The Effects of Mismatch between SPECT and CT Images on Quantitative Activity Estimation – A Simulation Study

Background: Quantitative activity estimation is essential in targeted radionuclide therapy dosimetry. Misregistration between SPECT and CT images at the same imaging time point due to patient movement degrades accuracy. This work aims to study the mismatch effects between CT and SPECT data on attenuation correction (AC), volume-of-interest (VOI) delineation and registration for activity estimation.Methods: Nine 4D XCAT phantoms were generated at 1, 24, and 144 hrs post In-111 Zevalin injection, varying in activity distributions, body and organ sizes. Realistic noisy SPECT projections were generated by an analytical projection and reconstructed with quantitative OS-EM method. CT images were shifted from -5 to 5 voxels as well as according to clinical reference corresponding to SPECT images at each time point. For AC effect, mismatched CT images were used for AC in SPECT reconstruction while VOIs were mapped out from matched CTs. For VOI effect, target organs were mapped out using mismatched CTs with matched CTs for AC. For registration effect, non-rigid registrations were performed on sequential mismatched CTs to align corresponding SPECT images, with no AC and VOI mismatch. Bi-exponential curve fitting was performed to obtain time-integrated activity (TIA). Organ activity errors (%OAE) and TIA errors (%TIAE) were calculated.Results: According to clinical reference, %OAE was larger for organs near ribs for AC effect, e.g., -2.58%±0.81% for liver. For VOI effect, %OAE was larger for small and low uptake organs, e.g., -11.94%±10.34% for spleen. %OAE was proportional to mismatch magnitude, e.g., 4.77%±1.41%, 12.01%±3.97% and 42.81%±6.38% for 1-, 2-, and 5-voxel mismatch for lungs. For registration effect, %TIAE were larger when mismatch existed in more numbers of SPECT/CT images, while no substantial difference was observed when using mismatched CT at different time points for registration reference. %TIAE was highest for VOI, followed by registration and AC, e.g., 37.61%±5.08%, 14.25%±7.07% and 1.13%±0.90% respectively for kidneys.Conclusions: The mismatch between CT and SPECT images poses a significant impact on accuracy of quantitative activity estimation in dosimetry, attributed particularly from VOI delineation errors. It is recommended to perform registration between emission and transmission images at the same time point to ensure dosimetric accuracy.

Ultrasonography of kidney and spleen in clinically healthy llamas and alpacas

Background The ultrasonographic examination technique is a well-established, non-invasive diagnostic tool for diverse conditions in humans and different animal species. The purpose of our study was to describe ultrasonographic localisation, sonographic appearance and dimensions of the kidneys and spleen of clinically healthy llamas and alpacas. Differences between llamas and alpacas and the influence of sex and ages were investigated. Results of this study may aid veterinarians performing ultrasonography in diseased animals and the technique can be used for routine protocol screening. Results Ultrasonography was performed in 135 clinically healthy, non-sedated llamas and alpacas. Screening was performed with a 6.6 MHz curve linear transducer with only alcohol as contact medium between the probe and unclipped skin. The kidneys could be imaged from the paralumbar region. The right kidney only was visualized when scanning from the right and the left kidney only from the left. While the left kidney appeared in sagittal view as an oval shape in most llamas and alpacas, in one third of animals the left kidney had a triangular shape. The L-shaped base of the spleen, with its homogeneous, echoic pattern, could be seen craniolateral to the left kidney. Anechoic areas displaying vessels inside the spleen and a thin echoic capsule surrounding the splenic tissue could be differentiated. While sonographic appearances of the examined organs showed no differences between llamas and alpacas, selected dimensions of both of kidney and spleen showed significant differences between species. In terms of age and sex, significant differences in respect of kidney size could be found only in alpacas. Sex seemed to have no influence on kidney and spleen sizes in llamas. Conclusions The present study provides species-specific information on ultrasonographic appearance and reference values for kidney and spleen dimensions of clinically healthy llamas and alpacas. Results show differences in organ sizes between llamas and alpacas and in alpacas of different sex and age. The results of this study can be used as references for veterinarians performing ultrasound examinations in diseased animals.

Ultrasound examination of the liver: the search for the most reproducible and easy to operate measuring method of the right lobe oblique craniocaudal diameter

Introduction. Mismatching of the organ sizes to the standard measurements is the sign of pathology, so it is important to make measurements using the same method for the same type of assessment.Goal: to evaluate the intra- and inter-research reproducibility of the oblique craniocaudal diameter measurement of the right liver lobe with the application of Russian and European methods by different operators, and find out which of the methods is the most convenient for practical application.Materials and methods. 47 healthy volunteers and 3 operators were participated in the study. One of the operators participated in both stages of study.Results. Keeping conditions such as quiet breathing and longitudinal scanning in the anterior axillary line from the VII-X intercostal spaces increases reproducibility and provides well visualization of the lobe even if the patient is not prepared for the study.Conclusion. The oblique size of the right lobe is highly reproducible for both methods, but the European method (longitudinal scanning of right lobe) is more convenient for the practical application.

Diplodiscus mehrai Pande, 1937 and D. japonicus (): morphology of developmental stages and molecular data

Summary Specimens of the snails Anisus centrifugops were infected with two types of cercariae relating to the genus Diplodiscus, differing from each other by body and organ sizes were found in a pond in the territory of Vladivostok (Primorsky region, Russia). Further study of their morphology and life cycles allowed us to establish that these flukes belong to Diplodiscus japonicus (Yamaguti, 1936) and D. mehrai Pande, 1937. Morphological and molecular data confirmed the validity of D. japonicus which had previously been synonymized with D. amphichrus Tubangui, 1933 and D. mehrai Pande, 1937.

Self-organized patterning and morphogenesis in embryonic epithelia from antagonistic signals and fiber networks

A number of universals can be observed in the developing embryos of all phyla. An attempt is made here to describe some of these with a simple model, one consisting of two mutually repelling regions of gene patterning produced by signaling pathways, two acting at each growth phase. The diffusion of ligands is short range, nearest or near neighbors, but the transcription patterns extend over many cellular diameters. The universals discussed are: gastrulation, formation of a blastopore, patterning of stem cells as surrounding compartments (propagating anew with each growth phase, to the adult), the origin of bilaterality, the prevalence of segmentation, and the general ability to regenerate and duplicate. The origin of organ sizes are determined by the parameters of the signaling pathways involved, independent of cell sizes or numbers. The important fiber mesh, or fiber network that can also extend over many cell diameters is also briefly discussed, and is seen as a partner with the signaling pathways in the overall patterning.