Subhash Chand Kheruka

Utility of single photon emission computed tomography perfusion scans in radiation treatment planning of locally advanced lung cancers

Purpose: Lung perfusion scan provides a map of the spatial distribution of lung perfusion. This can be used to design radiation portals to spare functional lung (FL), potentially reducing lung toxicity. The purpose of this study was to assess the utility of lung perfusion single photon emission computed tomography (SPECT) in treatment planning for lung cancer patients. Materials and Methods: Radiotherapy treatment planning computed tomography (CT) scans and SPECT scans of 11 patients of lung cancer suitable for external radiotherapy were co-registered. Conventional treatment plans (anatomic plan) and plans with FL information (functional plan) was generated. The difference in dose volume parameters (V20, V30 and mean lung doses) due to these two plans were compared using Bland-Altman plots. Results: Functional plans produced a more favorable plan compared with anatomic plan in all except three cases. FL V20 values and FL mean lung dose were reduced for all patients by an average of 5.45 Gy and 7.72 Gy respectively which were statistically significant. Conclusions: Lung perfusion scans provide functional information which is not provided by CT scans. SPECT-guidance aids in reducing the dose delivered to highly perfused regions which could reduce the incidence of pneumonitis.

A study to improve the image quality in low-dose computed tomography (SPECT) using filtration

Background: The output of the X-ray tube used in computed tomography (CT) provides a spectrum of photon energies. Low-energy photons are preferentially absorbed in tissue; the beam spectrum shifts toward the higher energy end as it passes through more tissue, thereby changing its effective attenuation coefficient and producing a variety of artifacts (beam-hardening effects) in images. Filtering of the beam may be used to remove low-energy photon component. The accuracy of attenuation coefficient calculation by bilinear model depends highly upon accuracy of Hounsfield units. Therefore, we have made an attempt to minimize the beam-hardening effects using additional copper filter in the X-ray beam. The quantitative evaluation were made to see the effect of additional filters on resulting CT images. Materials and Methods: This study was performed on dual-head SPECT (HAWKEYE 4, GE Healthcare) with low-dose CT which acquires images at peak voltages of 120/140 kV and a tube current of 2.5 mA. For the evaluation of image quality, we used CT QA Phantom (PHILIPS) having six different density pins of Water, Polyethylene, Nylon (Aculon), Lexan, Acrylic (Perspex) and Teflon. The axial images were acquired using copper filters of various thicknesses ranging from 1 to 5 mm in steps of 1 mm. The copper filter was designed in such a manner that it fits exactly on the collimator cover of CT X-ray tube. Appropriate fixation of the copper filter was ensured before starting the image acquisition. As our intention was only to see the effect of beam hardening on the attenuation map, no SPECT study was performed. First set of images was acquired without putting any filter into the beam. Then, successively, filters of different thicknesses were placed into the beam and calibration of the CT scanner was performed before acquiring the images. The X-ray tube parameters were kept the same as that of unfiltered X-ray beam. All the acquired image sets were displayed using Xeleris 2 (GE Healthcare) on a high-resolution monitor. Moreover, Jaszaks SPECT Phantom after removing the spheres was used to see the different contrast intensities by inserting the different contrast materials of iodine and bismuth in water as background media. Images were analyzed for visibility, spatial resolution and contrast. Results: Successive improvement in the image quality was noticed when we increased the filter thickness from 1 to 3 mm. The images acquired with 3-mm filter appeared almost with no artifacts and were visibly sharper. Lower energy photons from X-ray beam cause a number of artifacts, especially at bone–tissue interfaces. Additional filtrations removed lower energy photons and improved the image quality. Degradation in the image quality was noticed when we increased the filter thickness further to 4 and 5 mm. This degradation in image quality happened due to reduced photon flux of the resulting X-ray beam, causing high statistical noise. The spatial resolution for image matrix of 512 × 512 was found to be 1.29, 1.07, 0.64 and 0.54 mm for without filter, with 1, 2 and 3 mm filters, respectively. The image quality was further analyzed for signal-to-noise ratio (SNR). It was found to be 1.72, 1.78, 1.98 and 1.99 for open, with 1, 2 and 3 mm filters respectively. This shows that 3-mm filter results in an improvement of 15.7% in SNR. Conclusion: On the basis of this study, we could conclude that use of 3-mm copper filter in the X-ray beam is optimal for removing the artifacts without causing any significant reduction in the photon flux of the resulting X-ray beam. We also propose that as artifacts have been removed from the images, the value of Hounsfield units will be more accurate and hence the value of attenuation coefficients lead to better contrast and visualization of SPECT images.

Evaluation of single-photon emission computed tomography images obtained with and without copper filter by segmentation.

Background: Measurement of accurate attenuation of photon flux in tissue is important to obtain reconstructed images using single-photon emission computed tomography (SPECT). Computed tomography (CT) scanner provides attenuation correction data for SPECT as well as anatomic information for diagnostic purposes. Segmentation is a process of dividing an image into regions having similar properties such as gray level, color, texture, brightness, and contrast. Image segmentation is an important tool for evaluation of medical images. X-ray beam used in CT scan is poly-energetic; therefore, we have used a copper filter to remove the low energy X-rays for obtaining correct attenuation factor. Images obtained with and without filters were quantitatively evaluated by segmentation method to avoid human error. Materials and Methods: Axial images of AAPM CT phantom were acquired with 3 mm copper filter (low intensity) and without copper filter (high intensity) using low-dose CT (140 kvp and 2.5 mA) of SPECT/CT system (Hawkeye, GE Healthcare). For segmentation Simulated Annealing Based Fuzzy c-means, algorithm is applied. Quantitative measurement of quality is done based on universal image quality index. Further, for the validation of attenuation correction map of filtered CT images, Jaszczak SPECT phantom was filled with 500 MBq of 99m Tc and SPECT study was acquired. Low dose CT images were acquired for attenuation correction to be used for reconstruction of SPECT images. Another set of CT images were acquired after applying additional 3 mm copper filter. Two sets of axial SPECT images were reconstructed using attenuation map from both the CT images obtained without and with a filter. Results and Conclusions: When we applied Simulated Annealing Based Fuzzy c-means segmentation on both the CT images, the CT images with filter shows remarkable improvement and all the six section of the spheres in the Jaszczak SPECT phantom were clearly visualized.

Polylactide-co-glycolide nanoparticles of antitubercular drugs: formulation, characterization and biodistribution studies

BACKGROUND The present study was designed to prepare and characterize poly lactide-co-glycolide nanoparticles of antitubercular drugs (ATDs) for delivery through oral route to alveolar macrophages. METHODS Nanoparticles were prepared by double emulsification solvent evaporation method. Ex vivo and in vivo drug accumulation studies were performed in alveolar macrophages, harvested by broncheoalveolar lavaging. Internalization of nanoparticles was studied by confocal laser scanning microscopy. γ-scintigraphy imaging using technetium-99m was done to study the biodistribution pattern of nanoparticles. RESULTS High intracellular concentrations of ATDs were observed in macrophages within 30 min of administration of nanoparticles. Intense radioactivity recorded in liver, spleen and lungs revealed uptake of nanoparticles in macrophages, abundantly present in mononuclear phagocyte system present in these organs. CONCLUSION Targeted delivery of ATDs will help reduce dose and associated side effects including hepatotoxicity of ATDs. Further studies are required to assess the potential therapeutic advantages for treatment of TB.

Extraosseous 99mTc-methylene diphosphonate uptake on bone scan: Unusual scenario

In nuclear medicine, 99mTc-methylene diphosphonate. (MDP) bone scan is one of the most commonly performed procedures. MDP uptake in nonosseous tissues is occasionally found in bone scan, and the knowledge of these kinds of extraosseous uptakes is of much clinical relevance. We report here two cases where bone scan showed extraosseous MDP uptake either hepatic or splenic apart from the physiological skeletal uptake.

A new method to correct the attenuation map in simultaneous transmission/emission tomography using 153Gd/ 67Ga radioisotopes

Reconstruction of the tomographic images without attenuation correction can cause erroneously high count densities and reduced image contrast in low attenuation regions. In order to solve the problem of photon attenuation, one needs to know the attenuation coefficient for the individual patient being studied. Therefore, we made an attempt to correct the attenuation map in simultaneous transmission/emission tomography with 153Gd/67Ga using maximum likelihood method using the expectation maximization (ML-EM) algorithm to correct the transmission window for both the spillover and downscatter. Spillover fraction, scatter fraction and parameters for the scatter function (A, b and c) were determined experimentally and optimized using the optimization program written in IDL based on simplex theory. All measurements were performed on a Vertex gamma camera using the anthropomorphic thorax phantom for validation of data obtained by the proposed method. It was observed that without spillover and downscatter correction, the mean counts were 19.29 in liver and 26.90 in lung, whereas after after applying the corrections, the mean counts were reduced to 3.80 and 15.10 in liver and lung, respectively, which were close to true mean counts (liver 2.15 and lung 14.89). In this proposed method, we introduced the set of Ft(spillover) and Kt(downscatter) to account for the variations in projection pixels (ft and kt) with the density and thickness. The Ft and Kt were determined using the transmission data by an iterative process. The quantitative error was reduced by 98.0% for lung and 90.0% for liver when the corrected transmission images were obtained after the subtraction of spillover and downscatter fraction.

Design and development of novel p-aminobenzoic acid derivatives as potential cholinesterase inhibitors for the treatment of Alzheimer’s disease

Based on the quantitative structure-activity relationship (QSAR), some novel p-aminobenzoic acid derivatives as promising cholinesterase enzyme inhibitors were designed, synthesized, characterized and evaluated to enhance learning and memory. The in vitro enzyme kinetic study of the synthesized compounds revealed the type of inhibition on the respective acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. The in vivo studies of the synthesized compounds exhibited significant reversal of cognitive deficits in the animal models of amnesia as compared to standard drug donepezil. Further, the ex vivo studies in the specific brain regions like the hippocampus, hypothalamus, and prefrontal cortex regions also exhibited AChE inhibition comparable to standard donepezil. The in silico molecular docking and dynamics simulations studies of the most potent compound 22 revealed the consensual interactions at the active site pocket of the AChE.

Contamination, a Major Problem in Nuclear Medicine Imaging: How to Investigate, Handle, and Avoid It

We present a case study in which artifacts from collimator contamination and patient motion were seen on a bone scan. Any identified artifact must be further investigated and documented so as to detect its source and thus prevent its future occurrence.

Hypothyroidism in mccune–albright syndrome and role of bone scan in management of fibrous dysplasia: An unusual case scenario with review of literature

The McCune–Albright syndrome (MAS) is a triad of café-au-lait skin pigmentation, precocious puberty (PP), and polyostotic fibrous dysplasia of bone (FD). In general, FD seems to be the most common component of MAS but very rarely precocious puberty can be found in association with café-au-lait skin pigmentation in the absence of FD (about 1% of the cases). Therefore, a more clinically relevant definition of MAS is fibrous dysplasia of bone (FD) and at least one of the typical hyperfunctioning endocrinopathy and/or café-au-lait spots, with almost any combination possible. Bone scan can be the modality of choice to look for bone disease burden of fibrous dysplasia in most patients of MAS and may change the management accordingly. Most of the cases of MAS reported worldwide are associated with hyperthyroidism, up to best of our knowledge on the basis of literature search in pubmed and Google; no case was reported with hypothyroidism. Herein, we report a 12-year-old girl diagnosed with MAS and associated hypothyroidism.We have also reviewed the MAS related literature.

Gallbladder visualization on Tc-99m-labeled red cell scintigraphy: A rare finding with an emphasis on role of single-photon emission computed tomography/computed tomography

Tc-99m labeled red blood cell (RBC) scintigraphy is one of the most sensitive tests to diagnose occult gastrointestinal (GI) bleed. Visualization of gallbladder is a rare finding in this study. Most of the previously reported cases with similar false-positive finding were associated chronic renal failure, anemia, and received multiple blood transfusions. Thus, while interpreting GI bleed scan, a thorough clinical history is of utmost importance to avoid any false-positive findings. Here, we report a case of gallbladder visualization in 99mTc-RBC scintigraphy confirmed by single-photon emission computed tomography/computed tomography in a patient with chronic renal failure and anemia with failed renal transplant within 3 months.