Low-energy All-purpose Collimator Research Articles

99mTc-DMSA renal cortical quantitative SPECT/CT imaging in diabetic patients: Feasibility and initial results

Introduction Diabetes mellitus is a common cause of chronic kidney disease. Radionuclide imaging of the kidneys using technetium-99m-labeled dimercaptosuccinic acid (99mTc-DMSA) is a well-established method for the evaluation of kidney parenchyma. We hypothesize that early preclinical detection of renal affection in diabetic patients can be done by quantitative single-photon emission computed tomography (SPECT) imaging using 99mTc-DMSA. Patients and methods In this study we included 29 patients: 13 diabetic and 16 volunteers as control. All must have within normal renal function. We excluded patients with known history of renal disease or abnormal renal function, patients with systemic diseases directly affect kidney function rather than diabetes. All patients included in our study were subjected to detailed clinical history, renal function, and quantitative 99mTc-DMSA renal imaging using SPECT/computed tomography techniques. About 5 mCi of 99mTc-DMSA were injected intravenously. Then imaging was acquired after 2–4 h in the supine position using a dual-head gamma camera with a low-energy all-purpose collimator. SPECT/computed tomography images are then taken. Data were reconstructed; then a 3D ball region of interest is drawn over each kidney to assess the counts of the kidney. Results There was a significant difference in the mean of the BMI-corrected counts divided by the injected dose (P = 0.024). The same results were obtained when the counts were summed and corrected according to the injected dose between the two groups (P = 0.034). Conclusion Quantitative SPECT 99mTc-DMSA imaging may have a role in the evaluation of renal functions in diabetics with no clinical evidence of renal affection.

Simultaneous fluoroscopic and nuclear imaging: impact of collimator choice on nuclear image quality.

X-ray-guided oncological interventions could benefit from the availability of simultaneously acquired nuclear images during the procedure. To this end, a real-time, hybrid fluoroscopic and nuclear imaging device, consisting of an X-ray c-arm combined with gamma imaging capability, is currently being developed (Beijst C, Elschot M, Viergever MA, de Jong HW. Radiol. 2015;278:232-238). The setup comprises four gamma cameras placed adjacent to the X-ray tube. The four camera views are used to reconstruct an intermediate three-dimensional image, which is subsequently converted to a virtual nuclear projection image that overlaps with the X-ray image. The purpose of the present simulation study is to evaluate the impact of gamma camera collimator choice (parallel hole versus pinhole) on the quality of the virtual nuclear image. Simulation studies were performed with a digital image quality phantom including realistic noise and resolution effects, with a dynamic frame acquisition time of 1 s and a total activity of 150 MBq. Projections were simulated for 3, 5, and 7 mm pinholes and for three parallel hole collimators (low-energy all-purpose (LEAP), low-energy high-resolution (LEHR) and low-energy ultra-high-resolution (LEUHR)). Intermediate reconstruction was performed with maximum likelihood expectation-maximization (MLEM) with point spread function (PSF) modeling. In the virtual projection derived therefrom, contrast, noise level, and detectability were determined and compared with the ideal projection, that is, as if a gamma camera were located at the position of the X-ray detector. Furthermore, image deformations and spatial resolution were quantified. Additionally, simultaneous fluoroscopic and nuclear images of a sphere phantom were acquired with a physical prototype system and compared with the simulations. For small hot spots, contrast is comparable for all simulated collimators. Noise levels are, however, 3 to 8 times higher in pinhole geometries than in parallel hole geometries. This results in higher contrast-to-noise ratios for parallel hole geometries. Smaller spheres can thus be detected with parallel hole collimators than with pinhole collimators (17 mm vs 28 mm). Pinhole geometries show larger image deformations than parallel hole geometries. Spatial resolution varied between 1.25 cm for the 3 mm pinhole and 4 cm for the LEAP collimator. The simulation method was successfully validated by the experiments with the physical prototype. A real-time hybrid fluoroscopic and nuclear imaging device is currently being developed. Image quality of nuclear images obtained with different collimators was compared in terms of contrast, noise, and detectability. Parallel hole collimators showed lower noise and better detectability than pinhole collimators.

The Role of Salivary Gland Scintigraphy in the Evaluation of Salivary Gland Dysfunction in Uncontrolled Type II Diabetic Patients.

The aim of the present study was to evaluate the salivary gland dysfunction in patients with uncontrolled type II diabetes using salivary gland scintigraphy and then to compare these ratios with quantitative whole salivary secretion rates. Using a gamma camera (siemens-diacam) equipped with a low energy all-purpose collimator, 32 uncontrolled type II diabetic patients and 30 normal healthy patients were studied by injecting a radio isotope (technetium 99m pertechnetate) about 5 mCi was injected intravenously in to anticubital vein and the activity was measured for the 1st, 20th and 40th min. At 20 min after injection, vitamin C chewable tablet was given to stimulate the secretion and continued until the end of the study period (40 min). Before scintigraphy, salivary sampling was carried out in both diabetic and normal individuals in a quiet room, saliva was allowed to accumulate and was expectorated into the collecting vessel approximately once a minute for 15 min and the volume was recorded as Unstimulated salivary flow rate and after 5 min break vitamin C chewable tablet was given to stimulate the secretion and the patient was asked to expectorate the saliva in the collecting vessel for 5 min. The expectorated volume was recorded as stimulated salivary flow rate. The mean of the measurements of scintigraphic ratio and salivary secretion rates were compared using the paired Student's t-test. The scintigraphic mean uptake and excretory ratio (ER) and the salivary flow rates were correlated. The result shows that there was a significant correlation between salivary flow rate and scintigraphic uptake and ER. However, statistically significant result could not be derived as it may be due to smaller sample size and marginal difference in the scintigraphic values between the groups. Salivary gland scintigraphy plays a significant role in the evaluation of salivary gland dysfunction. However, its role as an independent investigative procedure in the evaluation of salivary gland dysfunction requires a study with a larger sample size, may yield a statistical significant result and it can also act as an adjunct along with salivary flow rate procedure.

A new imaging modality in detection of caustic oesophageal injury: Technetium-99m pyrophosphate scintigraphy

Early oesophagoscopy is usually recommended in children after caustic ingestion to assess the severity of the initial digestive lesions. An oesophagoscopic procedure in children always demands to be performed under sedation and bears a certain risk of iatrogenic injury. The purpose of the study is to determine the value and sensitivity of Tc-99m pyrophosphate (99mTc-PYP) scintigraphy for the detection of caustic oesophageal injury. The caustic oesophageal burns were created with 25% NaOH in an experimental rat model. Seventeen rats were divided into two groups. The BURN group (n=9) included caustic oesophageal burning rats. Non-BURN group (n=8) included sham-operated rats. All animals underwent 99mTc-PYP scintigraphy 72 h after the burning experiment. Anterior static and single-photon emission computed tomography images were obtained using a low-energy all-purpose collimator, 2.55 zoom factor, 3h after intravenous injection of 10 mCi 99mTc-PYP. After the imaging, all the oesophagi were explored for external determination of the injury sites and macroautoradiographic scintigraphy as well. Rectangular region of interest were placed in the visually determined lesion of oesophagus (O) as well as non-lesion area (N), and an ON ratio was created. The severity and extension of oesophageal burn were assessed 3 days after burning by histopathologic evaluation. The injuries were graded according to the ulcer depth, ulcer width, thrombus formation, and the development of perivascular fibrinoid necrosis. The oesophageal burning areas were demonstrated by visual evaluation of the Tc-99m PYP scintigraphy on all animals. The mean ON ratio of 99mTc-PYP was 21.61+/-7.01 in the BURN group and in the non-BURN group, was 2.25+/-0.24 (p<0.001). The best cut-off point of the ON ratio for caustic oesophageal injury was 5.45, with sensitivity and specificity of 100%. PYP scan findings were also confirmed by histological evidence of ulcer depth, ulcer width, thrombus formation, and perivascular fibrinoid necrosis in the same areas. The caustic oesophageal injuries have been demonstrated by 99mTc-PYP scintigraphy in burning experiment. 99mTc-PYP scintigraphy is sensitive for detection of caustic oesophageal injury. This new imaging tool is found to be sensitive and specific for the detection of caustic oesophageal injury in the rats.

THYROID TO SALIVARY RATIOS DETERMINED BY TECHNETIUM‐99MPERTECHNETATE IMAGING IN THIRTY‐TWO EUTHYROID CATS

Thyroid to salivary (TS) ratio is the most commonly used scintigraphic parameter for differentiating euthyroid and hyperthyroid cats. Studies to determine the normal TS ratio have been performed in small cat populations. In this study, the TS ratio was determined in 32 cats between 8 and 13 years of age. The study population was documented to be euthyroid based on normal initial and 6-week follow-up serum thyroid concentrations and normal T3 suppression tests. All images were obtained with a low-energy all-purpose collimator between 20 and 40 min after the injection of approximately 111 MBq (3.0 mCi) pertechnetate. Manual regions of interest (ROI) were made of the thyroid and salivary glands of the ventral image A 95% prediction interval based on the natural log of the TS ratio was computed to provide a normal range of 0.48-1.66. This range is similar to previous studies, but suggests a slightly higher upper limit than previously reported.

Sentinel node detection in patients with breast cancer: low-energy all-purpose collimator or medium-energy collimator?

Sentinel node detection in patients with breast cancer: low-energy all-purpose collimator or medium-energy collimator?

Sentinel node detection in patients with breast cancer: low-energy all-purpose collimator or medium-energy collimator?

Sentinel node detection in patients with breast cancer: low-energy all-purpose collimator or medium-energy collimator?

Least squares algorithm for region-of-interest evaluation in emission tomography

An accurate model of the nonstationary geometrical response of a camera-collimator system is discussed. The algorithm is compared to three other algorithms that are specialized for region-of-interest evaluation, as well as to the conventional method for summing the reconstructed quantity over the regions of interest. For noise-free data and for regions of accurate shape, least-squares estimates were unbiased within roundoff errors. For noisy data, estimates were still unbiased but precision worsened for regions smaller than resolution: simulating typical statistics of brain perfusion studies performed with a collimated camera, the estimated standard deviation for a 1-cm-square region was 10% with an ultra-high-resolution collimator and 7% with a low-energy all-purpose collimator. Conventional region-of-interest estimates show comparable precision but are heavily biased if filtered backprojection is used for image reconstruction. Using the conjugate-gradient iterative algorithm and the model of nonstationary geometrical response, bias of estimates decreased on increasing the number of iterations, but precision worsened, thus achieving an estimated standard deviation of more than 25% for the same 1-cm region.