Patient doses from PET-CT procedures.

Positron emission tomography (PET) was installed for the first time in Bulgaria in 2009, and nowadays two hybrid PET-computed tomography (CT) systems are in operation. The aim of this work is to estimate patient doses from PET-CT procedures and to explore potential for optimisation. Data were retrospectively collected for 50 patients examined with the system Philips Gemini TF and for 58 patients examined with the system GE Discovery 600. Whole-body examinations with radiopharmaceutical (18)F-2-fluoro-2-deoxy-D-glucose (FDG) were performed on all patients. Patient effective doses from the CT component of the examination were calculated with CT Expo software and compared with doses estimated applying the National Radiological Protection Board (NRPB) conversion coefficients. Effective doses from the PET component were calculated applying the ICRP 80 conversion coefficients. For the first system, average effective doses from CT component were 8.0 and 8.9 mSv, applying CT Expo and NRPB coefficients, respectively, and 4.9 mSv from PET component. For the second system, the corresponding values were 7.8, 8.7 and 5.9 mSv. These results for patient effective doses are relatively lower or comparable to other similar surveys. Reasons for the observed differences are analysed and presented.

Patient doses from hybrid SPECT-CT procedures.

The aim of this work is to estimate patient doses from hybrid single-photon emission computed tomography (SPECT) and computed tomography (CT) procedures. The study involved all four SPECT-CT systems in Bulgaria. Effective dose was estimated for about 100 patients per system. Ten types of examinations were considered, representing all diagnostic procedures performed in the SPECT-CT systems. Effective doses from the SPECT component were calculated applying the ICRP 53 and ICRP 80 conversion coefficients. Computed tomography dose index and dose length product were retrospectively obtained from the archives of the systems, and effective doses from the CT component were calculated with CT-Expo software. Parallel estimation of CT component contribution with the National Radiological Protection Board (NRPB) conversion coefficients was performed where applicable. Large variations were found in the current practice of SPECT-CT imaging. Optimisation actions and diagnostic reference levels were proposed.

Positron emission tomography combined with computed tomography for diagnosis of synchronous tumors.

BACKGROUND: The hybrid method 18F-FDG PET/ CT has been proven as a method of choice in oncology for diagnostics, staging, restaging of the tumor and evaluation of the therapeutic effect. The aim of the study was to determine the value of 18F-FDG PET/ CT for detection of synchronous tumors and consequently the influence on the patients management. MATERIAL AND METHODS: The examinations were performed on Discovery, GE Healthcare PET/ CT using standard protocol. Among the patients, examined by 18F FDG  PET/ CT for one year (n = 1 408), unsuspected synchronous tumors were detected in 11 cases (0.8%). RESULTS: Five pulmonary carcinomas, four head and neck squamous cell carcinomas (HNSCC), one ovarian carcinoma and one tumor of the sigma were detected as second malignancies. The histology verification was done in five cases (all HNSCC and one sigma carcinoma). In one patient with ovarian carcinoma, histology was obtained after surgery. In the rest of patients, no verification was undertaken because of the patients refusal and the advanced stage of the diseases, demanding systemic chemotherapy. Four patients (three with HNSCC and one with ovarian secondary malignancy) had favorable outcome during the nine  month  follow up. CONCLUSION: The hybrid method PET/ CT, combining the metabolic and morphologic findings, can help detection of synchronous malignancies in a small percentage of cases, but with a positive influence on management of considerable part of such patients.

[Gated SPECT myocardial perfusion stress scintigraphy for evaluation of the ischemic risk in coronary artery disease].

The aim of study is to identify the sensitivity of gated SPECT myocardial perfusion stress scintigraphy (MPSS) for detection of multi - vessel coronary artery disease (MVD) and in the evaluation of their functional impact for ischemic risk determination. Thirty three patients were examined with Tc99m sestamibi MPSS in rest and after exercise in order to identify the involved vessel territories by the perfusion and kinetic stress abnormalities and the development of ischemic left ventricular (LV) dysfunction by the decrease in LV ejection fraction (LVEF) and by the transient LV dilation (TID). A semiquantitative evaluation of the perfusion abnormalities by the summed difference index (SDI) (according to 20- segments model in 5 degree scale) was done. All patients had coronary angiography in the previous 2-3 months. According to angiography MVD had 51% of patients. A good coincidence for the concrete abnormal vessel territories existed between angiography and MPSS. A good sensitivity and specificity of the perfusion abnormalities were found (87.94%). Lower sensitivity with better specificity were found for kinetic abnormalities. This way the combination between them was convenient for detection of attenuation artifacts. A stress included dysfunction represented by decrease in LVEF was found in 33 % of patients (91 % of them with MVD). TID was present in 30%. A significant difference between LVD and MVD patient existed in SDI values (2.5 +/- 2.87 versus 5.12 +/- 2.57,). CONCLUSION. Gated SPECT MPSS is with good sensitivity and specificity for MVD detection and convenient for evaluation of its functional impact and ischemic determination.

[The use of radiopharmaceuticals for myocardial perfusion in oncological diagnosis]. / Prilozhenie na radiofarmatsevtitsite za miokardna perfuziia v onkologichnata diagnostika.

Recently, radiopharmaceutics for myocardial perfusion are widely used in oncological diagnosis, not merely supplementing the other methods of examination, but having also an independent role both in terms of making exact diagnosis, and in evaluating the diffusion of malignant tumors, as well as in estimating the results of the therapy undertaken. Their widespread implementation in practice is still not well enough studied, and awaits further clarification.

[Radionuclide ventriculography in the diagnosis of a postinfarct aneurysm and the evaluation of its impact on left ventricular function]. / Radionuklidnata ventrikulografiia za diagnostirane na postinfarktna anevrizma i pretsenka na otrazhenieto ì vurkhu levokamernata funktsiia.

This is a report on thirty-four patients subjected to radionuclide ventriculography because of suspected post-infarction aneurysm. To discover eventual kinetic disorders, apart from visual assessment of the wall kinetics, amplitude-phase analysis is also employed. The sensitivity of the method is compared with that of bi-dimensional echocardiography. The assessment of post-infarction left ventricular function by either of the methods is also compared. A correlation is established between left ventricular area involved by kinetic disorders, and reduction of the radionuclide total ejection fraction. The values of the latter, estimated echocardiographically, are consistently elevated.

[Radionuclide ventriculography for the diagnosis of postinfarct aneurysm and the assessment of its impact on left ventricular function]. / Radionuklidnata ventrikulografiia za diagnostirane na postinfarktna anevrizma i pretsenka na otrazhenieto i vurkhu levokamernata funktsiia.

Radionuclide ventriculography was performed in 34 patients suspected of having postinfarction aneurysm. In addition to visual appraisal of wall kinetics, amplitude-phase analysis was used for detecting kinetic disorders. The sensitivity of the method was compared with that of two-dimensional echography, and postinfarction left ventricular function was assessed by the two methods. Correlation was recorded between left ventricular plane affected by kinetic disturbances and the decrease of radionuclide total ejection fraction. Systematically higher were the values determined by echography.

[Volumetric indices of the left ventricle in patients with ischemic heart disease]. / Obemni pokazateli na liavata kamera pri bolni s IBS.

In addition to the conventional indices of radionuclide angiography with ECG-gait in equilibrium, the authors determined the volume indices of the left ventricle at rest by the so-called nongeometric method in 30 patients with ischemic heart disease. Patients without myocardial infarct (13 subjects) had decreased total left-ventricular ejection fraction (EF), as a result of increase in the end systolic volume index (ESVI) in one of the tested patients. Changes in the regional fractions and in the wall kinetics were detected in 6, resp. in 8 patients. Patients with myocardial infarct--13 subjects--had decreased total left ventricular EF, as a result increased ESVI in 4 patients. Disturbances in the regional fraction and in the wall kinetics had 9 patients. Estimated for the whole group, the mean ESVI level was significantly higher than in the former group of patients. Patients with postinfarction aneurysm, in addition to the marked decrease of the total left ventricular EF, had increased and-systolic and diastolic volume index, which in some of the patients was associated with reduced stroke volume index. The minute flow levels were significantly lower than in the former two groups. Determination of the volume indices is an important supplement to the efforts to gain precise information on the functional state of the left ventricle and for evaluation of the hemodynamics and of the effect of complications which occur with the advancing of the ischemic heart disease.

[Clinico-scintigraphic studies of bone disease (renal osteodystrophy) in patients on chronic hemodialysis (preliminary report)]. / Kliniko-stsintigrafski prouchvaniiana kostnata bolest (renalna osteodistrofiia) pri patsienti na khronokhemodializa (predvaritelno suobshtenie).

10 patients with chronic renal failure (6 women, 4 men), 19 to 59 years of age, duration of the disease form 3 up to 21 years, treated by hemodialysis from 2 to 5 years, were examined. The scintigraphic examination of the bones with 99mTc pyrophosphate (166.5.10(6) MBq) on the third hour after the i.v. application of the radiocolloid, registered by the scanning device SELO-DS-2, allows the discovery of the initial changes of the so called renal osteodystrophy (bone disease in patients on chronic hemodialysis). The coefficient bones/soft tissues may be used as a quantitative index of the renal osteodystrophy in these patients whereas the coefficient calvaria/sternum has not the same diagnostic value.