CHAPTER 3 Imaging methods for guidance of aspiration cytology
Percutaneous biopsy is a well-established and routine practice in imaging departments,1,2 and is a frequently performed interventional radiographic procedure, either as an inpatient or outpatient examination, by most trained radiologists. The technique, indications and complications are extensively described in basic imaging textbooks.3 Development of expertise often occurs by ‘apprenticeship’ during undergraduate training for radiologists and for many other clinicians. The procedure is safe, inexpensive and minimally invasive. An understanding of the imaging modalities, the lesion to be biopsied and overall experience of the proceduralist contribute to the success of the procedure.
There have been continuous improvements in needles, biopsy guides and mechanical biopsy devices, together with technological advances in the major imaging methods of computed tomography (CT) and ultrasonography (US). The use of magnetic resonance imaging (MRI), and the development of stereotactic guidance, particularly for brain and breast biopsies, is now more readily available. Previously inaccessible lesions can be safely sampled and many more areas of the body are now routinely biopsied under guidance. Radiological guidance has allowed the development of more invasive procedures such as catheter drainage, villus biopsy, fetal blood and tissue sampling and core biopsy.4 This leads to a reduction in open biopsy and two-stage surgical procedures by providing a definitive diagnosis prior to primary surgical treatment.
All the imaging techniques have advantages and disadvantages in various parts of the body.
The presence of a pathologist at the biopsy generally facilitates a more efficient process. Optimal results can only be obtained by meticulous localization before biopsy and this may occupy most of the procedural time; fortunately, this can be performed prior to the arrival of the pathologist (Fig. 3.1). The pathologist may direct the radiologist to a different area of the lesion, for example to the viable periphery rather than the central necrotic area of a solid lesion, and may request additional tissue for ancillary tests, such as special stains, electron microscopy or culture, or to determine the need for a core biopsy.5
Ultrasound
Ultrasound (US) is the only real-time guidance which allows imaging in any plane and is the only suitable guidance for biopsy of fetal tissues. Its use is limited in certain areas, as ultrasound is not transmitted through air or bone. Some parts of the body,6 such as the chest wall and musculoskeletal system, though neglected in the past, have undergone an increase in interest for both diagnostic and interventional studies. Developments such as operative probes and vaginal and rectal transducers are now combined with portable, handheld (as compared to mobile) US units, for use in intensive care areas and operating theaters, wards and clinics, and to regional and remote areas.7
CT scanning
There are very few areas of the body which cannot be biopsied under CT control, and extremely small lesions can be sampled. Focal masses of several millimeters within the lung and skull base (Fig. 3.2) can be biopsied and retroperitoneal biopsies are limited only by availability of needles long enough to traverse the abdomen of large patients. Traversing with fine needles offers fewer risks compared with the larger-caliber needles.7 CT gantry tilt also further facilitates lesion access where appropriate.
Localization of the needle tip within a lesion is very accurate with CT (Fig. 3.3). It provides detailed cross-sectional images of the body which are not limited by the same physical properties as are ultrasound images, such as interference from bowel gas and bone.
Successful biopsy of lung lesions is often dependent on the coordination of patient breath holding, CT fluoroscopic imaging and needle positioning. Confirmation of the location of the needle tip should be obtained prior to sampling. Extrapleural approaches to medially situated lesions, particularly lesions in the anterior mediastinal, subcarinal or paraspinal regions, avoids the traversing of aerated lung, thereby negating the potential for pneumothorax or air leak after transthoracic needle biopsy.8 When a paraspinal extrapleural approach is used, successive 10-ml aliquots of a mixture of equal saline and 1% lidocaine (lignocaine) are injected and intermittent scanning is performed to assess the needle route. Once a safe extrapleural route to the lesion has developed, a coaxial needle system or biopsy gun is advanced into the lesion for sampling.
The CT scans allow cross-sectional localization of needle placement.
![](https://freepngimg.com/download/social_media/63059-media-icons-telegram-twitter-blog-computer-social.png)
Stay updated, free articles. Join our Telegram channel
![](https://clinicalpub.com/wp-content/uploads/2023/09/256.png)
Full access? Get Clinical Tree
![](https://videdental.com/wp-content/uploads/2023/09/appstore.png)
![](https://videdental.com/wp-content/uploads/2023/09/google-play.png)