1、Radial Endobronchial Ultrasound (Radial-EBUS)径向超声径向超声Radial-EBUS:For What?Peripheral pulmonary lesions(PPLs)were defined as those that were surrounded by pulmonary parenchyma and not visible by bronchoscopy(no evidence of endobronchial lesion,extrinsic compression,submucosaltumour,or narrowing,infla
2、mmation or bleeding of the bronchus).PPLs are common problems in clinical practice.Clinical data and radiographic finding,such as chest radiography and computed tomography (CT)can provide some clues for diagnosis.However,in some circumstances,definite diagnosis is required before deciding on the app
3、ropriate treatment.Therefore,respiratory specimens are needed to identify the etiology of the lesions.Flexible brochoscopy(FB)can reach into the airway up to the subsegmental bronchi;beyond the visual range,the airway continually divides into many generations before the peripheral target is reached.
4、Without guidance,FB cannot guarantee an accurate sampling at the exact location of the PPL.Diagnostic yield for routine bronchoscopy for investigation of PPL(i.e.lesions not endobronchially visible)may be 20%.The highest diagnostic yield for bronchoscopic evaluation of PPLs appears to be associated
5、with use of Radial Endobronchial ultrasound (Radial-EBUS).Radial EBUS has a 20-MHz(12-30 MHz available)rotating transducer that can be inserted together with or without a guide sheath(GS)through the working channel(2.0-2.8 mm)of a standard flexible bronchoscope.Radial EBUS transducer probes come in
6、different sizes with external diameters of 1.4-2.6 mm.EBUS Central probes are utilised with balloon sheaths in the proximal airways for either bronchial wall assessment or to guide TBNA of lymph nodes.EBUSperipheral probes without balloon sheaths are used to identify parenchymal lung lesions for bio
7、psy.EBUS was further combined with the guide-sheath(GS)technique.Biopsy forceps covered with a GS can be moved to the lesions under EBUS guidance,after which biopsy and brushing specimens can be sequentially obtained by keeping the GS in the lesion.1)to confirm the precise location of PPLs by EBUS i
8、maging even when such lesions are not visible on X-ray fluoroscopy;2)to facilitate obtaining biopsy and brushing specimens repeatedly by leaving the GS in the PPLs;3)to obtain biopsy specimens from PPLs that are accessible only through the use of a curette via the GS;4)to decrease bleeding resulting
9、 from trapping the GS in the bronchus;and 5)to assess the internal structure of PPLs.Points 2),3)and 4)are additional values of the GS technique above Radial EBUS alone.Radial EBUS:How to Use?Radial EBUS is typically performed after standard bronchoscopic examination of the tracheobronchial tree,inc
10、luding the subsegmental bronchi.EBUS was performed using an endoscopic ultrasound system(EU-M30S;Olympus,Tokyo,Japan),equipped with a 20-MHz mechanical radial-type probe(XUM-S20-17R;Olympus),having an external diameter of 1.4 mm.FBs with a working channel of 2.0 mm in diameter were used(BF-P-260F,BF
11、-P-240,BF-P-200;Olympus).Endobronchial ultrasonography(EBUS)-guide-sheath(GS)-guided transbronchial biopsy(TBB).a)EBUS probe with GS is advanced to the PPL via FB.After confirmation by EBUS imaging,b)the US probe is pulled out,and c)TBB and bronchial brushing are performed via the GS.When the lesion
12、 is not identified by EBUS imaging,d)a curette is inserted into the GS and the appropriate bronchus is selected.e)The curette is then pulled out and f)the EBUS probe is again inserted into the GS to perform EBUS imaging.After confirmation by EBUS imaging,g)TBB and bronchial brushing are performed.Pu
13、lmonary masses have a hypoechoic texture when compared with the surrounding tissue,and have sharply defined borders due to the strong reflective interface produced between the aerated lung and the lesions.Radial EBUS,snow storm pattern of normal EBUS image in lung periphery.Radial probe endobronchia
14、l ultrasound image indicating presence of peri-bronchial mass lesion.The position of the probe is indicated by the central black circle and the hyper-echoic line(arrows)demonstrates the solid tissueair interface between the peribronchial pulmonary mass lesion(P)and the surrounding lung (L).An 82-yr-
15、old male who underwent right upper lung lobectomy for pulmonary adenocarcinoma and who had thyroid carcinoma 12 yrs previously was admitted to the study hospital with an abnormal chest shadow.a)Chest radiograph and b)computed tomography showed a pulmonary nodule of 8 mm in diameter in the left S3a(a
16、rrows).c)Endobronchial ultrasonography showed a lowe-choic nodule surrounded by a strong reflected interface produced between the aerated lung and the lesion(arrowheads;scale bar=0.5 cm).Metastatic adenocarcinoma of the thyroid was diagnosed by EBUS-guide-sheath-guided transbronchial biopsy.Typical
17、endobronchial ultrasonographic image of a single solid pulmonary nodule,in this case a nodule of 14 mm in diameter in the left upper lobe of a 53-yr-old male with a suspected diagnosis of lung cancer.Radial EBUS,image of the peripheral pulmonary lesion.Radial EBUS image of the transducer probe withi
18、n a peripheral lung lesion that was proven to be adenocarcinoma on histology.Radial EBUS:The Sensitivity Results for sensitivity for detection of malignancy in individual studies ranged from 49%to 88%.The point sensitivity for pooled data was 0.73(95%CI 0.700.76).Pooled statistics demonstrated a dia
19、gnostic yield of 56.3%(95%CI 51 61%)and 77.7%(95%CI 7382%)for lesions=20 mm(364 patients)and lesions 20 mm(367 patients),respectively.Radial EBUS:Complication Rates Complication rates in studies varied from 0%to 7.4%.Experienced only minor self-limiting bleeding.No patients in any study experienced
20、bleeding requiring intervention.Pneumothorax rate varied from 0%to 5.1%,with a pooled rate of pneumothorax across studies of 1.0%(11 out of 1,090).The pooled rate of intercostal catheter drainage of pneumothorax was 0.4%.No deaths were reported in any Radial EBUS studies.Radial EBUS:Advantages over
21、Alternative Techniques for PPLs1.Routine bronchoscopy Diagnostic yield for routine bronchoscopy for investigation of PPLs(i.e.lesions not endobronchially visible)may be 20%.2.FB under X-ray fluoroscopic guidance Nodules of 20 mm in diameter are difficult or impossible to visualise with fluoroscopic
22、guidance.Thus,for these nodules,an overall diagnostic sensitivity of 33%(range 576%)in a meta-analysis.Accuracy of diagnosing PPLs using FB under X-ray fluoroscopic guidance is reportedly 1471%.One factor that potentially limits the diagnostic accuracy of the standard bronchoscope is lesion size,as
23、lesions2 cm have very low yields ranging 1142%.3.Electromagnetic navigation (EMN)An alternative to fluoroscopic guidance is electromagnetic navigation,which can guide the biopsy of peripheral lesions.The reported success in sampling lesions of 30 mm in diameter is 65%.However,electromagnetic navigat
24、ion is not widely available and requires thin-section computed tomography(CT)for planning and expensive disposables.EMN is an alternate guidance mechanism however it is very expensive and diagnostic accuracy is not significantly better than EBUS-TBLB.4.CT-guided percutaneous needle aspiration(CT-PNB
25、)CT-guided transthoracic needle aspiration may result in a diagnosis in 7496%of patients,again depending on lesion size,but is associated with reported pneumothorax rates that range 1544%.CT-guided needle biopsy and observed that sensitivity for detection of malignancy using CT-PNB in most studies e
26、xceeds 90%;however,20%of procedures were non-diagnostic,reflecting the lower yield of CT-PNB in benign conditions.4.CT-guided percutaneous needle aspiration(CT-PNB)Although success rates CT-PNB might be very high,with 7697%diagnostic accuracy,these techniques have several problems.First,they have th
27、e potential to spread malignant cells from the tumour into the pleural cavity.For patients with poor pulmonary function,these techniques result in an increased risk of pneumothorax.Moreover,systemic arterial air embolism is a rare but severe complication.4.CT-guided percutaneous needle aspiration(CT
28、-PNB)In comparison,many studies describing CT-PNB report pneumothorax rates 25%,and as high as 69%,with many of these patients requiring admission or even intercostal catheter drainage.Pulmonary haemorrhage is less frequent,but still complicates 110%of CT-PNB.5.Radial EBUS:Initial procedure With add
29、itional use of a GS,localization of the lesion has consistently translated to better diagnostic yields ranging from 73 to 92 percent.EBUS-TBLB has improved diagnostic yield of bronchoscopic investigation of PPLs to a level more comparable to CT-PNB,with improvement in sensitivity most apparent for s
30、maller lesions.5.Radial EBUS:Initial procedure The major advantage of EBUS-TBLB over CT-PNB is its safety profile.A meta-analysis demonstrated an overall pneumothorax rate of just 1.0%,and an overall intercostal drain insertion rate of 0.4%.Radial EBUS:Prospect With excellent specificity and sensiti
31、vity markedly higher than for routine bronchoscopy,although a little lower than for CT-PNB,an extremely favourable safety profile of EBUS-TBLB,supporting initial investigation of patients with PPLs using EBUS-TBLB.EBUS has the potential to become part of standard bronchoscopy because of negligible c
32、omplications,improved diagnostic yield and short learning curve.Radial EBUS:Influencing Factors of Sensitivity Lesion size?-Most important,variation in size of PPLs.Lobe?-YAMADA et al.noted a higher yield for PPLs positioned in the right middle lobe and lingular lobe,EBERHARDT et al.noted higher yie
33、ld in the right middle and right lower lobes and KURIMOTO et al.noted a significantly lower yield for the apicoposterior left upper lobe segment.Malignant?-Higher sensitivity for detection of malignant compared to benign lesions.Probe within lesion?-Unsurprisingly,identification of PPL position by t
34、he EBUS probe was associated with higher diagnostic.Central or peripheral lesion?-Proximity of PPL to the pulmonary hilum was reported to be associated with increased diagnostic,a lower sensitivity in pleurally based or sub-pleural lesions.Number of samples?-Noted an improved yield to a plateau of f
35、ive biopsies.Radial EBUS:Images PPLs Radial endobronchial ultrasound images for ground-glass opacity pulmonary lesions Since the introduction of low-dose helical computed tomography(CT)scanning for lung cancer screening,the frequency of detecting pulmonary ground-glass opacity(GGO)has been about 20%
36、.GGOs commonly represent a variety of diseases such as interstitial pneumonia,pulmonary lymphoproliferative disease,organising pneumonia,and pre-invasive,minimally invasive or moderately/poorly differentiated carcinoma.Radial EBUS images The R-EBUS images of GGOs were named blizzard or mixed blizzar
37、d.Blizzard sign The blizzard sign was defined as a subtle,but noticeable increase in the intensity and radius of the whitish acoustic shadow while scanning from normal lung tissue to the ground-glass area.This change in the ultrasound signal is similar to a whiteout and has a relatively larger radiu
38、s from the centre of the probe compared with the R-EBUS snowstorm appearance generated while scanning the area of normal alveolar tissue.On meticulous inspection,the details that constitute the acoustic signal are relatively thick and crude compared with the details that constitute the refined snows
39、torm appearance of normal lung tissue.Mixed blizzard sign In the mixed blizzard sign the internal echo of the lesions demonstrated diffuse heterogeneity with several hyperechoic dots,linear arcs and vessels that were distributed irregularly or combined with the blizzard sign.Blizzard sign-mechanisms
40、 Blizzard sign on the R-EBUS image was consistently observed in lesions with more GGO component.The mechanism behind this change is diffraction phenomenon.Pure and GGO-dominant lesions demonstrate this pattern on R-EBUS(blizzard)and this could be explained by the large amount of residual air in the
41、intact alveoli(without stromal invasion).Mixed blizzard sign-mechanisms The mixed blizzard sign on the R-EBUS image was not found in any pure GGO lesion,but was consistently observed in lesions with a larger proportion of solid component.All blizzard lesions were on the spectrum of adenocarcinoma in
42、 situ to well-differentiated adenocarcinoma,while the majority of mixed blizzard lesions were well-differentiated invasive lepidic-predominant and moderately to poorly differentiated adenocarcinoma.This signal,mixed blizzard,may represent tumour invasion beyond the alveolar spaces,which usually happ
43、ens when a GGO lesion develops a solid component.Mixed blizzard sign-mechanisms The ultrasound image can be easily recognized because it appears hypoechoic compared with the snowstorm appearance of normal lung and can be explained by the difference in the medium through which the ultrasound wave was
44、 propagated(i.e.,air-filled alveolar space versus alveolar space with less or no air).The GGO component that usually surrounds the periphery of a part-solid lesion corresponds to the area that generates a blizzard signal in the R-EBUS image.a)Normal lung.b)A subtle,but noticeable increase in the int
45、ensity and radius of the whitish acoustic shadow(blizzard sign).c)Mixed blizzard sign,a diffusely heterogenous acoustic shadow(with some hyperechoic dots,linear arcs and vessels)that is distributed irregularly within a blizzard.A representative case in a 74-year-old woman with pure ground-glass opac
46、ity(GGO)in the right upper lobe.a)Thin-section computed tomography scan showing a pure GGO in the right S3b.b)Radial endobronchial ultrasound(EBUS)showed a subtle but noticeable increase in the intensity and radius of the whitish acoustic shadow (blizzard sign).c)Real-time fluoroscopy image of the c
47、hest during radial EBUS scanning.d)Histopathological specimen from transbronchial biopsy showing cuboidal tumour cells lining the entrapped alveolar space.e)Histopathological specimen from surgical biopsy showing a well-differentiated microinvasive adenocarcinoma.A representative case in a 80-year-o
48、ld man with a part solid ground-glass opacity(GGO)in the left lower lobe.a)Thin-section computed tomography scan showing a part solid GGO in the left S10a.b)Radial endobronchial ultrasound(EBUS)showing mixed blizzard sign,a diffuse heterogeneity(with some hyperechoic dots,linear arcs and vessels)tha
49、t is distributed irregularly within a blizzard.c)Real-time fluoroscopy image of the chest during radial EBUS scanning.d)Histopathological specimen from the transbronchial biopsy showing adenocarcinoma with lepidic growth pattern.e)Histopathological specimen from the surgical biopsy showing a well di
50、fferentiated invasive lepidic-predominant adenocarcinoma.It is important to note that the R-EBUS image depends on which part of the lesion the probe is in.EBUS generates an acoustic shadow from the area the probe touches.If the probe is in a bronchus that is close tothe GGO portion the R-EBUS image
