Quantitative SPECT and planar 32P bremsstrahlung imaging for dosimetry purpose - an experimental phantom study

In this study, Quantitative 32P bremsstrahlung planar and SPECT imaging and consequent dose assessment were carried out as a comprehensive phantom study to define an appropriate method for accurate Dosimetry in clinical practice. CT, planar and SPECT bremsstrahlung images of Jaszczak phantom containing a known activity of 32P were acquired. In addition, Phantom contour was determined for attenuation correction and image registration. Reconstructed SPECT slices were corrected for attenuation effect using two different methods: conventional Chang's method and an expectation maximization algorithm followed by CT and SPECT image registration. Cumulated activity was calculated by a predefined calibration factor. Both attenuation correction algorithms were quantitatively assessed by the Monte Carlo SIMIND program. Acquired planar Bremsstrahlung images were quantified by the Conjugate View Method, as well. Calculated activities were statistically different among various quantification methods [P= 0.0001]. When iterative expectation maximization algorithm and applied methods were used, mean calculated activity had the least difference with real activity of +/- 3%. Quantitative 32P Bremsstrahlung SPECT imaging could accurately determine administered activity and assess radiation dose if precise attenuation correction and appropriate registration with CT were done even without sophisticated scatter correction or when SPECT/CT machines are not available. Therefore, it has the potential of specific tumor/organ dosimetry in clinical practice. The best method for calculating activity is quantitative SPECT using iterative expectation maximization algorithm. Additionally, applied method for determining phantom contour was practical for attenuation correction and image registration

rare presentation of osteoid osteoma in a rib and unexpected "double density sign": a case report and review of literature

Osteoid osteoma [OO] is a relatively common skeletal neoplasm, frequently involves long bones. OO of rib is extremely rare, including 0.23-2% of OO cases. Most of them arose in posterior arc, frequently in its head or neck and might lead to painful scoliosis. Involvement of anterior aspect of a rib is extremely rare. Skeletal scintigraphy is highly sensitive for detection of OO. "Double density sign"; a typical pattern in bone scintigraphy is usually seen in OO of cortical bones. The current study presents a case of 22-year-old man with OO in anterior arc of a rib, revealed double density sign on 99mTc-MDP scan

[Comparison of acceptance tests for SPECT systems in Tehran]

Acceptance test is a necessary procedure after SPECT system installation. The goal of this test is to reveal system's present condition, to compare it with manufacturer's specifications and also as a base for later tests. This study investigated four SPECT systems in Tehran. All of the quality control tests are performed on the basis of NEMA and IAEA recommendations and by a same group. These tests include intrinsic spatial resolution, intrinsic energy resolution, temporal resolution, intrinsic linearity, maximum count rate, pixel size, intrinsic and extrinsic uniformity, sensitivity, reconstruction spatial resolution with and without scatter and centre of rotation. Results of this investigation show that three systems have minimum acceptance conditions, but the fourth one due to it's suboptimal energy resolution and spatial resolution lacked the required specifications for acceptance. It was shown during the next six months after installation that this system showed frequent impairments and even had been out of service for a while. However, other systems did not show any considerable problems. The acceptance test is an essential step after installation of any SPECT system. If there is no considerable deficits at the initial acceptance test of a SPECT system, it won't become troublesome for a long time

Imaging of medullary thyroid carcinoma with Tc-99m [V] DMSA

Twenty-one patients with medullary thyroid carcinoma were studied prospectively with Tc-99m [V] DMSA after surgery. Pentavalent DMSA scintigram demonstrated abnormal uptake in 13 and equivocal uptake in 6 patients. Finally, seven patients with surgical or other imaging documentation were selected for this paper. Most of these patients were asymptomatic. Six patients had hypercalcitonemia and serum calcitonine was not measured in one patient. Whole body scan with Tc-99m [V] DMSA demonstrated abnormal radiotracer uptake in all patients locating in the neck [3 cases], mediastinum [5 cases], bone [2 cases], liver [1 case] and thyroid lobes [2 cases]. This preliminary study with the locally developed Tc-99m [V] DMSA showed that it is a useful imaging agent for localization of metastatic lesions in asymptomatic patients with medullary thyroid carcinoma and high serum calcitonine