Transthoracic Elastography in Differentiation of Lung Lesions in Dogs

doi:10.21203/rs.3.rs-4612317/v1

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Transthoracic Elastography in Differentiation of Lung Lesions in Dogs

https://doi.org/10.21203/rs.3.rs-4612317/v1

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The objective of this study was to evaluate the applicability of ARFI elastography in 36 prospective cases in differentiating parenchymal lung abnormalities in dogs: consolidations, atelectasis and neoplasms, the latter being subdivided into nodules and masses; and correlates the data obtained by the technique with B-mode ultrasound parameters, cytology results, histopathology and information from the analysis of pleural effusions when present, in addition to clinical data, indicating cut-off values in dogs. Characteristics of lung lesions were evaluated using radiography as a screening test to locate the lesions and B-mode ultrasound. Subsequently, elastographic characteristics (qualitative and quantitative) were evaluated. B-mode ultrasound assessments and qualitative elastography were not statistically demonstrated in the parameters studied to differentiate between malignant and benign lesions (p > 0.05); while in the quantitative elastographic evaluation, less atelectatic lesions (1.48 m/s) were affected when compared to nodules (2.84 m/s), consolidations (2.94 m/s) and masses (3.12 m/s), in ascending order of complaint, demonstrating statistical significance (p = 0.023), even though a diagnostic cut-off value was not obtained. It is concluded that ARFI can contribute to the differentiation of lung lesions, complementing clinical data in the evaluation of dogs.

Health sciences/Health care/Medical imaging/Ultrasonography

Health sciences/Diseases/Respiratory tract diseases

Health sciences/Oncology

shear

malignancy

ventilation

Lung diseases represent around 4% of cases in small animal medical clinics [1] and disorders of the lung parenchyma are routinely diagnosed in dogs and cats, with infectious pneumonia and neoplasms being among the most common causes of parenchymal diseases [2]. Animals with primary or metastatic lung cancer present varied and non-specific clinical signs that can be confused with findings of cardiac or intrathoracic diseases, such as chronic cough, exercise intolerance, progressive weight loss, tachypnea, among others, often resulting in a late and incidental diagnosis. [3, 4, 5, 6]. Due to non-specific clinical signs, it is necessary to use additional tests such as radiography and ultrasound.

Primary lung neoplasms, on radiographic examination, present very variable standards, including expansive, isolated circumscribed lesions, lobar consolidation, multiple circumscribed masses and diffuse involvement. Cavitations of expansive lesions, hilar lymph node enlargement and calcification of lesions can also be observed; however, a solitary nodular density is more frequently observed in the caudal lobes [7]. Metastatic lung neoplasms typically present a reticular interstitial pattern with multiple nodules throughout the entire length of the lung fields and may also vary from a well-defined to a poorly defined nodular interstitial pattern, associated or not with an alveolar condition; These radiographic patterns can be confused with infections (especially fungal), foreign body reactions, hypersensitivity, immune-mediated diseases and lung lobe torsion [8]. Corroborating this information, in most patients the establishment of a definitive diagnosis is not possible and alternative techniques such as ultrasound, for example, can be used to complement the diagnostic information not obtained by conventional radiology [9, 10].

Ultrasonography plays an increasingly important role in the detection of various pulmonary, pleural and mediastinal conditions, providing information about the location, size, extent and nature of the lesion [11]. However, the method is considered not very accurate in differentiating various abnormalities, such as fungal pneumonia, diffuse neoplastic processes and chronic abscesses [12]. Therefore, the inclusion of new ultrasound methods can increase the detail in the evaluation of the morpho functional aspects of abnormal tissues, such as stiffness, assessed by elastography, contributing to increasing the precision of the method.

ARFI is an elastographic technique that can provide quantitative and qualitative measures of tissue stiffness with minimal variability between observers, as the compression force is constant when produced directly by the device [13]. In humans, some studies have verified the applicability of elastography in the assessment of lung lesions, such as the study carried out by Wei et al. [14] who found higher shear velocities in malignant lung lesions (2.47 ± 0.92 m/s) than in benign lesions (1.85 ± 0.92 m/s), using the ARFI technique. These authors also found that ARFI was more effective at distinguishing malignant tumors from benign lesions than compressive elastography. In veterinary medicine, there is no description of the use of this method for this purpose in small animals.

Considering the diagnostic limitations for differentiating between malignant and benign lesions in dog lung tissue and the applicability of the elastographic technique in medicine, the objectives of this study were: 1) to obtain qualitative characteristics and quantitative data on the stiffness of lung lesions in dogs - consolidation, atelectasis and masses; and 2) to evaluate the applicability of the elastographic method for detecting malignant lung lesions in canines.

A total of 36 lung lesions were assessed, including 16 lung masses, 8 nodules, 4 areas of atelectasis and 8 consolidations. In some cases, the same patient had 2 different types of lung lesion at the same time. There were 7 analyses of pleural effusion, 4 histopathological exams, 4 cytology and in 21 cases the clinical history was considered in conjunction with the findings of imaging exams, such as radiography and ultrasound, as in the case of metastases (Table 1).

Table 1.

Table 1

Table of B-mode ultrasound data, ARFI elastography (qualitative and quantitative), biopsy analysis and clinical data for the patients in this study.
MASSES		E.Q	SWV median	Lin.B	E.P	Len	Wid	Ecogen.	Ecot.	Marg	Cont	P.E.	A.C.	N.	Analysis
	PA 01	1	3,125 m/s	0	0	3,6	4,2	1	2	1	1	1	0	1	Histopathological
	PA 02	2		0	1	4,7	4,2	3	2	2	1	1	1	1	Histopathological
	PA 03	1		0	1	3,4	2,1	1	1	1	1	0	0	2	Pleural effusion
	PA 04	2		0	0	3,2	4,1	1	1	2	1	0	0	2	Clinical history(metastasis)
	PA 05	3		0	1	3,4	1,2	3	2	2	1	1	0	1	Pleural effusion
	PA 06	1		1	0	4,98	4,5	1	2	2	1	0	1	2	Histopathological
	PA 07	1		0	0	5,3	4,5	3	2	2	1	1	0	1	Cytological
	PA 08	1		0	0	5,7	3,77	1	2	2	1	0	0	2	Cytological
	PA 09	1		0	0	5,3	4,6	3	2	2	1	1	1	2	Clinical history(metastasis)
	PA 10	1		0	1	3,47	4,82	3	2	2	2	0	1	2	Clinical history(metastasis)
	PA 11	1		0	0	4,5	6,8	3	2	2	2	1	1	2	Cytological
	PA 12	1		0	0	5,35	5,03	1	1	1	1	0	0	2	Clinical history(metastasis)
	PA 13	1		0	0	8,71	8,18	3	2	2	1	0	1	2	Clinical history(metastasis)
	PA 14	1		0	1	3,5	2,11	3	2	2	1	1	0	2	Cytological
	PA 15	1		0	0	5,72	4,09	3	2	2	1	0	0	1	Histopathological
	PA 16	1		0	0	4,95	4,95	3	2	2	1	0	0	1	Clinical history(metastasis)
NODULES
	PA 01	1	2,845 m/s	1	0	1,6	1,2	1	1	1	1	0	0	2	Clinical history(metastasis)
	PA 02	2		0	0	2,3	2	3	2	1	1	0	1	2	Clinical history(metastasis)
	PA 03	1		0	1	1,5	1,2	3	2	2	2	0	0	2	Pleural effusion
	PA 04	2		0	0	1,14	1,23	1	2	2	1	0	0	2	Clinical history(metastasis)
	PA 05	2		0	0	0,4	0,6	1	1	1	1	0	0	2	Clinical history(metastasis)
	PA 06	1		0	1	1,87	0,8	1	2	1	1	0	0	2	Clinical history(metastasis)
	PA 07	1		0	0	0,81	0,48	1	1	1	1	0	0	2	Clinical history(metastasis)
	PA 08	1		0	0	2,22	2,46	3	2	2	1	0	1	2	Clinical history(metastasis)
ATELECTASIS
	PA 01	1	1,48 m/s	0	1			2	1	2	1	0	0		Atelectasis due to hemorrhagic effusion
	PA 02	1		0	1			2	1	2	1	0	0		Atelectasis due to neoplasia associated with effusion
	PA 03	1		0	1			2	1	2	1	0	0		Atelectasis due to neoplasia associated with effusion
	PA 04	1		0	1			2	1	2	1	0	0		Atelectasis due to neoplasia associated with effusion
CONSOLIDATION
	PA 01	1	2,94 m/s	0	0			1	2	1	1	1	0		Lung Consolidation
	PA 02	1		0	0			1	2	1	1	1	0		Lung Consolidation
	PA 03	1		0	0			3	2	2	1	0	1		Lung Consolidation
	PA 04	2		0	0			3	2	2	1	1	0		Lung Consolidation
	PA 05	1													Lung Consolidation
	PA 06	1		0	0			1	2	2	1	1	0		Lung Consolidation
	PA 07	1		0	0			1	2	1	1	0	0		Lung Consolidation
	PA 08	2		0	0			1	1	2	1	0	0		Lung Consolidation

Legend: E.Q = Qualitative elastography, predominant colors: blue and green (1) green and yellow (2) yellow and red (3); SWV: Quantitative elastography expressed in m/s; Lin. B (B Lines): (0) absent (1) present; E.P (Pleural Effusion): (0) absent (1) present; Len.= Length; Wid = Width; Ecog. = Echogenicity: (1) hypoechogenic; (2) hyperechogenic; (3) mixed; (4) anechogenic; Ecot = Ecotexture: (1) Homogeneous; (2) Heterogeneous; Marg.(Marging), (1) regular (2) irregular; Cont.(Contour): (1) well defined (2) poorly defined. P.E (Echogenic Points): (0) absent (1) present; A.C (Cystic Areas): (0) absent (1) present; N.: (Number of Masses): Single (1), multiple nodules (2).

Radiography was used as a screening test to locate lesions when lung disease was suspected and as a comparative study with ultrasound. It was observed that lesions located in deep lung regions surrounded by air observed on radiography were not amenable to ultrasound evaluation, due to the overlapping of the aerated lung, generating reverberation, thus making it impossible to form a b-mode ultrasound image or an elastographic study. On the other hand, lesions located in the periphery of the lung, even if they were small, were also characterized by ultrasound and could be assessed using b-mode and elastography. Masses and nodules were the predominant lesions observed, with a prevalence of structured interstitial lung patterns. Radiography proved to be an excellent screening test, complementing ultrasound (Fig. 1).

On ultrasound examination of lung abnormalities, the presence of a B-line, pleural effusion, heterogeneous echotexture, irregular margins, irregular contours, echogenic spots and cystic areas were similarly observed between benign and malignant lesions (p = 0.5429; 0.9999; 0.1569; 0.9999; 0.5361; 0.9999, 0.1193; respectively). However, the consolidation group showed predominantly hypoechogenic lung characteristics, with the presence of echogenic spots permeating the consolidated lobe, characterizing air bronchograms, giving a heterogeneous appearance.

Atelectasis could be characterized when pleural effusion was present and generally appeared as triangular, hyperechogenic, homogeneous areas with slightly irregular margins and well-defined contours, overlying the pleural effusion.

Most of the nodules were hypoechogenic, with regular margins and well-defined contours. The mass group had mixed echogenicity in 62.5% of cases, the remaining formations were hypoechogenic and, when the echotexture was studied, 81.25% of the masses had a heterogeneous appearance. However, the heterogeneous appearance was also a common feature of the consolidation and nodule groups. The lesions studied in mode B are shown in (Fig. 2).

The qualitative elastography of the lesions studied did not show any diagnostic capacity (p > 0.05), because there was a predominance of the "soft" aspect, indicating less rigid tissue, in the elastogram, observed in the blue and green colors, which were the most frequent colors in all the groups evaluated.

The results obtained by SWV (Table 2), which refers to quantitative elastography, were lower in atelectatic lesions (p = 0.0187) than in the others, with median SWV corresponding to 1.48m/s in pulmonary atelectasis; 2.84m/s in nodular neoplastic lesions; 2.94m/s in consolidations; and 3.12m/s in neoplastic masses. As for qualitative elastography and echogenicity, the results were similar between the types of lesions evaluated (p = 0.5541; 0.3866 respectively).

Table 2

Results obtained from the statistical analysis comparing the types of lung lesions for SWV.
	Atelectasis	Consolidation	Noduless	Masses	P- value
Mediana	1,48	2,94	2,845	3,125	0,023
IQR	0,35	0,643	1,402	1,45	0,023

Repeated SWV measurements of the lesions studied resulted in similar values (p = 0.3831). When comparing benign and malignant lesions, SWV (Table 2), qualitative elastography (Table 3) and echogenicity resulted in similar data (p = 0.0888; 0.6176; 0.3449; respectively) and did not have the diagnostic capacity to differentiate these lesions (p = 0.0870; 0.6627; 0.3649; respectively).

Table 3

Results obtained by statistical analysis in relation to comparing the types of lung lesions for qualitative elastography.
	Atelectasis	Consolidation	Nodules	Masses	P- value
Mediana	1	1	1	1	0,554
IQR	0	0,75	1	0	0,554

In each image evaluated, qualitative elastography was obtained, corresponding to the elastogram (color scale map of tissue stiffness) for qualitative assessment of tissue stiffness: blue colored regions considered to be more elastic tissues (less rigid) and red regions (more rigid),and then quantitative elastography was performed, obtaining tissue shear wave propagation velocity values (SWV m/s) from each of the regions of interest (ROIs) and the average was calculated for each region or lesion studied (Figure. 3).

This study assessed the applicability of B-mode ultrasound characteristics and qualitative and quantitative ARFI elastography data in predicting the malignancy of the lung lesions studied. It was observed that the parameters evaluated had no diagnostic value for predicting malignancy, but there was statistical significance in the quantitative elastography values, observing an increasing order of stiffness in atelectasis, nodules, consolidations and masses, respectively. It was also possible to carry out an important B-mode characterization of masses, especially in cases with pleural effusion, making it possible to guide the collection of material for analysis. Thus, in addition to the novelty of the results obtained, it is possible to recognize the possibility of using the methods to complement the evaluation of lung lesions in dogs.

Radiographs were of great importance in the study, preceding ultrasound evaluations, with the aim of defining the location and type of disorder found, determining the appropriate place to start the ultrasound examination, as described by [16]. However, when pleural fluid associated with lung diseases was present, it was not possible to characterize the type of lung lesion by radiographic examination. In this way, ultrasound allowed for greater detail of the intrathoracic structures, with the presence of the fluid serving as an acoustic window, allowing excellent visualization of most of the structures, in agreement with [17]. It also provides real-time guidance for any pleural intervention [18]. All the masses seen on the lung surface X-ray were easily identified and characterized on ultrasound examination.

This ultrasound contribution to patients with little radiographic contribution, in this project as mentioned above, corroborates the quality observed in humans for ultrasound examination. In human patients, lung ultrasound has shown an accuracy of 90 to 100% for detecting interstitial abnormalities and 90–98% for alveolar alterations and is considered to be within the diagnostic accuracy range close to radiography and tomography [19]. In medicine, when comparing this method with radiography, ultrasound detects alveolar and interstitial abnormalities, especially when there is pleural effusion which impairs radiographic evaluation, helps to determine diagnoses and contributes as a guide for collecting biological samples for diagnostic conclusion (example: FNAB - fine needle aspiration puncture and biopsy), unlike radiography which is inaccurate and limited in these points [11, 20, 21].

In terms of the B-mode findings, pleural effusion, although not statistically significant in predicting malignancy, it was observed that not all patients with malignant neoplasia had effusion associated with the condition, but 90% of patients with effusion had malignant neoplasia. Of the 16 patients with malignant neoplasms in the mass group, 5 had effusion; in the atelectasis group, of the 4 patients who had pulmonary atelectasis because of pleural effusion, 3 had effusion associated with malignant neoplasms; and in the nodule group, 2 patients with a history of metastasis also had effusion. These observations corroborate those of Antunes et al [22], who cite voluminous exudative pleural effusions as suspicious of malignant etiology. Furthermore, according to Teixeira [23], lung carcinoma is the most common cause of pleural effusion, accounting for almost a third of metastatic effusions, and this was the most common neoplasm in this study when cytology and histopathology results were obtained.

In general, the B-mode characteristics were unable to predict malignancy. Wei et al. [14], in a study conducted in humans to assess lung lesions, observed in B-mode that lesions greater than or equal to 5 cm, with irregular contours, the presence of air bronchograms and non-abundant vascularization were identified as predictive factors of malignancy. In our study, we believe that the size of the lesions was not significant since it is not possible to accurately measure extensive lesions such as consolidations, for example, and atelectasis. In these cases, a more diffuse and less focal appearance was observed, unlike masses and nodules; thus, making measurements difficult and consequently not being possible to compare in a statistical analysis.

The presence of air bronchograms in this study was only observed in the pulmonary consolidation group, which is why it was not a parameter assessed by the statistics to predict malignancy. However, 87.5% of the consolidations were caused by neoplastic infiltrates, in agreement with the findings of Wei et al [14]. The study by Wei et al. [14] also assessed B-mode parameters such as margination and echogenicity, which in turn were not predictive of malignancy, which according to the authors could be explained by the existence of overlapping sonographic characteristics between malignant and benign lesions due to the various types of lung lesions. As was the case in our study, where these parameters were also not predictive and, in some cases, there was more than one type of lung lesion concomitantly in the same patient. In addition, the researchers of the study considered that the sensitivity and specificity of the ultrasound characteristics varied considerably, 30.9–87.3% and 16.7%-55.6%, respectively, and the results were not satisfactory, thus suggesting that additional methods should be adopted to diagnose peripheral lung lesions. This corroborates our results in relation to B-mode parameters, which were unable to differentiate between benign and malignant lesions.

The qualitative elastography of the lesions studied did not show any diagnostic capacity, because there was a predominance of the "soft" aspect, indicating less rigid tissue, in the elastogram, observed in the blue and green colors, which were the most frequent colors in all the groups evaluated. This characteristic was expected in the nodule, consolidation and atelectasis groups, which according to Lim et al. [24], have less rigidity when compared to masses, but one assumption for this finding also in masses (malignant neoplasia) is based on the hypothesis that they have areas of necrosis. According to Daleck [25], neoplasms can have a mixed tissue constitution, explaining soft areas in the elastographic evaluation, present in possible necrosis processes, and rigid areas in the warm color tones of the elastogram (yellow and red).

Regarding quantitative elastography, atelectasis is believed to be the softest lesion found compared to the others, due to its tissue characteristics. Since the alveoli are surrounded and separated from each other by an extremely thin layer of connective tissue [26], containing blood capillaries which in turn have no connective tissue in their wall, in addition to the capillaries, the alveolar interstitial contains elastic and collagen fibers produced by interstitial fibroblasts [27]. The characteristics of the morphology of the atelectatic process and the elastographic findings of this study prove the reason for the high deformation in atelectasis (alveolar collapse), corroborating Konofagou [28], who mentions that the presence of collagen fibers, elastin, water and fat molecules provide specific attributes of the elasticity and rigidity of this tissue in the face of the forces exerted on it.

The mean quantitative elastography of nodules (malignant neoplasms) in this study was 2.84 m/s and was less rigid when compared to consolidation lesions (2.94 m/s), contrary to what was observed in the Lim et al. study [24], where neoplasms had greater rigidity when compared to consolidations. However, the authors performed compressive elastography, which is an operator-dependent technique, unlike ARFI where the shear waves are generated by the device itself. Another hypothesis for this result is that of the 8 consolidations studied in this study, only one was related to pneumonia and all the others were the result of neoplastic infiltrates.

This finding was also observed by Cole et al. [29], who found that lung neoplasia was the most frequent cause of consolidation in a population of dogs with respiratory disorders. It is believed that the tissue constitution related to the infiltrate present contributed to this finding, since in pulmonary consolidation there is the filling of the alveoli by different materials such as exudate, transudate, blood, neoplastic cells and others [30]. In many cases, the small nodules were still partially covered in air, suggesting that the tissue was still poorly structured, thus justifying their lower rigidity when compared to pulmonary consolidation. According to Konofagou [28], the mechanical properties of tissues are correlated to their molecular constitution and structuring, which affects the stiffness of the tissue, as observed in small nodules.

In this study, the groups with malignant neoplasms were separated according to the presentation of nodules and masses. In medicine, nodule size and density are factors that directly affect the prognosis and diagnosis of patients, and nodular structures are classified according to their density [31].

In our study, formations smaller than 7 mm did not have a visible tissue composition on radiographic examination, and it was not possible to identify them according to Thrall [32]. However, formations smaller than 7 mm when located in the lung periphery or when pleural effusion was present, were well characterized on ultrasound [12]. However, a B-mode assessment of the density of nodular structures is inaccurate, but when associated with the elastography technique, it allows an assessment of tissue hardness [33, 34], showing promise for screening, assessment and diagnostic accuracy of small nodules, smaller than 1 cm, where identification is not possible on radiographic examination [35].

The masses had greater tissue rigidity than the other lesions studied (3.12 m/s) and this is directly related to their morphological characteristics. According to Daleck [25], every neoplasm has a stroma and parenchyma, and the stroma is made up of fibrous and vascular connective tissue, providing support and nutrition for the parenchyma. This fibrous connective tissue is probably the cause of the increased tissue stiffness observed on quantitative elastography.

However, this pattern was not predominant in the masses evaluated, as there was also a wide variation in stiffness along the length of the formations studied, and "soft" areas of low tissue stiffness were also identified. This phenomenon can be explained by the fact that in fast-growing malignant neoplasms, the vascular stroma may not be proportional to the volume of the parenchyma, so angiogenesis occurs at a slower rate than the proliferation of the parenchyma and, consequently, large areas of the neoplasm suffer ischemic (coagulation) necrosis or infarction [25], thus creating areas of less rigidity in certain tumor regions.

This study has some limitations that should be addressed: 1) One hypothesis for why this study did not obtain cutoff values for predicting malignancy is due to the challenge of assessing benign lesions on a routine basis, with the number of cases of malignant neoplasms in the lung parenchyma being much higher in this study; since thoracic ultrasound is mostly requested when there is a suspicion of malignancy, thus reducing the number of assessments of patients with benign lesions, in agreement with Kuo et al. [2]

Thoracic assessment with the linear probe in large patients was challenging due to the limited range of its depth, and attenuation of the shear waves was observed, forming an elastogram with few areas of good quality in these patients; 3) The presence of fluid also proved to be a limitation for the elastographic study, as was the case with cavitary masses, where it was not possible to obtain an elastogram suitable for studying stiffness, only in adjacent parenchymal areas; and 4) Adjacent normal tissue is generally used as a comparative site, but the aerated normal lung reverberates the ultrasound wave, so it is impossible to use it for comparison.

B-mode ultrasound evaluations and qualitative elastography were not statistically significant in the parameters studied for differentiating between malignant and benign lesions (p > 0.05); while quantitative elastography revealed lower stiffness in atelectatic lesions (1.48 m/s) when compared to nodules (2.84 m/s), consolidations (2.94 m/s) and masses (3.12 m/s), in increasing order of stiffness, showing statistical significance (p = 0.023), although no diagnostic cut-off value was obtained. It is concluded that ARFI elastography can help differentiate lung lesions, complementing the clinical data obtained in the assessment of canine patients. A larger sample of patients with benign parenchymal lung lesions is needed for more accurate statistical results in future elastography studies.

This prospective case-control study was conducted under the approval of the Ethics Committee for the Use of Animals (CEUA) of the Faculty of Agricultural and Veterinary Sciences, UNESP/Jaboticabal (Protocol n 799/21). All methods were carried out in accordance with relevant guidelines and regulations. The research was carried out using patients seen routinely at the "Governador Laudo Natel" Veterinary Hospital of the Faculty of Agricultural and Veterinary Sciences, UNESP/Jaboticabal, Brazil, in conjunction with the Veterinary Hospital of the Faculty of Zootechnics and Food Engineering (HOVET-FZEA)

The entire experimental procedure was carried out by a veterinarian with seven years' experience in ultrasound. The owners were consulted beforehand and informed of all the details of the study; they also agreed to the proposed assessments in an informed consent form, allowing their animals to take part in this project. The study was reported in accordance with ARRIVE guidelines.

The experimental group included dogs with acute or chronic signs of respiratory disease related to pulmonary alterations, such as coughing, sneezing, bilateral nasal secretion, dyspnea, abdominal breathing, exercise intolerance, syncope, cyanosis, as well as the detection of neoplasms in other regions (example: mammary neoplasms). The animals with the above-mentioned clinical signs were referred for radiographic examination at the radiology department of the Faculty of Agricultural and Veterinary Sciences, UNESP/Jaboticabal, with the aim of establishing the location and appearance of the pathology found, as well as determining the appropriate site for better targeting of the ultrasound examination. The elastographic characteristics of consolidated lung areas with atelectasis and neoplasms (nodules and masses) were evaluated and compared (n = 36 lesions)

All the patients assessed during the radiographic examination were in full condition and in a stable state for the examination to be carried out. Patients with respiratory discomfort underwent ultrasound assessment as an initial approach, using T-Fast thoracic ultrasound protocols associated with Vet BLUE as standardized by [15], for adequate screening and better therapeutic management.

Radiography

Conventional X-ray machines (Siemens® RG150/100gl) were used to carry out the radiographic examinations, obtaining chest images in the left lateral, right lateral, ventrodorsal and dorsoventral projections. The radiographic images were important for detecting lung abnormalities, so that they could be compared with ultrasound and elastography findings.

The images were obtained from computerized reading chassis (Imaging plate) of various sizes from the AGFA brand and a digital scanner from the same brand, model CR-30. The digital radiographs were analyzed using the DICOM® program (Digital Imaging and Communications in Medicine, Rosslyn, VA, USA) by resident veterinarians and the researcher responsible for this project, who has nineteen years' experience in diagnostic imaging. The images were archived for later comparison with the other variables obtained in the study.

Ultrasound

To carry out the ultrasound exams, focal trichotomy was performed when necessary, considering the findings of the radiographic exam, and this was expanded as necessary. After trichotomy, the patients were restrained manually, with their heads towards the monitor and their bodies parallel to the device. Before the examination, a specific gel was applied for ultrasound. The examinations were carried out with the animals in stationary, sternal and lateral decubitus (right and/or left), according to the access required for the ultrasound windows and the clinical condition of the patients, avoiding any respiratory discomfort that could put their health at risk.

The SIEMENS ACUSON S2000™ (Siemens®, Munich, Germany) and X8 Mylab (ESAOTE, Italy) devices were used, with matrix and linear multifrequency transducers from 9.0 to 13.0 MHz. Considering the importance of assessing the entire length of the lung, a scanning protocol was used which includes approaches in intercostal windows, in the right and left hemithorax [12], with the transducer being systematically slid along the intercostal spaces, assessing the extent of the lung fields (caudal, peri-hilar, middle and cranial regions);

The B-mode assessed possible changes in the appearance of the "alligator sign", discontinuity or absence of A-lines, presence of B-lines and detection of consolidated lung areas, with atelectasis, nodules, masses, or the presence of more than one lesion at the same time, which were characterized according to their echogenicity (hypoechoic, hyperechoic or mixed - presence of echogenic points, cystic areas, shadowing or acoustic reinforcement), hyperechoic or mixed - presence of echogenic spots, cystic areas, shading or acoustic reinforcement), echotexture (homogeneous or heterogeneous), contours (regular or irregular), border (defined or not), number (single or multiple), dimensions (length and width) and presence or absence of associated pleural effusion.

ARFI Lung Elastography

After B-mode ultrasound, the animals were subjected to ARFI elastography, using the same equipment and transducer as described above, but only the specific software was activated for qualitative assessment (elastogram) and quantification using the elastographic method. In each image evaluated, an elastogram (color scale map of tissue stiffness) was obtained for qualitative assessment of tissue stiffness: blue regions were considered more elastic tissues (less stiff) and red regions stiffer, as well as their distribution (homogeneous or heterogeneous).

After the qualitative assessment, five (05) regions of interest were randomly selected (ROI − 1 x 1 mm) from each area assessed, trying to include as much tissue as appeared on the screen, using the quantitative analysis tool in the same software. Tissue shear wave propagation velocity (SWV m/s) values were automatically obtained for each of these ROIs and the average was calculated for each region or lesion studied

Cytological and/or Histopathological Analysis

To collect the material, the animals underwent neuroleptanalgesia or general anesthesia, conducted by the Veterinary Anesthesiology Department, following the pharmacological and motorization protocols used by these professionals. After authorization from the anesthetic team, the skin in the area was extensively antisepticised with 70% ethyl alcohol and then punctured and/or biopsied with a tru-cut using ultrasound guidance according to the routine of the Diagnostic Imaging department. The tests were scheduled in the morning so that the patients could be monitored every 2 hours throughout the day

The material collected by aspiration puncture, using a 20-to-27-gauge needle, was placed on smear slides, fixed and sent to the Pathology Department for subsequent staining and evaluation by microscopy. The fragments taken by biopsy with a 16-to-18-gauge tru-cut were fixed in a 10% formaldehyde solution, buffered with phosphates (pH 7.4) and sent to the Pathology Department for routine processing, with hematoxylin and eosin staining, and analyzed by an experienced pathologist under light microscopy to issue the histopathological report and diagnosis.

In cases where it was not possible to obtain cytology and/or histopathology samples, clinical findings, ultrasound and X-ray data were taken into account, as well as information obtained by analyzing pleural effusions when present, in order to separate the groups into malignant and benign lesions, at the medical clinic and oncology department of the "Governador Laudo Natel" Veterinary Hospital of the School of Agricultural and Veterinary Sciences, UNESP/Jaboticabal, Brazil.

Statistical analysis

Initially, the repeated measurements of SWV, corresponding to the speed of propagation of the tissue shear wave, expressed in (m/s), obtained from each lesion were compared with each other to determine their variation, using the paired Friedman test; if the results were similar, the median values were used for the subsequent tests. Subsequently, the quantitative variables SWV, EQ (Qualitative Elastography) and echogenicity were compared between benign and malignant lesions using the Mann-Withney test and their diagnostic capacity was studied by analyzing the ROC curves using the Wilson/Brown method.

The proportion of binary variables (B lines, pleural effusion, echotexture, margins, contours, echogenic points and cystic areas) in benign and malignant lesions were compared using Fisher's exact test and the relative risk, sensitivity and specificity of these assessments for identifying malignancy were calculated. Finally, the quantitative variables (SWV, EQ and echogenicity) were compared between the types of lesions assessed (masses, nodules, atelectasis and consolidation) using the Kruskal-Wallis’s test and Dunns' post-test. Significance for all tests was set at p < 0.0500 and the data is presented as the median ± interquartile range (IQR).

Additional information

Competing interests:

The authors declare that they have no competing interests.

Author Contribution

Bruna Bressianini Lima: Conceptualization, Methodology, Resources, Investigation, Data Curation, Formal Analysis, Writing – Original Draft, Writing – Review and Editing, Project Administration, Funding Acquisition. Rafael Kretzer Carneiro, Brenda Santos Pompeu Miranda, Beatriz Gasser, Luiz Paulo Nogueira Aires and Danuta Pulz Doiche: Methodology, Resources, Investigation, Data Curation. Ricardo Andrés Ramirez Uscategui, Antônio Carlos Cunha Lacreta Junior and Marcus Antônio Rossi Feliciano: Conceptualization, Methodology, Supervision, Resources, Formal analysis, Writing – review & editing, Project administration, Funding acquisition.

Acknowledgements

The authors would like to thank São Paulo Research Foundation (FAPESP) for funding the research (grant process number 2022/07366-0). This work was carried out with the support received from the support of the Coordination for the Improvement of Higher Education Personnel - Brazil (CAPES) - Funding Code 001 and and National Council for Scientific and Technological (CNPq) for funding the research (productivity scholarship : 305182/2020-0).

Data Availability

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request. The author [email protected] should be contacted if someone wants to request the data from this study.

Ferian, PE, Silva, EF, Guedes, RC, Tôrres, RCS & Carneiro, RA. Cytological diagnosis of pulmonary neoplasia using bronchoalveolar lavage in a female dog: case report. Arq. Bras. Med. Vet. Zootec.58, 776-780. (2006). https://doi.org/10.1590/S0102-09352006000500012
Reinero, CR & Cohn, LA. Interstitial lung diseases. Vet. Clin. North Am. Small Anim. Pract. 37, 937-947. (2007). https://doi.org/10.1016/j.cvsm.2007.05.008
Couto, CG. Small animal internal medicine 241-243 (Guanabara Koogan, 1998).
Hawkins, E. C. Treatise on veterinary internal medicine 1131- 1138 (Guanabara Koogan, 2004).
Wilson, DW. Tumors in domestic animals 467-498 (John Wiley & Sons, 2017).
Bello, AM, Anselmi, C. Frau, M, Berman, KG, Novellas, R, Espada, Y, Longley, MP & Dhumeaux, M. P. Pulmonary carcinoma associated with cystic air spaces in two dogs. .J Small Anim. Pract. 63, 486-491 (2022). https://doi.org/10.1111/jsap.13451
Lamb, C. Veterinary Diagnostic Radiology 367-383 (Elsevier Health Sciences, 2002).
Burk, RL & Ackerman, N. Small animal radiology and ultrasonography: a diagnostic atlas and text 158-188 (Saunders, 1996).
Schwarz, L A & Tidwell, A S. Alternative imaging of the lung. Clin. Tech. Small Anim. Pract.14, 187-206 (1999). https://doi.org/10.1016/S1096-2867(99)80011-5
Jung, C & Bostedt, H. Thoracic ultrasonography technique in newborn calves and description of normal and pathological findings. Vet. Radiol. Ultrasound. 45, 331-335 (2004). https://doi.org/10.1111/j.1740-8261.2004.04063.x
Reichle, JK & Wisner, ER. Non‐cardiac thoracic ultrasound in 75 feline and canine patients. Vet. Radiol. Ultrasound. 41, 154-162. (2000). https://doi.org/10.1111/j.1740-8261.2000.tb01470.x
Assis, AR & Feliciano, MAR. Ultrasonography in dogs and cats 426-474 (MedVet, 2019).
Goddi, A, Bonardi, M & Alessi, S. Breast elastography: a literature review. J. Ultrasound. 15, 192-198 (2012). https://doi.org/10.1016/j.jus.2012.06.009
Wei, H, Lu, Y, Ji, Q, Zhou, H & Zhou, X. The application of conventional us and transthoracic ultrasound elastography in evaluating peripheral pulmonary lesions. Exp. Ther. Med.16, 1203-1208. (2018). https://doi.org/10.3892/etm.2018.6335
Lisciandro, GR, Fosgate, GT & Fulton, RM. Frequency and number of ultrasound lung rockets (B lines) using a regionally based lung ultrasound examination named vet BLUE (veterinary bedside lung ultrasound exam) in dogs with radiographically normal lung findings. Vet. Radiol. Ultrasound.55, 315-322 (2014). https://doi.org/10.1111/vru.12122
Mattoon, JS & Nyland, TG. Diagnostic Ultrasound in Small Animals 337364 (Rocca, 2005).
Hassan, M, Mercer, RM & Rahman, NM. Thoracic ultrasound in the modern management of pleural disease. Eur. Respir. Rev. 29, 190136 (2020). https://doi.org/ 10.1183/16000617.0136-2019
Corcoran, JP, Tazi-Mezalek, R, Maldonado, F, Yarmus, LB, Annema, JT, Koegelenberg, CF, Noble, VS & Rahman, NM. State of the art thoracic ultrasound: intervention and therapeutics. Thorax.72, 840-849 (2017). https://doi.org/10.1136/thoraxjnl-2016-209340
Lichtenstein, DA. Ultrasound in the management of thoracic disease. Crit. Care Med. 35, S250-S261. (2007). https://doi.org/10.1097/01.CCM.0000260674.60761.85
Lichtenstein, DA. Lung ultrasound in the critically ill. J. Med. Ultrasound.17, 125-142 (2009). https://doi.org/10.1016/S0929-6441(09)60120-X
Larson, MM. Ultrasound of the thorax (noncardiac). Vet. Clin. North Am. Small Anim. Pract.39, 733-745 (2009). https://doi.org/10.1016/j.cvsm.2009.04.006
Antunes, G, Neville, E, Duffy, J & Ali, N. BTS guidelines for the management of malignant pleural effusions. Thorax, 58(Suppl 2), ii29
Teixeira, LR, Pinto, JADF & Marchi, E. Neoplastic pleural effusion. J. Bras. Pneumol.32, S182-S189 (2006). https://doi.org/10.1590/S1806-37132006000900004
Lim, CK, Chung, CL, Lin, YT, Chang, CH, Lai, YC, Wang, HC & Yu, CJ. Transthoracic ultrasound elastography in pulmonary lesions and diseases. Ultrasound Med. Biol. 43, 145-152. (2017). https://doi.org/10.1016/j.ultrasmedbio.2016.08.028
Daleck, CR and Nardi, AB. Oncology in dogs and cats (Roca, 2016).
Ross, MH, Reith, EJ & Romrell, LJ. Histology text and atlas 779-779 (Panamericana, 1993).
Kierszenbaum, AL. Histology and cell biology: an introduction to pathology. (Elsevier, 2008).
Konofagou, EE. Quo vadis elasticity imaging? Ultrasonics.42, 331336 (2004). https://doi.org/10.1016/j.ultras.2003.11.010
Cole L, Pivetta M & Humm K. Diagnostic accuracy of a lung ultrasound protocol (Vet BLUE) for detection of pleural fluid, pneumothorax and lung pathology in dogs and cats. J. Small Anim. Pract.62, 178-186 (2021). https://doi.org/10.1111/jsap.13271
Marchiori E, Zanetti G & Hochhegger B. Dense consolidations. J. Bras. Pneumol. 41, 3882015 (2015). https://doi.org/10.1590/S1806-37132015000000076
Naidich, DP, Bankier, AA, MacMahon, H, Schaefer-Prokop, CM, Pistolesi, M, Goo, JM, Macchiarini, P, Crapo, JD, Herold, CJ, Austin, JH & Travis, WD. Recommendations for the management of subsolid pulmonary nodules detected at CT: a statement from the Fleischner Society. Radiology. 266, 304-317 (2013). https://doi.org/10.1148/radiol.12120628
Thrall, DE. Veterinary radiology diagnosis. (Elsevier, 2019).
Ophir, J, Cespedes, I, Ponnekanti, H, Yazdi, Y & Li, X. Elastography: a quantitative method for imaging the elasticity of biological tissues. Ultrason. Imaging. 13, 111-134 (1991). https://doi.org/10.1177/016173469101300
Garcia, PHS, Feliciano, MAR, Carvalho, CF, Crivellenti, LZ, Maronezi, MC, Almeida, VT & Uscategui, RR. Acoustic radiation force impulse (ARFI) elastography of kidneeys in healthy adult cats: preliminary results. J. Small. Anim. Pract.55, 505-509 (2015). https://doi.org/10.1111/jsap.12373
Nemanic, S, London, CA & Wisner, ER. Comparison of thoracic radiographs and single breath‐hold helical CT for detection of pulmonary nodules in dogs with metastatic neoplasia. J. Vet. Intern. Med.20, 508-515. (2006). https://doi.org/10.1111/j.1939-1676.2006.tb02889.x
Kuo, YW, Chen, YL, Wu, HD, Chien, YC, Huang, CK & Wang, H. C. Application of transthoracic shear-wave ultrasound elastography in lung lesions. Eur. Respir. Rev. 57, 2002347 (2021). https://doi.org/ 10.1183/13993003.02347-2020

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Transthoracic Elastography in Differentiation of Lung Lesions in Dogs

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Radiography

Ultrasound

ARFI Lung Elastography

Cytological and/or Histopathological Analysis

Statistical analysis

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Data Availability

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