Applications of different types of transrectal probes in puncture

With the continuous expansion of ultrasound applications, ultrasound-guided intracavitary puncture has become an indispensable technique in clinical departments. Among them, puncture guided by transrectal probes is particularly common in prostate biopsies.

Prostate cancer is a malignant tumor that usually occurs in the epithelial cells of the prostate gland. Due to its high incidence rate, prostate cancer has become a serious global health problem. Worldwide, prostate cancer ranks third in the incidence rate of male tumors and sixth in the mortality rate of malignant tumors. In China, with the influence of factors such as social aging, the introduction of Western diets, improved diagnostic levels, and increased public awareness of prostate cancer, the incidence rate of prostate cancer has been increasing year by year. The 2012 China Cancer Yearbook shows that prostate cancer ranks sixth in the incidence rate of male tumors in China and ninth in malignant tumor deaths. To determine the nature of prostate lesions, prostate puncture is necessary.

Currently, there are roughly four types of transrectal probes on the market: micro-convex intracavitary probes (end-scanning), linear intracavitary probes (longitudinal section), dual micro-convex probes (convex + convex), and dual-plane probes (linear + convex). The following is a brief description of the puncture of different types of transrectal probes from various ultrasound manufacturers.

1. Clinical Application of Micro-convex Intracavitary Probes (End-scanning)

End-scanning intracavitary probes are the most common in various hospitals, generally included as standard equipment when purchasing devices. When departments first started performing transrectal intracavitary biopsies, they would use end-scanning micro-convex intracavitary probes with a frequency range of 6-10MHz. The figure shows an end-scanning intracavitary probe after configuring a puncture frame. When using this type of probe for prostate puncture, the patient can adopt the left lateral decubitus position, lithotomy position, or knee-chest position, with the left lateral position being the most convenient. Since this probe can only be used for transrectal puncture, a disposable protective sheath should be used on the outside of the probe, the puncture frame should be strictly sterilized as required, and the probe should be inserted into the rectum 4-6cm. The longitudinal section of the prostate should be clearly displayed on the ultrasound monitor. With the cooperation of the puncture frame, the puncture needle is inserted along the puncture guide line, and the entire insertion path can clearly display the needle tip.

The advantages of using this probe for puncture are: readily available, no need to configure a special transrectal probe, only a puncture frame is needed to perform transrectal prostate puncture, and the cost is low. The disadvantages are: only one scanning plane, the sound beam direction is mostly parallel to the intestinal wall, which is not conducive to displaying the layered structure of the intestinal wall. When performing prostate puncture, the direction of the probe needs to be adjusted according to the different puncture sites.

2. Clinical Application of Linear Intracavitary Probes (Longitudinal Section)

Because linear array probes have a relatively high frequency and good image resolution, in order to clearly display the layers of the intestinal wall, a few manufacturers have developed transrectal linear array probes. This type of probe has only one scanning plane. Because the sound beam direction is generally perpendicular to the intestinal wall, it has a greater advantage in displaying the layered structure of the intestinal wall. In prostate biopsy puncture, the needle insertion of this probe can only use the perineal approach, as shown in the figure.

3. Clinical Application of Dual Micro-convex Intracavitary Probes (Convex + Convex)

Dual micro-convex probes have two micro-convex sound heads on the head of the probe, used for coronal and sagittal plane scanning. Due to their many advantages, various manufacturers have now launched similar transrectal probes. The main advantages of this type of probe are: (1) Using a dual-convex array design, the size of the sound head can be designed to be relatively small, and patients have good pain tolerance during scanning; (2) Using a dual-convex array design, it can achieve large-angle scanning of the prostate or its space-occupying lesions in multiple axial planes. Because the span occupied by the two sets of sound heads is small, only a shallow insertion of the probe into the patient's rectum is needed to achieve scanning of the entire prostate, which is convenient and easy to perform; (3) Simultaneous scanning and real-time display of dual sound heads, allowing simultaneous observation of sagittal and transverse sections, greatly improving the accuracy and safety of puncture; (4) Multi-angle and wide-range puncture function, making puncture easy, accurate, and fast. However, due to the dual-sound head design, as a special probe, the difficulty in processing technology is relatively large, so the Price is expensive.

Because this probe has been increasingly recognized by more and more clinical departments in ultrasound examination and biopsy puncture, various ultrasound manufacturers have now launched corresponding Models of dual micro-convex probes, such as BK, GE, PHILIPS, SIEMENS, Hitachi-Aloka, TOSHIBA, MINDRAY, Sonoscape, and SIUI.

4. Clinical Application of Dual-plane Probes (Linear + Convex):

With the promotion of transrectal ultrasound examination and treatment, more and more hospitals in China have adopted dual-plane rectal ultrasound probes (linear + convex). This probe uses a 1 convex array + 1 linear array design. The central frequency of the convex array is around 6.5MHz, and the central frequency of the linear array is around 7.5MHz. Due to its advantages, it is widely used in routine transrectal ultrasound diagnosis and treatment, such as prostate examination and biopsy puncture, radioactive particle implantation, perianal examination, and examination of complex anal fistulas:

(1) Using a dual-plane probe design, it can achieve large-angle scanning of the prostate or its space-occupying lesions in multiple axial planes;

(2) Two array transducers work simultaneously, with real-time dual-plane display, allowing for simultaneous observation of sagittal and transverse planes, significantly improving puncture accuracy;

(3) Dual array transducers feature high ultrasonic frequency and high image resolution, clearly displaying the blood flow distribution characteristics of the examined area. During the puncture procedure, the linear array transducer can display the entire process.

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