FDG-PET/CT in the prediction of pulmonary function improvement in nonspecific interstitial pneumonia. A Pilot Study

Mesenchymal-epithelial Transition Exon 14-skipping Mutation-positive Invasive Mucinous Adenocarcinoma of the Lung: First Case Treated with Mesenchymal-epithelial Transition-tyrosine Kinase Inhibitors

Mesenchymal-epithelial transition (MET) exon 14-skipping mutation (METex14) is rare in pulmonary invasive mucinous adenocarcinomas (IMAs), and the clinical impact of MET-tyrosine kinase inhibitors (TKIs) remains unknown. We herein report a 75-year-old woman with IMA harboring METex14 who was treated with the MET-TKI tepotinib. The lung tumor regressed over six months; however, the patient ultimately died of exacerbated interstitial lung disease (ILD), possibly associated with tepotinib. An autopsy revealed diffuse alveolar damage in pre-existing chronic fibrosis. We discuss how to pre-evaluate ILD deterioration risks and monitor TKI-induced lung toxicity during treatment.

Imaging at the nexus: how state of the art imaging techniques can enhance our understanding of cancer and fibrosis

Both cancer and fibrosis are diseases involving dysregulation of cell signaling pathways resulting in an altered cellular microenvironment which ultimately leads to progression of the condition. The two disease entities share common molecular pathophysiology and recent research has illuminated the how each promotes the other. Multiple imaging techniques have been developed to aid in the early and accurate diagnosis of each disease, and given the commonalities between the pathophysiology of the conditions, advances in imaging one disease have opened new avenues to study the other. Here, we detail the most up-to-date advances in imaging techniques for each disease and how they have crossed over to improve detection and monitoring of the other. We explore techniques in positron emission tomography (PET), magnetic resonance imaging (MRI), second generation harmonic Imaging (SGHI), ultrasound (US), radiomics, and artificial intelligence (AI). A new diagnostic imaging tool in PET/computed tomography (CT) is the use of radiolabeled fibroblast activation protein inhibitor (FAPI). SGHI uses high-frequency sound waves to penetrate deeper into the tissue, providing a more detailed view of the tumor microenvironment. Artificial intelligence with the aid of advanced deep learning (DL) algorithms has been highly effective in training computer systems to diagnose and classify neoplastic lesions in multiple organs. Ultimately, advancing imaging techniques in cancer and fibrosis can lead to significantly more timely and accurate diagnoses of both diseases resulting in better patient outcomes.

[68Ga]FAPI PET for Imaging and Treatment Monitoring in a Preclinical Model of Pulmonary Fibrosis: Comparison to [18F]FDG PET and CT

PURPOSE

This study aimed to evaluate the feasibility of using [68Ga]-fibroblast-activating protein inhibitor (FAPI) positron emission tomography (PET) imaging for diagnosing pulmonary fibrosis in a mouse model. We also examined its value in monitoring treatment response and compared it with traditional [18F]-fluorodeoxyglucose (FDG) PET and computed tomography (CT) imaging.

METHODS

A model of idiopathic pulmonary fibrosis was established using intratracheal injection of bleomycin (BLM, 2 mg/kg) into C57BL/6 male mice. For the treatment of IPF, a daily oral dose of 400 mg/kg/day of pirfenidone was administered from 9 to 28 days after the establishment of the model. Disease progression and treatment efficacy were assessed at different stages of the disease every week for four weeks using CT, [18F]FDG PET, and [68Ga]FAPI PET (baseline imaging performed at week 0). Mice were sacrificed and lung tissues were harvested for hematoxylin-eosin staining, picrosirius red staining, and immunohistochemical staining for glucose transporter 1 (GLUT1) and FAP. Expression levels of GLUT1 and FAP in pathological sections were quantified. Correlations between imaging parameters and pathological quantitative values were analyzed.

RESULTS

CT, [18F]FDG PET and [68Ga]FAPI PET revealed anatomical and functional changes in the lung that reflected progression of pulmonary fibrosis. In untreated mice with pulmonary fibrosis, lung uptake of [18F]FDG peaked on day 14, while [68Ga]FAPI uptake and mean lung density peaked on day 21. In mice treated with pirfenidone, mean lung density and lung uptake of both PET tracers decreased. Mean lung density, [18F]FDG uptake, and [68Ga]FAPI uptake correlated well with quantitative values of picrosirius red staining, GLUT1 expression, and FAP expression, respectively. Conclusions: Although traditional CT and [18F]FDG PET reflect anatomical and metabolic status in fibrotic lung, [68Ga]FAPI PET provides a means of evaluating fibrosis progression and monitoring treatment response.

Can FDG-PET/CT imaging be used to predict decline in quality of life in interstitial lung disease? A prospective study of the relationship between FDG uptake and quality of life in a UK outpatient setting

BACKGROUND

18Fluorine-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) CT imaging has been used in many inflammatory and infectious conditions to differentiate areas of increased metabolic activity. FDG uptake differs between areas of normal lung parenchyma and interstitial lung disease (ILD).

OBJECTIVES

In this study, we investigated whether FDG-PET/CT parameters were associated with a change in the quality of life (QoL) in patients with ILD over 4 years of follow-up.

METHODS

Patients underwent PET-CT imaging at diagnosis and were followed up with annual QoL assessment using the St George's Respiratory Questionnaire (SGRQ) until death or 4 years of follow-up. Maximum standard uptake value (SUVmax) and Tissue-to-Background Ratio (TBR) were assessed against SGRQ overall and subscale scores.

RESULTS

193 patients (94 patients in the idiopathic pulmonary fibrosis (IPF) subgroup and 99 patients in the non-IPF subgroup) underwent baseline FDG-PET/CT imaging and QoL assessment. Weak-to-moderate correlation was observed between baseline SUVmax and SGRQ scores in both ILD subgroups. No relationship was observed between baseline SUVmax or TBR and change in SGRQ scores over 4 years of follow-up. In the IPF subgroup, surviving patients reported a decline in QoL at 4 years post diagnosis whereas an improvement in QoL was seen in surviving patients with non-IPF ILD.

CONCLUSIONS

Weak-to-moderate positive correlation between baseline SUVmax and SGRQ scores was observed in both ILD subgroups (IPF:rs=0.187, p=0.047, non-IPF: rs=0.320, p=0.001). However, baseline SUVmax and TBR were not associated with change in QoL in patients with IPF and non-IPF ILD over 4 years of follow-up. At 4 years post diagnosis, surviving patients with IPF reported declining QoL whereas improvement was seen in patients with ILD who did not have IPF.

Novel tracers for molecular imaging of interstitial lung disease: A state of the art review

Interstitial lung disease is an overarching term for a wide range of disorders characterized by inflammation and/or fibrosis in the lungs. Most prevalent forms, among others, include idiopathic pulmonary fibrosis (IPF) and connective tissue disease associated interstitial lung disease (CTD-ILD). Currently, only disease modifying treatment options are available for IPF and progressive fibrotic CTD-ILD, leading to reduction or stabilization in the rate of lung function decline at best. Management of these patients would greatly advance if we identify new strategies to improve (1) early detection of ILD, (2) predicting ILD progression, (3) predicting response to therapy and (4) understanding pathophysiology. Over the last years, positron emission tomography (PET) and single photon emission computed tomography (SPECT) have emerged as promising molecular imaging techniques to improve ILD management. Both are non-invasive diagnostic tools to assess molecular characteristics of an individual patient with the potential to apply personalized treatment. In this review, we encompass the currently available pre-clinical and clinical studies on molecular imaging with PET and SPECT in IPF and CTD-ILD. We provide recommendations for potential future clinical applications of these tracers and directions for future research.

Assessment of disease outcome measures in systemic sclerosis

The assessment of disease activity in systemic sclerosis (SSc) is challenging owing to its heterogeneous manifestations across multiple organ systems, the variable rate of disease progression and regression, and the relative paucity of patients in early-phase therapeutic trials. Despite some recent successes, most clinical trials have failed to show efficacy, underscoring the need for improved outcome measures linked directly to disease pathogenesis, particularly applicable for biomarker studies focused on skin disease. Current outcome measures in SSc-associated interstitial lung disease and SSc skin disease are largely adequate, although advancing imaging technology and the incorporation of skin mRNA biomarkers might provide opportunities for earlier detection of the therapeutic effect. Biomarkers can further inform pathogenesis, enabling early phase trials to act as reverse translational studies through the incorporation of routine high-throughput sequencing.

Positron Emission Tomography to Improve Assessment of Interstitial Lung Disease in Patients With Systemic Sclerosis Eligible for Autologous Stem Cell Transplantation

Positron emission tomography (PET) is a promising technique to improve the assessment of systemic sclerosis associated interstitial lung disease (SSc-ILD). This technique could be of particular value in patients with severe diffuse cutaneous SSc (dcSSc) that are possibly eligible for autologous hematopoietic stem cell transplantation (aHSCT). aHSCT is a potentially effective therapy for patients with severe dcSSc and ILD, leading to stabilization or improvement of lung function. However, there is a high need to improve patient selection, which includes (1) the selection of patients with rapidly progressive ILD for early rather than last-resort aHSCT (2) the prediction of treatment response on ILD and (3) the understanding of the mechanism(s) of action of aHSCT in the lungs. As previous studies with 18F-FDG PET in SSc-ILD and other forms of ILD have demonstrated its potential value in predicting disease progression and reactivity to anti-inflammatory treatment, we discuss the potential benefit of using this technique in patients with early severe dcSSc and ILD in the context of aHSCT. In addition, we discuss the potential value of other PET tracers in the assessment of ILD and understanding the mechanisms of action of aHSCT in the lung. Finally, we provide several suggestions for future research.

Nonmalignant Thoracic Disorders: An Appraisal of Fluorodeoxyglucose and Non-fluorodeoxyglucose PET/Computed Tomography Applications

PET/computed tomography (CT) with fluorodeoxyglucose and nonfluorodeoxyglucose PET tracers has established itself in the management of malignant disorders. Its role in the assessment of nonmalignant conditions, such as infectious and noninfectious inflammatory diseases and other benign conditions, has emerged independently and alongside its role being evaluated in malignancy and continues to evolve. It is evident that PET/CT has the potential to play a significant role in various nonmalignant disorders of the thorax. This review highlights current developments and areas where PET/CT has a potential to impact the clinical management of nonmalignant thoracic conditions with special focus on nonfluorodeoxyglucose tracers.

18F-FDG PET/CT and HRCT: a combined tool for risk stratification in idiopathic inflammatory myopathy-associated interstitial lung disease

OBJECTIVES

Rapidly progressive interstitial lung disease (RP-ILD) is a life-threatening form of idiopathic inflammatory myopathy (IIM)-associated interstitial lung disease (ILD). We aimed to assess the combination of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) and high-resolution computed tomography (HRCT) for the quantification of IIM-ILD activity and risk stratification for RP-ILD.

METHOD

Patients with IIM and undergoing ¹⁸F-FDG PET/CT were included in this retrospective study. Pulmonary FDG uptake was assessed using the maximum standardized uptake value (SUV_lung) and visual score (PET score). HRCT was evaluated using visual analysis (HRCT score). Multivariable logistic regression was used to identify risk factors for RP-ILD.

RESULTS

Seventy-three patients with IIM (17 with RP-ILD, 38 with non-RP-ILD, and 18 without ILD) were included. SUV_lung, PET score, and HRCT score were significantly higher in RP-ILD than in non-RP-ILD. Strong positive correlations were observed between SUV_lung, PET score, and the HRCT parameters. The area under the curve (AUC) of the PET score to differentiate between RP-ILD and non-RP-ILD (AUC = 0.860) was higher than that of the SUV_lung (AUC = 0.802) and HRCT scores (AUC = 0.806). We developed a risk score based on the number of positive risk factors (PET score > 18, HRCT score > 140, and positive anti-melanoma differentiation-associated gene 5 (MDA5) antibody) to differentiate between RP-ILD and non-RP-ILD (AUC = 0.955). Patients with higher risk scores had significantly worse prognoses.

CONCLUSIONS

¹⁸F-FDG PET/CT is useful for assessing disease activity in patients with IIM-ILD. The combination of PET score, HRCT score, and anti-MDA5 antibody can be used to identify patients at increased risk of RP-ILD and with poor prognoses.

Overview of positron emission tomography in functional imaging of the lungs for diffuse lung diseases

Positron emission tomography (PET) is a quantitative molecular imaging modality increasingly used to study pulmonary disease processes and drug effects on those processes. The wide range of drugs and other entities that can be radiolabeled to study molecularly targeted processes is a major strength of PET, thus providing a noninvasive approach for obtaining molecular phenotyping information. The use of PET to monitor disease progression and treatment outcomes in DLD has been limited in clinical practice, with most of such applications occurring in the context of research investigations under clinical trials. Given the high costs and failure rates for lung drug development efforts, molecular imaging lung biomarkers are needed not only to aid these efforts but also to improve clinical characterization of these diseases beyond canonical anatomic classifications based on computed tomography. The purpose of this review article is to provide an overview of PET applications in characterizing lung disease, focusing on novel tracers that are in clinical development for DLD molecular phenotyping, and briefly address considerations for accurately quantifying lung PET signals.

Pulmonary functional imaging (PFI): A historical review and perspective

PFI Pulmonary Functional Imaging (PFI) refers to visualization and measurement of ventilation, perfusion, gas flow and exchange as well as biomechanics. In this review, we will highlight the historical development of PFI, describing recent advances and listing the various techniques for PFI offered per modality. Challenges PFI is facing and requirements for PFI from a clinical point of view will be pointed out. Hereby the review is meant as an introduction to PFI.

Side Effects of Oncologic Treatment in the Chest: Manifestations at FDG PET/CT

Fluorodeoxyglucose (FDG) PET/CT is a vital imaging technique used for staging, assessing treatment response, and restaging following completion of therapy in patients who are undergoing or have completed oncologic treatment. A variety of adverse effects from chemotherapy, targeted therapy, immunotherapy, and radiation therapy are commonly encountered in oncologic patients. It is important to be aware of the manifestations of these adverse effects seen on FDG PET/CT images to avoid misinterpreting these findings as disease progression. Furthermore, early identification of these complications is important, as it may significantly affect patient management and even lead to a change in treatment strategy. The authors focus on the FDG PET/CT manifestations of a broad spectrum of oncologic therapy-related adverse effects in the thorax, as well as some treatment-related changes that may potentially mimic malignancy. Online supplemental material is available for this article. ^©RSNA, 2021.

ACR Appropriateness Criteria® Diffuse Lung Disease

Diffuse lung disease, frequently referred to as interstitial lung disease, encompasses numerous disorders affecting the lung parenchyma. The potential etiologies of diffuse lung disease are broad with several hundred established clinical syndromes and pathologies currently identified. Imaging plays a critical role in diagnosis and follow-up of many of these diseases, although multidisciplinary discussion is the current standard for diagnosis of several DLDs. This document aims to establish guidelines for evaluation of diffuse lung diseases for 1) initial imaging of suspected diffuse lung disease, 2) initial imaging of suspected acute exacerbation or acute deterioration in cases of confirmed diffuse lung disease, and 3) clinically indicated routine follow-up of confirmed diffuse lung disease without acute deterioration. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Prone position [18F]FDG PET/CT to reduce respiratory motion artefacts in the evaluation of lung nodules

OBJECTIVES

2-Deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) positron-emission tomography/computed tomography (PET/CT) is widely used to evaluate lung nodules, although respiratory motion artefacts may occur. We investigated the value of prone position PET/CT (pPET/CT) in lung nodule evaluation compared with standard supine position PET/CT (sPET/CT).

METHODS

We retrospectively reviewed 28 consecutive patients (20 men; age, 65.6 ± 12.1 years) with a lung nodule (size, 16.8 ± 5.5 mm) located below the sub-carinal level who underwent [¹⁸F]FDG PET/CT in a standard supine position and additional prone position. The maximum standardised uptake value (SUV_max), metabolic tumour volume (MTV), difference of diaphragm position between PET and CT (DDP), Dice's similarity coefficient (DSC) and occurrence of mis-registration were analysed. The [¹⁸F]FDG uptake of 20 biopsy-confirmed (15 malignant) nodules was evaluated visually.

RESULTS

pPET/CT yielded a significantly higher SUV_max, lower MTV and shorter DDP than with sPET/CT (p = 0.043, 0.007 and 0.021, respectively). Mis-registration occurred in 53.6% of cases in sPET/CT and in 28.6% of cases in pPET/CT (p = 0.092). Among the 15 patients with mis-registration in sPET/CT, 10 patients (66.7%) did not show mis-registration in pPET/CT. DSC was higher in pPET/CT than in sPET/CT in 18 out of 28 patients (64.3%). In visual analysis, malignant nodules exhibited a higher [¹⁸F]FDG uptake positivity than benign nodules in pPET/CT (93.3% vs. 40.0%, p = 0.032) but not in sPET/CT (80.0% vs. 40.0%, p = 0.131).

CONCLUSIONS

pPET/CT reduces respiratory motion artefact and enables more-precise measurements of PET parameters.

KEY POINTS

• In prone position PET/CT, the decrease in the blurring effect caused by reduced respiratory motion resulted in a higher SUV_max and lower MTV in lung nodules than that with supine position PET/CT. • Prone position PET/CT was useful to interpret correctly malignant lung nodules as being positive in individual cases that had a negative result in supine position PET/CT.

18F-FDG positron emission tomography scanning in systemic sclerosis-associated interstitial lung disease: a pilot study

Background

Interstitial lung disease is a common complication of systemic sclerosis (SSc-ILD), and it remains difficult to accurately predict its course. Progressing ILD could be more metabolically active, suggesting that the ¹⁸F-FDG tracer could be a tool in the managing of SSc-ILD.

Methods

In our center, SSc patients and controls (non-Hodgkin lymphoma cured after first-line regimen) who had received a PET/CT were screened retrospectively. The FDG uptake (visual intensity, pattern, SUV_max) was systematically recorded in > 30 regions of interest (ROIs) linked to SSc in a blind reviewing by 2 independent nuclear medicine physicians using a standardized form.

Results

Among the 545 SSc patients followed up in our center, 36, including 22 SSc-ILDs, had a PET/CT, whose indication was cancer screening in most cases. The mean ± SD age was 57.9 ± 13.0 years with 20/36 females. Fourteen patients had a disease duration of less than 2 years. A third had anti-centromere antibodies and 27.8% had anti-topoisomerase antibodies. Pulmonary FDG uptakes were higher in SSc patients than in controls (n = 89), especially in those with ILD compared with those without ILD. Pulmonary FDG uptakes were positively correlated with the ILD severity (fibrosis extent, %FVC, and %D_LCO). No significant difference was found in the FDG uptakes from extrathoracic ROIs. Progressing SSc-ILDs within the 2 years after PET/CT (n = 9) had significant higher pulmonary FDG uptakes at baseline than stable SSc-ILDs (n = 13).

Conclusion

PET/CT could be a useful tool in the assessment of the severity and the prediction of pulmonary function outcome of SSc-ILD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02460-8.

Correlation between preoperative 18F-FDG PET/CT findings and postoperative short-term prognosis in lung cancer patients with idiopathic interstitial pneumonia after lung resection

BACKGROUND

The present study aimed to investigate the correlation between preoperative 2-deoxy-2-[¹⁸F]fluoro-d-glucose (¹⁸F-FDG) PET/CT findings and short-term survival in lung cancer patients with idiopathic interstitial pneumonia (IIP).

METHODS

We retrospectively reviewed the data of 425 patients who underwent lung resection for non-small cell lung cancer without preoperative radiation therapy between November 2012 and October 2017. The maximum SUV (SUVmax) in the IIP area except the lung cancer site was measured in each patient.

RESULTS

Thirty-one of the 425 patients (7.3%) showed findings of IIP in chest CT. Five of the 31 patients (16.1%) developed acute exacerbation (AE) after lung resection (AE+ group). Twenty-six of the 31 patients (83.9%) did not develop AE (AE- group). In the AE+ group, ¹⁸F-FDG SUVmax in the IIP area was significantly higher (1.9 ± 0.6 vs. 2.7 ± 0.7, p = 0.02) compared with that in the AE- group. The receiver operating characteristic analysis identified an SUVmax threshold score of 2.55 (p = 0.02) for AE. There was no 90-day mortality in the patients with SUVmax < 2.55 (n = 25). On the other hand, the 90-day mortality rate in patients with SUVmax ≥ 2.55 (n = 6) was 33.3% (2 patients).

CONCLUSIONS

¹⁸F-FDG PET/CT may predict AE after lung resection and could be related to short-term survival in lung cancer patients with IIP. Further investigations are needed to improve the prognosis in patients with high SUVmax in the IIP area.

Multimodality imaging in connective tissue disease-related interstitial lung disease

Interstitial lung disease is a well-recognised manifestation and a major cause of morbidity and mortality in patients with connective tissue diseases. Interstitial lung disease may arise in the context of an established connective tissue disease or be the initial manifestation of an otherwise occult autoimmune disorder. Early detection and characterisation are paramount for adequate patient management and require a multidisciplinary approach, in which imaging plays a vital role. Computed tomography is currently the imaging method of choice; however, other imaging techniques have recently been investigated, namely ultrasound, magnetic resonance imaging, and positron-emission tomography, with promising results. The aim of this review is to describe the imaging findings of connective tissue disease-related interstitial lung disease and explain the role of each imaging technique in diagnosis and disease characterisation.

The quantitative assessment of interstitial lung disease with positron emission tomography scanning in systemic sclerosis patients

Objectives

The reversibility of interstitial lung disease (ILD) in SSc is difficult to assess by current diagnostic modalities and there is clinical need for imaging techniques that allow for treatment stratification and monitoring. ¹⁸F-Fluorodeoxyglucose (FDG) PET/CT scanning may be of interest for this purpose by detection of metabolic activity in lung tissue. This study aimed to investigate the potential role of ¹⁸F-FDG PET/CT scanning for the quantitative assessment of SSc-related active ILD.

Methods

¹⁸F-FDG PET/CT scans and high resolution CT scans of eight SSc patients, including five with ILD, were analysed. For comparison, reference groups were included: eight SLE patients and four primary Sjögren’s syndrome (pSS) patients, all without ILD. A total of 22 regions of interest were drawn in each patient at apical, medial and dorsobasal lung levels. ¹⁸F-FDG uptake was measured as mean standardized uptake value (SUVmean) in each region of interest. Subsequently, basal/apical (B/A) and medial/apical (M/A) ratios were calculated at patient level (B/A-p and M/A-p) and at tissue level (B/A-t and M/A-t).

Results

SUVmean values in dorsobasal ROIs and B/A-p ratios were increased in SSc with ILD compared with SSc without ILD (P = 0.04 and P = 0.07, respectively), SLE (P = 0.003 and P = 0.002, respectively) and pSS (P = 0.03 and P = 0.02, respectively). Increased uptake in the dorsobasal lungs and increased B/A-t ratios corresponded to both ground glass and reticulation on high resolution CT.

Conclusion

Semi-quantitative assessment of ¹⁸F-FDG PET/CT is able to distinguish ILD from non-affected lung tissue in SSc, suggesting that it may be used as a new biomarker for SSc-ILD disease activity.

Experimental and quantitative imaging techniques in interstitial lung disease

Interstitial lung diseases (ILDs) are a heterogeneous group of conditions, with a wide and complex variety of imaging features. Difficulty in monitoring, treating and exploring novel therapies for these conditions is in part due to the lack of robust, readily available biomarkers. Radiological studies are vital in the assessment and follow-up of ILD, but currently CT analysis in clinical practice is qualitative and therefore somewhat subjective. In this article, we report on the role of novel and quantitative imaging techniques across a range of imaging modalities in ILD and consider how they may be applied in the assessment and understanding of ILD. We critically appraised evidence found from searches of Ovid online, PubMed and the TRIP database for novel and quantitative imaging studies in ILD. Recent studies have explored the capability of texture-based lung parenchymal analysis in accurately quantifying several ILD features. Newer techniques are helping to overcome the challenges inherent to such approaches, in particular distinguishing peripheral reticulation of lung parenchyma from pleura and accurately identifying the complex density patterns that accompany honeycombing. Robust and validated texture-based analysis may remove the subjectivity that is inherent to qualitative reporting and allow greater objective measurements of change over time. In addition to lung parenchymal feature quantification, pulmonary vessel volume analysis on CT has demonstrated prognostic value in two retrospective analyses and may be a sign of vascular changes in ILD which, to date, have been difficult to quantify in the absence of overt pulmonary hypertension. Novel applications of existing imaging techniques, such as hyperpolarised gas MRI and positron emission tomography (PET), show promise in combining structural and functional information. Although structural imaging of lung tissue is inherently challenging in terms of conventional proton MRI techniques, inroads are being made with ultrashort echo time, and dynamic contrast-enhanced MRI may be used for lung perfusion assessment. In addition, inhaled hyperpolarised ¹²⁹Xenon gas MRI may provide multifunctional imaging metrics, including assessment of ventilation, intra-acinar gas diffusion and alveolar-capillary diffusion. PET has demonstrated high standard uptake values (SUVs) of ¹⁸F-fluorodeoxyglucose in fibrosed lung tissue, challenging the assumption that these are ‘burned out’ and metabolically inactive regions. Regions that appear structurally normal also appear to have higher SUV, warranting further exploration with future longitudinal studies to assess if this precedes future regions of macroscopic structural change. Given the subtleties involved in diagnosing, assessing and predicting future deterioration in many forms of ILD, multimodal quantitative lung structure-function imaging may provide the means of identifying novel, sensitive and clinically applicable imaging markers of disease. Such imaging metrics may provide mechanistic and phenotypic information that can help direct appropriate personalised therapy, can be used to predict outcomes and could potentially be more sensitive and specific than global pulmonary function testing. Quantitative assessment may objectively assess subtle change in character or extent of disease that can assist in efficacy of antifibrotic therapy or detecting early changes of potentially pneumotoxic drugs involved in early intervention studies.

Impact of FDG-PET on the Detection of Patients with Lung Cancer at High Risk for ILD

BACKGROUND/AIM

Idiopathic pulmonary fibrosis IPF is a type of interstitial lung disease (ILD) with poor prognosis. Lung cancer (LC) is a frequent complication in IPF, where all therapeutic options are potential triggers for acute exacerbation of IPF.

PATIENTS AND METHODS

Patients with 2-deoxy-2-fluoro-D-glucose-positron emission tomography/computer tomography (FDG-PET/CT) results before lobectomy for LC with and without (n=10 each) signs of ILD in initial imaging and after-care CT were retrospectively analyzed. FDG uptake was calculated as the maximum standardized uptake value (SUV_max) in the lung periphery divided by the SUV_max of the mediastinal blood pool (rSUV_max). Regional increase of fibrosis and ground-glass features in lobe-based CT analysis was used as standard reference.

RESULTS

Patients with LC with ILD presented a significantly higher rSUV_max of 0.57 compared to patients without ILD with rSUV_max 0.47 (p<0.001).

CONCLUSION

rSUV_max seems to be a valuable imaging surrogate in predicting patients with LC with increased risk for progressive ILD associated with thoracic surgery.

Visualisation of interstitial lung disease by molecular imaging of integrin αvβ3 and somatostatin receptor 2

OBJECTIVE

To evaluate integrin αvβ3 (alpha-v-beta-3)-targeted and somatostatin receptor 2 (SSTR2)-targeted nuclear imaging for the visualisation of interstitial lung disease (ILD).

METHODS

The pulmonary expression of integrin αvβ3 and SSTR2 was analysed in patients with different forms of ILD as well as in bleomycin (BLM)-treated mice and respective controls using immunohistochemistry. Single photon emission CT/CT (SPECT/CT) was performed on days 3, 7 and 14 after BLM instillation using the integrin αvβ3-targeting ¹⁷⁷Lu-DOTA-RGD and the SSTR2-targeting ¹⁷⁷Lu-DOTA-NOC radiotracer. The specific pulmonary accumulation of the radiotracers over time was assessed by in vivo and ex vivo SPECT/CT scans and by biodistribution studies.

RESULTS

Expression of integrin αvβ3 and SSTR2 was substantially increased in human ILD regardless of the subtype. Similarly, in lungs of BLM-challenged mice, but not of controls, both imaging targets were stage-specifically overexpressed. While integrin αvβ3 was most abundantly upregulated on day 7, the inflammatory stage of BLM-induced lung fibrosis, SSTR2 expression peaked on day 14, the established fibrotic stage. In agreement with the findings on tissue level, targeted nuclear imaging using SPECT/CT specifically detected both imaging targets ex vivo and in vivo, and thus visualised different stages of experimental ILD.

CONCLUSION

Our preclinical proof-of-concept study suggests that specific visualisation of molecular processes in ILD by targeted nuclear imaging is feasible. If transferred into clinics, where imaging is considered an integral part of patients' management, the additional information derived from specific imaging tools could represent a first step towards precision medicine in ILD.

ACR Appropriateness Criteria® Chronic Dyspnea-Noncardiovascular Origin

Chronic dyspnea may result from a variety of disorders of cardiovascular, pulmonary, gastrointestinal, neuromuscular, systemic, and psychogenic etiology. This article discusses guidelines for the initial imaging of six variants for chronic dyspnea of noncardiovascular origin: (1) Chronic dyspnea of unclear etiology; (2) Chronic dyspnea with suspected chronic obstructive pulmonary disease; (3) Chronic dyspnea with suspected central airways disease; (4) Chronic dyspnea with suspected interstitial lung disease; (5) Chronic dyspnea with suspected disease of the pleura or chest wall; and (6) Chronic dyspnea with suspected diaphragm dysfunction. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Interstitial lung diseases: Imaging contribution to diagnosis and elementary radiological lesions

Interstitial pneumonias comprise a heterogeneous group of disorders in which a multidisciplinary approach is important for accuracy in diagnosis; indeed, one might say, even mandatory. The team of collaborators should include radiologists, because high resolution computed tomography (HRCT) of the thorax is the first, and most of times, the only imaging examination to be prescribed after chest X-ray. Elementary lesions of the interstitium can be accurately described with HRCT, inasmuch as lung windowing with sharp filtering in this technique reproduces the microscopic features of the lung. Guidance of bronchoalveolar lavage and biopsy procedures is also possible with HRCT.