ultrasound examinations have become the routine technique for the evaluation of the inflammatory changes in the musculoskeletal system in children in the course of systemic inflammatory conditions such as jia . they allow to identify the inflamed structures of the locomotor system such as e.g. joints , bursae , and tendon sheaths , and to determine the type of the inflammatory changes ( the presence of fluid and/or synovial hypertrophy ) and their severity . however , even though where there are no inflammatory changes within the examined area , the classical ultrasound examination rules them out with a probability nearing 100% , where they are present , an accurate evaluation of their severity is subjective and tends to depend on numerous factors , such as the examiner 's experience , the position of the limb in the case of peripheral joints , or the device and the transducer used . in pediatric patients the considerable variations in the size of the joints depending on the child 's age , and the presence , especially in the youngest children , of large quantities of hypoechogenic cartilage tissue easily mistaken for inflammatory changes , make up for additional difficulties . in compliance with the ultrasound examination standards , the severity of inflammatory changes is determined in a semi - quantitative 3-degree scale , describing them as slight , moderate and severe . some authors score the fluid and the synovial membrane jointly , whereas others score them separately . this may lead to substantial variations between researches in the scoring of the fluid and the synovium , to the effect of different assessment of the effectiveness of the undertaken treatment . this is where the application of 3d imaging option , routinely used e.g. for fetus assessment , becomes helpful . 3d imaging may facilitate an objective evaluation of the severity of the inflammatory changes , and their quantitative presentation . this paper discusses the suitability and the limitations of 3d imaging for the sake of ultrasound examinations of the musculoskeletal system in pediatric patients with rheumatologic conditions . ultrasound examinations are crucial for the vascularity assessment of inflammatory changes detected in the structures of the locomotor system . rheumatologic patients are evaluated with the help of power doppler and color doppler options . these , however , are not always sufficiently sensitive to detect synovial vascularity , which prompted search for other ways of determining the flow within the inflamed structures . the introduction of third generation uca , which are readily mobile within the vascular bed and reach the vascularized synovium with the blood stream , while at the same time being resistant to the pressure in the left heart ventricle , has facilitated more sensitive detection of the flow within the synovial membrane . even though the role of uca for rheumatology has not yet been fully determined , they hardly seem to find routine application in future clinical practice . the role of 3d imaging is to present the examined region in a spatial way , thereby facilitating evaluation which is accurate and as objective as possible . the examined structures are frequently recorded in the form of  tissue blocks  which are processed and assessed after the examination has been completed , allowing a thorough , comprehensive analysis of the examined region , and calculation of various parameters whose assessment in the course of a routine , gray - scale ultrasound is difficult , if not impossible altogether . additional volumetric transducers ( for the locomotor system ultrasound , a linear one ) facilitating data acquisition , as well as suitable software for further processing are required to carry out a 3d examination . the acquisition of 3d data takes place while the transducer is statically placed over the assessed area which is then automatically swept by the ultrasound beam . the collected data are presented in three planes : x , y and z ( fig . 1 ) . the 3d option allows imaging in a plane parallel to the front - face of the transducer  z or c plane ( also known as  bird 's eye view  ) , inaccessible in typical 2d imaging . a valuable 3d option in ultrasound examinations in rheumatology is the presentation of the revealed inflammatory changes in the form of a solid ( fig . this gives the possibility to calculate accurately the volume of the involved structures , such as joints or bursae . due to their irregular shape , their volume should not be estimated with the aid of standard algorithms used for volumetric evaluation , employing three dimensions or one dimension and the area of the change . the unquestionable advantage of calculating the volume of an inflamed structure presented in 3d consists in the feasibility to objectively assess both the severity of the inflammation process , and the changes potentially occurring in response to treatment ( fig . 3d imaging of the subacromial - subdeltoid bursa ( sasd ) also revealing the vascularity of the bursa walls in color doppler option 3d imaging . fig . 2 sasd volume , 6 weeks after topical administration of glucocorticoids this type of imaging , however , has numerous limitations . it is impossible to present as one solid some structures that are larger and longer ( e.g. some involved tendon sheaths ) , and which exceed the size swept by the ultrasound beam . also , there is the problem of assessing larger joints through osseous structures , impermeable to the ultrasound beam . cartilage elements of poor echogenicity present in children 's skeleton structures can be mistaken for inflammatory changes , making the examination more difficult . in 2d imaging , dynamic examination aids such cases , helping to successfully distinguish inflammatory changes and cartilage structures . the small size of the examined structures in younger children causes some problems too , and so does poor adherence of the transducer to the examined region e.g. the ankle . moreover , 3d investigations are sensitive to motion artifacts , therefore the examined region should be stabilized and still upon data acquisition , which is naturally more challenging in pediatric patients than in adults , of tentimes requiring multiple attempts . it also seems that 3d evaluation should be applied for structures in which the inflammation process occurs mainly in the form of synovial membrane hypertrophy , since inflammatory changes visible predominantly in the form of effusion , which is prone to pressure and readily mobile , may render varying images during a single examination . a 3d examination may also be combined with the doppler option , as in 3d power doppler ultrasound ( 3d pdu ) . it facilitates three - dimensional imaging of the distribution of vascular segments within an involved structure , t hu s enabli ng to a ssess t he va scu la r a rch itect u re of a given change ( fig . 4 ) . the additional benefit is a quantitative assessment of the vascularity of the region of interest , e.g. the hypertrophic synovium in the joint or in the bursa , and presenting it in the form of parameters such as the vascular index ( vi ) , the flow index ( fi ) or an index combining both preceding parameters , the vascular - flow index ( vfi ) . determining these parameters for specific inflamed synovial structures allows to evaluate treatment effectiveness accurately , and to detect potential remission in the course of follow - up examinations . assessment of the sasd vascular architecture visible in examination 1 all things considered , 3d imaging is an interesting option for the sake of assessment of inflammatory changes visible in an ultrasound examination of patients suffering with rheumatologic conditions . it makes the examinations more objective and provides new parameters valuable for the analysis of the vascularity of the changes , and thereby of the inflammation process activity . hence , it aids follow - up examinations and helps to evaluate remission in response to treatment . it is , nonetheless , considerably limited by factors such as the necessary equipment ( specialized transducer and software ) , anatomy , and the time required for the examination ( a technically valid examination and its further processing are substantially more time - consuming than the classical ultrasound method ) . as a result currently , third generation uca are used in clinical practice , such as sonovue from bracco , that is sulphur hexafluoride stabilized by a phospholipid shell . the investigation uses a suspension of gas - filled microbubbles of a diameter < 10 m allowing the agent to move easily within the vascular tree , without the risk of occluding the microcirculation . with the blood flow , the bubbles reach also inflamed regions such as the thickened and hypertrophic synovium present in jia , thereby finding use in rheumatology diagnostics . contrast - enhanced ultrasound examinations were first employed for rheumatology , including jia patients , in the beginning of the last decade . yet , originally , the agents were used to enhance doppler signal in vessels , hence facilitating vessel detection in the classical doppler options like contrast - enhanced power/ color doppler ( cepd / cecd ) . these days , the flow of uca in blood vessels is rendered as gray - scale image with low mechanical index ( mi ) , known as contrast - enhanced ultrasound ( ceus ) ( fig . 5 ) , and is carried out with special software . even in the beginning , it was noted that regardless of the used method , uca in rheumatology increase the sensitivity of vascular detection in the synovium as compared to the classical doppler options . the agents help to detect vessels of a diameter < 40 m , invisible in classical doppler options , bringing us closer to evaluation of flow at tissue level . contrast - enhanced ultrasound of the wrist joints . on the left side , visible contrast - enhanced synovium within the midcarpal and the radiocarpal joint ; synovial membrane enhancement in the radiocarpal joint is partial , with an area of unvascularized synovium . on the right side , view of the evaluated area in b - mode option the test is carried out upon administering the uca suspension intravenously , e.g. into the basilic vein . then , the flow of the agent into the inflamed region , displaying hypertrophic and thickened synovial membrane , is observed in real time . fluid and inactive changes , such as  old ,  fibrous synovium are not enhanced . hence , contrast - enhanced ultrasound helps to distinguish active changes in need of treatment or treatment modification , from inactive ones found e.g. in the case of a long - established jia with a persisting residual synovial hypertrophy . the effect may also be evaluated quantitatively by analyzing time intensity curve ( tic ) and then estimating the area under curve ( auc ) . it is not only peripheral joints that may be evaluated in this way , as some reports have suggested the usefulness of uca e.g. for the assessment of sacroiliac joints . the examination has numerous limitations , including the cost of the contrasting agent , and invasiveness ( intravenous administration of the agents ) . uca are safe substances which are quickly removed from the body , and rarely cause any side effects , yet so far they have not been registered for use in rheumatology or pediatric rheumatology . oftentimes , the vascularity assessment performed with the aid of classical doppler options is sufficient . the sensitivity of traditional examinations using power doppler option is comparable to the sensitivity of postcontrast mri . jia cases with subclinical course of disease , where classical doppler ultrasound does not reveal synovial inflammatory activity , would be where contrast agents should be employed to confirm the activity of the inflammation process . as of now , ceus examinations remain a highly sensitive method of synovial vascularity assessment , yet one without practical indications . 3d imaging is an option enabling a more accurate assessment of inflamed structures such as joints or bursae , which moreover provides new parameters useful for the assessment . also , it contributes to an increased comparability of assessment by various examiners , and helps to determine treatment effectiveness in follow - up ultrasound examinations . due to limitations arising from equipment requirements and technical difficulties , the method is rarely used in clinical practice . contrast - enhanced ultrasound is the most sensitive ultrasound method available , allowing to detect the synovial vascularity in rheumatologic patients , and to confirm the vascular flow where it is impossible to determine by classic doppler ultrasound . due to the high cost of the contrast agents , the invasiveness of the method , and the fact that uca have not yet been registered for pediatric rheumatology examinations author does not report any financial or personal links with other persons or organizations , which might affect negatively the content of this publication and/or claim authorship rights to this publication .