Computed Tomography of the Prostate

One of the most important advantages of CT of the prostate is the relatively low operator-dependence of the method: the results of a survey performed according to a standard procedure can be reviewed and interpreted by different specialists without the need for a re-examination.

Advantages of multispiral computed tomography of the prostate:

• high spatial resolution;
• high speed of research;
• the possibility of three-dimensional and multi-plane reconstruction of images;
• low operator-dependency of the method;
• the possibility of standardizing the research;
• relatively high availability of equipment (by the number of devices and the cost of the survey).

[1], [2], [3], [4], [5]

Purpose of computed tomography of the prostate

The main goal of the CT scan is to determine the stage of the regional prevalence of prostate cancer (primarily in the detection of metastatic lesions of the lymph nodes).

Indications for computed tomography of the prostate

The main indications for the implementation of MSCT of pelvic organs:

• detection of regional lymphadenopathy in patients with verified prostate cancer;
• revealing the spread of the tumor to the pelvic organs in patients at high risk of local onco-proliferation (PSA level> 20 ng / ml, the sum of scores to Gleason is 8-10);
• planning radiation therapy.

To detect distant metastases, CT of the lungs, brain, liver, adrenal glands are performed.

Preparing for computed tomography of the prostate

The preparation of patients for the MSCT of the pelvic organs and the abdominal cavity includes oral contrasting of the small and large intestine with a positive or negative substance necessary for precise differentiation of the lymph nodes and intestinal loops. A 3-4% solution of sodium amidotrizoate (urographine) or hypaca is used as a positive contrast preparation 40 ml contrast preparation per 1000 ml of water), it is divided into 2 parts of 500 ml and taken in the evening before the study, as well as on the morning of the day of the study. As a negative contrast preparation, water (1500 ml for 1 h before the test) can be used, which is especially important when performing MSCT with intravenous contrast and three-dimensional image reconstruction.

MSCT of the small pelvis is performed with a filled bladder, Some researchers suggest filling the rectum with a contrast medicine or inflated balloon. MSCT of the abdominal cavity and retroperitoneal space can be performed at least 3-4 days after the radiographic examination of the digestive tract with barium sulfate because of possible artifacts in CT.

MSKG with intravenous contrast in patients with risk factors for developing contrast-induced nephropathy (diabetic nephropathy, dehydration, congestive heart failure, age over 70) can only be performed after appropriate preparation in the form of intravenous or oral hydration (2.5 liters of fluid for 24 hours h before the study). The admission of nephrotoxic drugs (non-steroidal anti-inflammatory drugs, dipyridamole, metformin) should be stopped as much as possible 48 hours before the MSCT with intravenous contrast.

Method for the study of computed tomography of the prostate

When the MSCT is performed, the patient is placed on his back with his arms raised. Study of pelvic organs and retroperitoneal space (the range of scanning - from the diaphragm to the ischiatic tubercles) is performed with collimation of the x-ray beam 0.5-1.5 mm, reconstruction of thin sections of 1.5-3 mm in three planes, viewing tomograms in soft tissue and bone windows.

Intravenous contrasting is necessary to clarify the boundaries of the tumor and to identify the invasion of surrounding structures. Contrast preparation (concentration of 300-370 mg iodine per 1 ml) is injected with an automatic injector in a volume of 100-120 ml at a rate of 3-4 ml / s and subsequent administration of about 50 ml of saline. The study of the small pelvis begins with a delay of 25-30 seconds from the time of intravenous injection of the contrast preparation, which allows images to be obtained in the early arterial phase of contrasting. Additionally, an interstitial phase of contrasting (delay of 60-70 s), more informative for evaluating the tumor boundaries .

Contraindications to the computed tomography of the prostate

Absolute contraindications for the CT scan of the prostate does not exist. Patients with severe allergic reactions to iodine-containing contrast agents in anamnesis are contraindicated in carrying out CT with intravenous contrast.

[6], [7]

Interpretation of the results of computed tomography of the prostate

The normal prostate gland

At MSCT it has a uniform density (sometimes with fine calcinations) without zone differentiation.

The gland volume is calculated by the ellipse formula:

V (mm ³ or ml) = x • y • z • π / 6, where x is the transverse dimension; y - anteroposterior size; z is the vertical dimension; π / 6 - 0.5.

Normally, the seminal vesicles have a tubular structure, symmetrical, up to 5 cm in size, separated from the bladder by a layer of fatty tissue, the absence of which serves as a criterion for tumor invasion.

Benign prostatic hyperplasia

The increase in the volume of the prostate gland (more than 20 cm ³ ) is detected due to the proliferation of the nodes of the paraurethral zone, which in some patients is accompanied by vestipubulous growth. In addition, when MSCT is performed with intravenous contrasting in the excretory phase (after 5-7 min after the drug administration), it is possible to reveal the uplift of the distal ureters (due to an increase in the volume of the prostate gland), the trabecularity of the wall and the diverticula of the bladder due to hypertrophy of the muscle that pushes urine , in response to partial urethral obstruction. When performing multiciliary multislice cystourethrography after filling the bladder with a contrast drug, you can visualize the urethra, and reveal its strictures.

[8], [9]

Adenocarcinoma of the prostate

Foci of adenocarcinoma within the prostate gland can be detected by the active accumulation of a contrast agent in the arterial phase (25-30 seconds from the moment of intravenous administration). The extraprostroic spread of prostate cancer can be detected with local swelling, often with an asymmetric increase in the seminal vesicle and the disappearance of fluid contents. CT-sign of the invasion of adjacent organs and structures (bladder, rectum, muscle and pelvic wall) - the absence of differentiation of the layers of fatty tissue.

Assessment of pelvic and retroperitoneal lymph nodes with the help of MSCT is based on the definition of their quantitative and qualitative changes. Methol allows to visualize the most typical zones of their lesion in prostate cancer (obstructive, internal and external iliac groups). Obstructive lymph nodes are referred to the medial chain of the external iliac group; they have a gay on the lateral wall of the pelvis at the level of the acetabulum. The main CT-sign of lymphadenopathy is the size of the lymph nodes. The upper limit of the CT norm is the transverse (smallest) diameter of the lymph node, equal to 15 mm. However, the sensitivity and specificity of CT in the detection of lymphadenopathy varies from 20 to 90%, since the method does not allow to detect metastases in unimportant lymph nodes and often gives false-negative results.

Analysis of tomogram of the pelvis and retroperitoneal space necessarily includes viewing images in the bone window, which allows to identify the hyperdense foci of osteosclerosis corresponding to typical osteoblastic metastases of prostate cancer in the pelvic bone, lumbar and thoracic spine, femurs, ribs.

[10], [11], [12], [13], [14]

Operational characteristics

MSCT does not allow to differentiate zonal anatomy and visualize the capsule of the prostate gland, which limits the possibilities of this method in detecting PCa and determining the local prevalence of the oncoprocess. The high frequency of false negative results of MSCT in staging PCa is due to the fact that stage T3 is established only in the presence of a large tumor with extra-prostatic growth and involvement of the seminal vesicle. The detection of stage T3a, especially with limited extracapsular tumor growth, or the initial involvement of seminal vesicles with MSCT is almost impossible. MSCT is not sufficiently informative in assessing the effectiveness of prostate cancer treatment and detecting local relapse.

Complications of computed tomography of the prostate

The modern MSCT prostate is an almost safe method of diagnosis, acceptable for most patients. The development of iodine-containing contrast preparations, the appearance of non-ionic drugs (iopromide, yogexol) was accompanied by a 5-7-fold decrease in the frequency of severe adverse reactions. Due to this, MSCT with intravenous contrasting became available as an outpatient examination method. Despite the lower cost of ionic contrast agents compared to non-ionic drugs, the latter became the drugs of choice for MSCT by the end of the 1990s. XX century. When using non-ionic contrast preparations in cases of moderate allergic reactions in history, premedisolone (30 mg per os for 12 and 2 hours prior to the study) can be premedicated.

[15], [16], [17], [18], [19], [20], [21]

Aftercare

Intravenous or oral hydration should be continued for 12-24 hours after the study.

[22], [23], [24]

Prospects for computed tomography of the prostate

Prospects for the development of CT diagnostics of prostate cancer are associated with the use of multislice (64-256) tomography, which makes it possible to conduct a study with a cut thickness of about 0.5 mm, isotropic voxels, and image reconstruction in any planes. Thanks to an increase in the speed of tomography, it becomes possible to perform a perfusion MSCT of the prostate gland with the detection of foci of tumor neoangiogenesis. Currently, perfusion assessment is performed using MRI with intravenous contrast or ultrasound.