the experience gained in the first 5 years from the installation of a 3.0-T magnet.

[Magnetic resonance angiography of the peripheral vessels with automatic moving bed infusion tracking]. / Angiografia con Risonanza Magnetica del circolo periferico con spostamento automatico del tavolo portapaziente.

PURPOSE: To investigate the actual diagnostic reliability of the Mobitrack technique with a slow intravenous infusion of paramagnetic contrast agent (CA) in MR Angiography of the peripheral arterial district. MATERIAL AND METHODS: Twelve healthy volunteers (mean age: 34) with no personal or family history of peripheral arterial pathologic conditions, underwent MR Angiography of the peripheral vascular district. A 1.5 T superconductive magnet equipped with automatic table feed was used. In the preliminary phase, the circulation time at the abdominal aorta was optimized and customized for each patient. This was done by performing a pre-targeting Fast Field Echo 2D (FFE 2D) sequence with intravenous administration of 1-2 mL CA by an injector, to evaluate the delay time. A 2D Time of Flight (2D TOF) sequence was then performed for topographic purposes. The partially overlapping volumes were acquired using Fast T1-weighted sequences, intravenous CA administration and an automatic table feed of 10 mm/s. A Fast Field Echo 3D (FFE 3D) T1-weighted sequence with TR/TE/FA: of 6.3/1.6/40 degrees and a slice thickness of 1.5 mm were also performed. Thirty to forty mL CA were slowly administered intravenously at a rate of 0.3-0.6 mL/s. Two blinded readers independently evaluated the images giving one of three diagnostic judgements: 1) arteries were well visualized, 2) heterogeneous arteries with(out) the presence of veins, and 3) arteries seen poorly or not at all. The first two judgements were considered diagnostic. The readers considered 19 different anatomical districts for each patient, giving a total of 190 evaluations. RESULTS: A blinded evaluation of the readers judgements did not indicate a statistically significant difference (agreement: 100%). Overall, 82% of the images were rated as 1, 8.5% as 2 and 8.4% as 3. DISCUSSION: In 174/190 judgements the vessels were rated as 1 or 2, that is of diagnostic value. Judgement 3 was always due to the inability to visualize the medial and/or distal third of the arterial circulation of the leg. CONCLUSIONS: The results of this technique optimization study confirm the overall validity of the Mobitrack technique. However they also indicate that further technical advances are required to ensure maximum diagnostic accuracy in this vascular district.

[Angiography with magnetic resonance of the body with contrast media. Experience with a 0.5 tesla device]. / Angiografia con Risonanza Magnetica del corpo con mezzo di contrasto. Esperienza con apparecchio da 0,5 tesla.

INTRODUCTION: We optimized the technique of contrast-enhanced Magnetic Resonance Angiography (MRA) with a .5 T superconductive magnet. MATERIAL AND METHODS: Forty patients with normal blood pressure and heart rate gave their informed consent to MRA studies with contrast agent administration. The carotid arteries were studied in 10 patients, the pulmonary arteries in 10, the thoracic aorta in 10 and the abdominal aorta and renal arteries in 10. All the examinations were performed with a .5 T superconductive magnet (Philips T5) acquiring 3D T1-weighted GE sequences with contrast agent administration. The parameters were: TR/TE/FA 13 ms/4 ms/60 degrees; 256 x 256 MA; 2 mm slice thickness; 1 NEX. The contrast agent was administered with an automatic injector (.2 mmol/kg at 1.5 flowrate) after a bolus test to evaluate circulation time. The images were studied by a radiologist rating artery visualization as "good" or "poor" on a multiple choice card. The signal-to-noise ratio was evaluated using regions of interest positioned on the examined vessels (signal) and muscles (noise). RESULTS: The mean start delay was 12.2 s for the abdominal aorta, 10.3 s and 8.7 s for the thoracic aorta and pulmonary arteries, and 10.3 for the carotid arteries. Fifty-eight of 70 vessels were well visualized and 12 were poorly visualized. The signal-to-noise ratio exceeded 1 in all districts. CONCLUSIONS: Our experience shows that enhanced MRA provides diagnostic images of body arteries even at .5 T.