Prof. Dr. med. P. Jecker

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1 Prof. Dr. med. P. Jecker The A-Scan-Sonography

2 Introduction In the diagnostics of diseases located in the paranasal sinuses the ultrasonic has a particular significance. The examination can be performed quickly and efficiently by the doctor even in between the usual clinical diagnostics. As the patient doesn t need to be transferred to doctors of different medical disciplines no unnecessary loss of time is created until a final diagnosis is made. The side effects of this technique are negligible in clinical routine so that the examination can be performed repeatedly and thus finds its eligibility in follow-up examinations. This results in the ultrasonic examination to be an ideal examination method for pregnant patients and children. The A-Scan-Sonography Even though it is also possible to examine the paranasal sinuses with the B-Scan- Sonography the A-Scan-Sonography is used primarily. The advantage of the A-Scan is that the small transducer can be attached easily to the facial soft tissue. For this advantage is paid with the disadvantage of not receiving directional information from the one-dimensional A-Scan examination. Therefore one is reliant on the correct assumption of the anatomy of the examined region by the examining doctor to such an extent as in no other imaging examination. Thus the examination requires a great amount of practice to avoid misinterpretations of the results. In the A-Sacn-Sonography of the paranasal sinuses sound frequencies of 3MHz are used. The low sound frequencies are necessary because the paranasal sinuses lie behind a more or less thick bone lamella. This leads to a reflection of a major part of the ultrasonic waves on the bone and only a small amount remains to examine pathologic processes in the paranasal sinuses. If the examined paranasal sinus is filled with air the remaining amount of ultrasonic waves is reflected, too, so that the only signal comes from the front wall area of the paranasal sinus (Fig.1, 2). In cases where the paranasal sinus is filled with a pathological process the remaining amount of ultrasonic waves which penetrate the bone are used for diagnostics. Then the ultrasonic waves are reflected on the dorsal end of the pathologic process and a socalled back wall echo (Fig.2) is received. 2

3 Fig. 1: In case of a paranasal sinus which is filled with air (L) the ultrasonic waves emitted by the transducer (K) are reflected completely on the front wall of the paranasal sinus (A). In the A-Scan image (red) only the front wall echo can be seen. In case of a pathological process in the paranasal sinus (S) a part of the ultrasonic waves are reflected on the back wall which leads to the display of the so-called back wall echo in the A-Scan. 3

4 Fig. 2: A-Scan-Sonography of a healthy maxillary sinus (bottom) and a healthy frontal sinus (top). In both sinuses only the front wall echo is visible. The back wall echo would be expected at a depth of approx. 5-6cm in the case of a maxillary sinus and in case of a frontal sinus at a depth of approx. 2cm (arrows) in accordance with a sagittal reconstructed CT. Thereby the examination is restricted to such paranasal sinuses which are close to the surface which are the maxillary sinus and the frontal sinus. In clinical routine these are the sinuses which are mainly affected by acute inflammable processes. The anterior ethmoidal cells are hardly accessible with the A-Scan examination the sphenoid bone not at all. As opposite to the remaining sonographic diagnostics of the head and throat region the examination of the paranasal sinuses is generally performed on the sitting patient. Thereby the maxillary sinuses and the frontal sinuses are scanned in the sound directions given below (Fig. 3). 4

5 Fig. 3: Examination of the maxillary and frontal sinus with the A-Scan. The arrows mark the recommended examination directions. 5

This examination position which contrasts the examination position of the throat, is inalienable as the secretion retention which might be found in the paranasal sinuses needs to be in contact with

6 This examination position which contrasts the examination position of the throat, is inalienable as the secretion retention which might be found in the paranasal sinuses needs to be in contact with the front wall in order to be able to be diagnosed (Fig. 4). Fig. 4: In the case of a paranasal sinus (S) which is partially overshadowed with secretion the examination in a dorsal position (A) would lead to a wrong negative diagnosis as an air sickle (L) would be created between the maxillary sinuses front wall and the secretion. This results in the total reflection of the ultrasonic waves emitted by the transducer (K) on the front wall (red line). If the examination is performed in a sitting position with the head tilted downwards (B) a back wall echo can be detected. If a partially overshadowed paranasal sinus were examined in a dorsal position an air sickle would be created between the front wall of the examined paranasal sinus and the secretion (Fig. 4a). This consequently leads to a total reflection of the ultrasonic waves. The wrong negative diagnosis would then match a healthy, air-filled paranasal sinus. Furthermore the examiner has to be cautious not to be in a too lateral position with the transducer, especially when examining the maxillary sinus. Otherwise the danger of a wrong positive diagnosis is given as the ultrasonic waves might be reflected from soft tissue, lateral to the maxillary sinus, in such a way that it creates the impression of a back wall echo. The main application of the A-Scan-Sonography in paranasal sinus examination is to diagnose the acute maxillary sinusitis and the acute sinusitis frontalis. Thereby the 6

A-Scan-Sonography is especially often used in emergency service where a quick diagnosis for adequate treatment planning is necessary. In some places it is also used in follow-up examinations.

7 A-Scan-Sonography is especially often used in emergency service where a quick diagnosis for adequate treatment planning is necessary. In some places it is also used in follow-up examinations. The A-Scan-Sonography is also useful for a preoperative check up on radiological diagnoses of the paranasal sinuses which were done a while back (Fig. 5). Fig. 5: The diagnosis of an overshadowed maxillary sinusitis which has been seen on CT months before is preoperatively checked by an A-Scan. In the case of an acute maxillary sinusitis it is usually distinguished by a back wall echo in a depth of 5cm in A-Scan-Sonography (Fig. 6). Due to the lower depth of the frontal sinus an acute sinusitis frontalis can be detected via the back wall echo in a depth of 2-3cm (Fig. 7). By using the A-Scan-Sonography the examiner is not able to differentiate between a liquid retention and solid tissue in the paranasal sinus, e.g. a polyposis or even a tumour. 7

Fig.6: Typical diagnosis of an acute maxillary sinusitis on the left. The right maxillary sinus and the frontal sinus are without pathological findings. Fig.

Hereby it is possible that even with a correct procedure of the A-Scan-Sonography a wrong negative diagnosis results as it might happen that the pathological

8 Fig.6: Typical diagnosis of an acute maxillary sinusitis on the left. The right maxillary sinus and the frontal sinus are without pathological findings. Fig. 7: Typical diagnosis of an acute sinusitis frontalis on the right. The diagnosis of a partially overshadowed paranasal sinus is also problematic. Hereby it is possible that even with a correct procedure of the A-Scan-Sonography a wrong negative diagnosis results as it might happen that the pathological diagnosis is missed with the ultrasonic waves. Furthermore it is possible that the back wall echo is registered earlier than expected for the correlating paranasal sinus (Fig. 8). 8

Fig. 8: If the paranasal sinus is partially overshadowed, in this case the right maxillary sinus, the back wall echo might be displayed earlier than expected.

9 Fig. 8: If the paranasal sinus is partially overshadowed, in this case the right maxillary sinus, the back wall echo might be displayed earlier than expected. In this case the saggital CT reconstruction proofs that the measurement of the back wall echo in a depth of 3cm might indeed be correct. This can usually be evaded by thoroughly scanning the complete paransal sinus as suggested in figure 3 and by making sure that the transducer is thoroughly placed on the paranasal sinus and not just quickly which mostly happens under time pressure. All summed up one might say that the A-Scan-Sonography provides a diagnostic procedure which, coupled with sufficient experience and under circumspection of possible sources of error, delivers a fast and effective diagnosis of diseases concerning the paranasal sinuses. 9

10 10 For your notes

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12 ATMOS-Slogan Open Sans Regular 6pt 17pt Durchschuß Laufweite 100 ATMOS MedizinTechnik GmbH & Co. KG Ludwig-Kegel-Str Lenzkirch / Germany Tel: atmos@atmosmed.de P092.xxxx.x 20xx-xx Index: xx

Chronic Sinusitis. Acute Sinusitis. Sinusitis. Anatomy of the Paranasal Sinuses. Sinusitis. Medical Topics - Sinusitis

Chronic Sinusitis. Acute Sinusitis. Sinusitis. Anatomy of the Paranasal Sinuses. Sinusitis. Medical Topics - Sinusitis 1 Acute Chronic is the inflammation of the inner lining of the parnasal sinuses due to infection or non-infectious causes such as allergies or environmental pullutants. If the inflammation lasts more than