difference between pet and spect pdf

Difference between pet and spect pdf

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Nuclear Medicine

PET versus SPECT: strengths, limitations and challenges

New SPECT and PET Radiopharmaceuticals for Imaging Cardiovascular Disease

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Functional imaging modalities enable practitioners to identify functional lung regions.

Nuclear Medicine

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Functional imaging modalities enable practitioners to identify functional lung regions. This analysis evaluated the feasibility of nuclear medicine imaging to avoid doses to the functional lung in radiotherapy RT planning for patients with lung cancer.

In subgroup analysis, the functional plan using perfusion was significantly lower than the anatomical plan in all planning parameters, but there was no significant difference for ventilation. RT planning with nuclear functional lung imaging has potential to reduce radiation-induced lung injury. Perfusion imaging seems to be more promising than ventilation imaging for all planning parameters.

There were not enough studies using ventilation imaging to determine what the effect is on the lung plan parameters.

Radiotherapy RT plays a critical role in the management of early or locally advanced stage lung cancer. RT requires adequate coverage of the gross lung tumor as well as adjacent micrometastases for tumor control and sparing of the critical organs including the spinal cord and esophagus to minimize complications. Dose—volume histogram DVH is a plot of a cumulative dose—volume frequency distribution, which graphically summarizes the simulated radiation distribution within a volume of interest of a patient that would result from a proposed radiation treatment plan based on computed tomography CT imaging 2.

However, recent studies have shown that these parameters may not be sufficient to predict the risk of lung toxicity 3 , 4. Since lung cancer is common especially in patients with respiratory comorbidities, such as chronic obstructive pulmonary disease COPD or emphysema related to long-standing smoking or interstitial lung disease, their lung tissue function may be spatially heterogeneous 5.

Local lung function and distribution have been attempted to be quantitatively visualized in a quantitative way with various functional imaging modalities such as single photon emission computed tomography SPECT , positron emission tomography PET , CT ventilation with or without-dimensional 4D technique, and hyperpolarized helium or xenon magnetic resonance imaging MRI. SPECT is a representative modality to design RT field and to provide a direct incidental irradiation away from volumes of well-functioning lung.

Radiation oncologists have information on functional lung regions, and try to avoid irradiation to highly functioning lung tissue and ultimately to reduce pulmonary toxicity. Functional lung avoidance RT prioritizes delivery of high radiation dose to the lung cancer while minimizing RT dose to uninvolved and functional lung, through treatment planning system optimization algorithms 7.

Dose—functional histogram DFH is an emerging concept calculating the dose distribution throughout the functioning and non-functioning lung regions defined by functional imaging, compared to DVH.

There is growing evidence that dose-volume parameters obtained DFH using functional imaging is a better predictor of radiation-induced lung injury RILI than those obtained DVH alone 3 , 4. A recent meta-analysis by Bucknell et al. Currently the clinical standard for functional lung imaging is the nuclear imaging of perfusion. CT ventilation imaging is a new modality that offers a higher resolution images compared with nuclear ventilation images and prove more convenient for patients undergoing RT planning.

However, it showed a weak correlation with perfusion and ventilation SPECT on voxel-wise analysis, thus it needs to be validated against nuclear imaging 9. In this study, we evaluated the feasibility of accurate prediction with nuclear medicine imaging in functional lung avoidance RT planning. Our research questions regarding the patients, intervention, comparison, outcome and study design PICOS approach are described in Table 1.

Two authors S. Lee and H. The studies identified from the literature search were evaluated for duplicates, and then full-text assessments were independently performed by two authors into four indications of the eligibility of an article, based on title and abstract screening.

Many studies were not relevant to our study and were eliminated. All searches were limited to human studies and English language. We did not limit the types of publication or numbers of included patients per study. The inclusion criteria for the relevant studies were as follows:. The publications such as review articles, conference papers, or letters, which do not contain the original data, were excluded.

When the data were published in more than one article, the latest one was included. Two reviewers independently extracted data from each article and recorded them on a standardized form.

Any disagreement in data extraction was resolved by consensus. The following data were extracted from each study:. A quality assessment was developed based on the appraisal standard of the Newcastle—Ottawa scale NOS. Consensus was reached by discussion when disparity occurred.

All analyses and corresponding plots were performed using the statistical software R, version 3. A meta-analysis was performed for the differences in V10, V20, and MLD between anatomical and functional plans. Not all studies provided the mean values and SDs. If raw data were not available and median values with confidence intervals were provided, these were calculated using the methods described The meta-analysis was performed for the standard mean differences SMD between means using inverse variance and random effects.

Publication bias was assessed by Funnel plots and trim-and-fill analysis. After the removal of duplicates, a total of remained. From reading the titles and abstracts, publications judged as potentially relevant were acquired for more detailed evaluation.

Another publications were excluded based on the full text, as they did not meet the eligibility criteria. Subsequently, 18 publications, including 7 articles and 11 conference papers, were excluded due to insufficient data to assess the differences between anatomical and functional plans for RT therapy. Finally, a total of patients with RT plan sets from 15 publications were included for the meta-analysis. According to NOS scale, high and low quality studies were 13 and 2, respectively.

Table 2 shows the characteristics of the included publications. All patients were diagnosed with lung cancer of various stages. The number of included patients per study ranged from 5 to 58 median 15, range 5— Seven studies had a prospective study design, and eight were retrospective studies. Among 15 publications, eleven studies performed perfusion scans for RT, two studies did ventilation scans, and two studies performed both perfusion and ventilation scans.

Among the 13 studies using SPECT, only three mentioned the scanning protocols including projections, acquisition times, and matrix sizes 3 , 15 , Five studies described inadequate scanning information 17 , 18 , 19 , 20 , and the remaining five, including two conference papers, did not mention any information 4 , 21 , 22 , The two studies using PET provided detailed information 24 , The functional images obtained from each modality were co-registered to CT planning images to provide combined datasets for RT planning.

The thresholds of functional lung were variable. There was no threshold in five studies. If there was at least one threshold in the study for functioning lung definition, the highest value of lung volume was selected for the meta-analysis data set. The data of no threshold in nine among 13 publications using perfusion images and in two among four publications using ventilation images were selected for meta-analysis.

Of the patients with lung cancer, DVH and DFH dose-function histograms were computed and compared between the two sets of plans. The SPECT images were resampled to the same voxel dimensions as the planning CT, creating a common frame of reference to allow dose-volume calculations. All of the voxels of the SPECT images were weighted linearly according to SPECT count, and the weighting function was normalized such that its mean value averaged over all lung voxels was one 3 , Table 4 shows the details of RT planning of the 15 included studies.

Each study adopted various definitions of functional lung and dose-volume parameters most included V20 and MLD. Nine studies reported statistically significant benefits in terms of functional lung sparing utilizing functional imaging. One study reported no benefit, and five studies did not report benefits from functional imaging. The 13 articles and two conference papers were eligible for the meta-analysis. In four studies, data were estimated from medians with lowest and highest values using the method of reference The analyses were performed separately for perfusion and ventilation images.

The 14 studies were selected for V20 meta-analysis. Forest plots of standard mean difference between anatomical plan and functional plan. Funnel plots were symmetric, showing an absence of publication bias, which confirmed by trim-and-fill analysis Supplemental Fig. Thirteen studies were selected for the MLD meta-analysis. Two studies included both types of functional images.

Seven studies were included for V10 meta-analysis. Perfusion scans were performed in six studies and ventilation scans were done in two studies. One study included both types of functional images. No significant differences were found in combined or ventilation images.

Funnel plots were asymmetric, showing publication bias, which confirmed by trim-and-fill analysis for MLD and V Supplemental Fig. The current evaluation of RT planning assumes that all lung tissues function equally. However, the 15 studies included in this analysis have suggested that lung function distribution varies among lung regions by visualizing it with nuclear functional lung imaging, and this may enable functional lung avoidance in RT planning.

There were significant improvements with perfusion images, but not with ventilation images. Although our results showed that planning parameters can be improved by integrating nuclear functional imaging with RT planning, there are insufficient data regarding whether functional planning parameters could predict lung toxicity better than standard planning parameters.

Only two studies included in this analysis dealt with the predictive value of functional parameters in RILI. Farr et al. Similarly, Xiao et al. Thomas et al. The effort to preserve lung function without compromising clinical outcomes is crucial for lung RT, considering lung cancer patients are usually old, and have respiratory comorbidities such as COPD or interstitial lung disease, and poor performance status.

Risk-adaptive RT planning using functional lung imaging could be attempted based on our meta-analyses, especially in high-risk lung cancer patients. The modalities and acquisition methods to obtain functional images can influence both image registration and validation between functional images and planning CT. However, the acquisition and processing parameters SPECT acquisition, acquisition time per projection, collimator, matrix size, reconstruction, post-reconstruction filter, etc.

PET versus SPECT: strengths, limitations and challenges

Positron emission tomography PET [1] is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes , and in other physiological activities including blood flow , regional chemical composition, and absorption. Different tracers are used for various imaging purposes, depending on the target process within the body. For example, 18F-FDG is commonly used to detect cancer , NaF-F18 is widely used for detecting bone formation, and oxygen is sometimes used to measure blood flow. PET is a common imaging technique , a medical scintillography technique used in nuclear medicine. Gamma rays are emitted and detected by gamma cameras to form a three-dimensional image, in a similar way that an X-ray image is captured. PET scan images can be reconstructed using a CT scan performed using one scanner during the same session. One of the disadvantages of a PET scanner is its high initial cost and ongoing operating costs.


In SPECT, Single Photon Emission Computerized Tomography, the radionuclide decays by emitting one or more photons, while in PET, Positron Emission Tomography, the radionuclide emits a positron, in order to reach a lower energy level.


New SPECT and PET Radiopharmaceuticals for Imaging Cardiovascular Disease

Oyebola O. Schindler, Lihui Wei, R. Glenn Wells, Terrence D. Nuclear cardiology has experienced exponential growth within the past four decades with converging capacity to diagnose and influence management of a variety of cardiovascular diseases. Single photon emission computed tomography SPECT myocardial perfusion imaging MPI with technetiumm radiotracers or thallium has dominated the field; however new hardware and software designs that optimize image quality with reduced radiation exposure are fuelling a resurgence of interest at the preclinical and clinical levels to expand beyond MPI.

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Nuclear medicine is a medical specialty that uses radioactive tracers radiopharmaceuticals to assess bodily functions and to diagnose and treat disease. Specially designed cameras allow doctors to track the path of these radioactive tracers. Radioactive tracers are made up of carrier molecules that are bonded tightly to a radioactive atom. These carrier molecules vary greatly depending on the purpose of the scan. For example, in cases where doctors need to know the exact source of intestinal bleeding, they may radiolabel add radioactive atoms to a sample of red blood cells taken from the patient.

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3 comments

  • Intimliti1961 22.05.2021 at 11:28

    The moral revolution in atlas shrugged pdf strategic role of human resource management pdf

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  • Emma C. 23.05.2021 at 01:32

    What is the difference between a cardiac PET scan and a cardiac. SPECT scan? This article compares and contrasts these two cardiac imaging techniques.

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  • Evangelina R. 24.05.2021 at 07:27

    Corresponding author.

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