Etiology of solitary extrapulmonary positron emission tomography and computed tomography findings in patients with lung cancer.

PURPOSE: The aim of this prospective study was to assess the incidence and the nature of solitary extrapulmonary [18F] fluorodeoxyglucose (FDG) accumulations in patients with non-small-cell lung cancer (NSCLC) staged with integrated positron emission tomography and computed tomography (PET/CT) and to evaluate the impact on management. PATIENTS AND METHODS: A total of 350 patients with NSCLC underwent whole-body PET/CT imaging. All solitary extrapulmonary FDG accumulations were evaluated by histopathology, further imaging, or clinical follow-up. RESULTS: PET/CT imaging revealed extrapulmonary lesions in 110 patients. In 72 patients (21%), solitary lesions were present. A diagnosis was obtained in 69 of these patients, including 37 (54%) with solitary metastases and 32 (46%) with lesions unrelated to the lung primary. Histopathologic examinations of these 32 lesions revealed a second clinically unsuspected malignancy or a recurrence of a previous diagnosed carcinoma in six patients (19%) and a benign tumor or inflammatory lesion in 26 patients (81%). The six malignancies consisted of carcinoma of the breast in two patients, and carcinoma of the orbit, esophagus, prostate, and non-Hodgkin's lymphoma in one patient each. Benign tumors and inflammatory lesions included eight colon adenomas, four Warthin's tumors, one granuloma of the lower jaw, one adenoma of the thyroid gland, one compensatory muscle activity due to vocal chord palsy, two occurrences of arthritis, three occurrences of reflux esophagitis, two occurrences of pancreatitis, two occurrences of diverticulitis, one hemorrhoidal inflammation, and one rib fracture. CONCLUSION: Solitary extrapulmonary FDG accumulations in patients with newly diagnosed lung cancer should be analyzed critically for correct staging and optimal therapy, given that up to half of the lesions may represent unrelated malignancies or benign disease.

Comparison of brain activation after sustained non-fatiguing and fatiguing muscle contraction: a positron emission tomography study.

The concept of fatigue refers to a class of acute effects that can impair motor performance, and not to a single mechanism. A great deal is known about the peripheral mechanisms underlying the process of fatigue, but our knowledge of the roles of the central structures in that process is still very limited. During fatigue, it has been shown that peripheral apparatus is capable of generating adequate force while central structures become insufficient/sub-optimal in driving them. This is known as central fatigue, and it can vary between muscles and different tasks. Fatigue induced by submaximal isometric contraction may have a greater central component than fatigue induced by prolonged maximal efforts. We studied the changes in regional cerebral blood flow (rCBF) of brain structures after sustained isometric muscle contractions of different submaximal force levels and of different durations, and compared them with the conditions observed when the sustained muscle contraction becomes fatiguing. Changes in cortical activity, as indicated by changes in rCBF, were measured using positron emission tomography (PET). Twelve subjects were studied under four conditions: (1) rest condition; (2) contraction of the m. biceps brachii at 30% of MVC, sustained for 60 s; (3) contraction at 30% of MVC, sustained for 120 s, and; (4) contraction at 50% of MVC, sustained for 120 s. The level of rCBF in the activated cortical areas gradually increased with the level and duration of muscle contraction. The fatiguing condition was associated with predominantly contralateral activation of the primary motor (MI) and the primary and secondary somatosensory areas (SI and SII), the somatosensory association area (SAA), and the temporal areas AA and AI. The supplementary motor area (SMA) and the cingula were activated bilaterally. The results show increased cortical activation, confirming that increased effort aimed at maintaining force in muscle fatigue is associated with increased activation of cortical neurons. At the same time, the activation spread to several cortical areas and probably reflects changes in both excitatory and inhibitory cortical circuits. It is suggested that further studies aimed at controlling afferent input from the muscle during fatigue may allow a more precise examination of the roles of each particular region involved in the processing of muscle fatigue.

Linguistic processing in visual and modality-nonspecific brain areas: PET recordings during selective attention.

Positron emission tomography (PET) was used to investigate the neural basis of selective processing of linguistic material during concurrent presentation of multiple stimulus streams ("cocktail-party effect"). Fifteen healthy right-handed adult males were to attend to one of three simultaneously presented messages: one presented visually, one to the left ear, and one to the right ear. During the control condition, subjects attended to visually presented consonant letter strings and ignored auditory messages. This paper reports the modality-nonspecific language processing and visual word-form processing, whereas the auditory attention effects have been reported elsewhere [Cogn. Brain Res. 17 (2003) 201]. The left-hemisphere areas activated by both the selective processing of text and speech were as follows: the inferior prefrontal (Brodmann's area, BA 45, 47), anterior temporal (BA 38), posterior insular (BA 13), inferior (BA 20) and middle temporal (BA 21), occipital (BA 18/30) cortices, the caudate nucleus, and the amygdala. In addition, bilateral activations were observed in the medial occipito-temporal cortex and the cerebellum. Decreases of activation during both text and speech processing were found in the parietal (BA 7, 40), frontal (BA 6, 8, 44) and occipito-temporal (BA 37) regions of the right hemisphere. Furthermore, the present data suggest that the left occipito-temporal cortex (BA 18, 20, 37, 21) can be subdivided into three functionally distinct regions in the posterior-anterior direction on the basis of their activation during attentive processing of sublexical orthography, visual word form, and supramodal higher-level aspects of language.

Hemispheric lateralization of cerebral blood-flow changes during selective listening to dichotically presented continuous speech.

Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET) while subjects were selectively listening to continuous speech delivered to one ear and ignoring concurrent speech delivered to the opposite ear, as well as concurrent text or letter strings running on a screen. rCBF patterns associated with selective listening either to the left-ear or right-ear speech message were compared with each other and with rCBF patterns in two visual-attention conditions in which the subjects ignored both speech messages and either read the text or discriminated the meaningless letter strings moving on the screen. Attention to either speech message was associated with enhanced activity in the superior temporal cortex of the language-dominant left hemisphere, as well as in the superior and middle temporal cortex of the right hemisphere suggesting enhanced processing of prosodic features in the attended speech. Moreover, enhanced activity during attention to either speech message was observed in the right parietal areas known to have an important role in directing spatial attention. Evidence was also found for attentional tuning of the left and right auditory cortices to select information from the contralateral auditory hemispace.

Changes in human regional cerebral blood flow following hypertonic saline induced experimental muscle pain: a positron emission tomography study.

A positron emission tomography imaging study was performed on 16 healthy volunteers to reveal changes in cortical activation during acute muscle pain induced by intra-muscular injection of hypertonic saline into the left triceps brachii muscle. Changes in regional cerebral blood flow (rCBF) were measured with the use of [(15)O] labelled water during 'Rest1', 'Needle' (insertion of a needle without injection), 'Rest2' and 'Pain' conditions. Differences in rCBF were found in the comparison of Pain and Needle, and Pain and Rest2 conditions, revealing activation of the contralateral insula and putamen. The results are discussed with respect to possible differences in brain processing of muscle and cutaneous noxious inputs.

Comparison of brain activity during different types of proprioceptive inputs: a positron emission tomography study.

It has been shown that the primary and secondary somatosensory cortex, as well as the supplementary motor area (SMA), are involved in central processing of proprioceptive signals during passive and active arm movements. However, it is not clear whether different cortical areas are involved in processing of different proprioceptive inputs (skin, joint, muscle receptors), what their relative contributions might be, where kinesthetic sensations are formed within the CNS, and how they interact when the full peripheral proprioceptive machinery acts. In this study we investigated the representation of the brain structures involved in the perception of passive limb movement and illusory movement generated by muscle tendon vibration. Changes in cortical activity as indicated by changes in regional cerebral blood flow (rCBF) were measured using positron emission tomography (PET). Twelve subjects were studied under four conditions: (1) passive flexion-extension movement (PM) of the left forearm; (2) induced illusions of movements (VI) similar to the real PM, induced by alternating vibration of biceps and triceps tendons (70-80 Hz) at the elbow; (3) alternating vibration of biceps and triceps tendons (with 20-50 Hz) without induced kinesthetic illusions (VN); and (4) rest condition (RE). The results show different patterns of cortex activation. In general, the activation during passive movement was higher in comparison with both kinds of vibration, and activation during vibrations with induced illusions of movement was more prominent than during vibrations without induced illusions. When the PM condition was contrasted with the other conditions we found the following areas of activation -- the primary motor (MI) and somatosensory area (SI), the SMA and the supplementary somatosensory area (SSA). In conditions where passive movements and illusory movements were contrasted with rest, some temporal areas, namely primary and associative auditory cortex, were activated, as well as secondary somatosensory cortex (SII). Our data show that different proprioceptive inputs, which induce sensation of movement, are associated with differently located activation patterns in the SI/MI and SMA areas of the cortex. In general, the comparison of activation intensities under different functional conditions indicates the involvement of SII in stimulus perception generation and of the SI/MI and SMA areas in the processing of proprioceptive input. Activation of the primary and secondary auditory cortex might reflect the interaction between somatosensory and auditory systems in movement sense generation. SSA might also be involved in movement sense generation and/or maintenance.