Musculoskeletal MRI: dedicated systems.

The "dedicated" MRI units have characteristics of high diagnostic accuracy and lower installation and management costs as compared with whole-body systems. The dedicated MRI units are easy to install. The low weight allows their installation also under unfavorable circumstances. In a dedicated system cost-effectiveness and ease of installation must be accompanied by the capability of providing high-quality images. In our experience, the high number of examinations performed, the most part of which provided with the surgical controls, allowed an accurate evaluation of the diagnostic potentialities of the dedicated magnet. We were not able to perform the examinations in only 3 % of cases due to the physical shape of the patient and the clinical condition of the patient which may hinder the correct positioning of the limb. The overlapping of the diagnostic accuracy of the E-scan and Artoscan units in the study of the lower limbs, compared with whole-body units and surgery, prompted us to exploit the potentialities of the E-Scan in the study of the shoulder. We had a good correlation between E-Scan, whole-body units, and surgical findings, which confirmed the high diagnostic accuracy of the dedicated system. In conclusion, in our experience carried out in the musculoskeletal system, the dedicated magnets showed promising results. Their diagnostic reliability and utility was comparable to that obtained from conventional units operating at higher magnetic fields.

[New prospects in the assessment of the knee extensor complex with dynamic magnetic resonance]. / Nuove prospettive nella valutazione con Risonanza Magnetica dinamica del complesso estensore del ginocchio.

INTRODUCTION: Altered patellofemoral biomechanics may result in pain, instability and early involutive processes. Magnetic Resonance Imaging (MRI), with its panoramic capabilities, has proved to be an effective technique in the study of knee extensor complex changes. The diagnostic advantages of dynamic studies of patellofemoral kinetics are reported in the recent scientific literature. We investigated the diagnostic potentials of passive studies of the knee extensor complex with sagittal and axial cine MRI. Then, we developed and optimized an innovative study method overcoming the limitations of the other dynamic techniques for the correct assessment of patellofemoral biomechanics. MATERIAL AND METHODS: We studied the knee with a .2 T permanent magnet dedicated to the limbs and acquired the images in different positions of flexion-extension with T1-weighted SE and T2-weighted GE sequences. We examined 21 healthy volunteers and 37 of 38 patients with anterior knee joint pain of suspected patellofemoral origin. All the images needed for dynamic studies were acquired in about 20 minutes. For the scan planes not to be affected by patellar motion in the different degrees of knee extension, it is necessary to acquire single axial images to be edited in cine motion afterwards. Each acquisition is aligned along sagittal reference planes depiciting always the same patellar aspect. RESULTS: Significant correlations were found between clinical and cine MR findings in 25 patients. In particular we depicted some extensor complex impingement conditions missed at conventional MRI, which clarified the role played by patellar dysplastic changes in cartilage microtraumas. Our technique was accurate, quite easy to perform and repeatable. We performed cost-effective dynamic studies which were useful in the evaluation of patients with anterior knee pain in whom conventional MRI had failed to provide enough information. CONCLUSIONS: Our technique differs from other passive or active dynamic studies reported on in the literature because the patellar volume does not change during acquisitions. This permits to decrease morphological changes and to simplify, on cine MR reconstructions, the specific analysis of patellofemoral dynamics during flexion-extension. Fewer morphological changes also mean a more accurate analysis showing the role of patellar dysplasia in cartilage microtraumas. Our dynamic MR protocol is accurate, easy to perform and to repeat; it allows dynamic studies in the patients with poor static MR findings.

[Technologic advances in magnetic resonance imaging: permanent low-field magnets dedicated to the study of the joints. Clinical results]. / Innovazioni tecnologiche nella Tomografia con Risonanza Magnetica: magneti permanenti con basso campo dedicati allo studio articolare. Risultati clinici.

Magnetic Resonance Imaging (MRI) has had a significant impact on the diagnosis of musculoskeletal conditions. Technologic advances in the last years allowed the development of cost-effective, compact and easy-to-install MR systems. After an early phase to optimize the units, a 14-month multicentric study was performed to define the possible clinical applications of the system. The obtained data are reported by the authors in the present study to assess the diagnostic accuracy of the new MR system for the study of the limbs. The system consists of an 0.2 T permanent unit, weighting 800 Kg, with a built-in radiofrequency shield and 10 mT/m gradients. October, 1992, to February, 1994, 2437 limbs examinations were carried out in patients whose age ranged 5 to 83 years. In 93% of cases, the exam was performed to study one joint, mostly the knee. MR diagnosis was verified in 311 patients, who were subsequently submitted to surgery. Quite satisfying overall results were obtained, particularly in case of knee traumas, comparable to those provided by units with more potentials. The particular structure of the magnet allowed the comfortable management of the pediatric, aged and acute patients. Nevertheless, in 3% of the investigated knee or elbow conditions, the examinations could not be performed due to technical limitations related to magnet size. In addition, the authors believe that a limited field of view (11-16 cm) does not allow accurate staging of the malignant lesions involving soft tissue and bone, which require a wider locoregional staging.

[The interactions between metal stapes prostheses and high-intensity magnetic fields during magnetic resonance tomography]. / Interazioni tra protesi stapediali metalliche e campi magnetici di elevata intensità in corso di tomografia a risonanza magnetica.

The ever-increasing use of magnetic resonance tomography (MR) as an investigation mean has created a new interest in the biological effects of magnetic fields (MF) and in finding protective measures to be taken in their event. At the moment, use of MR is contraindicated in the presence of pacemakers, vascular clips, liquoral shunts and orthopedic prostheses, all of which may be dislocated by the MF created by MR or may interact with the MF itself creating distorted or falsified images. The aim of our study was to verify if metallic stapedectomy prostheses are dislocated by the MF and if they produce enough interference to falsify MR images. Five types of metallic stapedial prostheses exposed to a MF of 0.5T were studied. We may conclude from our results that MR does not create any otological risks for patients with these prostheses in that none of them were dislocated during exposure. However, all the prostheses studied did instead bring about alterations in the MF and the MR image to varying degrees. In some cases (Robinson) there was notable image distortion, while in others (Schuknecht wire teflon and platinum piston) the distortion was practically negligible. It is our opinion, however, that even if the image distortion does not interfere with routine MR, use of prostheses made of materials not affected by MF are advisable in view of an eventual development of visualization of the labyrinth and intratemporal facial nerve portion with MR.

Magnetic resonance imaging of the penis: normal anatomy.

This study was undertaken to investigate the magnetic resonance anatomy of the normal penis, by means of the use of a new designed surface coil specific for the study of male external genital organs. The combined evaluation of T1- and T2-weighted images obtained by choosing different repetition and echo time values together with an appropriate selection of scanning planes oriented according to various angles of incidence strongly contributed to perform a complete morphological analysis of the penis and constantly revealed fine anatomical details of diagnostic and clinical significance. Among these, the magnetic resonance examination (data referred to a 0.5 T apparatus) allowed a precise morphological differentiation of the penile covering tissues, such as outer skin, dartos tunica and hypodermal connective; the vascular characterization of cavernous tissue, belonging to corpora cavernosa and spongiosum urethrae, of deep arteries and superficial dorsal vein(s); the resolution of the albuginea and the identification of the urethral lumen. Such a capability of magnetic resonance imaging in providing accurate demonstration of penile structures without technical artifacts and use of ionizing radiations makes the actual technology able to cooperate efficaciously with computerized tomography and diagnostic sonography for an efficient clinical assessment of penis diseases.

[Clinical experimentation with a new antihistaminic molecule in allergic conjunctivitis]. / Sperimentazione clinica con una nuova molecola antistaminica nelle congiuntiviti allergiche.

Current pathogenetic and symptomatological knowledge of allergic conjunctivitis and its treatment with a recently synthesised antihistaminic molecule, Astemizole, is reported.

Comparative effects of nonionic (iopamidol) and ionic (sodium and meglumine diatrizoate) contrast media for urography on urinary excretion of water and solutes.

Urinary water and solute excretion before and for 40 minutes after intravenous bolus injection of a nonionic (iopamidol) or an ionic medium (sodium meglumine diatrizoate) have been studied in subjects with normal renal function. Iopamidol produced less urinary losses of water, potassium, sodium, and chloride than did diatrizoate; uric acid excretion was also less enhanced. Surprisingly, both contrast agents produced a comparable increase in urinary pH and bicarbonate excretion. These data show that nonionic agents produce fewer changes in urinary excretion of water and solutes; the less enhanced excretion of uric acid after a nonionic medium may be an important reason to choose the latter agents for urography in patients at risk for urate neophropathy.