RU2452388C1 - Method of determining boundaries of sphacelous parts of long tubular bones - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medicine, namely to methods of radiodiagnostics, and can be used in carrying out computed tomography of bone parts in various diseases. Computed tomography is performed. Obtained images of bone at each of the levels of scanning are divided into sectors of 30-60°. In peripheral part of each of them densitometric indices of bone tissue are determined in units of Haunsfield scale. If said index is 15% higher in comparison with its value for healthy bone part in examined patient, state of necrosis is diagnosed on said part. Reconstruction of image of affected segment is performed in minimum two perpendicular planes. After that, boundaries of bone affection are determined by connection of extreme points of necrosis parts.

EFFECT: method makes it possible to increase accuracy of determining boundaries of sphacelous parts of long tubular bones.

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Description

The invention relates to medicine, in particular to methods of radiation diagnostics, and can be used to perform computed tomography of bone sites in their various diseases.

A known method for identifying necrotic areas of bone and the line of demarcation between necrotic and viable areas of bone based on the analysis of their x-ray image (Mikhailov MK, Volodina GI, Laryukova EK Differential X-ray diagnosis of diseases of bones and joints. Study guide. - Leningrad, 1985, 66 pp.).

However, the visible demarcation band is a late symptom corresponding to the stage of sequestration of the necrotic area of the bone, and the insufficient number of gradations of contrast of standard analog radiographs does not allow differentiating the areas of bone necrosis at the previous stage. In addition, the demarcation shaft revealed in the radiographs in the form of a strip deprived of the bone structure surrounding the sequestration cannot be considered the exact boundary between the healthy and damaged bone, since it does not allow to determine the true extent of the changed bone area.

A known method of visualizing the boundaries of the necrosis of the end sections of bone fragments before the formation of an obvious demarcation band according to computed tomography (Vasiliev, N.A. Computed tomographic diagnosis of chronic osteomyelitis of the long tubular bones of the lower extremities. / N.A. Vasiliev, G.G. / Bulletin of radiology and radiology. - 1992. - No. 1. - P.47-48).

However, this method also does not allow to determine the boundaries of necrosis sites with the necessary accuracy due to the complexity of visual perception, especially in cases where differences in the optical density of the image of adjacent viable and necrotic areas of the bone are slightly expressed.

The objective of the invention is to increase the accuracy of determining the boundaries of necrotic sections of long tubular bones.

This problem is solved in that in the method for determining the boundaries of necrotic sections of long tubular bones, including computed tomography, the obtained bone images at each scan level are divided into sectors of 30-60 °, in the peripheral part of each of them densitometric parameters of bone tissue are determined in units of the Hounsfield scale, when the specified indicator is exceeded by 15%, in comparison with its value for a healthy section of bone in the patient being examined, a diagnosis on this section of bone iruyut state of necrosis, perform image reconstruction of the affected segment in at least two perpendicular planes and connecting the extreme points of necrosis areas, define the boundaries of the bone lesions.

The method is illustrated by a description, an example of practical use and illustrative material, which shows:

Figure 1 - overview topogram of the patient's hips with the allocation of scan levels.

Figure 2 - axial tomogram of the thigh at the level of the middle third of the diaphysis with dividing the image into sectors.

Figure 3 - MPR reconstruction in the frontal plane with a distinguished border of necrotic lesion of the tibia.

4 and 5 - MPR reconstruction of the image of the thigh in the frontal and sagittal planes one year after the end of treatment.

The method is as follows.

After laying the patient, the zone of interest (FOV), the initial level and the direction of scanning are determined by the previously obtained topogram - a digital analogue of the survey radiograph.

For the study, a computer tomograph of the type "SOMATOM AR.HP" from Siemens is used in the transverse discrete scanning mode using the Extremity program with the technical characteristics:

topo-parameters - a) kV 130; b) sec / mAs 3/210; c) slice 2 mm; d) tube position anterior; d) length 512 mm; e) algorithm standart; g) gentry tilt 0;

tomo parameters - a) kV 130; 6) sec / mAs 3/210; c) slice 5 mm; d) algorithm standart; d) FOV up to 260; e) gentry tilt 0.

The functions “Evaluate statistics”, “Evaluate profile”, “Evaluate distance”, “Evaluate angle”, “Evaluate statistics” are used to perform individual operations.

The first scan slice is produced, as a rule, 1-1.5 cm above the border of visible pathological changes, and then with an interval of 3-5 mm in the direction from the proximal limb to the distal.

Determining the boundaries of necrosis is carried out in two stages. At the first stage, the obtained bone images at each of the scan levels are divided into sectors of 30-60 ° and in the peripheral part of each of them, which corresponds to the image of the bone wall, bone densitometric parameters are determined in units of the Hounsfield scale (HU). The obtained data is analyzed and when the specified indicator is exceeded by 15%, in comparison with its value for a healthy bone section in the patient being examined, a state of necrosis is diagnosed in this bone section. As a rule, the average density of necrotic bone is 1384.58 ± 70.41 HU, and the average value of the viable density corresponds to 1211.45 ± 125.51 HU.

At the second stage, using the MPR (multiplanar reconstruction) software function, secondary reconstruction of the images of the affected segment is performed in at least two perpendicular, usually sagittal and frontal planes. If necessary, they will be supplemented with similarly reconstructed images in arbitrarily taken planes. In the images obtained in this way, the extreme points of the areas of necrosis defined on the scans are connected together and, thereby, the boundaries of the necrotic lesion of the bone are determined.

The practical use of the method is illustrated by the following clinical observation.

Patient E., 27 years old, turned to FGUN RSC “WTO” after 6 months. after an injury due to chronic post-traumatic osteomyelitis of the left femur. He complained of the presence of fistulas with purulent discharge, inability of the left lower limb, shortening of the left thigh by 7 cm. Previously, the patient underwent intramedullary osteosynthesis, and then osteosynthesis with Ilizarov's apparatus. Despite the treatment, fracture fusion did not occur. After 3 months after injury, fistulas opened (Figure 1).

Before sequestration necrotectomy and repeated osteosynthesis with an external fixation apparatus, due to poor visualization of the border of necrotic lesions of the ends of the fragments, the patient underwent computed tomography. The resulting images were divided into sectors, in the peripheral part of each of which the bone density was determined in units of Hounsfield (HU) (Figure 2). Considering that the density of healthy bone sections in this patient was, on average, 1258 HU, sections of the bone were identified on the analyzed scans, the density of which exceeded that indicated by 15%, amounting to 1438-1536 HU. After this, a secondary computer reconstruction of the affected segment was performed, by which, by connecting the extreme points of the identified areas of necrosis, the border of the necrotic lesion of the bone was determined. At the end section of the proximal fragment, the size of the necrosis site was 6.4 cm on the inside and 1 cm on the outside (Figure 3).

At the operation, the presence of osteonecrosis of this localization and size was fully confirmed, which allowed sequestration necrosis to be performed with maximum preservation of viable tissues. As a result of the treatment, the patient stopped the osteomyelitis process, restored the integrity and length of the thigh (Fig.4, 5).

Using the method in the RRC "WTO" them. Acad. G.A. Ilizarova showed that its use improves the accuracy of determining the boundaries of necrotic sections of long tubular bones.

Claims (1)

A method for determining the boundaries of necrotic sections of long tubular bones, including computed tomography, characterized in that the obtained bone images at each of the scan levels are divided into sectors of 30-60 °, in the peripheral part of each of them bone densitometric parameters are determined in units of the Hounsfield scale , when the indicated indicator is exceeded by 15%, in comparison with its value for a healthy bone section in the patient being examined, the conditions are diagnosed in this bone section necrosis, perform image reconstruction of the affected segment in at least two perpendicular planes and connecting the extreme points of necrosis areas, define the boundaries of the bone lesions.

Images