AN APPARATUS FOR USE IN ULTRASONIC EXAMINATION

Abstract: The apparatus comprises expansible means in the form of latex balloons (1, 2) by means of which a volume (10) to receive an ultrasound transducer may be defined between two cross-sections of the gastrointestinal canal, as well as a channel (13) for introducing liquid into the defined volume. The liquid is in complete contact with the sound window of the ultrasound transducer and the mucous membrane (6) and constitues the acoustic transmission medium between these.

Description: An apparatus for use in ultrasonic examination The invention concerns an apparatus for use in examination of tubular structures not filled with liquid, in particu¬ lar the gastrointestinal canal in humans and animals by means of ultrasound and in particular the parts of the gastrointestinal canal which are accessible by means of endoscopes, viz. the oesophagus, ventricle and duodenum as well as rectum and colon. Certain diseases in the mentioned parts of the gastroin¬ testinal canal can advantageously be diagnosted by means of ultrasound. An oblong, rod-shaped ultrasound transducer is used for this purpose or an endoscope with built-in ultrasound transducer. Owing to the generally limited space the transducer or the scope must be as thin as pos¬ sible. Transducers for this purpose are known and can mainly be divided into two types. One type of transducers images the examined structures in a plane at right angles to the longitudinal axis of the transducer, while the. other type images in a plane containing the longitudinal axis of the transducer. In examinations of this type it is important that the dis¬ tance between the sound window of the transducer and the examined anatomic structures is "acoustically transpa¬ rent". It is known to establish this acoustically transpa¬ rent distance by means of a liquid, e.g. water in a casing surrounding the transducer with some spacing, the gap be¬ tween the transducer and the casing being filled with the liquid. The dimensions of the casing are adapted such that it can easily be inserted transorally or transrectally into the gastrointestinal canal and engage along its outer surface with the mucous membrane. The casing is made of an acoustically transparent material, such as e.g. a thin rubber membrane. However, this structure has certain drawbacks. Ideally, the casing or the membrane will intimately engage with the mucous membrane, where, owing to its presence, it can create artifacts in the form of acoustic reflections which are difficult to distinguish from the mucous membrane on the ultrasound image and thereby impairs the diagnostic value of the image. This is unfortunate since it is often precisely structures close to the mucous membrane it is desired to examine. Further, any protuberances on the mu¬ cous membrane, e.g. in the form of irregularly shaped pathological polypi or tumors, which are especially to be examined, will prevent the membrane from creating good acoustic contact with the entire mucous membrane precisely here. This impairs the imaging or makes it impossible, just as it involves the risk that when engaging such pro¬ tuberances the membrane can deform or damage them with unfortunate consequences. The engagement of the membrane with even a fairly regular mucous membrane always involves the risk of air pockets being formed between the membrane and the mucous membrane, and even very small air pockets will give artifacts caused by strong acoustic reflections and prevent image formation of rearwardly disposed struc- tures. In many cases a tissue sample is to be taken for biopsy, and this may expediently be performed with ultrasound guidance. Special transducers for this purpose have a channel for insertion of a biopsy needle, which is then imaged together with the anatomic structures on the ultra¬ sound image. Of course, a transducer arranged in a liquid- filled casing cannot be used in this form of biopsy be¬ cause the membrane of the casing disposed between the transducer and the examined anatomic structure would be punctured by the biopsy needle. The object of the present invention is to provide an appa¬ ratus for use in ultrasound examination where these draw¬ backs are eliminated. This object is achieved with an apparatus as defined in claim 1. The two expansible means define between them a volume which may be filled with an acoustically transpa¬ rent liquid through the channel in the apparatus, and in which the ultrasound transducer may be present. The space between the transducer and the mucous membrane is filled with liquid in complete contact with these. The mucous membrane and the rearwardly disposed structures can hereby be imaged without the mentioned artifacts, and any protu¬ berances on the mucous membrane may be imaged completely and in their natural form. A biopsy needle inserted through the transducer then has unobstructed and direct access through the liquid to the structures from which a tissue sample is to be taken. The two expansible means may advantageously be latex mem¬ branes as stated in claim 2. These are expanded by infla¬ tion with air or water after the apparatus has been in¬ serted into the gastrointestinal canal. The advantage is that anatomic and possible pathological and vulnerable structures are not unnecessarily disturbed or irritated during the insertion. The selection of latex is particu¬ larly expedient since this material is extremely elastic. In inflated state, the latex membranes will be in intimate engagement with the mucous membrane, and the high elasti- city of the material permits the apparatus to be rotated about its longitudinal axis without interfering friction against the mucous membrane, and even with a considerable rotation of the adaptor it will merely be stretched or twisted without being broken. The apparatus can advantageously be constructed as an endoscope as stated in claim 3, of which the ultrasound transducer forms an integral part, it being hereby pos¬ sible to obtain a particularly compact apparatus. The invention will be explained more fully below with re¬ ference to the drawing, which shows preferred embodiments, and in which fig« 1 shows the apparatus of the invention in the form of an endoscope introduced in the oesophagus of a patient, fig. 2 shows the apparatus in the form of an adaptor for a separate ultrasound transducer, fig. 3 is a rear view partially in longitudinal section of the adaptor of fig. 2, and fig. 4 is a longitudinal section through the apparatus of figs. 2 and 3 with an introduced ultrasound transducer and introduced into the rectum. Fig. 1 shows the invention integrated in an endoscope 17 with an ultrasound transducer 11, and whose front end has been inserted into the oesophagus of a patient. A front latex balloon 1 is secured along its edge 9 to the endo¬ scope at a distance from the end 15 thereof which it sur¬ rounds. A rear latex ballon 2 surrounds the endoscope on a ring-shaped extent and is secured to the endoscope along its two edges 9. The balloons 1 and 2 are placed on their respective sides of the ultrasound transducer 11. Electric signal leads to the ultrasound transducer 11 are not shown, but extend in a known manner in the endoscope and are connected to an ultrasound apparatus 19, in which the electric signals are processed for image formation. The balloons 1 and 2 may be expanded by pumping with air or water, which is passed through channels 12 and 14 in the endoscope, and which are connected with filling pumps 18, which establish a suitable pressure in the balloons so that these are expanded and engage the mucous membrane 6. The balloons 1 and 2 thus define a closed cavity 10 be¬ tween two cross-sections of the oesophagus without connec¬ tion to the rest of the oesophagus. An acoustically trans¬ parent liquid, e.g. water, may be passed through a channel 13 in the endoscope into the cavity 10, which may be filled completely by the liquid, and the liquid will par¬ ticularly be in complete contact with both the ultrasound transducer 11 and the mucous membrane 6 and form an acous¬ tically transparent transmission medium for the ultrasound signals. Figs. 2 and 3 show the apparatus of the invention in the form of an adaptor 16 for an ultrasound transducer. The apparatus has a cavity 4 to receive an ultrasound trans- ducer which is inserted from the rear end 8 of the appa¬ ratus and is so placed in the cavity 4 that its sound window will be aligned with an opening 5 in the apparatus 16. The front balloon 1 surrounds the front end 7 of the apparatus, and the rear balloon 2 surrounds a ring-shaped portion of the appartus. Fig. 3 shows the channels 12 and 14 for pumping the balloons 1 and 2 as well as the channel 13 for insertion of liquid into the cavity. The balloons 1 and 2 are here shown unexpended, and the apparatus may un- obstructedly be introduced e.g. into the patients rectum. Fig. 4 shows the adaptor 16 in which an ultrasound trans¬ ducer 15 has been inserted, the sound window 11 of said ultrasound transducer being aligned with the opening 5 in the adaptor 16, which is shown inserted into the rectum of a patient. The balloons 1 and 2 are shown expanded such that they engage the mucous membrane 6 and define together with it a cavity 10 which is filled through the channel 13 with an acoustically transparent liquid in complete con¬ tact with the sound window 11 of the ultrasound transducer as well as the mucous membrane 6. A seal (not shown) against the surface of the transducer, e.g. in the form of an 0-ring, is provided in a known manner in the adaptor 16 near the rear end 8. Before insertion into the patient, the transducer may for hygienic reasons e.g. be coated with a tight latex coating with a bead which can also provide the necessary seal. The opening in the rear end of the adaptor 16 can be adapted to various commercially available ultrasound transducers which are useful for the purpose, and the transducer can be inserted into the opening 4 after the insertion of the adaptor 16 into the patient, or the adap¬ tor 16 and the transducer can be coupled together in a simple manner before insertion in that the adaptor is e.g. provided with means for this.

Claims: P a t e n t C l a i m s : 1. An apparatus for use in the examination of the gastro- intestinal canal and comprising expansible means (1, 2) adapted to define a volume (10) between two cross-sections of the gastrointestinal canal as well as a channel (13) for introducing liquid into the defined volume (10), c h a r a c t e r i z e d in that the apparatus is adapted to receive an ultrasound transducer (11) in the defined volume (10), and that the introduced liquid is acoustically transparent. 2. An apparatus according to claim 1, c h a r a c t e r - i z e in that the expansible means (1, 2) comprise la¬ tex membranes. 3. An apparatus according to claims 1-2, c h a r a c ¬ t e r i z e d in that it is an integral part of an endo- scope ( 17 ) .

Inventors: DRUE HERBERT RENALD CHRISTIAN, DRUE, HERBERT, RENALD, CHRISTIAN
Applicants: DRUE HERBERT RENALD CHRISTIAN, DRUE, HERBERT, RENALD, CHRISTIAN
Application year: 1990
Main classification: A61B8
IPC codes: A61B1, A61B8, A61M25