There are several artifacts unique to PET/CT imaging, with CT-based attenuation correction (AC) artifacts being among the most commonly reported. AC artifacts from calcified lymph nodes represent clinically significant and easily misinterpreted PET/CT artifacts that have received little attention in the literature. In this case series, we report three cases of calcified lymph nodes causing an AC artifact and one case of a highly calcified lymph node without an AC artifact. All three cases of calcified lymph nodes causing an AC artifact would have resulted in a change in patient staging, and likely management, if the nodes had been misinterpreted as malignant nodes. In PET/CT imaging, this artifact needs to be considered as a potential cause of apparent FDG activity when calcified lymph nodes are present on the CT portion of a PET/CT study in order to avoid misinterpretation and potential patient mismanagement.
Rabies virus N2C can be employed to transneuronally trace the neural pathways regulating activity of a particular muscle. Unlike many transneuronal tracers, rabies virus is not avidly transported by autonomic pathways, and results in little lysis of infected neurons. In the present study, rabies virus N2C was injected into the diaphragm of adult cats, which were euthanized following survival periods of 2.5–6 days. Animals were classified by the extent of infection observed in the CNS. In animals with minimal infection, the labeled spinal neurons were comprised of large cells in the C5–C6 ventral horn (presumed diaphragm motoneurons) as well as smaller presumed interneurons confined mainly to the ventral horn and the region near the central canal. Considerably more infected spinal interneurons were present in most cats, which were distributed throughout the dorsal and ventral horns in all cervical segments as well as the thoracic spinal cord. Brainstem labeling in animals with the least infection was confined to the regions known to contain the medullary and pontine respiratory groups, the retrotrapezoid and raphe nuclei, the medial medullary and pontine reticular formation, and the region ventral to the spinal trigeminal nucleus. In animals with intermediate levels of infection, the number of labeled neurons in the respiratory groups and medial reticular formation was considerably larger, and infected cells were also evident in the lateral vestibular nucleus, locus coeruleus, and the cerebellar fastigial nucleus. Infected cells in the medial reticular formation and vestibular and fastigial nuclei likely have roles other than mediating breathing‐related contractions, such as adjusting diaphragm activity during postural alterations or vomiting.
As musculoskeletal disorders are a common cause of emergency department visits in the United States, it is vital for nurses and nurse practitioners to understand the decision rules for ordering imaging tests when triaging patients with musculoskeletal complaints. Proper knowledge and command of selecting the most appropriate imaging for these frequent emergency department presentations will help reduce costs, decrease ionizing radiation exposure, and increase patient throughput. This article reviews the current evidence-based literature for musculoskeletal imaging in the emergency department and discusses the epidemiology, etiology, management, and prevention of the most common musculoskeletal disorders.
The transneuronal tracer rabies virus N2C can be utilized to the multisynaptic inputs controlling the activity of a muscle, since infected neurons do not quickly exhibit lysis or pathology. In the present study, we injected rabies virus N2C into the diaphragm of cats in order to map the locations of neurons in the midbrain, diencephalon, and cerebral cortex that participate in regulating breathing. Labeled cells in these regions were not evident until after a large number of brainstem neurons were infected, suggesting that the higher centers regulate diaphragm activity indirectly through connections with bulbospinal pathways. The earliest‐infected neurons in the midbrain were located in the nucleus coeruleus, red nucleus, periaqueductal gray, Edinger‐Westphal nucleus, and tegmental fields. When infection became more advanced, additional midbrain areas also exhibited labeling, including the cuneiform nucleus, raphe nuclei, inferior colliculus, and substantia nigra. The earliest‐infected diencephalon neurons were observed in the dorsal and lateral hypothalamic nuclei, although animals with advanced infections also exhibited labeling in a number of hypothalamic areas, the ventral tegmental area, zona incerta, fields of Forel, and a variety of other regions. The first‐infected cortical neurons were located anterior and posterior to the cruciate sulcus (motor cortex), as well as in prefrontal cortical areas. These data suggest that a complex, distributed network of neurons indirectly contributes to controlling diaphragm contractions.
Purpose: Vertebral artery injuries (VAIs) can be seen in cervical injuries. This investigation was conducted to assess the impact of head and neck computed tomography (CT) angiography (CTA) on planning treatment of vertebral artery injuries, if these tests were ordered appropriately, and to estimate cost and associated exposure to radiation and contrast material. Methods : This retrospective review included all patients who underwent CT of the cervical spine and CTA of the head and neck from March 2011 to October 2012 at a single institution. Patients were divided into two groups, those with and those without cervical spine fracture appreciated on CT of the cervical spine. The frequency of vascular injury on CTA in those with a cervical fracture was assessed. The frequency of vascular injury treatment and modifications owed to a positive CTA of head and neck were also assessed. A study was considered appropriate if it was ordered in accordance with the modified Denver Screening criteria. Effective radiation dose (mSv) was calculated by multiplying dose length product (DLP) from the scanner with the standard conversion coefficient (k) (k = 0.0021 mSv/mGy x cm). Results: In the 387 CTAs of head and neck, a cervical injury was recorded in 128 patients. Twenty CTA scans were correctly ordered for non-spinal indications, and 19 were ordered off protocol. CTA was found positive in 1 patient for whom the imaging was off protocol and 1 for whom the clinical indication was non-cervical. There were 19 positive CTA cases of head and neck, none of which underwent surgical intervention. CTA was positive in 13 of 48 patients who had suffered a C2 fracture; this accounted for 13 of the 19 positive CTA studies (p < 0.01). Estimated fee for CTA was $3783, and radiation exposure was 4 mSv with a standard deviation (±1.3). Conclusion : CTA of head and neck ordered off an institutional imaging protocol has a low probability of being positive. Adherence to protocols for CTA of head and neck can reduce costs and decrease unnecessary exposure to radiation and contrast medium. --------------------------------------- Cite this article as: Shuaib W, Khan AA, Mehta AS, Vijayasarathi A, Hidalgo J. Utility of CT angiography in cervical spine trauma: analysis of radiation and cost. Int J Cancer Ther Oncol 2014; 2 (4):02043. DOI : 10.14319/ijcto.0204.3
Stimulation of vestibular receptors produces changes in respiratory muscle activity as well as alterations in sympathetic outflow. Unlike vestibular reflexes acting on the limbs, vestibulo‐respiratory and ‐sympathetic responses are elicited by otolith organ inputs, particularly those generated by body rotations in the pitch plane. Recent studies have shown that thoracic interneurons make connections with respiratory motoneurons and sympathetic preganglionic neurons, but the responses of these cells to vestibular stimulation have not been explored. In the present study, recordings were made from thoracic interneurons in decerebrate, paralyzed cats. 60% of thoracic interneurons were activated by electrical stimulation of vestibular afferents at short latency. The majority of these cells exhibited response dynamics similar to those of otolith organs. 75% of the units were activated by tilts in the roll plane or the planes of the vertical semicircular canals; few cells responded best to pitch rotations. These data show that vestibular signals to thoracic interneurons are distinct from those transmitted to the cervical and lumbar spinal cord; however the spatial properties of the responses of the cells to body rotation differ from that of respiratory and sympathetic outflow. Presumably, the latter responses are synthesized through the integration of signals.
