Krotova, A. D.

Kruzhalov, A. V.

Pankina, S. V.

Pankina, V. V.

Sarycheva, M. N.

Surdoa, A. I.

Zelenind, A. V.

Ural State Medical University Repository

Contents lists available at ScienceDirectRadiation Measurementsjournal homepage: www.elsevier.com/locate/radmeasA portable radiometric system for nuclear medicineS.V. Pankina,∗, A.I. Surdoa,b, A.D. Krotova, M.N. Sarycheva, V.V. Pankina,c, A.V. Zelenind,A.V. KruzhalovaaUral Federal University, Mira Street 19, Ekaterinburg, 620002, Russiab Institute of Industrial Ecology UB RAS, Sophy Kovalevskoy Street 20, Ekaterinburg, 620137, RussiacUral State Medical University, Repina Street 3, Ekaterinburg, 620014, Russiad Regional Children's Clinical Hospital, Serafimy Deryabinoy Street 32, Ekaterinburg, 620149, RussiaA R T I C L E I N F OKeywords:Nuclear medicineDynamic scintigraphyRadiopharmaceuticalPhantomA B S T R A C TIt's shown suggested methods for diagnosing pathological processes in biological objects using a developedportable radiometric system with four gamma-ray detectors. Designed portable radiometric system was used tomake 2D imaging of anatomical structures. The system can value pharmacokinetics in several points of wide areaof interest at the patient body. In this study specially designed phantoms were used. Phantom models of the liverand blood circulation system were made to assay radiometric system. The construction concept and possibleapplications of the system in the practice of radionuclide diagnostic studies in vivo are presented.1. IntroductionThe main goal of radionuclide diagnostics in vivo is quantitativeassessment of a radiopharmaceutical (RFC) in a biological object. In themiddle of the 20th century, scintigraphy studies in vivo were conductedby means of single-detector and multi-detector radiometric systemsbased on scintillation counters with vacuum photomultipliers (Pankinet al., 2016). The old systems had some disadvantages: stationary pla-cement, large size, heavy weight, high-voltage needs (more than1000 V) and lack of digital data processing capabilities (the systemswere manufactured before the era of personal computers). Currently,the most common technical solution for conducting radionuclide di-agnostics is the use of a gamma camera (Rosental et al., 1995). It isimportant to note that these technical devices also feature dis-advantages that limit their functionalities. Because of its large dimen-sions, medical staff cannot move a gamma camera around the medicalinstitution. Its detectors have a limited field of view, which does notallow dynamic pharmacokinetic parameters to be investigated in areasof interest which are apart from each other more than 50 cm. The abovedrawbacks can be overcome by using a radiometric system (RS). Such asystem can employ several detectors (Pankin et al., 2018). The mainadvantages of this system are small size and weight enabling an ex-amination to be carried out by placing a number of detectors in severalzones of interest. Each detector can be attached to the patient's bodymaking it possible to conduct functional tests using a RS. This approachcould allow the functionality of the radionuclide diagnostics to be tosignificantly expanded.The RS being developed (Fig. 1) includes a set of gamma radiationdetectors (see Fig. 1, pos. 1, 2, 3, and 4). The detection units areequipped with a set of replaceable collimators (pos. 5) enabling one toeffectively record RFC accumulation in zones of interest. The detectorof the RS consists of CsIeTl scintillation crystals (pos. 6) and modernsmall-sized silicon photoelectronic multipliers (pos. 7) or SiPM, con-nected with analog to digital converter (pos. 8). Each of detection unitsmeasures 3×3×2 cm3. Also system has a microcontroller (pos. 9) anda personal computer (pos. 10) to control measurement, data acquisitionand processing, and data analysis (Pankin et al., 2018). The systemunder development could be particularly useful where it is essential toassess the dynamics of RFC passage, accumulation in and excretionfrom organs and tissues which are located at several points at somedistance from each other and which would not be captured by a to-mograph's field of view. Scintigraphy in the static 2D imaging mode canbe carried out by step-by-step scanning using the RS where the patientcannot be delivered to a stationary installation (for example, in thesurgical field). The purpose of this study is to develop a technique fordiagnosing pathological processes in the liver and heart using a radio-metric system and develop phantoms of the liver and single-chamberheart.2. Experiment and resultPhantom tests are required to be carried out before putting any newhttps://doi.org/10.1016/j.radmeas.2018.12.003Received 21 October 2018; Received in revised form 4 December 2018; Accepted 5 December 2018∗ Corresponding author.E-mail address: savva.pankin@urfu.ru (S.V. Pankin).Radiation Measurements 121 (2019) 10–12Available online 06 December 20181350-4487/ © 2018 Elsevier Ltd. All rights reserved.Tmedical technique into use. The purpose of these tests is to verify thedevice as a whole, its configuration, ability to scan certain systems ofthe body, and the selection of collimation system parameters. The RSbeing developed has been tested using models of such biological objectsas the liver and heart including mathematical descriptions to enablechecking the key parameters of the prototype. The study was carriedout at the Radionuclide Diagnosis Department of Regional Children'sClinical Hospital No. 1 in Ekaterinburg.2.1. Static scintigraphy using the PRS in the 2D scanning mode for liverpathology diagnosis as an exampleTo enable the RS detector to be moved in two coordinates and studyRFC distribution in the patient's body, we have developed a specialmovement device. The experimental setup consists of a RS detector, ascanning device, RFC solution, a liver phantom. Scanning device allows2D scanning at a minimum step of 1mm (Pankin et al., 2018). Liverradionuclide diagnostics implies identifying low RFC accumulationzones which characterize the pathological process as a tumor. The maintask of imaging is to assess the size, shape and position of the liverrelative to the other anatomical structures and to assess the severity andnature of damage to this organ.Medical institutions use a liver phantom (Fig. 2) for modeling liverpathologies (Zedgenidze et al., 1968). A schematic view of the phantomis shown in Fig. 2. It had three steps with two plastic cylinders placedFig. 1. General view of the radiometric system and its structure scheme.Fig. 2. Liver phantom.Fig. 3. Result of scanning the liver phantom with RS.Fig. 4. General view of the single-chamber heart phantom for dynamic studies.Fig. 5. Curves for changes in the activity of the first passage, measured at pos. 1(1), pos. 2 (2), pos. 3 (3) and pos. 4 (4).S.V. Pankin et al. Radiation Measurements 121 (2019) 10–1211on each step to simulate reduced RFC accumulation in the liver. Thecylinders located on the first step measured ∅15× 20mm3 and∅20× 20mm3 (see Fig. 2, pos.1, 2); on the second, ∅20×20mm3and ∅30× 20mm3 (pos.3, 4); and on the third one, ∅30×20mm3and ∅40× 20mm3 (pos.5, 6). The phantom was filled with 1.5 L of anRFC solution based on Tc99m with an activity of 27 MBq. The height ofthe liquid level was 25mm over the first step, 60mm over the secondand 100mm over the third. For these parameters of the phantom and adistance of 20mm from the detector to the liquid surface, the resolutionwas 15mm for the first step, 25mm for the second, and 35mm for thethird. The technique used for calculating the collimators for the PRSand its resolving power were described in (Pankin et al., 2016).A Z-phantom scan was obtained using the scanning unit at a scan-ning step of 4mm and a measurement time of 1 s as shown in Fig. 3“Cold areas” and the boundaries of the phantom steps are marked withwhite dashed lines showing the dimensions. It can be seen that for thegiven parameters the setup can recognize “cold areas” located on thefirst and second steps of the phantom. On the third step, it can distin-guish only the largest “cold area”. These data enable the resolvingpower of the 2D scanning system to be estimated. At a depth of 25mm,it is 20mm; at a depth of 60mm, 30mm; and at a depth of 100mm,40mm. Thus, the obtained resolution values are close to those calcu-lated above.2.2. Dynamic scintigraphic studies using RSTests in the dynamic mode were carried out using a prototype forthe central circulation system. To this end, we developed a phantom(Fig. 4) simulating the pulmonary circuit. The phantom mimicked apulsating single-chamber heart with one circulation circuit. The pro-totype used was the phantom previously developed by Pieter deBondt,MD (Pieter De Bondt, 2005). The installation consisted of 4 RS detectors(Fig. 4, pos. 1, 2, 3, 4), a single-chamber heart model (pos. 5), a cir-culation circuit (pos. 6), a pump (pos. 7), two check valves (pos. 8, 9)ensuring the circulation of the liquid in one direction only and a syringefor injecting the RFC (pos. 10). Using the phantom, we modeled thefollowing simple processes: injection of RFC in various ways, bloodcirculation at a “cardiac pace”, and dilution of the drug in the blood.Each injection contained 1ml of Tc99m solution (12 MBq activity)stained with methylene blue. The activity of the solution was monitoredby an “RIS-A1″ radiometer (“Amplitude” company). The RS detectorcollimators were made from lead and reduced the background signal.The collimators are of divergent design to ensure that the detector fieldof view captures just a small area of the phantom, 1–2 times larger thanthe dimensions of the detector. Injections were made into the tube withan insulin syringe through a needle, with three detectors located nearthe tube so that the distances from them to the injection site were 5, 25and 60 cm, respectively. The fourth detector was located at the bottomof the heart vessel so that its field of view captured the entire volume ofthis vessel.Fig. 5 presents data on the pharmacokinetics obtained with the RSon the single-compartment heart phantom. The positions of the RSdetectors are shown in Fig. 4 as detectors 1–4. Data processing allowedmonitoring the process of bolus dilution depending on the distance ofits traveling along the tube (curves 1–3) and the pulsations of the heartseen as a sawtooth change in activity (curve 4). An analysis of phar-macokinetic data helps to determine optimal distances between the RFCinjection points and the positions of the detectors for the given ex-perimental conditions, as well as blood vessel clamping options beforeRFC injection. Moreover, as shown in (Krotov and Pankin, 2017), thistechnique allows one to estimate the total volume of blood circulatingin the patient's body. According to (Krotov and Pankin, 2017), it can becalculated from the area of the bolus first passage peak (on either of thecurves 1, 2 or 3), and after a certain time with the same integrationparameters, from the area under the total dilution plateau. The peakarea of the first bolus passage can be determined on either of the curves1, 2 or 3, but there are limitations associated with the patient's bio-metric parameters and time-periodic blood flow characteristics. Placinga detector near the heart chamber vessel made it possible to determinethe cardiac ejection fraction of the phantom. The tests have confirmedthe possibility of using the RS for evaluating patients' hemodynamicparameters. The advantage of the system is that its detectors can beplaced on patient's limbs for evaluating the dynamic parameters of thepharmacokinetics.3. ConclusionThe possibilities of using the developed radiometric system for staticand dynamic studies on liver and heart phantoms, respectively, havebeen considered. Importantly, joint use of RS and gamma camera makesit possible to supplement the time-lapse recording of pharmacokineticsin a certain part of the patient's body with information that is obtainedfrom areas of interest outside the detector's field of view.ReferencesDe Bondt, Pieter, Tom Claessens, Rys, Bart, De Winter, Olivier, Vandenberghe, Stijn,Patrick, Segers, Pascal, Verdonck, Andre Dierckx, Rudi, 2005. Accuracy of 4 differentalgorithms for the analysis of tomographic radionuclide ventriculography using aphysical, dynamic 4-chamber cardiac phantom. J. Nucl. Med. 1 (46), 165–171.Krotov, A.D., Pankin, V.V., 2017. Automated processing of first-pass radioisotope ven-triculography data to determine essential central circulation parameters. AIP Conf.Proc. 1886, 020097. https://doi.org/10.1063/1.5002994.Pankin, S.V., Sarychev, M.N., Surdo, A.I., Ivanov, V.Y., 2016. Design of collimationsystem for gamma probe. Izvestiya vuz. Fizika. 59 (9–2), 180–183 (In Russian). ISSN:0021-3411.Pankin, S.V., Sarychev, M.N., Pankin, V.V., Surdo, A.I., Krotov, A.D., Ivanov, V.Yu,Zelenin, A.V., 2018. Portable radiometric system for radionuclide diagnostics. J.ANRY. 2 (93), 40–47 (In Russian). ISSN: 2075-1338.Rosenthal, M.S., Cullom, J., Hawkins, W., Moore, S.C., Tsui, B.M.W., Yester, M., 1995.Quantitative SPECT imaging: a review and recommendations by the focus committeeof the society of nuclear medicine computer and instrumentation council. J NuciMed36 (8), 1489–1513.Zedgenidze, G.A., Zubovskiy, G.A., 1968. Izucheniye Gemodinamiki S PomoshyuRadioaktivnyh Izotopov. Klinicheskaya Radioizotopnaya Diagnostika, Moscow (InRussian).S.V. Pankin et al. Radiation Measurements 121 (2019) 10–1212

A portable radiometric system for nuclear medicine

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A portable radiometric system for nuclear medicine

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