scholarly journals CT Protocols for Attenuation Correction and Segmentation in 99mTc-MAA SPECT/CT for 90Y Radioembolization Treatment Planning – a Simulation Study

2020 ◽  
Author(s):  
Zhonglin Lu ◽  
Greta S. P. Mok
Keyword(s):  
Treatment Planning ◽  
Attenuation Correction ◽  
Respiratory Motion ◽  
Absorbed Dose ◽  
Normal Liver ◽  
Detector Response ◽  
Dose Estimation ◽  
Respiratory Motion Artifact ◽  
4D Ct ◽  
Significant Difference

Abstract Background Conventional 99mTc-macroaggregated albumin (99mTc-MAA) planar scintigraphy overestimates lung shunt fraction (LSF) as compared to SPECT/CT in 90Y radioembolization treatment planning. However, the respiratory motion artifact due to the temporal mismatch between static SPECT and helical CT (HCT) may compromise the SPECT quantitation accuracy by incorrect attenuation correction (AC) and volume-of-interest segmentation. The goal of this study is to systematically assess different AC and segmentation protocols for LSF, tumor-to-normal liver (TNR), organ absorbed dose and injected activity (IA) estimation in 99mTc-MAA SPECT/CT.Methods The 4D XCAT phantom was used to simulate 10 patient anatomies with 99mTc-MAA distribution based on the clinical data, each with LSF of 5%, 10%, 15% and 20%, axial respiratory motion of 2 cm, different TNR and tumor size. An analytical projector for low energy high resolution parallel-hole collimator was used to simulate realistic noisy planar acquisitions, and 128 projections over 360o for SPECT, both modeling attenuation, scatter and geometric collimator-detector-response. Five attenuation maps, i.e., (i) HCT at end-inspiration (HCT-IN), (ii) HCT at mid-respiration (HCT-MID), (iii) HCT at end-expiration (HCT-EX), (iv) cine averaged CT (CACT) and (v) interpolated average CT (IACT) were applied for SPECT AC and segmentation in LSF, dosimetric and IA evaluation. Mid-respiratory phases were also extracted from CACT/IACT for VOI segmentation while CACT/IACT were used for AC, i.e., hybrid CT protocols.Results For LSF estimation, SPECT/CACT has the least absolute errors. Planar significantly overestimates LSF and lung absorbed dose compared to SPECT especially for LSF of 5%. SPECT-based is better than CT-based segmentation in TNR estimation. There is no statistically significant difference for different CT protocols for TNR, normal liver and tumor absorbed dose estimation. Hybrid CTs and HCT-MID performed the best for IA especially for higher LSF.Conclusions 99mTc-MAA SPECT/CT with an appropriate choice of CT protocol for AC and segmentation is superior to planar in LSF and lung absorbed dose estimation. The 4D CT protocols are recommended for AC and segmentation to alleviate respiratory artifacts and improve quantitation accuracy in 90Y radioembolization treatment planning. HCT-EX would also be a recommended choice if 4D CT is not available.

Stereotactic radiotherapy (SRT) for primary and metastatic liver tumors with functional treatment planning.

2013 ◽  
Vol 31 (4_suppl) ◽  
pp. 222-222
Author(s):  
Alexander V. Kirichenko ◽  
Ngoc Thai ◽  
Erik Lappinen ◽  
Olivier Gayou ◽  
Ellen Day ◽  
...  
Keyword(s):  
Liver Disease ◽  
Treatment Planning ◽  
Hepatic Cirrhosis ◽  
Liver Tumors ◽  
Progression Free Survival ◽  
Normal Liver ◽  
Phase Iii ◽  
Free Survival ◽  
4D Ct ◽  
True Value

222 Background: We report on outcomes and toxicity of liver SRT/SBRT based on 3D-CT/SPECT treatment planning with conformal avoidance of well perfused functional normal liver volumes (FNLV). Methods: 51 patients with unresectable metastatic (36) or primary (15) hepatic tumors (65 targets) completed SRT planning with 99mTc sulfur colloid 3D-SPECT/CT to define FNLVs. Various degrees of FNLV retraction as a result of hepatic cirrhosis or systemic or intrahepatic chemotherapy were observed. For conformal avoidance of the residual FNLV, total dose and fractionation were adapted to FNLV constraints. 4D-CT and SPECT-based dosimetry were compared and treatment outcomes and toxicity were analyzed with medium followup 14.5 months (3-36months). Results: The in-field local control rate was 95%, hepatic failure free survival - 88%, hepatic progression free survival - 78% and overall survival - 70%. 25% patients developed Grade ≤ 2 elevation of liver enzymes with no incidence of “classic” radiation-induced liver disease. No patients with hepatic cirrhosis had Child-Pugh score progression. The most common toxicity was Grade ≤ 2 fatigue. For the group, FNLVs were significantly reduced compared to CT-derived NLV (p<0.01) with marked FNLV contraction in patients with Child-Pugh ≥ B cirrhosis, those who completed hepatic resections or received TACE within 2 months prior to SRT. Treatment planning with incorporated SPECT/CT helps to reduce volumes of functionally active liver parenchyma receiving doses above prescription threshold in patients with HCC compared to conventional 4D-CT treatment planning (p<0.01). There was no such correlation for non-HCC patients. Conclusions: 3D-SPECT/CT treatment planning allows identification and conformal avoidance of FNLV from high radiation doses facilitating safety of liver SRT in patients with preexisting liver disease. Outcomes are favorable, however participation in prospective Phase III trial would estimate true value of this method.

EQUIVALENT UNIFORM DOSE SENSITIVITY TO CHANGES IN ABSORBED DOSE DISTRIBUTION

2013 ◽  
Vol 06 (01) ◽  
pp. 1250069
Author(s):  
FRANCISCO CUTANDA-HENRÍQUEZ ◽  
SILVIA VARGAS-CASTRILLÓN
Keyword(s):  
Treatment Planning ◽  
Dose Distribution ◽  
Absorbed Dose ◽  
Target Volume ◽  
Simple Expression ◽  
External Beam Radiation ◽  
Equivalent Uniform Dose ◽  
Beam Radiation ◽  
Dose Volume Histograms ◽  
Small Change

Treatment planning in external beam radiation therapy (EBRT) utilizes dose volume histograms (DVHs) as optimization and evaluation tools. They present the fraction of planning target volume (PTV) receiving more than a given absorbed dose, against the absorbed dose values, and a number of radiobiological indices can be computed with their help. Equivalent uniform dose (EUD) is the absorbed dose that, uniformly imparted, would yield the same biological effect on a tumor as the dose distribution described by the DVH. Uncertainty and missing information can affect the dose distribution, therefore DVHs can be modeled as samples from a set of possible outcomes. This work studies the sensitivity of the EUD index when a small change in absorbed dose distribution takes place. EUD is treated as a functional on the set of DVHs. Defining a Lévy distance on this set and using a suitable expansion of the functional, a very simple expression for a bound on the variation of EUD when the dose distribution changes is found. This bound is easily interpreted in terms of standard treatment planning practice.

Bony-based and prostate-based image guidance for lo-calized prostate cancer radiotherapy

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Saulo Santos Fortes ◽  
Luiz Antonio Ribeiro Da Rosa
Keyword(s):  
Prostate Cancer ◽  
Normal Tissue ◽  
Bone Structure ◽  
Absorbed Dose ◽  
Target Volume ◽  
Image Guided Radiotherapy ◽  
Beam Modulation ◽  
Significant Difference ◽  
Treatment Volume ◽  
Treatment Plans

An important modality for the treatment of prostate cancer is teletherapy. The use of image-guided radiotherapy (IGRT) is a valuable tool in this treatment. This study retrospectively compared how repositioning the patient based on bone structure (B-ISO) and the prostate itself (P-ISO) affected the volumetric dose in the rectum, bladder, and clinical treatment volume (CTV). Additionally, the probability of normal tissue complication (NTCP) for the rectum was computed. We evaluated 155 cone-beam computed tomography (CBCT) from 8 patients. The treatment plans used beam modulation techniques. The planning target volume (PTV) margin adopted in both scenarios was 1 cm. The organs of interest were outlined over each CBCT and then treatment plans were applied so that the absorbed dose could be computed. NTCP values were calculated for the rectum. Analyzing dose-volume metrics published by the Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC), there was no significant difference between the two repositioning strategies for the rectum and bladder. There was a slight degradation in CTV coverage for the B-ISO strategy, but still with adequate coverage. Analysis of the uniform equivalent dose (EUD) and NTCP for the rectum showed little sensitivity to the strategy used. The present study showed that the use of CBCT in radiotherapy for prostate cancer treatment did not significantly improve volumetric doses for the rectum, bladder, and CTV, as well as NTCP for the rectum.

scholarly journals Antifibrotic effect of Pluchea sagitallis (Lam.) cabrera aqueous extract in grx cell lineage

2018 ◽  
Vol 10 (1) ◽  
pp. 30
Author(s):  
Fabiana Garbachi De Oliveira Mendes Ouri ◽  
Paula Bacaicoa Caruso ◽  
Gabriela Viegas Da Silva ◽  
Henrique Dias ◽  
Juliana Romeu Marques ◽  
...  
Keyword(s):  
Aqueous Extract ◽  
Lipid Content ◽  
Complex Disease ◽  
Stellate Cell ◽  
Normal Liver ◽  
Phenotypic Change ◽  
Quiescent State ◽  
Antifibrotic Effect ◽  
Significant Difference

<p>Liver fibrosis is a complex disease that is caused by inappropriate tissue repair due to the deposition of connective tissue. When a chronic lesion affects the liver, regenerative response fails and hepatocytes are replaced with abundant extracellular matrix (ECM). The imbalance between production and degradation of ECM will result in the accumulation of proteins that change normal liver architecture, and thus its functionality. The main source of ECM is the activated hepatic stellate cell (HSC). In order, to clarify possible therapeutic approaches to the disease, this work aimed to evaluate the possible antifibrotic action of <em>Pluchea sagitallis </em>(Lam.) Cabrera on an activated HSC immortalized lineage (GRX).</p><p>Our results demonstrated that the <em>P. sagittalis</em> aqueous extract at 0.039 and 0.078 mg/mL concentrations was able to reduce cell growth and proliferation. Regarding to oxidative stress evaluation, there was no statistically significant difference between the treated group and the control. Staining with OilRed-O (ORO) showed a statistically significant increase in intracellular lipid content after 5 days of treatment, exerting <em>in vitro</em> effect on the GRX phenotypic change of activated towards the quiescent state. These results were confirmed by colorimetric quantification of lipid content. Regarding the TGF-β1 and collagen production, there were no statistically significant differences observed between the groups.</p><p>In conclusion, the <em>P. sagittalis</em> aqueous extract reduces the growth and proliferation of GRX cells and induces the reversal of activated towards a quiescent phenotype. There was no decrease in cell proliferation either by necrosis or by apoptosis via activation of the senescence. Thus, our data suggest that the extract showed an antifibrotic effect, possibly by activating phenotype reversal.</p>

scholarly journals Experimental and Simulated Spectral Gamma-Ray Response of a NaI(Tl) Scintillation Detector used in Airborne Gamma-Ray Spectrometry

2021 ◽  
Author(s):  
David Breitenmoser
Keyword(s):  
Monte Carlo ◽  
Gamma Ray ◽  
Radiation Transport ◽  
Natural Uranium ◽  
Detector Response ◽  
Gamma Ray Spectrometry ◽  
Response Analysis ◽  
Maximum Relative Error ◽  
Potassium Sources ◽  
Significant Difference

&lt;p&gt;The objective of this work is to simulate the spectral gamma-ray response of NaI(Tl) scintillation detectors for airborne gamma-ray spectrometry (AGRS) using Monte Carlo radiation transport codes. The study is based on a commercial airborne gamma-ray spectrometry detector system with four individual NaI(Tl) scintillation crystals and a total volume of 16.8 l. Monte Carlo source-detector simulations were performed in an event-by-event mode with the commercial multi-purpose transport codes MCNP6.2 and FLUKA. Validation measurements were conducted using &lt;sup&gt;241&lt;/sup&gt;Am, &lt;sup&gt;133&lt;/sup&gt;Ba, &lt;sup&gt;60&lt;/sup&gt;Co, &lt;sup&gt;137&lt;/sup&gt;Cs and &lt;sup&gt;152&lt;/sup&gt;Eu radiation sources with known activities and source-detector geometries. Energy resolution functions were derived from these measurements combined with additional measurements of natural Uranium, Thorium and Potassium sources. The simulation results are in good agreement with the experimental data with a maximum relative error in the full-energy peak counts of 10%. In addition, no significant difference between the two Monte Carlo radiation transport codes was found with respect to a 95% confidence level. The validated detector model presented herein can be adopted for angular detector response analysis and calibration computations relating radionuclide activity concentrations with spectral detector counts.&lt;/p&gt;

Absorbed dose and image quality in examinations of the colon with digital and analogue techniques

1997 ◽  
Vol 38 (6) ◽  
pp. 1010-1014 ◽  
Author(s):  
J. Persliden ◽  
P. Larsson ◽  
B. Norén ◽  
S. Wirell
Keyword(s):  
Image Quality ◽  
Absorbed Dose ◽  
Image Intensifier ◽  
Incident Radiation ◽  
Conventional Technique ◽  
Digital System ◽  
Digital Technique ◽  
Significant Difference ◽  
Total Examination Time ◽  
Area Product

Purpose: Image quality and the absorbed dose to the patient are issues of primary interest in the change-over from the conventional analogue technique to the digital technique in the examination of the colon by means of fluoroscopy. the aim of this study was to compare the incident radiation and to evaluate the image quality in two different X-ray equipment types, one digital and one analogue Material and Methods: A kerma-area product meter was used to measure the incident radiation to the patient. Both fluoroscopy and total-examination times were measured as was the number of images. an evaluation of image quality was made and statistically analysed Results and Conclusion: No significant difference in the irradiation dose was observed between the two techniques. the fluoroscopy time was significantly lower with the conventional technique but the total-examination time decreased by 18% with the digital technique. the total number of images taken was higher with the digital technique (25 images compared to 19) owing to the limited field of the image intensifier. Significantly more noise and less sharpness were observed with the digital system but there was no significant difference in contrast or image quality in the various anatomical structures. Although the change-over to the digital system produced a reduction in sharpness and an increase in noise, and no significant dose saving was measured, the digital system was faster to work with and could well be used for diagnostic purposes

Cytogenetic Damage of Human Lymphocytes in Humanized Mice Exposed to Neutrons and X Rays 24 h After Exposure

2021 ◽  
Vol 161 (6-7) ◽  
pp. 352-361
Author(s):  
Qi Wang ◽  
Younghyun Lee ◽  
Monica Pujol-Canadell ◽  
Jay R. Perrier ◽  
Lubomir Smilenov ◽  
...  
Keyword(s):  
Dna Damage ◽  
Radiation Exposure ◽  
Human Lymphocytes ◽  
Absorbed Dose ◽  
Chromosome 1 ◽  
X Rays ◽  
Chromosomal Dna ◽  
Humanized Mouse Model ◽  
Significant Difference

Detonation of an improvised nuclear device highlights the need to understand the risk of mixed radiation exposure as prompt radiation exposure could produce significant neutron and gamma exposures. Although the neutron component may be a relatively small percentage of the total absorbed dose, the large relative biological effectiveness (RBE) can induce larger biological DNA damage and cell killing. The objective of this study was to use a hematopoietically humanized mouse model to measure chromosomal DNA damage in human lymphocytes 24 h after in vivo exposure to neutrons (0.3 Gy) and X rays (1 Gy). The human dicentric and cytokinesis-block micronucleus assays were performed to measure chromosomal aberrations in human lymphocytes in vivo from the blood and spleen, respectively. The mBAND assay based on fluorescent in situ hybridization labeling was used to detect neutron-induced chromosome 1 inversions in the blood lymphocytes of the neutron-irradiated mice. Cytogenetics endpoints, dicentrics and micronuclei showed that there was no significant difference in yields between the 2 irradiation types at the doses tested, indicating that neutron-induced chromosomal DNA damage in vivo was more biologically effective (RBE ∼3.3) compared to X rays. The mBAND assay, which is considered a specific biomarker of high-LET neutron exposure, confirmed the presence of clustered DNA damage in the neutron-irradiated mice but not in the X-irradiated mice, 24 h after exposure.

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