Normal Dual Isotope V/Q SPECT Model for Monte-Carlo Studies

Scintigraphic Diagnosis of Acute Pulmonary Embolism: From Basics to Best Practices

In this article the technique, interpretation, and diagnostic performance of scintigraphy for the diagnosis of acute pulmonary embolism (PE) are reviewed. Lung scintigraphy has stood the test of time as a reliable and validated examination for the determination of PE. Ventilation/perfusion (V/Q) lung scintigraphy assesses the functional consequences of the clot on its downstream vascular bed in conjunction with the underlying ventilatory status of the affected lung region, in contrast to CT pulmonary angiography (CTPA), which visualizes presence of the clot within affected vessels. Most-commonly used ventilation radiopharmaceuticals are Technetium-99m labeled aerosols (such as 99mTechnetium-DTPA), or ultrafine particle suspensions (99mTc-Technegas) which reach the distal lung in proportion to regional distribution of ventilation. Perfusion images are obtained after intravenous administration 99mTc-labeled macro-aggregated albumin particles which lodge in the distal pulmonary capillaries. Both planar and tomographic methods of imaging, each favored in different geographical regions, will be described. Guidelines for interpretation of scintigraphy have been issues by both the Society of Nuclear Medicine and Molecular Imaging, and by the European Association of Nuclear Medicine. Breast tissue is particularly radiosensitive during pregnancy due to its highly proliferative state and many guidelines recommend use of lung scintigraphy rather than CTPA in this population. Several maneuvers are available in order to further reduce radiation exposure including reducing radiopharmaceutical dosages or omitting ventilation altogether, functionally converting the study to a low-dose screening examination; if perfusion defects are present, further testing is necessary. Several groups have also performed perfusion-only studies during the COVID epidemic in order to reduce risk of respiratory contagion. In patients where perfusion defects are present, further testing is again necessary to avoid false-positive results. Improved availability of personal protective equipment, and reduced risk of serious infection, have rendered this maneuver moot in most practices. First introduced 60 years ago, subsequent advances in radiopharmaceutical development and imaging methods have positioned lung scintigraphy to continue to play an important clinical and research role in the diagnosis of acute PE.

Association of Body Composition with Pulmonary Function in Ningxia: The China Northwest Cohort

BACKGROUND

In recent decades, obesity has become an epidemic worldwide and is a risk factor for many chronic diseases. Lung function is also a predictor of various chronic diseases. However, research results on the association between obesity and lung function are inconsistent and few studies have evaluated the association between central obesity indicators and lung function. Therefore, this study explored the correlation between central obesity and lung function.

METHODS

This study is a cross-sectional study. The basic participant characteristics were collected by questionnaire. A tape measure was used to measure waist circumference (WC) and hip circumference (HC). Body fat percentage was measured using an InBody370. Lung function parameters were measured using a digital spirometer connected to a computer (Chestgraph HI-101). R (R4.0.5) software was used for data analysis. A generalized linear model was used to analyze the association between obesity and lung function.

RESULTS

This study found that body mass index (BMI) adjusted for WC was negatively correlated with forced vital capacity (FVC) (β=-0.05 [-0.06, -0.03] in men, β=-0.05 [-0.07, -0.04] in women) and forced expiratory volume in 1 s (FEV1)(β=-0.02 [-0.03, -0.00] in men, β=-0.03 [-0.04, -0.02] in women). Body fat percentage was negatively correlated with FVC (β=-0.01 [-0.01, -0.01] in men, β=-0.01 [-0.01, -0.00] in women).

CONCLUSION

Central obesity and combined central and general obesity were more strongly positively correlated with lung function. WC-adjusted BMI was negatively correlated with lung function. Body fat percentage was negatively correlated with lung function.

Automatic delineation and quantification of pulmonary vascular obstruction index in patients with pulmonary embolism using Perfusion SPECT-CT: a simulation study

Background

In patients with pulmonary embolism (PE), there is a growing interest in quantifying the pulmonary vascular obtruction index (PVOI), which may be an independent risk factor for PE recurrence. Perfusion SPECT/CT is a very attractive tool to provide an accurate quantification of the PVOI. However, there is currently no reliable method to automatically delineate and quantify it. The aim of this phantom study was to assess and compare 3 segmentation methods for PVOI quantification with perfusion SPECT/CT imaging.

Methods

Three hundred ninety-six SPECT/CT scans, with various PE scenarios (n = 44), anterior to posterior perfusion gradients (n = 3), and lung volumes (n = 3) were simulated using Simind software. Three segmentation methods were assesssed: (1) using an intensity threshold expressed as a percentage of the maximal voxel value (MaxTh), (2) using a Z-score threshold (ZTh) after building a Z-score parametric lung map, and (3) using a relative difference threshold (RelDiffTh) after building a relative difference parametric map. Ninety randomly selected simulations were used to define the optimal threshold, and 306 simulations were used for the complete analysis. Spacial correlation between PE volumes from the phantom data and the delineated PE volumes was assessed by computing DICE_PE indices. Bland-Altman statistics were used to calculate agreement for PVOI between the phantom data and the segmentation methods.

Results

Mean DICE_PE index was higher with the RelDiffTh method (0.85 ± 0.08), as compared with the MaxTh method (0.78 ± 0.16) and the ZTh method (0.67 ± 0.15). Using the RelDiffTh method, mean DICE_PE index remained high (> 0.81) regardless of the perfusion gradient and the lung volumes. Using the RelDiffTh method, mean relative difference in PVOI was − 12%, and the limits of agreement were − 40% to 16%. Values were 3% (− 75% to 81%) for MaxTh method and 0% (− 120% to 120%) for ZTh method. Graphycal analysis of the Bland-Altman graph for the RelDiffTh method showed very close estimation of the PVOI for small and medium PE, and a trend toward an underestimation of large PE.

Conclusion

In this phantom study, a delineation method based on a relative difference parametric map provided a good estimation of the PVOI, regardless of the extent of PE, the intensity of the anterior to posterior gradient, and the whole lung volumes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-021-00396-1.