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8of radiopharmaceuticals, which provides information on activity in these areas of interest. Osteoblast activity can be used to assess the healing process at an early stage of implant treatment and can assess any variable in the process of osseointegration.
References:
1. Albrektsson T, Johansson C. Osteoinduction, osteoconduction and osseointegration. Eur Spine J 2001;10(suppl 2): S96-S101
2. Alberto PL. Implant reconstruction of the jaws and craniofacial skeleton. Mt Sinai J Med 1998;65: 316-21
3. Bambini F, Meme L, Procaccini M, Rossi B, Lo Muzio L. Bone scintigraphy and SPECT in the evaluation of the osseointegrative response to immediate prosthetic loading of endosseous implants: a pilot study. Int J Oral Maxillofac Implants. 2004 Jan-Feb;19(1):80-6
4. Bhandari SK, Mondal A. Role of single photon emission computerised tomography in evaluating osseointegration of indigenous DRDO implants: An in vivo study. Med J Armed Forces India. 2016 Jan;72(1):48-53
5. Bragger U, Burgin W, Lang NP, Baser D. Digital subtraction radiography for the assessment of changes in peri-implant bone density. Int J Oral Maxillofac Implants 1991;6:160-6
6. Cerevelli V, Cipriani C, Migliano E, et al. SPECT in the longterm evaluation of osseointegration in intraoral and extraoral implantology.3 J Craniofac Surg. 1997 Sep;8(5):379-382
7. Gahlert M, Rohling S, Wieland M, Sprecher CM, Kniha H, Milz S. Osseointegration of zirconia and titanium dental implants: a histological and
histomorphometrical study in the maxilla of pigs. Clin Oral Implants Res. 2009;20(11):1247-1253
8. Galasko CS. Proceedings: the pathological basis for skeletal scintigraphy. Br J Radiology 1975;48:72-6
9. Jamil MU, Schliephake H, Berding G. Prosthetic scintigraphic study of healing of implants combined with bone transplantation in extreme atrophy and after tumor resection.4 Mund Kiefer Gesichtschir. 1999;3:35-39
10. Khan O, Ell PJ, Jarrit PH, Cullum ID. Emission and transmission computed tomography in the detection of space occupying diseases of the liver. Br Med J 1981;283:1212-4
11. Khan O, Archibald A, Thomson E, Maharaj P. The role of quantitative single photon emission computerized tomography (SPECT) in the osseous integration process of dental implants. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2000 Aug;90(2):228-32
12. Meidan Z, Weisman S, Baron J, Binderman I. Technetium 99m-MDP scintigraphy of patients undergoing implant prosthetic procedures: a follow up study.27 J Periodontal. 1994 April;65(4):330-335
13. Schliephake H, Berding G, Neukam FW, Bothe KJ, Gratz KF, Hundeshagen H. Use of sequential bone scintigraphy for monitoring onlay grafts to grossly atrophic jaws. Dentomaxillofac Radiol. 1997 Mar;26(2):117-24
14. Schliephake H, Berding G. Evaluation of bone healing in patients with bone grafts and endosseous implants using SPECT.2 Clin Oral Implants Res. 1998;9(1):34-42
15. Subramanian G, McAfee JG. A new complex of 99mTc for skeletal imaging. Radiology. 1971 Apr;99(1):192-6
Hristov I. G.
Assistant of Department of Periodontology and Dental Implantology
Medical University - Varna, Bulgaria
Peev St.V.
doctor of medical sciences, professor, Medical University - Varna, Bulgaria Chaushev B.G. doctor of medicine, associate professor Medical University - Varna, Bulgaria
APPLICATION OF SPECT EXAMINATION WITH 99MTC MDP IN DENTAL IMPLANTOLOGY
ХристовИвайло Георгиев
ассистент кафедрыПародонтология и дентальная имплантология Медицинский университет - Варна, Болгария Пеев Стефан Василев доктор медицинских наук, профессор, Медицинский университет - Варна, Болгария Чаушев Борислав Георгиев доктор медицины, доцент Медицинский университет - Варна, Болгария
ПРИМЕНЕНИЕ ОФЭКТ ИССЛЕДОВАНИЯ С 99MTC MDP В СТОМАТОЛОГИЧЕСКОЙ
ИМПЛАНТОЛОГИИ
DOI: 10.31618/ESSA.2782-1994.2021.2.76.207
Summary. Treatment with intraosseous osteointegrable dental implants is a modern therapeutic method that achieves complete rehabilitation by fully restoring the patient's masticatory function and aesthetics. The success of their application is closely related to the process of osseointegration. Osteointegration is the process of bone formation between the alloplastic material and the surrounding biological environment. The quality and quantity of bone available is a major prognostic factor for the success of dental implants. Some authors evaluate metabolic activity of bone after placement of dental implants or bone grafts using conventional scintigraphy and singlephoton emission computed tomography (SPECT). The aim of the publication is to present the application of the SPECT study with 99mTc MDP in dental implantology.
Аннотация. Лечение внутрикостными остеоинтегрируемыми дентальными имплантатами -современный терапевтический метод, позволяющий добиться полной реабилитации за счет полного восстановления жевательной функции и эстетики пациента. Успех их применения тесно связан с процессом остеоинтеграции. Остеоинтеграция - это процесс формирования кости между аллопластическим материалом и окружающей биологической средой. Качество и количество доступной кости является основным прогностическим фактором успеха имплантации зубов. Некоторые авторы оценивают метаболическую активность кости после установки дентальных имплантатов или костных трансплантатов с помощью традиционной сцинтиграфии и однофотонной эмиссионной компьютерной томографии (ОФЭКТ). Цель публикации — представить применение исследования ОФЭКТ с 99mTc MDP в дентальной имплантологии.
Key words: SPECT, 99mTc MDP, dental implants, osseointegration, bone,
Ключевые слова: ОФЭКТ, 99mTc MDP, дентальные имплантаты, остеоинтеграция, кость
Introduction: In contrast to the large and growing number of dental implant systems, the parameters used to assess their clinical status and peri-implant environment are still limited. Clinical evaluation of peri-implant tissue is usually made on the basis of X-ray images, implant mobility, sensitivity and percussion sound. Although these tests are very useful for diagnosing and assessing the periodontal tissues of natural dentition, they can be misleading in assessing peri-implant tissue. It has been proven that even X-ray examinations do not adequately describe the condition around the implant [37].
Computed tomography (CT) quantifies bone and morphological changes in it, but cannot account for the dynamics of osteoblast activity. [5, 15, 40, 58]
Bone scintigraphy is a well-established imaging technique that accurately reflects osteoblast activity. [26] In most clinical situations, information from conventional bone scintigraphy is sufficient for diagnosis, but accurate quantitative analysis may be difficult due to tissue deposition.
Bone scintigraphy allows the study of bone metabolism in the peri-implant area, providing not only anatomical images, but also information about the physiological and dynamic changes that occur during osseointegration. SPECT methods allow the reconstruction of three-dimensional images with the distribution of radiopharmaceuticals that have accumulated in bone structures. [16]
Single-photon emission computed tomography (SPECT) is a medical imaging technique that is based on conventional imaging methods in nuclear medicine and tomographic reconstruction. The images reflect functional information about the patient's condition, similar to that obtained by positron emission tomography (PET) [17].
SPECT and PET provide information based on the spatial concentration of injected radiopharmaceuticals, unlike other medical imaging methods used for clinical diagnostic purposes. [1, 13, 16, 33]
Radioisotope scintigraphy using technetium-99m-methylene diphosphonate (Tc-99m-MDP) proved to be a reliable method for measuring increased metabolic activity at specific sites of skeletal tissue [7, 52, 54, 57].
This technique allows to obtain a three-dimensional representation of the distribution of radioactivity in the area / organ of interest, corresponding to greater diagnostic accuracy, volumetric measurements, morphological details and details of physiological activity through accurate volumetric measurements, ie. by quantizing the distribution of radioactivity per unit volume of tissue, [22] which helps to ensure accurate measurement of quantitative physiological events such as osteoblast activity and bone healing.
Aim: The aim of the publication is to present the application of the SPECT study with 99mTc MDP in dental implantology.
Exposition: The principles of nuclear medical tomography were laid down in 1917 with the work of the Austrian mathematician Radon, who proved that a three-dimensional image of an object can be reconstructed from a number of its projections. [60]
The method was first practically applied by Bracewall in 1956. SPECT is single photon emission computed tomography. The modern tomography gamma camera is combined in one device with a low-dose computer tomograph SPECT / CT. This device allows for functional and anatomical examination of the object [28].
The main principle of operation of SPECT is based on the circular motion of a detector around the patient's body, registering photons emitted by it. The activity data are processed by specialized software, subjected to mathematical processing and reconstruction of the studied object. [28].
SPECT device
Collimator
The collimator is an essential part of the nuclear medical equipment, an element of the visualization system that plays an essential role in the formation of
the sensitivity and resolution of the gama camera. It is used for the transmission of certain y-quanta, which move perpendicularly, providing sharp and clear contours of the studied object.
The collimator covers the inlet side of the second element - scintillation crystal.
Scintillation crystal
Scintillation is a short-lived glow in a substance caused by an ionizing particle, optical excitation is obtained and photons of light are emitted. Sodium iodide with thallium NaJ (Tl) is most commonly used as a scintillation detector. Pure sodium iodide scints only at low temperatures. The introduction of waist as an impurity in a very small concentration - 0.2% creates the so-called luminescent centers, which can be excited by ionizing radiation at room temperature.
The scintillation crystal has a high atomic number and is sealed in aluminum foil because it is highly hygroscopic. The photons from one scintillation are distributed throughout the crystal and to all photoelectronic amplifiers (VEMs).
Photoelectronic amplifiers
They are an electronic vacuum device that transforms light pulses into electric ones and amplifies them.
Fiber optic
It is a transparent plexiglass that improves the optical connection between the crystal and the photomultiplier tube.
Radioactive isotopes have been used as indicators to monitor bone metabolism since 1961, when 85Sr was first used in humans for scintigraphic imaging of bone lesions. [23]
Phosphate complexes with technetium-99m (99mTc) were developed in the early 1970s) [55], and today 99mTc methylenediphosphonate (MDP) is routinely used for bone scintigrams due to its favorable physical properties for imaging with a conventional gamma camera [3]. The 99mTc-MDP complex accumulates in areas of bone activity depending on vascularization and the degree of metabolic activity [10, 11, 12, 14, 21, 27, 31, 39, 53].
One of the main advantages of nuclear medicine research methods, compared to other imaging methods, is the ability to visualize the function of the organ before the appearance of structural changes.
Functional imaging provides both qualitative and quantitative assessment of normal and / or altered organ function.
SPECT uses conventional two-dimensional images of nuclear medicine obtained from different views around the patient, and provides an estimate of the three-dimensional distribution of radioactivity using multi-projection image reconstruction methods. SPECT differs from X-ray computed tomography (CT) in that the source of radiation is inside instead of outside the patient. The purpose of SPECT is to determine the exact three-dimensional distribution of radioactivity resulting from the introduction of a radiopharmaceutical inside the patient (instead of the distribution of the attenuation coefficient from different tissues obtained from conventional CT). SPECT uses
radiopharmaceuticals that are common in nuclear medicine clinics, rather than those that emit positrons with the subsequent generation of two photons of 511 keV annihilation, as in the case of PET. [34]
The amount of radiopharmaceutical that can be administered is limited by the patient's allowable radiation dose. This requirement results in a limited number of photons that can be used for imaging. Also, the angle of reception or the geometric response of the collimator further limits the proportion of photons that are acceptable for projection data. The collimator can be designed to allow the detection of more photons, but increased detection efficiency can usually only be achieved by a simultaneous loss of spatial resolution. The main goal of the development of the SPECT toolkit is to increase the efficiency of detection, while improving the spatial resolution of the imaging system, goals that are pursued by adding more detectors around the patient [22].
The process of SPECT imaging imposes difficulties and challenges in image reconstruction. For example, before leaving the patient, many photons of y-rays experience photoelectric interactions that cause photons to be absorbed, and thus many experience Compton scattering, which changes the direction and energy of the original photons. When conventional reconstruction techniques (eg, X-ray CT algorithms) are used in SPECT, the reconstructed images are severely affected by statistical noise fluctuations, poor spatial resolution, low contrast, and inaccurate quantitative information [34].
The literature on the assessment of peri-implant bone changes and the study of osseointegration shows the use of radio frequency analysis (RFA), histological and histomorphometric methods, X-rays, tomography, scintigraphy and SPECT studies [16, 30, 41, 49]. The reliability of RFA for predicting implant stability and determining loading time remains questionable [2]. The use of histological and histomorphometric methods [25, 51] for this purpose it requires sacrifice of the area of interest together with the implant. Radiological examination provides only a two-dimensional morphological quantification of the area of interest in a single plane. [42] Tomography can provide quantification of morphological changes in all three planes, but fails to provide information on physiological activity. [44] Scintigraphy can reflect physiological activities in one plane, [26] with an inherent limitation of accurate quantitative analysis attributed to distortion and overlap of unwanted anatomical structures; whereas SPECT studies provide further refinement compared to scintigraphy as it provides accurate qualitative and quantitative analysis, [32, 33] but with restrictions on additional radiation exposure and increased cost. [38]
Wahl examined peri-implant tissue when placing dental implants in dogs and showed an increase in osteoblast activity during the first 4 weeks after implantation and 4-6 weeks after loading with a prosthetic structure. [59] In 1994, Zeev et al. performed a 99mTc-MDP scintigraphic examination of the peri-implant bone in 26 patients and placed a total of 55
implants - 25 screwed and 30 knife-shaped. They determine the "bone scan index" (BSI) - the result of the ratio of counts in the peri-implant area and counts in the contralateral, untreated jaw area, as well as counts in the temporal bone area. In all patients examined, the "bone scan index" showed high values every 2-4 weeks and a decrease in activity to baseline around the 20th week after implantation. [41]
Meidan Z et al. [41] in 1994 they used scintigraphy to assess peri-implant tissue. They used the term bone scan index (BSI) to reflect metabolic activity in the peri-implant area. The mean BSI using these implants peaks after 2.5 weeks and gradually decreases to preoperative values after 16 weeks,
Cervelli et al. [16] in 1997 they used the SPECT study to assess the dynamics of osseointegration in 25 patients who were admitted to intraoral and extraoral implantology with different prostheses. Patients were followed at week 3 and at 3, 6, 12, and 24 months after implant placement. This study showed a peak in osteoblast activity, reached 3 weeks after surgery, which gradually decreased. After 6 months, there is an increase in osteoblast activity around intraoral implants associated with prosthetic loading.
Schliephake and Berding evaluated the bone healing process by SPECT of autologous grafts in atrophic edentulous jaws in connection with the placement of intraosseous implants in 24 patients. Nuclear medical examination is performed after intravenous administration of 8 MBq 99mTc-methylene diphosphonate (MDP) per kg / body weight for each patient immediately after surgery, before implant placement, after implant placement and before abutment placement. The scintigram is displayed with a spatial resolution of 15 mm. ROI areas of interest are placed on the calvary to estimate the semiquantitative distribution of the radiopharmaceutical by comparing the counting density (count / pixel) ratios between the ROI at the graft site and the reference ROI. The authors demonstrate that bone scintigraphy is useful for assessing the tissue and cellular response of autografts. [49]
In order to evaluate the healing process in autogenous grafts on edentulous jaws after tumor ablation and subsequent implantation Jamil MU et al. [30] conduct a SPECT study. They examined a total of 24 patients with secondary implant placement 21.4 weeks after transplantation. The authors found that there is a significant reduction in marker uptake during graft healing, which increases significantly after implant placement and subsequently decreases during implant healing. As the values of osteoblast activity and time of the SPECT study are not provided by the author, the study cannot be compared with another. The authors document that in patients with compromised healing, the absorption of the radiopharmaceutical indicator (OAI) is significantly lower than in patients with trouble-free healing.
The latest gamma cameras are fully digitalized and equipped with high-resolution collimators, which provide a spatial resolution of approximately 7 mm at a distance of 5 cm from the surface of the collimator. [50]
Khan et al in 2000 [34] evaluate the integration process in Astra Tech, Swedish intraosseous dental implants, using SPECT. They placed implants in the edentulous jaws of 5 patients and performed a SPECT examination before prosthetic restoration and regularly at intervals of 5 months after loading the implants. Periimplant bone activity is compared to activity in reference ROI areas placed on the skull. The authors distinguish the following phases: 1) increase of cellular activity immediately after implant placement; 2) peak in activity, registered 30 days after implant placement; 3) gradual decrease in activity, which returns to normal physiological levels after 4 months
npe3 2004 r. Bambini et al. [9] conducted a SPECT study in two patients, in which intraosseous implants were placed in the area of the lower second premolars. The implants in the right half of the jaw are loaded 48 hours after the manipulation of their placement (test area), and those in the left half are left unloaded (control area). On the 30th and 90th day after implant placement, a SPECT test is performed. Identify three areas of interest ROI - 1) around the immediately loaded implant; 2) around the unloaded implant and 3) on the skull. The count / pixel ratio obtained from each ROI is used for semi-quantitative evaluation. The authors found a peak in osteoblast activity in both implanted areas, which decreased on the 90th day. They also draw conclusions about the higher degree of osteoblast activity in implants whose surface has been pre-treated by the sandblasting / acid-etching method.
Jaffin et al. and Roccuzzo et al. emphasize the advantage of sandblasted / acid-etched implant surfaces in immediate and early implant loading [29, 47].
According to Albrektsson and Johansson, osseointegration is a process that involves implantation in the bone through direct titanium tissue contact. [4]
A number of authors in their studies have shown success in the immediate loading of implants whose surface has been pre-treated - sandblasted / acid-etched. This proves that the implant surface plays an important role in the process of osseointegration due to the affinity of osteoblasts for rough surfaces. [18, 35, 45, 46, 56]
In 2012, Bhandari et al. conducted a study of 21 patients. They monitor osteoblast activity by SPECT in the bone around implants placed by the indigenous implant system. The study was performed 5 times, starting 7 days before implantation with subsequent examinations on the 14th, 42nd, 56th and 84th day of implantation. The aim is to determine the time required for a complete healing process, as well as the time for loading the implants. The authors compare the pixel / count activity in the area of interest with the activity in the control area - the skull area. Based on these results, they establish a peak in osteoblast activity 14 days after implantation and a decline that reaches pre-implant levels about 3 months after implantation, which indicates a completed healing process and the possibility of exercise. [13]
The diagnostic capabilities of nuclear medicine are largely determined by the variety of different radiopharmaceuticals. Radiopharmaceuticals are
chemical compounds and are a combination of a radioactive element - a radionuclide (pH) and a biologically active substance - a carrier, responsible for their distribution in the body.
Radiopharmaceuticals are also called labeled tracers, monitor biological processes, illustrate organ function and exhibit different tissue specificity. [8]
The distribution of radiopharmaceutical accumulation in skeletal tissues can be represented by planar scintigrams with a spatial resolution of 9-15 mm [24]. This technique is widely used in the monitoring of peri-implant bone remodeling, as well as in patients with bone grafts with or without one-time implant placement. [48]
Unlike planar scintigrams, SPECT can reflect the accumulation of a radioactive isotope in more detail by phasing out layers of activity. This allows three-dimensional analysis of bone metabolism without superimposing deeper or superficial tissue layers. [36]
Technetium (TC) was discovered in 1937 at the University of Palermo, Italy by Carlo Perrier and Emilio Serge. It gets its name from the Greek "technetius" -artificial. Technetium is a metal with a silver-gray color, with a crystalline hexagonal structure. 34 isotopes of technetium are known. The most common isotope in nature is 99Tc - a product of the spontaneous decay of uranium ore 235 U. From a nuclear medical point of view the most important is the metastable isotope - 99mTc [20].
Radioactive isotopes have been used as tracers to monitor bone metabolism since 1961, with 85Sr being the first isotope used in humans to scintigraph bone lesions. [23] Phosphate-labeled 99mTc was developed in the 1970s, and today 99mTc-MDP is standardly used for bone scintigraphy due to its good physical properties and is imaged with a gamma camera. [3, 55]
99mTc-MDP complex accumulates in areas with increased bone activity, depending on the degree of vascularization and metabolic activity [10, 11, 12, 21, 27, 31, 39, 53].
99mTc is a pure y-emitter with high energy - 141 keV - energy in the optimal range for detectors. Stable for labeling and clinical application. It has seven valence electrons, making it chemically universal for marking a large number of radiopharmaceuticals. The isotope is prepared by a 99-Mo / 99mTc generator. Half-life T1 / 2 = 6.02 hours, compared to 99Ts - 211 years. 99mTc radiopharmaceuticals have an optimal benefit-risk balance [6].
The 99mTc radioisotope is derived from a 99-Mo / 99mTc generator. The starting radionuclide (mother) is produced by controlled neutron bombardment of uranium 235 in a nuclear reactor. The resulting eluate is subjected to quality control by checking: . The presence of 99-Mo may be due to excessive elution, disruption of column integrity, elution with saline with pH> 7. The presence of 99-Mo in the eluate is undesirable because it increases the radiation load on the patient and impairs the quality of the diagnostic image; chemical purity - chemical impurities of all non-radioactive materials that may cause adverse biological effects are checked, e.g. alumina test; radiochemical
frequency - radiochemical impurities have different biodistribution, which affects the image quality and accurate diagnosis; color and transparency of the eluate obtained; pH of the solution - norm pH 4-8. [6]
Technetium radiopharmaceuticals are widely used in nuclear medicine. In the 99mTc-MDP radiopharmaceutical, technetium binds to a chelating molecule diphosphonate in the MDP complex. It is widely used in the diagnosis of bone diseases: tumor metastases (lesions are detected up to 6 m earlier than in conventional X-ray examination), osteomyelitis, fractures, osteoporosis, assessment of osseointegration in implants (99mTc-MDP has increased absorption). in areas with increased bone metabolism) [50].
The radiation dose absorbed by bone tissue is 7.03 mGy for 740 MBq of 99mTcMDP, which is lower than the absorbed dose from the eyes, thyroid gland and bone marrow during a computed tomography scan of the head. A test that is often performed before implants are placed [19, 43].
They are obtained from radionuclide generators as a result of natural decay of another radionuclide -parent, which is fixed to the generator column.
Conclusions: The possibility of reconstruction of a multiplane image gives greater diagnostic accuracy. SPECT provides an excellent model applicable to the objective evaluation of bone grafts used in reconstructive surgery, and the technique is able to further quantify the osteoblast index when implanted materials are inserted into bone grafts.
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