Nami Yeyin

Evaluation of radiation safety in (177)Lu-PSMA therapy and development of outpatient treatment protocol.

The aim of this study is to investigate the outpatient treatment protocol and radiation safety of a new-emerging lutetium-177 ((177)Lu) prostate specific membrane antigen (PSMA) therapy. This work analyzed the dose rate of 23 patients treated with 7400 MBq (177)Lu-PSMA at different distances (0, 0.25, 0.50, 1.0 and 2.0 m) and variable time marks (0, 1, 2, 4, 18, 24, 48 and 120 h) after the termination of infusion. Blood samples were withdrawn from 17 patients within the same group at 3, 10, 20, 40, 60 and 90 min and 2, 3, 24 h after termination of infusion. Seven different patients were asked to collect urine for 24 h and a gamma well counter was used for counting samples. Family members were invited to wear an optically stimulated luminescence dosimeter whenever they were in the proximity of the patients up to 4-5 d. The total dose of the medical team including the radiopharmacist, physicist, physician, nurse, and nuclear medicine technologist was estimated by an electronic personnel dosimeter. The finger dose was determined using a ring thermoluminescent dosimeter for the radiopharmacist and nurse. The mean dose rate at 1 m after 4 h and 6 h was 23  ±  6 μSv h(-1) and 15  ±  4 μSv h(-1) respectively. The mean total dose to 23 caregivers was 202.3  ±  42.7 μSv (range: 120-265 μSv). The radiation dose of the nurse and radiopharmacist was 6 and 4 μSv per patient, respectively, whereas the dose of the physicist and physician was 2 μSv. The effective half life of blood distribution and early elimination was 0.4  ±  0.1 h and 5  ±  1 h, respectively. Seven patients excreted a mean of 45% (range: 32%-65%) from the initial activity in 6 h. Our findings demonstrate that (177)Lu-PSMA is a safe treatment modality to be applied as an outpatient protocol, since the dose rate decreases below the determined threshold of  <30 μSv h(-1) after approximately 5 h and degrades to 20 μSv h(-1) after 6 h.

The evaluation of urine activity and external dose rate from patients receiving radioiodine therapy for thyroid cancer

The aim of this study was to determine the external dose rate of iodine retention as a function of time in the bodies of thyroid cancer patients during their isolation period in the hospital. Urine samples were collected at 6th, 12th, 18th, 24th h and 2nd, 3rd, 4th, 5th d from 83 patients after oral administration of (131)I and counted. The external dose rates were also simultaneously determined at the same time points. Then, it was expressed as retained radioiodine body activity versus dose rate. Effective half life calculated from urine sample measurements was found as 18.4±1.8 h within the first 24 h and 64±2.7 h between 48 and 120 h. According to this results, the external dose rate (<20 µSv h(-1)), which patients could be discharged, was achieved after 48 h for 3700 and 5550 MBq, and after 72 h for 7400 MBq of (131)I treatments.

Lu-177-PSMA-617 Prostate-Specific Membrane Antigen Inhibitor Therapy in Patients with Castration-Resistant Prostate Cancer: Stability, Bio-distribution and Dosimetry

Objective: The aim of the study was to estimate the radiation-absorbed doses and to study the in vivo and in vitro stability as well as pharmacokinetic characteristics of lutetium-177 (Lu-177) prostate-specific membrane antigen (PSMA)-617. Methods: For this purpose, 7 patients who underwent Lu-177-PSMA therapy were included into the study. The injected Lu-177-PSMA-617 activity ranged from 3.6 to 7.4 GBq with a mean of 5.2±1.8 GBq. The stability of radiotracer in saline was calculated up to 48 h. The stability was also calculated in blood and urine samples. Post-therapeutic dosimetry was performed based on whole body and single photon emission computed tomography/computed tomography (SPECT/CT) scans on dual-headed SPECT/CT system. Results: The radiochemical yield of Lu-177-PSMA-617 was >99%. It remained stable in saline up to 48 h. Analyses of the blood and urine samples showed a single radioactivity peak even at 24 hours after injection. Half-life of the distribution and elimination phases were calculated to be 0.16±0.09 and 10.8±2.5 hours, respectively. The mean excretion rate was 56.5±8.8% ranging from 41.5% to 65.4% at 24 h. Highest radiation estimated doses were calculated for parotid glands and kidneys (1.90±1.19 and 0.82±0.25 Gy/GBq respectively). Radiation dose given to the bone marrow was significantly lower than those of kidney and parotid glands (p<0.05) (0.030±0.008 Gy/GBq). Conclusion: Lu-177-PSMA-617 is a highly stable compound both in vitro and in vivo. Lu-177-PSMA-617 therapy seems to be a safe method for the treatment of castration-resistant prostate cancer patients. The fractionation regime that enables the longest duration of tumor control and/or survival will have to be developed in further studies.

Dosimetric Approach in Metastatic Differentiated Thyroid Cancer and Hyperthyroidism

Radioiodine (131I) therapy has been widely used for well-differentiated thyroid cancer and its metastases for many years. Two approaches, namely, empirical dosage and dosimetry-based methods, are currently utilized to manage the therapeutic iodine activity.

ESTIMATION OF THE ORGAN ABSORBED DOSES AND EFFECTIVE DOSE FROM 68Ga-PSMA-11 PET SCAN†

68Ga-PSMA-11 PET/CT has been proven to have high clinical value for imaging of prostate cancer and rapidly gained popularity. In this study, we aimed to investigate absorbed doses of 68Ga-PSMA-11. Seven patients (mean age = 66.9 ± 6.6 years, range: 57-79 years) were enrolled in the study. Whole body PET images were acquired with multiple time points. MIRD method, NUKFIT and OLINDA/EXM software were used for dosimetry calculations. Kidneys, bladder wall, salivary and lacrimal glands received the highest absorbed dose. Estimated absorbed doses to these organs after injection of 150 MBq 68Ga-PSMA-11 were 37.0, 12.6, 14.4 and 6.3 mSv, respectively. Effective dose from PET scanning with 150 MBq injected 68Ga-PSMA-11 was 2.5 mSv. In conclusion, 68Ga-PSMA-11 has a favorable dosimetry profile similar to the 68Ga labeled octreotide analogs, which are used safely in routine clinical practices for many years. No adverse effects were reported. The kidneys were the dose-limiting organs.

Evaluation of PET Scanner Performance in PET/MR and PET/CT Systems: NEMA Tests

Objective: The aim of the present study was to compare the performance of positron emission tomography (PET) component of PET/computed tomography (CT) with new emerging PET/magnetic resonance (MR) of the same vendor. Methods: According to National Electrical Manufacturers Association NU2-07, five separate experimental tests were performed to evaluate the performance of PET scanner of General Electric GE company; SIGNATM model PET/MR and GE Discovery 710 model PET/CT. The main investigated aspects were spatial resolution, sensitivity, scatter fraction, count rate performance, image quality, count loss and random events correction accuracy. Results: The findings of this study demonstrated superior sensitivity (~ 4 folds) of PET scanner in PET/MR compared to PET/CT system. Image quality test exhibited higher contrast in PET/MR (~ 9%) compared with PET/CT. The scatter fraction of PET/MR was 43.4% at noise equivalent count rate (NECR) peak of 218 kcps and the corresponding activity concentration was 17.7 kBq/cc. Whereas the scatter fraction of PET/CT was found as 39.2% at NECR peak of 72 kcps and activity concentration of 24.3 kBq/cc. The percentage error of the random event correction accuracy was 3.4% and 3.1% in PET/MR and PET/CT, respectively. Conclusion: It was concluded that PET/MR system is about 4 times more sensitive than PET/CT, and the contrast of hot lesions in PET/MR was ~ 9% higher than PET/CT. These outcomes also emphasize the possibility to achieve excellent clinical PET images with low administered dose and/or a short acquisition time in PET/MR.

Radiation Safety Process for the Patient and People Around during Diagnostic Radionuclide Studies

Feray Aras1, Suna Kıraç2, Aslı Ayan3, Meral Değer4, Mustafa Demir5, Semra Dönmez3, Bengül Günalp3, Mehmet İnce6, Bilal Kovan7, Kamil Köseoğlu8, İnci Alıç Özaslan9, Leyla Poyraz7, Türkay Toklu10, Bağnu Uysal11, Nami Yeyin5 1Celal Bayar Üniversitesi Tıp Fakültesi, Nükleer Tıp Anabilim Dalı, Manisa, Türkiye 2Yakın Doğu Üniversitesi Tıp Fakültesi, Nükleer Tıp Anabilim Dalı, Lefkoşa, KKTC 3T.C. Sağlık Bakanlığı Gülhane Eğitim ve Araştırma Hastanesi, Nükleer Tıp Kliniği, Ankara, Türkiye 4Marmara Üniversitesi Pendik Eğitim ve Araştırma Hastanesi, Nükleer Tıp Kliniği, İstanbul, Türkiye 5İstanbul Üniversitesi Cerrahpaşa Tıp Fakültesi, Nükleer Tıp Anabilim Dalı, İstanbul, Türkiye 6Epsilon Elektronik, İstanbul, Türkiye 7İstanbul Üniversitesi İstanbul Tıp Fakültesi, Nükleer Tıp Anabilim Dalı, İstanbul, Türkiye 8Ege Üniversitesi Tıp Fakültesi, Nükleer Tıp Anabilim Dalı, İzmir, Türkiye 9Üsküdar Devlet Hastanesi, Nükleer Tıp Kliniği, İstanbul, Türkiye 10Yeditepe Üniversitesi Tıp Fakültesi, Nükleer Tıp Anabilim Dalı, İstanbul, Türkiye 11Dokuz Eylül Üniversitesi Tıp Fakültesi, Nükleer Tıp Anabilim Dalı, İzmir, Türkiye *Üçüncü ve sonraki sırada yer alan yazarlar soy ismi sırasına göre yazılmıştır Nuclear Medicine Seminars / Nükleer Tıp Seminerleri 2016;3:172-175 UYGULAMA KILAVUZU DOI:10.4274/nts.024

Effects of hemodialysis on iodine-131 biokinetics in thyroid carcinoma patients with end-stage chronic renal failure.

ObjectivesRadioiodine therapy could be challenging in chronic renal failure patients requiring hemodialysis. The aim of this study was to establish the effects of hemodialysis on elimination of radioiodine from the body in thyroid carcinoma patients with end-stage chronic renal failure and to determine its effects on environmental radiation dose. Materials and methodsThree end-stage chronic renal failure patients (four cases) diagnosed with differentiated thyroid carcinoma requiring radioiodine therapy were included in our study. Each patient was given 50–75 mCi (1850–2775 MBq) iodine-131 with 50% dose reduction. Dose rate measurement was performed at the 2nd, 24th, and 48th hour (immediately before and after hemodialysis) after radioiodine administration. The Geiger–Müller probe was held at 1 m distance at the level of the midpoint of the thorax for the dose rate measurement. Results and conclusionThe effective half-life of iodine-131 for three patients was found to be 44 h. In conclusion, the amount of radioiodine excreted per hemodialysis session was calculated to be 51.25%.

Determining and Managing Fetal Radiation Dose from Diagnostic Radiology Procedures in Turkey.

Objective We intended to calculate approximate fetal doses in pregnant women who underwent diagnostic radiology procedures and to evaluate the safety of their pregnancies. Materials and Methods We contacted hospitals in different cities in Turkey where requests for fetal dose calculation are usually sent. Fetal radiation exposure was calculated for 304 cases in 218 pregnant women with gestational ages ranging from 5 days to 19 weeks, 2 days. FetDose software (ver. 4.0) was used in fetal dose calculations for radiographic and computed tomography (CT) procedures. The body was divided into three zones according to distance from the fetus. The first zone consisted of the head area, the lower extremities below the knee, and the upper extremities; the second consisted of the cervicothoracic region and upper thighs; and the third consisted of the abdominopelvic area. Fetal doses from radiologic procedures between zones were compared using the Kruskal-Wallis test and a Bonferroni-corrected Mann-Whitney U-test. Results The average fetal doses from radiography and CT in the first zone were 0.05 ± 0.01 mGy and 0.81 ± 0.04 mGy, respectively; 0.21 ± 0.05 mGy and 1.77 ± 0.22 mGy, respectively, in the second zone; and 6.42 ± 0.82 mGy and 22.94 ± 1.28 mGy, respectively, in the third zone (p < 0.001). Our results showed that fetal radiation exposures in our group of pregnant women did not reach the level (50 mGy) that is known to increase risk for congenital anomalies. Conclusion Fetal radiation exposure in the diagnostic radiology procedures in our study did not reach risk levels that might have indicated abortion.