Cell features
Tissue features
Cell density
Vascularization
Cell irregularities
Elasticity
Water content
Fig. 51.1
Principle of ‘backscattered ultrasound’ in a heterogeneous medium
51.2 Method of Examination and Imaging Processing
The patient urinates and takes an enema 3 h before the exam, in order to reduce the possible artifacts. The bed position is on the right side, with flexed knees. Thus, a preliminary prostate trans-rectal ultrasound (TRUS) is executed using a 9 MHz probe with the aim of defining the glandular volume, which can be visualized.
During the imaging acquisition time (whose duration is about 45 s), the silence and no movement by the patient are necessary. The probe automatically rotates on a sagittal plan with 180° from the right to the left lobe and vice versa. This leads the acquisition of 895 frames (a frame every 1/5 of grade). In this context, the operator has to manually define the margins of the prostate.
Thus, the total volume of the prostate is divided in single volumes of about 0.04 ml, with the help of a specific algorithm. These volumes are defined as ‘tagged units’; the number of the units is related to the dimensions of the gland. The suspicious adjacent ‘tagged units’ are considered all together, and the total volume is shown to the operator (Fig. 51.2) with red colour and in the three plans: axial, sagittal and coronal (Fig. 51.3, 51.4, 51.5 and 51.6).
Fig. 51.2
3D reconstruction of the prostate with the help of PHS algorithm, with a resolution of about 0.2 mm. The visualization and the study of the images are interactive
Fig. 51.3
Suspicious lesions are red marked. The margin of the prostate is evidenced with a continuous green line and it has to be traced by the operator
Fig. 51.4
The 2D images in the different plans are real-time visualized, in order to modify the position of the probe, according to the preference of the operator
Fig. 51.5
Single-focus lesion with a volume of 0.78 ml. The total volume of the prostate is about 32 ml
Fig. 51.6
Basal bilateral lesion
In this context, the artifacts play a fundamental role in interpreting the images (Table 51.2).
Table 51.2
Features causing artefacts in PHS images
Operator related | Patient related | Anatomical |
|---|---|---|
Excessive compression on the rectum (the compression in the medium part of the prostate is higher than the rest of the gland. The use of rotating piezoelectric crystals inside the probe may solve this problem) | Movements during the execution of the exam | Sphinteric muscular structures [1] |
Operator’s experience about US The interpretation of HS images is made by the same urologist who will execute PBx, accordingly also to HS results | Number of past PBx (first vs repeated) [3] | Calcifications |
Learning curve of about 80 procedures [3] | Seminal vesicles | |
Urethra | ||
Large prostates (reduction of evaluable tissue) [4] |
51.3 Possible Indications of Prostate HistoScanning
51.3.1 Prostate Biopsy
As it was shown that it can accurately visualize and locate lesions as small as 0.50 mL inside the prostate, PHS has the potential to assist in addressing many of the issues facing current biopsy procedure techniques [7–12].
Nevertheless, the role of PHS as guidance for prostate biopsy (PB) is still a matter of debate, also because most of the published trials are retrospective and involve a small number of patients (Table 51.3).
Table 51.3
Trials about PHS and PBx
