Effects of neurosurgical titanium mesh on radiation dose

The purpose of this study was to determine the dosimetric impact of a neurosurgical titanium mesh in patients treated with 6- and 18-MV photon beams. The effects of a 0.4-mm-thick titanium mesh on the dose profile at 3 regions within a solid water phantom were measured using extended dose range-2 (EDR2) film for 6- and 18-MV photon beams. All measurements were performed with the titanium mesh placed at a depth of 1.5 cm in the phantom. Films were exposed immediately above the mesh, immediately below the mesh, and at a depth of 5 cm from the surface of the phantom. The films were scanned using a scanning densitometer. In the region directly above the titanium mesh, there was an increase in dose of 7.1% for 6-MV photons and 4.9% for 18-MV photons. Directly below the titanium mesh, there was an average decrease in dose of 1.5% for 6-MV photons and an increase of 1.0% for 18-MV photons. At 5-cm depth, for 6- and 18-MV photons, there was a decrease in dose of 2.2% and 0.6%, respectively. We concluded that for cranial irradiation with high-energy photons, the dosimetric impact of a 0.4-mm titanium mesh is small and does not require modification in treatment parameters.     

PET measurement of cardiac and nigrostriatal denervation in Parkinsonian syndromes.

Scintigraphic imaging with (123)I-metaiodobenzylguanidine ((123)I-MIBG) has demonstrated extensive losses of cardiac sympathetic neurons in idiopathic Parkinson's disease (IPD). In contrast, normal cardiac innervation has been observed in (123)I-MIBG studies of multiple-system atrophy (MSA) and progressive supranuclear palsy (PSP). Consequently, it has been hypothesized that cardiac denervation can be used to differentiate IPD from MSA and PSP. We sought to test this hypothesis by mapping the distribution of cardiac sympathetic neurons in patients with IPD, MSA, and PSP by using PET and (11)C-meta-hydroxyephedrine ((11)C-HED). Also, the relationship between cardiac denervation and nigrostriatal denervation was investigated by measuring striatal presynaptic monoaminergic nerve density with PET and (11)C-dihydrotetrabenazine ((11)C-DTBZ). METHODS: (11)C-HED and (11)C-DTBZ scans were obtained for patients with IPD (n = 9), MSA (n = 10), and PSP (n = 8) and for age-matched control subjects (n = 10). Global and regional measurements of (11)C-HED retention were obtained to assess the extent of cardiac sympathetic denervation. (11)C-DTBZ binding was measured in the caudate nucleus, anterior putamen, and posterior putamen. RESULTS: As expected, extensive cardiac denervation was observed in several of the patients with IPD. However, substantial cardiac denervation was also seen in some patients with MSA and PSP. (11)C-DTBZ studies demonstrated striatal denervation in all patients with IPD and in most patients with MSA and PSP. No correlation was found between cardiac (11)C-HED retention and striatal (11)C-DTBZ binding. CONCLUSION: Cardiac sympathetic denervation was found to occur not only in IPD but also in other movement disorders, such as MSA and PSP. This finding implies that scintigraphic detection of cardiac sympathetic denervation cannot be used independently to discriminate IPD from other movement disorders, such as MSA and PSP. Cardiac sympathetic denervation was not correlated with striatal denervation, suggesting that the pathophysiologic processes underlying cardiac denervation and striatal denervation occur independently in patients with parkinsonian syndromes. These findings provide novel information about central and peripheral denervation in patients with neurodegenerative disorders.     

Expression of measles virus nucleocapsid protein in osteoclasts induces Paget's disease-like bone lesions in mice.

We targeted the MVNP gene to the OCL lineage in transgenic mice. These mice developed abnormal OCLs and bone lesions similar to those found in Paget's patients. These results show that persistent expression of MVNP in OCLs can induce pagetic-like bone lesions in vivo. INTRODUCTION: Paget's disease (PD) of bone is the second most common bone disease. Both genetic and viral factors have been implicated in its pathogenesis, but their exact roles in vivo are unclear. We previously reported that transfection of normal human osteoclast (OCL) precursors with the measles virus nucleocapsid (MVNP) or measles virus (MV) infection of bone marrow cells from transgenic mice expressing a MV receptor results in formation of pagetic-like OCLs. MATERIALS AND METHODS: Based on these in vitro studies, we determined if the MVNP gene from either an Edmonston-related strain of MV or a MVNP gene sequence derived from a patient with PD (P-MVNP), when targeted to cells in the OCL lineage of transgenic mice with the TRACP promoter (TRACP/MVNP mice), induced changes in bone similar to those found in PD. RESULTS: Bone marrow culture studies and histomorphometric analysis of bones from these mice showed that their OCLs displayed many of the features of pagetic OCLs and that they developed bone lesions that were similar to those in patients with PD. Furthermore, IL-6 seemed to be required for the development of the pagetic phenotype in OCLs from TRACP/MVNP mice. CONCLUSIONS: These results show that persistent expression of the MVNP gene in cells of the OCL lineage can induce pagetic-like bone lesions in vivo.     

A comparison of placement methods using a two-in-one dentin pin

Experiments were performed to determine the effect of pin channel preparation with standard and reduction speed handpieces, and pin seating by hand and with motor drive. The greatest retention was achieved by preparation with a standard handpiece at 6000 rpm, and manual pin placement with a hand driver. The most consistent retention values were achieved using the reduction handpiece. All preparation and placement combinations examined produced a clinically acceptable result.