Added Value of Respiratory Gating in Positron Emission Tomography for the Clinical Management of Lung Cancer Patients

Harnessing pseudogenes for lung cancer: A novel epigenetic target in diagnosis, prognosis and treatment

Pseudogenes are abundantly present in the human genome and are often thought of as nonfunctional nucleotide sequences, but a growing body of research suggests that pseudogenes can play important biological roles through a variety of pathways, and can be involved in the development of cancer. Lung cancer is one of the most prevalent cancers in the world and it is crucial to find new therapeutic strategies for the treatment of lung cancer. In recent years, studies on the effects of pseudogenes on lung carcinogenesis have increased rapidly. This has pointed to new directions in the diagnosis and treatment of lung cancer. Aim of this paper is to comprehensively discuss the role and influence of pseudogenes in the lung cancer, and the potential of pseudogenes as novel epigenetic targets in lung cancer diagnosis and prognosis and treatment, which is significant for realizing the clinical benefits of pseudogenes.

Effectiveness of Data-Driven Gating FDG PET/CT for Abdominal Region

This study aimed to validate the effectiveness of MotionFree (MF) in the abdominal region using 2 different PET/CT scanners to determine how to use MF efficiently. Methods: All 198 patients underwent respiratory-gated 18F-FDG PET/CT with MF. Imaging was performed using Discovery MI (DMI) and Discovery IQ (DIQ) PET/CT scanners, and all data were divided into 2 groups in each category (abdominal: upper and lower abdomen, lesion size, <20 mm and ≥20 mm; scanner group: DMI and DIQ). A physician assessed whether the respiratory motion artifacts were reduced with MF. The SUV change rate (ΔSUV) of 80 measurable lesions with and without MF was calculated. The relationship between the ΔSUVs and these groups was compared. Results: Motion artifacts were reduced in 62 of 198 patients (31.3%) in the upper abdomen, in 1 of 198 patients (0.5%) in the lower abdomen, in 51 of 98 patients (52.0%) in the DMI, and in 12 of 100 patients (12.0%) in DIQ with MF. ΔSUVs were significantly higher in the upper abdomen than in the lower abdomen. ΔSUV was up to 58.3% in DMI and up to 47.6% in DIQ. ΔSUVs of lesions with a size of less than 20 mm were significantly higher than those with a lesion size of 20 mm or greater. Although DMI was more effective than DIQ in terms of motion artifacts, both DMI and DIQ have the potential to increase the SUV with MF. MF significantly reduced the respiratory motion artifacts and increased the SUV for lesions smaller than 20 mm in the upper abdomen. Conclusion: MF reduced the motion artifacts in higher-spatial-resolution PET/CT images. In both PET/CT scanners, SUVs in lesions smaller than 20 mm and lesions in the upper abdomen increased significantly with MF. To use MF without increasing the acquisition time, it may be useful to apply it to the upper abdomen.

Assessment of pulmonary nodules using [18F]-FDG PET/CT in deep inspiration breath-hold

The characterization of pulmonary nodules (PN) is a primary indication for [18F]-FDG PET/CT. However, respiratory movements hinder this characterization, especially for PN located in the lower lobes. Various methods have been developed to improve image resolution.

OBJECTIVE

Our objective was to compare the diagnostic efficacy of [18F]-FDG PET/CT in deep inspiration breath-hold (DIBH) versus free-breathing corrected by software, in the evaluation of PN.

METHODS

We prospectively analyzed 51 patients to assess PN using [18F]-FDG PET/CT in DIBH and free-breathing corrected by software. A total of 84 nodules with an average size of 10 mm were analyzed, with pathological anatomy or medical treatment decide by a multidisciplinary tumor board used as reference.

RESULTS

A total of 84 PN were evaluated, comparing those in DIBH versus free-breathing, finding statistically significant differences in SUVmax values P(< 0.05) (mean SUVmax 3.7 in free-breathing vs. 5.33 in DIBH). When analyzed by location in lobes, we did not find statistically significant differences, though there was a trend towards higher SUVmax values in the lower lobes. [18F]-FDG PET/CT in DIBH showed high sensitivity (95%) and negative predictive value (NPV) (92%), indicating it may be a promising tool for PN characterization.

CONCLUSIONS

The acquisition of [18F]-FDG PET/CT in DIBH significantly improves the sensitivity and diagnostic efficacy in the assessment of PN. Although no statistically significant differences were found based on location, there is a potential benefit for the lower lobes. These findings could support its use in clinical practice.

Quantitative 18F-FDG PET-CT can assess presence and extent of interstitial lung disease in early severe diffuse cutaneous systemic sclerosis

BACKGROUND

This study aimed to assess the quantitative uptake of 18F-FDG PET-CT in the lungs of patients with early severe diffuse cutaneous systemic sclerosis (SSc) with and without interstitial lung disease (ILD), compared to controls. In patients with SSc-ILD, 18F-FDG uptake was correlated to high-resolution computed tomography (HRCT) and pulmonary function test (PFT) parameters.

METHODS

A prospective, cross-sectional study was conducted, involving 15 patients with SSc-ILD, 5 patients with SSc without ILD, and 7 controls without SSc. 18F-FDG PET-CT scans were performed following standardized protocols, and quantitative analysis of tracer uptake was conducted in predefined lung regions. In addition, HRCT scans were evaluated for ILD-related radiologic abnormalities. Between-group differences were compared with non-parametric tests, while correlations with PFT parameters were analyzed using Spearman correlation coefficients.

RESULTS

18F-FDG uptake was mainly increased in the dorsobasal lung fields of patients with SSc-ILD compared to SSc without ILD and controls (p = 0.03 and p < 0.001, respectively). 18F-FDG uptake was higher in SSc patients with extensive ILD (≥ 20% vs < 20%, p = 0.04) and correlated with lower DLCO% (R = -0.59, p = 0.02). Ground-glass opacities, with or without reticulation, corresponded to increased 18F-FDG uptake.

CONCLUSIONS

18F-FDG PET-CT can detect metabolic activity in the lungs of patients with early severe diffuse cutaneous SSc and ILD, correlating with higher ILD extent (≥ 20%) and lower DLCO%. These results suggest the potential utility of 18F-FDG PET-CT in the early detection of ILD (progression) and aiding in risk stratification.

Comparison of the variability and diagnostic efficacy of respiratory-gated PET/CT based radiomics features with ungated PET/CT in lung lesions

OBJECTIVES

To investigate the variability and diagnostic efficacy of respiratory-gated (RG) PET/CT based radiomics features compared to ungated (UG) PET/CT in the differentiation of non-small cell lung cancer (NSCLC) and benign lesions.

METHODS

117 patients with suspected lung lesions from March 2020 to May 2021 and consent to undergo UG PET/CT and chest RG PET/CT (including phase-based quiescent period gating, pQPG and phase-matched 4D PET/CT, 4DRG) were prospectively included. 377 radiomics features were extracted from PET images of each scan. Paired t test was used to compare UG and RG features for inter-scan variability analysis. We developed three radiomics models with UG and RG features (i.e. UGModel, pQPGModel and 4DRGModel). ROC curves were used to compare diagnostic efficiencies, and the model-level comparison of diagnostic value was performed by five-fold cross-validation. A P value < 0.05 was considered as statistically significant.

RESULTS

A total of 111 patients (average age ± standard deviation was 59.1 ± 11.6 y, range, 29 - 88 y, and 63 were males) with 209 lung lesions were analyzed for features variability and the subgroup of 126 non-metastasis lesions in 91 patients without treatment before PET/CT were included for diagnosis analysis. 101/377 (26.8 %) 4DRG features and 82/377 (21.8 %) pQPG features showed significant difference compared to UG features (both P<0.05). 61/377 (16.2 %) and 59/377 (15.6 %) of them showed significantly better discriminant ability (ΔAUC% (i.e. (AUCRG - AUCUG) / AUCUG×100 %) > 0 and P<0.05) in malignant recognition, respectively. For the model-level comparison, 4DRGModel achieved the highest diagnostic efficacy (sen 73.2 %, spe 87.3 %) compared with UGModel (sen 57.7 %, spe 76.4 %) and pQPGModel (sen 63.4 %, spe 81.8 %).

CONCLUSION

RG PET/CT performs better in the quantitative assessment of metabolic heterogeneity for lung lesions and the subsequent diagnosis in patients with NSCLC compared with UG PET/CT.

Data-driven gating (DDG)-based motion match for improved CTAC registration

BACKGROUND

Respiratory motion artefacts are a pitfall in thoracic PET/CT imaging. A source of these motion artefacts within PET images is the CT used for attenuation correction of the images. The arbitrary respiratory phase in which the helical CT ( CT helical ) is acquired often causes misregistration between PET and CT images, leading to inaccurate attenuation correction of the PET image. As a result, errors in tumour delineation or lesion uptake values can occur. To minimise the effect of motion in PET/CT imaging, a data-driven gating (DDG)-based motion match (MM) algorithm has been developed that estimates the phase of the CT helical , and subsequently warps this CT to a given phase of the respiratory cycle, allowing it to be phase-matched to the PET. A set of data was used which had four-dimensional CT (4DCT) acquired alongside PET/CT. The 4DCT allowed ground truth CT phases to be generated and compared to the algorithm-generated motion match CT (MMCT). Measurements of liver and lesion margin positions were taken across CT images to determine any differences and establish how well the algorithm performed concerning warping the CT helical to a given phase (end-of-expiration, EE).

RESULTS

Whilst there was a minor significance in the liver measurement between the 4DCT and MMCT ( p = 0.045 ), no significant differences were found between the 4DCT or MMCT for lesion measurements ( p = 1.0 ). In all instances, the CT helical was found to be significantly different from the 4DCT ( p < 0.001 ). Consequently, the 4DCT and MMCT can be considered equivalent with respect to warped CT generation, showing the DDG-based MM algorithm to be successful.

CONCLUSION

The MM algorithm successfully enables the phase-matching of a CT helical to the EE of a ground truth 4DCT. This would reduce the motion artefacts caused by PET/CT registration without requiring additional patient dose (required for a 4DCT).

Positron emission tomography in the diagnosis and management of primary pediatric lung tumors

Primary pediatric lung tumors are uncommon and have many overlapping clinical and imaging features. In contrast to adult lung tumors, these rare pediatric neoplasms have a relatively broad histologic spectrum. Informed by a single-institution 13-year retrospective record review, we present an overview of the most common primary pediatric lung neoplasms, with a focus on the role of positron emission tomography (PET), specifically 18F-fluorodeoxyglucose (FDG) PET and 68Ga-DOTATATE PET, in the management of primary pediatric lung tumors. In addition to characteristic conventional radiographic and cross-sectional imaging findings, knowledge of patient age, underlying cancer predisposition syndromes, and PET imaging features may help narrow the differential. While metastases from other primary malignancies remain the most commonly encountered pediatric lung malignancy, the examples presented in this pictorial essay highlight many of the important conventional radiologic and PET imaging features of primary pediatric lung malignancies.

Improving respiratory signal prediction with a deep neural network and simple changes to the input and output data format

Objective.To improve respiratory gating accuracy and radiation treatment throughput, we developed a generalized model based on a deep neural network (DNN) for predicting any given patient's respiratory motion.Approach.Our model uses long short-term memory (LSTM) based on a recurrent neural network (RNN), and improves upon common techniques. The first improvement is that the data input is not a one-dimensional sequence, but two-dimensional block data. This shortens the input sequence length, reducing computation time. Second, the output is not a scalar, but a sequence prediction. This increases the amount of available data, allowing improved prediction accuracy. For training and evaluation of our model, 434 sets of real-time position management data were retrospectively collected from clinical studies. The data were separated in a ratio of 4:1, with the larger set used for training models and the remaining set used for testing. We measured the accuracy of respiratory signal prediction and amplitude-based gating with prediction windows equaling 133, 333, and 533 ms. This new model was compared with the original LSTM and a non-recurrent DNN model.Main results.The mean absolute errors with the prediction window at 133, 333 and 533 ms were 0.036, 0.084, 0.119 with our model; 0.049, 0.14, 0.246 with the original LSTM-based model; and 0.041, 0.119, 0.16 with the non-recurrent DNN model, respectively. The computation time were 0.66 ms with our model; 0.63 ms the original LSTM-based model; 1.60 ms the non-recurrent DNN model, respectively. The accuracies of amplitude-based gating with the same prediction window settings and a duty cycle of approximately 50% were 98.3%, 95.8% and 92.7% with our model, 97.6%, 93.9% and 87.2% with the original LSTM-based model; and 97.9%, 94.3% and 89.5% with the non-recurrent DNN model, respectively.Significance.Our RNN algorithm for respiratory signal prediction successfully estimated tumor positions. We believe it will be useful in respiratory signal prediction technology.

Method for comparison of data driven gating algorithms in emission tomography

Objective.Multiple algorithms have been proposed for data driven gating (DDG) in single photon emission computed tomography (SPECT) and have successfully been applied to myocardial perfusion imaging (MPI). Application of DDG to acquisition types other than SPECT MPI has not been demonstrated so far, as limitations and pitfalls of current methods are unknown.Approach.We create a comprehensive set of phantoms simulating the influence of different motion artifacts, view angles, moving objects, contrast, and count levels in SPECT. We perform Monte Carlo simulation of the phantoms, allowing the characterization of DDG algorithms using quantitative metrics derived from the data and evaluate the Center of Light (COL) and Laplacian Eigenmaps methods as sample DDG algorithms.Main results.View angle, object size, count rate density, and contrast influence the accuracy of both DDG methods. Moreover, the ability to extract the respiratory motion in the phantom was shown to correlate with the contrast of the moving feature to the background, the signal to noise ratio, and the noise in the data.Significance.We showed that reporting the average correlation to an external physical reference signal per acquisition is not sufficient to characterize DDG methods. Assessing DDG methods on a view-by-view basis using the simulations and metrics from this work could enable the identification of pitfalls of current methods, and extend their application to acquisitions beyond SPECT MPI.

Nuclear medicine imaging methods as novel tools in the assessment of pulmonary drug disposition

INTRODUCTION

Drugs for the treatment of respiratory diseases are commonly administered by oral inhalation. Yet surprisingly little is known about the pulmonary pharmacokinetics of inhaled molecules. Nuclear medicine imaging techniques (i.e. planar gamma scintigraphy, single-photon emission computed tomography [SPECT] and positron emission tomography [PET]) enable the noninvasive dynamic measurement of the lung concentrations of radiolabeled drugs or drug formulations. This review discusses the potential of nuclear medicine imaging techniques in inhalation biopharmaceutical research.

AREAS COVERED

(i) Planar gamma scintigraphy studies with radiolabeled inhalation formulations to assess initial pulmonary drug deposition; (ii) imaging studies with radiolabeled drugs to assess their intrapulmonary pharmacokinetics; (iii) receptor occupancy studies to quantify the pharmacodynamic effect of inhaled drugs.

EXPERT OPINION

Imaging techniques hold potential to bridge the knowledge gap between animal models and humans with respect to the pulmonary disposition of inhaled drugs. However, beyond the mere assessment of the initial lung deposition of inhaled formulations with planar gamma scintigraphy, imaging techniques have rarely been employed in pulmonary drug development. This may be related to several technical challenges encountered with such studies. Considering the wealth of information that can be obtained with imaging studies their use in inhalation biopharmaceutics should be further investigated.

Editorial on Special Issue "Quantitative PET and SPECT"

Since the introduction of personalized (or precision) medicine, where individually tailored treatments are designed to deliver the right treatment to the right patient at the right time, the primary focus of imaging has moved from detection and diagnosis to tissue characterization, determination of prognosis, prediction of treatment efficacy, and measurement of treatment response [...].