Nitric oxide-haemoglobin interaction: a new biochemical hypothesis for signal changes in fMRI.

A new hypothesis on the origin of activation-induced signal changes in functional magnetic resonance imaging (fMRI) is presented, involving transient formation of paramagnetic species, i.e. methaemoglobin (Hb+) and nitrosylhaemoglobin (Hb-NO), by reaction of nitric oxide (NO) with oxy-(Hb-O2) and deoxyhaemoglobin (Hb). Hb+ and Hb-NO, generated in erythrocytes, were found to produce marked concentration-dependent signal intensity changes when examined by T1-, T2- and T2*-weighted MRI. Intravenous administration of ascorbic acid (3 g) to healthy volunteers, to specifically reduce any Hb+ formed during brain activation, markedly decreased fMRI signal changes during standard tasks, suggesting a blood flow-independent effect produced by the reductant. These results open a new perspective on the fMRI evaluation of physiological processes associated with task-specific activation of brain structures.

First experience with a new echographic contrast agent.

The intravenous injection of an ultrasound contrast agent can enhance signals from blood flow. Broad toxicological and pharmaceutical studies in animals confirmed the safety and efficacy of an ultrasound contrast agent made of microparticles of galactose with stabilised microbubbles in watery suspension (SH U 508 A). In this paper 10 patients with different malignant orbital and ocular tumours have been evaluated with an echo colour Doppler machine before and after the injection of SH U 508 A. An enhancement of the Doppler signals in the lesions in different degrees has been detected. This echographic contrast agent seems to be very important not only in the evaluation of vascular lesions, but also in evaluating the effectiveness of radiotherapy in malignant tumours and could spread the echographic indications in several other ophthalmic fields.

Exploring brain function with magnetic resonance imaging.

Since its invention in the early 1990s, functional magnetic resonance imaging (fMRI) has rapidly assumed a leading role among the techniques used to localize brain activity. The spatial and temporal resolution provided by state-of-the-art MR technology and its non-invasive character, which allows multiple studies of the same subject, are some of the main advantages of fMRI over the other functional neuroimaging modalities that are based on changes in blood flow and cortical metabolism. This paper describes the basic principles and methodology of fMRI and some aspects of its application to functional activation studies. Attention is focused on the physiology of the blood oxygenation level-dependent (BOLD) contrast mechanism and on the acquisition of functional time-series with echo planar imaging (EPI). We also provide an introduction to the current strategies for the correction of signal artefacts and other image processing techniques. In order to convey an idea of the numerous applications of fMRI, we will review some of the recent results in the fields of cognitive and sensorimotor psychology and physiology.

CT in the diagnosis of sellar and parasellar lesions.

The Authors review their recent experience in investigating 185 cases of sellar and parasellar lesions, using as preliminary procedure stratigraphy and CT; further examinations were performed only in cases with unclear diagnosis. Their data confirm the reliability of this non-invasive protocol that allowed the detection of pathological changes in nearly 95% of cases and was able to define with certainty the nature of the lesions in over 72% of cases. However, other investigations were performed in 116 cases (63%): in 57 (31%) for diagnostic purpose, in 59 (32%) as complementary pre-operative studies.

[Angiography in the diagnosis of neurinomas of the acoustic nerve (author's transl)]. / L'indagine angiografica nella diagnosi dei neurinomi del nervo acustico.

40 cases of neurinoma of the acoustic nerve, studied by vertebral arteriography and controlled at surgery are reviewed. The angiographic signs of the lesion are analysed and a number of examples presented.

Computed tomography for diagnosis of empty sella associated with enhancing pituitary microadenoma.

Ten cases of primary empty sella with clinical findings of a secreting pituitary adenoma were studied using computed tomography (CT). Scans performed before contrast medium infusion confirmed the diagnosis of empty sella. After infusion, eight cases were found to have a nodular area of increased density within the sella turcica. In two patients, the enhancement probably corresponded to the pituitary stalk; the other six patients demonstrated CT evidence of pituitary microadenoma. These six patients had surgical confirmation of the existence of neoplasm. Tomodensitometric diagnosis of empty sella combined with microadenoma allows transsphenoidal microsurgery for complete tumor removal with preservation of the residual pituitary gland. For comparison, in a series of 21 patients suspected of having microadenomas, but without evidence of empty or enlarged sella, enhancing microadenomas were shown in 13 (62%).

[Surgically treated Zenker diverticulum: a double-contrast radiologic study and videorecording]. / Diverticoli di Zenker operati: studio radiologico a doppio contrasto associato a video-registrazione.

Sixteen patients who had undergone the surgical resection of pharyngoesophageal diverticula were investigated with combined double-contrast radiology and video-recording. In 11 patients morphological or functional anomalies were identified. The authors report their results and stress the high incidence of postoperative stenoses (18%) and recurrences (43%). The combined use of double-contrast examination and video-recording is suggested to detect such functional disorders as those which were identified in 68% of the patients in this series of cases.

[Anomalies of the lumbosacral nerve roots]. / Le anomalie delle emergenze radicolari lombo-sacrali.

Three cases of lumbosacral nerve root anomalies at their emergence are presented. They have been diagnosed by using water soluble non ionic contrast medium myelography. They all belonged to Cannon's type I classification (conjoined roots) and they were all localized at L5-S1 level. The authors emphasize that such anomalies give no symptoms and they underline the importance of their recognition in view of a correct surgical treatment.

[Congenital spinal intradural and extradural cysts]. / Le cisti spinali congenite intra ed extradurali.

Two intradural and two extradural spinal cysts are reported. The authors compare these cases with others reported in the literature. They agree about the dorsal retromedullary site but they disagree about the age and sex. Although the cysts have been opacified only in two cases, the myelographic diagnosis was easy in every case except one. The myelo-CT is'nt necessary for diagnosis but it offers a better visualization of the relation between the lesion and the spinal cord.

[High resolution computerized tomography in the study of the lung parenchyma. Possibility of a low-dose protocol]. / La tomografia computerizzata con alta risoluzione nello studio del parenchima polmonare. Possibilità di un protocollo con basso dosaggio.

High-resolution CT (HRCT) is a useful technique to investigate minimal diffuse lung disease. Two major limitations of HRCT are the higher radiation dose to the patient than in conventional CT of the chest and therefore the impossibility to study the lungs completely. These limitations can be partially overcome by using a low-dose protocol with mAs reduction. In our preliminary experience on 19 patients affected with various lung diseases, the low-dose protocol exhibited poorer image quality but almost equivalent anatomical detailing; the diagnostic yield was higher than that of conventional HRCT. Thus, in our experience, low-dose HRCT makes an interesting compromise in the study of lung parenchyma.

[Dynamic single-slice computed tomography in the pretreatment evaluation of hepatocarcinoma in cirrhosis]. / La tomografia computerizzata dinamica con strato singolo nella valutazione pretrattamento dell'epatocarcinoma su cirrosi.

Hepatocellular carcinomas (HCCs) are currently treated with surgery, transcatheter chemoembolization and percutaneous alcoholization; all methods require accurate in vivo anatomopathology of the lesion. The authors report their personal experience with 58 HCCs on cirrhosis which were studied with dynamic single-slice CT after the injection of water-soluble iodate contrast medium with automatic injector in a peripheral vein. Three semiologic patterns were identified according to lesion density on pre- and post-contrast images. The active portion of the lesion could be differentiated from the necrotic one in 100% of cases. Moreover, the necrotic lesion was differentiated from possible still viable tumor portions but with vacuolar degeneration phenomena. These findings allowed the authors to calculate the growth rate and the infiltrative capability of the single neoplastic masses. Finally, the dynamic evaluation of parenchymal enhancement allowed abnormal tissue vascularization due to arterioportal communication to be demonstrated in 7 cases. The authors conclude the dynamic single-slice CT allows the accurate assessment of HCC foci, of tumor tissue vascularization and of perilesional liver parenchyma. Therefore, dynamic single-slice CT is suggested as the technique of choice to study small HCCs before treatment.

[Errors of magnetic resonance in the diagnosis of small renal tumors]. / Errori della risonanza magnetica nella diagnostica dei piccoli tumori renali.

MR examinations were performed on 16 patients with small (< 35 mm diameter) solid renal tumors previously diagnosed with US and/or CT. The study was aimed at assessing MR accuracy in the identification and characterization of this type of lesion. The studies were performed with a 0.5 T GE MR Max Plus unit, with no paramagnetic contrast medium administration. MRI detected the lesion in 15 cases (93.7%). In 3/15 patients (18.7%) the tumors had signal patterns similar to those of simple renal cysts--i.e., homogeneously hypointense on T1 and markedly hyperintense on T2-weighted images. In one patient (6.2%) MRI failed to detect the lesion. In the extant 12 cases the tumors were correctly demonstrated but had different signal patterns. On T1-weighted images 6 lesions were hypointense, 2 hyperintense because of hemorrhagic content, and 4 exhibited poor contrast with the surrounding renal parenchyma. On T2-weighted images 4 lesions were inhomogeneously hyperintense, 3 were hypointense because of fibrosis or old blood content, and in 5 cases contrast between the tumor and the renal parenchyma was poor. The authors conclude that T1-weighted MR images, in a midfield MR unit, are more sensitive than T2-weighted images in identifying small renal tumors. MRI is less accurate in the evaluation of these lesions than CT and US. In particular, since small renal lesions may be misdiagnosed as simple cysts, the use of other imaging modalities--e.g., US and CT--is recommended if a renal cyst is first identified on MR images.