Effect of field-of-view size on gray values derived from cone-beam computed tomography compared with the Hounsfield unit values from multidetector computed tomography scans

PURPOSE: This study aimed to evaluate the effect of field-of-view (FOV) size on the gray values derived from conebeam computed tomography (CBCT) compared with the Hounsfield unit values from multidetector computed tomography (MDCT) scans as the gold standard. MATERIALS AND METHODS: A radiographic phantom was designed with 4 acrylic cylinders. One cylinder was filled with distilled water, and the other 3 were filled with 3 types of bone substitute: namely, Nanobone, Cenobone, and Cerabone. The phantom was scanned with 2 CBCT systems using 2 different FOV sizes, and 1 MDCT system was used as the gold standard. The mean gray values (MGVs) of each cylinder were calculated in each imaging protocol. RESULTS: In both CBCT systems, significant differences were noted in the MGVs of all materials between the 2 FOV sizes (P < .05) except for Cerabone in the Cranex3D system. Significant differences were found in the MGVs of each material compared with the others in both FOV sizes for each CBCT system. No significant difference was seen between the Cranex3D CBCT system and the MDCT system in the MGVs of bone substitutes on images obtained with a small FOV. CONCLUSION: The size of the FOV significantly changed the MGVs of all bone substitutes, except for Cerabone in the Cranex3D system. Both CBCT systems had the ability to distinguish the 3 types of bone substitutes based on a comparison of their MGVs. The Cranex3D CBCT system used with a small FOV had a significant correlation with MDCT results.

In vitro evaluation of the fracture resistance and microleakage of porcelain laminate veneers bonded to teeth with composite fillings after cyclic loading

PURPOSE: There is insufficient data regarding the durability of porcelain laminate veneers bonded to existing composite fillings. The aim of the present study was to evaluate the fracture resistance and microleakage of porcelain laminate veneers bonded to teeth with existing composite fillings. MATERIALS AND METHODS: Thirty maxillary central incisors were divided into three groups (for each group, n=10): intact teeth (NP), teeth with class III composite fillings (C3) and teeth with class IV cavities (C4). Porcelain laminate veneers were made using IPS-Empress ceramic and bonded with Panavia F2 resin cement. The microleakage of all of the specimens was tested before and after cyclic loading (1 x 10(6) cycles, 1.2 Hz). The fracture resistance values (N) were measured using a universal testing machine, and the mode of failure was also examined. The statistical analyses were performed using one-way ANOVA and Tukey post hoc tests (alpha=0.05). RESULTS: There was a significant difference in the mean microleakage of group C4 compared with group NT (P=.013). There was no significant difference in the fracture loads among the groups. CONCLUSION: The microleakage and failure loads of porcelain laminate veneers bonded to intact teeth and teeth with standard class III composite fillings were not significantly different.

Catheter related artifacts on bone scans: report of two cases

Bone scanning using the 99mTc-phosphate analogs is an established diagnostic modality and a commonly requested radioisotope examination for a variety of pathologies involving the skeleton, such as osteomyelitis, bony metastases, and occult fractures. The bone scan is one of the most commonly requested procedure in most nuclear medicine department. The images show areas of increased and decreased activity usually related to the bone turnover. The bone scan is interpreted by evaluating the pattern of radioactive localization in the skeleton and identifying areas of increased uptake [hot spots] or, less frequently, decreased or absent activity [1]. Unfortunately, the findings are most often very nonspecific and do not tell us the exact underlying cause of the abnormal activity. A variety of factors may change the normal distribution of bone-seeking radiopharmaceuticals. Although most of the times these areas of abnormal radiotracer activities are due to true pathologic bone states, however, it is not infrequent that they are caused by technical errors such as urinary contamination, nonuniformity of gamma camera, and attenuation of activity by foreign bodies. These artifactual causes warrant careful attention to prevent unnecessary interventions. In certain conditions, nonosseous structures other than the urinary tract are seen on the bone scan. For example, there may be localized muscle uptake, such as myositis ossificans, or localization in a pleural effusion. Such serendipitous findings may constitute welcome diagnostic information [1]. On the other hand, soft-tissue uptake may at times hamper interpretation of the study by bringing in artifacts that degrade the quality of the images. Therefore, recognition of patterns of nonbony uptake is important for correct identification of artifacts and accurate interpretation of the scan [1]. This paper presents two cases of artifactual causes of odd radiotracer activity in bone scans. In both cases the artifact is at least somewhat related to an indwelling catheter

[Myocardial 99m Tc-MDP uptake on the bone scintigraphy in the hemodialysis-associated amyloidosis:a case report]

Amyloidosis is characterized by an abnormal extracellular deposition of amyloid in different organs, where it usually causes some type of dysfunction. Its cause is unknown. Five different types of amyloidosis have been described according to the underlying disease; immunoglobulin amyloidosis, familial amyloidosis, senile systemic amyloidosis, secondary amyloidosis and hemodialysis-associated amyloidosis. We report a case of hemodialysis-associated amyloidosis in a 56-year-old man that radionuclide imaging demonstrated intense uptake of Tc-99m MDP within the myocardium. The diagnosis of amyloidosis was established by analysis of aspirated abdominal fat, although other non- invasive modalities didn't reveal any positive findings. The first clue to the possible presence of amyloidosis in this case was provided by the radionuclide bone scan performed, which revealed intense tracer uptake in the heart suggesting amyloid deposit. We conclude that in cases of extraosseous accumulation of Tc-99 MDP especially as a diffuse pattern of myocardial uptake, a diagnosis of amyloidosis should be considered, in an appropriate clinical setting