Construction of an ultrasound biopsy phantom

Improving on the Do-It-Yourself Ultrasound-Guided Fine-Needle Aspiration Simulation Phantom

The increasing use of ultrasound (US) for the diagnostic workup of thyroid lesions has subsequently been met with an increasing demand for effective US and US-guided fine-needle aspiration models. Although numerous do-it-yourself phantoms have been previously described, to our knowledge, this is the first to describe a more realistic US thyroid model using inexpensive consumer-grade materials. A simple phantom was developed and successfully used to obtain US images that realistically mimic thyroid anatomy and echogenicity. The phantom was constructed for a total cost of $6.69. It served as an inexpensive and anatomically realistic means to simulate thyroid US and US-guided fine-needle aspiration.

Development of an anthropomorphic shoulder phantom model that simulates bony anatomy for sonographic measurement of the acromiohumeral distance

The purpose of this project was to create a sonographic phantom model of the shoulder that was accurate in bone configuration. Its main purpose was for operator training to measure the acromiohumeral distance. A computerized 3-dimensional model of the superior half of the humerus and scapula was rendered and 3-dimensionally printed. The bone model was embedded in a gelatin compound and set in a shoulder-shaped mold. The materials used had speeds of sound that were well matched to soft tissue and epiphyseal bone. The model was specifically effective in simulating the acromiohumeral distance because of its accurate bone geometry.

A review of the benefits and pitfalls of phantoms in ultrasound-guided regional anesthesia

With the growth of ultrasound-guided regional anesthesia, so has the requirement for training tools to practice needle guidance skills and evaluate echogenic needles. Ethically, skills in ultrasound-guided needle placement should be gained in a phantom before performance of nerve blocks on patients in clinical practice. However, phantom technology is varied, and critical evaluation of the images is needed to understand their application to clinical use. Needle visibility depends on the echogenicity of the needle relative to the echogenicity of the tissue adjacent the needle. We demonstrate this point using images of echogenic and nonechogenic needles in 5 different phantoms at both shallow angles (20 degrees) and steep angles (45 degrees). The echogenicity of phantoms varies enormously, and this impacts on how needles are visualized. Water is anechoic, making all needles highly visible, but does not fix the needle to allow practice placement. Gelatin phantoms and Blue Phantoms provide tactile feedback but have very low background echogenicity, which greatly exaggerates needle visibility. This makes skill acquisition easier but can lead to false confidence in regard to clinical ability. Fresh-frozen cadavers retain much of the textural feel of live human tissue and are nearly as echogenic. Similar to clinical practice, this makes needles inserted at steep angles practically invisible, unless they are highly echogenic. This review describes the uses and pitfalls of phantoms that have been described or commercially produced.

Ultrasound-guided biopsy of focal lesions using three-dimensional ultrasound with a matrix array transducer: comparison with 2-dimensional ultrasound in a phantom study

OBJECTIVES

To investigate the feasibility of biopsy-guided 3-dimensional (3D) ultrasound (US) with a matrix array transducer (3D US-MAT), using the lateral and/or elevation tilt modes.

MATERIALS AND METHODS

Both inexperienced and experienced examiners performed biopsy experiments using a freehand technique on agar-based phantoms with 2-dimensional (2D) US guidance and 3D US-MAT guidance allowing real-time biplane imaging, using the lateral tilt mode and/or elevation tilt mode. Each phantom contained 4 targets of different sizes, and there were 3 different types of phantom, each having a different distance between the target and the surface. In every session, each target was aimed at 3 times, with 3 different distances between the transducer and puncture site, which resulted in 36 biopsies (3 biopsies per target × 4 targets × 3 phantoms, each of which was uniquely identified by size, depth, and angle). This procedure was carried out by each of 2 examiner twice by 2D US and twice by 3D US-MAT, resulting in paired data for each biopsy and each examiner. Target variables were target specimen length (TSL), procedure time, and agreement between the TSL of the first and second procedure by each examiner with identical biopsy parameters as a reliability measure.

RESULTS

The intraexaminer agreements between the TSLs with the 3D US-MAT in both inexperienced (r = 0.84) and experienced (r = 0.93) examiners were higher than with the 2D US (r = 0.59 with P = 0.0066, and r = 0.87 with P = 0.06, respectively). However, the procedure time with the 3D US-MAT was significantly longer than with the 2D US. The TSL were significantly longer with 3D US-MAT than with 2D US for both the examiners; the inexperienced examiner (P < 0.001) benefited more than his experienced colleague (P = 0.024). In addition, the 3D US-MAT had significant benefits for the acquisition of TSL with small target diameters and for targets with shallow locations; with more acute puncture angles for both the examiners (all P < 0.05).

CONCLUSIONS

Using a 3D US-MAT guidance improves the reliability and precision of biopsies, particularly under difficult conditions and for inexperienced examiners.

Evaluation of the accuracy of 3-dimensional ultrasonography of the kidney using an in vitro renal model

OBJECTIVE

Three-dimensional ultrasonography (3DUS) has recently become a reality because of advances in ultrasound probes and machine processing ability. We have developed an anthropomorphic phantom of the human loin to assess both the accuracy of 3DUS of the kidney and its potential usefulness for training in ultrasonographically guided percutaneous renal intervention.

METHODS

The model was built with easily available and inexpensive materials such as agar and latex with known ultrasonographic properties. The accuracy of 2-dimensional ultrasonography (2DUS) and 3DUS was assessed by measuring the dimensions of the pelvicalyceal system (PCS) ultrasonographically (pelvis width and calyx diameters) and then comparing these with measurements obtained at the time of construction. Radiology interventional trainees then punctured the PCS with 2DUS and 4-dimensional ultrasonographic (real-time/time-resolved 3DUS) guidance and reported the phantom's performance.

RESULTS

The 3-dimensional nature of the model's PCS could be clearly visualized on 2DUS and 3DUS, and the scan characteristics were very similar to those in real life. Measurements using 3DUS proved to be closer to the true dimensions of the model's PCS than those using 2DUS. The mean error percentage for 2DUS measurements was -10.2%, and that for 3DUS was -2.2% (P < 0.0001). Interventional trainees were satisfied with the "tissue feel" and level of difficulty posed on puncturing the phantom.

CONCLUSIONS

Three-dimensional ultrasonography proved to be more accurate than 2DUS for intrarenal measurements using this in vitro renal model. Three-dimensional ultrasonography has the potential to ease diagnostic renal scanning with the ability to further scrutinize and postprocess the scanned volumes. The model was realistic in its anthropomorphic properties and simulated human tissue during puncture.