Observer accuracy in the detection of pulmonary nodules on CT: effect of cine frame rate.

AIM: To assess the effect of cine frame rate on the accuracy of the detection of pulmonary nodules at computed tomography (CT). MATERIALS AND METHODS: CT images of 15 consecutive patients with (n = 13) or without (n = 2) pulmonary metastases were identified. Initial assessment by two thoracic radiologists provided the "actual" or reference reading. Subsequently, 10 radiologists [board certified radiologists (n = 4) or radiology residents (n = 6)] used different fixed cine frame rates for nodule detection. Within-subjects analysis of variance (ANOVA) was used to evaluate the data. RESULTS: Eighty-nine nodules were identified by the thoracic radiologists (median 8, range 0-29 per patient; median diameter 9 mm, range 4-40 mm). There was a non-statistically significant trend to reduced accuracy at higher frame rates (p=0.113) with no statistically significant difference between experienced observers and residents (p = 0.79). CONCLUSION: The accuracy of pulmonary nodule detection at higher cine frame rates is reduced, unrelated to observer experience.

Expiratory neurons of the Bötzinger Complex in the rat: a morphological study following intracellular labeling with biocytin.

The term "Bötzinger Complex" (BOT) refers to a distinct group of neurons, located near the rostral portion of the nucleus ambiguus, which are known to play an important role in the control of respiratory movements. Previous studies conducted in cats have demonstrated that most of these neurons are active during expiration, exerting a monosynaptic inhibitory action on several subpopulations of inspiratory neurons in the medulla and spinal cord. The aim of this study was to examine morphological properties and possible synaptic targets of BOT neurons in the rat. Forty-one expiratory neurons were labeled intracellularly with biocytin; 12 were interneurons (BOT neurons) and 29 were motoneurons. The latter could not be antidromically activated following stimulation of the superior laryngeal or vagal nerves. BOT neurons showed extensive axonal arborisations in the ipsilateral medulla, with some projections to the contralateral side. Bouton-like axon varicosities mainly clustered in two areas: near the parent cell bodies, and in the area corresponding to the rostral part of the ventral respiratory group (VRG). In five pairs of labeled neurons, each consisting of one BOT neuron and one inspiratory neuron in the rostral VRG, no appositions were identified at the light microscopic level between axons of BOT neurons and dendrites or cell bodies of inspiratory neurons. These results demonstrate that some features of BOT expiratory neurons in the rat are similar to those previously described in cats. The differences include their more ventral location in relation to the compact formation of nucleus ambiguus (retrofacial nucleus), and the relative paucity in the rat of neurons displaying an augmenting pattern of activity and of neurons with spinally projecting axons. In addition, we were unable to find morphological evidence for contacts between labeled BOT neurons and ipsilateral inspiratory neurons near the obex level, a finding not consistent with previous electrophysiological studies in the cat in which such synaptic connections have been identified.

Reduction of radiation dose to patients in xeroradiography.

A method for reducing the radiation dose received by the patient in xeroradiography is described. It is shown, theoretically, that a dose reduction of about 50% can be achieved, and measurements of skin exposure confirm reductions of this order. There is no appreciable loss of image quality, and the theory suggests that it may even be possible to enhance the visualization of soft tissue by this method.

A rapid and sensitive method for measuring ribonucleic acid in ribosomal preparations.

By using the fluorescence enhancement of ethidium bromide when it binds to RNA, a very rapid, simple and sensitive assay for the concentration of ribosomal RNA in complex mixtures has been devised.

The hypertransradiant hemithorax: the importance of lateral decentring, and the explanation for its appearance due to rotation.

Experimental evidence is presented indicating that 80% of the increase in unilateral film blackening on the chest radiograph resulting from rotation of the patient is due to asymmetrical absorption of the X-ray beam. Scatter contributes 20% to this increase in blackening. The effect on the radiograph of lateral decentring is also described. In the rotated patient, the hypertransradiant hemithorax always occurs on the side to which the patient is rotated, and is independent of the projection. If this rule is broken, then decentring or a thoracic abnormality is present.