Radiation dose in computed tomography of the pelvis: Comparison of helical and axial scanning

An anthropomorphic Rando phantom was used to compare radiation doses sustained during helical and conventional axial CT of the pelvis. The values obtained with the Rando phantom were validated against cadaveric phantoms, and show good agreement. For the authors’particular CT unit, helical scanning was found to deliver a lower radiation dose than conventional axial scanning. This was most prominent at 1.0-s tube rotation times (average dose ratio 1.24). For realistic scanning parameters and exposure factors, the ratio of radiation dose to pelvic organs can be expected to lie in the range of 40-100 mGy. The whole-body effective dose (ED) depends on selection of scanning parameters and patient anatomy. In a favourable case scenario, the ED for CT scanning of the pelvis in a male can be expected to be between 10 and 20 mSv if the scrotum is not included in the radiation field, while the ED in a female will be ?20 mSv. An examination of scatter radiation fall-off curves from a single slice shows that the spread of scatter radiation is only marginally affected by slice thickness. A total of 10-12 cm of human soft tissue acts as a good barrier against internal scattered radiation. The use of such scatter fall-off curves, together with manufacturers’dosimetry specifications, allows a fast estimate of absorbed dose.     

Low-dose CT protocols for guiding radiofrequency ablation for the treatment of small renal cell carcinomas

Objective: Computed tomography (CT)-guided radiofrequency ablation (RFA) results in a high radiation dose. This study aimed to assess low-dose CT protocols for guiding RFA and oncologic outcomes for the treatment of small renal cell carcinoma (RCC).

Materials and methods: Between December 2011 and December 2014, CT-guided RFA was performed in 31 patients with 31 biopsy-proven RCCs (median, 2.1?cm). RFA included planning, targeting, monitoring and survey phases. The dose length product (DLP), CT dose index volume (CTDIvol), effective dose, number of scans, scan range, tube current and exposure time of RFA phases were compared. The 3-year recurrence-free survival rate was recorded. Nonparametric or parametric repeated-measures ANOVA with Dunn’s or Tukey–Kramer multiple comparisons and Kaplan–Meier analysis were used for statistical analysis.

Results: The median total DLP, CTDIvol and effective dose of CT-guided RFA procedures per session were 1238.8 mGy (range 517.4–3391.7 mGy), 259.7 mGy (10.7–67.9 mGy) and 18.6 mSv (7.8–50.9 mSv), respectively. The median DLP, CTDIvol, effective dose, number of scans, tube current and exposure time during the targeting phase were higher than those during the other phases (p?p?>?0.05) but smaller than those in the planning and survey phases (p?Conclusions: Low-dose CT protocols for guiding RFA may reduce radiation dose without compromising oncologic outcomes. Reducing the number of scans during the targeting phase contributes to dose reduction.     

Diagnostic imaging for suspected pulmonary embolism during pregnancy and postpartum: A comparative radiation dose study

Introduction

To compare the radiation dose exposure and diagnostic efficiency of computed tomographic pulmonary angiography (CTPA) and ventilation/perfusion imaging (V/Q) for clinically suspected pulmonary embolism (PE) in pregnant and postpartum women in a tertiary hospital setting.

Methods

A retrospective cohort study of 473 pregnant and postpartum women referred for CTPA or V/Q for clinically suspected PE between January 2013 and December 2018 at a tertiary hospital. Maternal effective radiation dose, breast-absorbed radiation dose and fetal-absorbed dose estimates were calculated. Diagnostic yield was evaluated from radiological findings.

Results

Computed tomographic pulmonary angiography (CTPA) was more commonly used for the imaging of suspected PE in pregnant and postpartum populations (51.9% vs. 48.1% and 77.1% vs. 22.9%, respectively). CTPA was associated with higher maternal effective and breast-absorbed doses (maternal effective CTPA 4.7 (±2.9) mSv (millisievert), V/Q 1.7(±0.8) mSv (mean difference 2.93 mSv P < 0.001), and breast-absorbed CTPA 8.0 (±5.2) mGy (milligray), V/Q 0.3 (±0.1) (mean difference 7.67 mGy P < 0.001), respectively). Fetal radiation dose exposure was low. The incidence of positive PE was 5.5%. Indeterminate rates of CTPA and V/Q were 3.0% and 5.5% (P = 0.176), respectively.

Conclusions

Compared to V/Q, CTPA is associated with higher maternal and breast radiation dose; however, modern CT scanners achieve lower radiation doses than historically described. Fetal radiation dose was comparably low. The diagnostic yield of the imaging modalities in pregnant and postpartum women is similar. Revision of guidelines should occur with the advances in CT technology.     

A systematic review of radiation dose associated with different generations of multidetector CT coronary angiography

The purpose of this paper is to perform a systematic review on radiation dose reduction in coronary computed tomography (CT) angiography that is done using different generations of multidetector CT (MDCT) scanners ranging from four-slice to 320-slice CTs, and have different dose-saving techniques. The method followed was to search for references on coronary CT angiography (CTA) that had been published in English between 1998 and February 2011. The effective radiation dose reported in each study based on different generations of MDCT scanners was analysed and compared between the types of scanners, gender, exposure factors and scanning protocols. Sixty-six studies were eligible for inclusion in this analysis. The mean effective dose (ED) for MDCT angiography with retrospective electrocardiogram (ECG) gating without use of any dose-saving protocol was 6.0 ± 2.8, 10.4 ± 4.90 and 11.8 ± 5.9 mSv for four-slice, 16-slice and 64-slice CTs, respectively. More dose-saving strategies were applied in recent CT generations including prospective ECG-gating protocols, application of lower tube voltage and tube current modulation to achieve a noteworthy dose reduction. Prospective ECG-gating protocol was increasingly used in 64, 125, 256 and 320 slices with corresponding ED of 4.1 ± 1.7, 3.6 ± 0.4, 3.0 ± 1.9 and 7.6 ± 1.6 mSv, respectively. Lower tube voltage and tube current modulation were widely applied in 64-slice CT and resulted in significant dose reduction (P < 0.05). This analysis has shown that dose-saving strategies can substantially reduce the radiation dose in CT coronary angiography. The fact that more and more clinicians are opting for dose-saving strategies in CT coronary angiography indicates an increased awareness of risks associated with high radiation doses among them.     

Relationship between specific organ doses and volumetric CT dose indices in multidetector CT studies

Organ doses are useful for estimating radiation doses to patients. However, it is impossible to determine specific organ doses for each patient. The aim of this study was to examine the relationship between specific organ doses and volumetric CT dose indices (CTDIvols) in multidetector CT studies to estimate specific organ doses in each patient. Radiophotoluminescent glass dosimeters were placed at locations corresponding to specific organs of an anthropomorphic phantom. Thereafter, the phantoms were examined with respect to various imaging ranges and protocols, including cranial, thoracic and abdominal acquisitions using a 64-section multidetector CT. Concurrently, we recorded the mean CTDIvol for each acquisition range. In the cranial acquisition, the displayed mean CTDIvol was 69.0mGy, and the absorbed doses for brain and intra-ocular lenses were 57.2±2.6 and 57.1±3.0mGy, respectively. In the thoracic acquisition, the displayed mean CTDIvol was 16.3mGy, and the absorbed doses for breast and lung were 19.1±6.4 and 31.7±2.2mGy, respectively. In the abdominal acquisition, the displayed mean CTDIvol was 21.6mGy, and the absorbed doses for stomach and colon were 28.2±6.1 and 28.0±8.6mGy, respectively. The displayed mean CTDIvols overestimated the specific organ doses in the cranial acquisition and underestimated them in the thoracic and abdominal acquisitions. However, the approximate specific organ doses may be estimated by multiplying the displayed mean CTDIvols with a conversion factor for each organ.     

低剂量CT在肺癌术后短期复查中的应用价值

  目的   通过常规CT和低剂量CT的对比研究,探讨低剂量CT在肺癌术后短期复查中的应用价值。   方法   83例肺癌术后短期内复查CT的患者,50例（A组）行常规CT扫描,33例（B组）行低剂量CT扫描。分别从图像质量和临床需求角度出发对所有CT图像进行评分,并记录每个病例的辐射剂量指标CTDIvol、DLP。比较二组之间的评分和辐射剂量是否存在显著性差异。   结果   二组在图像质量方面的平均得分分别为3.705±0.314、3.311±0.442,在临床需求方面的平均得分为2.670±0.373、2.561±0.410,CTDIvol分别为（19.248±1.532）mGy、（10.138±1.113）mGy,DLP分别为（170.180±19.259）mGy*cm、（99.061±14.504）mGy*cm。二组在图像质量、CTDIvol、DLP方面均存在显著性差异,在临床需求评分方面无显著性差异。   结论   低剂量CT完全能满足临床对于肺癌术后短期复查的需求,并明显降低了辐射剂量。      

Early Results of Lung Cancer Screening and Radiation Dose Assessment by Low-dose CT at a Community Hospital

Background

The National Lung Screening Trial showed a reduction in overall and cancer-specific mortality for patients screened with low-dose computed tomography (LDCT) versus chest radiograph. Some question whether this can be achieved in community healthcare settings. Our aim was to analyze lung cancer screening outcomes and administered radiation dose using LDCT scans at a community hospital.

99m Tc-HYNIC-TOC人体内照射剂量研究

背景与目的：放射性显像药物在人体内的剂量分布、各器官的吸收剂量及全身有效剂量数据非常重要。研究^99mTc标记的经肼基烟酰胺修饰的奥曲肽（^99mTc-Hydrazinonicotinyl-Tyr3-Octreotide,^99mTc-HYNIC-TOC）在人体内各器官的吸收剂量、全身吸收剂量及全身有效剂量。方法：对2018年5—6月复旦大学附属肿瘤医院收治的5例神经内分泌肿瘤患者静脉注射370 MBq^99mTc-HYNIC-TOC后于0.5、1.0、2.0、4.0和8.0 h行全身平面采集,其中2.0 h平面采集后即刻行全身断层采集。断层数据经迭代重建后,将数据导入GE Dosimetry Toolkit处理,在单光子发射计算机断层显像（single photon emission computedtomography,SPECT）/CT融合图像上勾画各器官生成感兴趣区（region of interest,ROI）,获得相应时间-活度曲线并计算曲线下面积得到滞留时间。依据美国核医学会医用内照射剂量学（Medical Internal Radiation Dose,MIRD）委员会提出的内照射剂量计算方法（MIRD体系）,利用OLINDA/EXM软件计算^99mTc-HYNIC-TOC在人体内各器官的吸收剂量、全身吸收剂量和全身有效剂量。结果：脾脏、膀胱、肾脏的单位活度吸收剂量较高,男性分别为0.042、0.019和0.016 mGy/MBq,女性分别为0.026、0.027和0.017 mGy/MBq。大脑、皮肤、甲状腺的单位活度吸收剂量较低,男性分别为0.000 3、0.000 5和0.000 5 mGy/MBq,女性分别为0.000 3、0.000 5和0.000 6 mGy/MBq。对放射线敏感的器官如骨原细胞、胸腺和红骨髓的单位活度吸收剂量均较低,范围为0.001 2~0.002 2 mGy/MBq。全身平均单位活度吸收剂量男性为0.001 7 mGy/MBq,女性为0.0016 mGy/MBq。全身单位活度有效剂量男性为0.004 58 mSv/MBq,女性为0.004 55 mSv/MBq。结论：^99mTc-HYNIC-TOC可安全地用于人体,其有效剂量低于允许范围上限。该研究结果可为临床安全使用^99mTc-HYNIC-TOC提供依据,也为其他放射性药物的安全性评估和加快临床转化提供新的可行方案。     

Significantly Low Effective Dose from 18FDG PET/CT Scans Using Dose Reducing Strategies: "Lesser is Better"

Background: Fluorodeoxyglucose (18FDG) PET/CT imaging has become an important component of the management paradigm in oncology. However, the significant imparted radiation exposure is a matter of growing concern especially in younger populations who have better odds of survival. The aim of this study was to estimate the effective dose received by patients having whole body 18FFDG PET/CT scanning as per recent dose reducing guidelines at a tertiary care hospital. Materials and Methods: This prospective study covered 63 patients with different cancers who were referred for PET/CT study for various indications. Patients were prepared as per departmental protocol and 18FDG was injected at 3 MBq/Kg and a low dose, nonenhanced CT protocol (LD NECT) was used. Diagnostic CT studies of specific regions were subsequently performed if required. Effective dose imparted by 18FDG (internal exposure) was calculated by using multiplying injected dose in MBq with coefficient 1.9?102 mSv/MBq according to ICRP publication 106. Effective dose imparted by CT was calculated by multiplying DLP (mGy.cm) with ICRP conversion coefficient "k" 0.015 [mSv / (mG. cm)]. Results: Mean age of patients was 49 18 years with a male to female ratio of 35:28 (56%:44%). Median dose of 18FDG given was 194 MBq (range: 139293). Median CTDIvol was 3.25 (2.46.2) and median DLP was 334.95 (246.70 576.70). Estimated median effective dose imparted by 18FDG was 3.69 mSv (range: 2.855.57). Similarly the estimated median effective dose by low dose (nondiagnostic) CT examination was 4.93 mSv (range: 2.14 10.49). Median total effective dose by whole body 18FDG PET plus low dose nondiagnostic CT study was 8.85 mSv (range: 5.5613.00). Conclusions: We conclude that the median effective dose from a whole body 18FDG PET/CT in our patients was significantly low. We suggest adhering to recently published dose reducing strategies, use of ToF scanner with CT dose reducing option to achieve the lower if not the lowest effective dose. This would certainly reduce the risk of second primary malignancy in younger patients with higher odds of cure from first primary cancer.     

Phantom and in-vivo measurements of dose exposure by image-guided radiotherapy (IGRT): MV portal images vs. kV portal images vs. cone-beam CT.

PURPOSE: Positioning verification is usually performed with treatment beam (MV) portal images (PI) using an electronic portal imaging device (EPID). A new alternative is the use of a low energy photon source (kV) and an additional EPID mounted to the accelerator gantry. This system may be used for PI or--with rotating gantry--as cone-beam CT (CBCT). The dose delivered to the patient by different imaging processes was measured. METHODS AND MATERIALS: A total of 15 in-vivo dose measurements were done in five patients receiving prostate IMRT. For anterior-posterior (AP) and lateral PI with MV and kV photons measurement points were inside the rectum and at the patient's skin. Dose for CBCT was measured in the rectum. Additional measurements for CBCT were done in a cylindrical CT-dose-index (CTDI) phantom to determine peripheral, central and weighted CTDI. RESULTS: The dose for AP MV PI was 57.8 mGy at the surface and 33.9 mGy in the rectum, for lateral MV PI 69.4 mGy and 31.7 mGy, respectively (5 MU/exposure). The dose for AP kV PI was 0.8 mGy at the surface and 0.2 mGy in the rectum, for lateral PI 1.1 mGy and 0. 1 mGy, respectively. For a CBCT the rectal dose was 17.2 mGy. The peripheral CTDI was 23.6 mGy and the center dose was 10.2 mGy, resulting in a weighted CTDI of 19.1 mGy in the phantom and an estimated surface dose of < or =28 mGy. CONCLUSIONS: Even taking into account an RBE (Relative Biological Effectiveness) of 2 for kV vs. MV radiation, for kV PI the delivered dose is lower and image quality is better than for MV PI. CBCT provides a 3D-image dataset and dose exposure for one scan is lower than for two MV PI, thus rendering frequent volume imaging during a fractionated course of radiotherapy possible.     

基于小鼠全身动态PET扫描估算16α-18F-17β-雌二醇的人体内辐射剂量

背景与目的：由小鼠全身动态PET显像数据获得药物在小鼠体内的生物分布,利用器官内剂量评估/指数模型分析软件(organ level inter dose assessment/exponential model,OLINDA/EXM)估算18F-fluo-roestradiol,18F-FES)在人体内的吸收剂量、全身有效剂量和有效剂量当量。方法：健康雌性KM小鼠尾静脉注射18F-FES后行160 min动态PET采集,经3D-OSEM/MAP算法重建获得PET图像。再行高分辨率CT显像,在PET/CT融合图像上,选取各脏器勾画感兴趣体积(volume of interest,VOI),获得相应时间-活度曲线和其曲线下面积、滞留时间、成年女性体模对应各器官的滞留时间。依据美国核医学会医用内照射剂量学委员会提出的内照射剂量计算方法(MIRD体系),利用OLINDA/EXM软件计算18F-FES在人体内的吸收剂量、全身有效剂量和有效剂量当量。最后所得数据与已公开发表计算18F-FES内照射剂量的文献数据行配对t检验,验证本文方法的有效性。结果：人体内胆囊壁、膀胱壁、小肠、上部大肠和肝脏的吸收剂量最高,分别为0.0725、0.0445、0.0430、0.0315和0.0282 mGy/MBq。大脑、皮肤、乳腺、心脏壁和甲状腺吸收剂量最低,分别为0.0052、0.0011、0.0012、0.0012和0.0013 mGy/MBq。对放射性敏感的器官如骨原细胞、胸腺和红骨髓的吸收剂量均较低,范围为0.0014~0.0218 mGy/MBq。全身平均吸收剂量为0.0147 mGy/MBq,全身有效剂量当量为0.0250 mGy/MBq,全身有效剂量为0.0190 mSv/MBq。对于常规注射185 MBq18F-FES,人体有效剂量为3.5150 mSv。与直接测量18F-FES在健康人体各主要脏器内吸收剂量的文献行配对t检验,差异无统计学意义(t=1.478,P=0.153)。结论：利用OLINDA/EXM软件根据小鼠全身动态PET/CT数据可有效估算18F-FES在人体内的吸收剂量和有效剂量。18F-FES可安全地用于人体,其有效剂量低于允许范围上限。该研究可为临床放心使用18F-FES提供依据。     

A feasibility study for image guided radiotherapy using low dose, high speed, cone beam X-ray volumetric imaging.

BACKGROUND AND PURPOSE: Image Guidance of patient set-up for radiotherapy can be achieved by acquiring X-ray volumetric images (XVI) with Elekta Synergy and registering these to the planning CT scan. This enables full 3D registration of structures from similar 3D imaging modalities and offers superior image quality, rotational set-up information and a large field of view. This study uses the head section of the Rando phantom to demonstrate a new paradigm of faster, lower dose XVI that still allows registration to high precision. MATERIALS AND METHODS: One high exposure XVI scan and one low exposure XVI scan were performed with a Rando Head Phantom. The second scan was used to simulate ultra low dose, fast acquisition, full and half scans by discarding a large number of projections before reconstruction. Dose measurements were performed using Thermo Luminescent Dosimeters (TLD) and an ion chamber. The reconstructed XVI scans were automatically registered with a helical CT scan of the Rando Head using the volumetric, grey-level, cross-correlation algorithm implemented in the Syntegra software package (Philips Medical Systems). Reproducibility of the registration process was investigated. RESULTS: In both XVI scans the body surface, bone-tissue and tissue air interfaces were clearly visible. Although the subjective image quality of the low dose cone beam scan was reduced, registration of both cone beam scans with the planning CT scan agreed within 0.1 mm and 0.1 degrees . Dose to the patient was reduced from 28mGy to less than 1mGy and the equivalent scan speed reduced to one minute or less. CONCLUSIONS: Automatic 3D registration of high speed, ultra low dose XVI scans with the planning CT scan can be used for precision 3D patient set-up verification/image guidance on a daily basis with out loss of accuracy when compared to higher dose XVI scans.     

A permanent breast seed implant as partial breast radiation therapy for early-stage patients: a comparison of palladium-103 and iodine-125 isotopes based on radiation safety considerations

PURPOSE: A permanent breast seed implant (PBSI) technique has been developed as a new form of partial adjuvant radiation therapy for early-stage breast cancer. This study compares iodine-125 ((125)I) and palladium-103 ((103)Pd) isotopes by examining the exposure and effective dose (ED) to a patient's partner. METHODS AND MATERIALS: A low-energy survey meter was used to measure exposure rates as a function of bolus thickness placed over (103)Pd or (125)I seeds. A general mathematical expression for the initial exposure rate at 1 m (x(o,1m)) from the skin surface as a function of the implant size, R, and the distance between the skin surface and the implant, d, was derived. Also, a second general equation is proposed to calculate the ED to the patient's partner. RESULTS: The initial exposure rate at 1 meter and the ED are calculated as follows: x(o,1m) = 3alpha2R(3) ; ;beta(3) [e(-beta(2R+d))(betaR + 1) + e(-betad)(betaR - 1)], and ED = aR(b) [e(-c(2R+d)) (cR + 1) + e(-cd) (cR - 1)]. For (125)I, the parameters are: alpha = 0.154409, beta = 0.388460, a = 197, b = -0.95, and c = 0.38846. For (103)Pd, they are: alpha = 0.06877, beta = 0.421098, a = 18.6, b = -0.78, and c = 0.421098. For implant diameters varying from 2 to 6 cm and skin-to-implant distances varying from 0.7 to 4 cm, the ED is consistently below 2.6 mSv using the (103)Pd isotope, but more than 5 mSv in many instances and possibly up to 20 mSv using (125)I. CONCLUSIONS: PBSI using (103)Pd seeds appears safe because the patient's partner ED is consistently below 5 mSv. The(125)I isotope is not recommended for PBSI.     

Radiation Dosimetry and Biodistribution of the Hypoxia Tracer (18)F-EF5 in Oncologic Patients

Abstract The primary goals of this study were to determine the biodistribution and excretion of (18)F-EF5 in oncologic patients, to estimate the radiation-absorbed dose and to determine the safety of this drug. Methods: Sixteen patients with histologically confirmed malignancy received a mean intravenous infusion of 217?MBq (range 107-364?MBq) of (18)F-EF5. Over a 4-6-hour period, four to five serial positron emission tomography (PET) or PET/computed tomography (CT) scans were obtained. To calculate the radiation dosimetry estimates, volumes of interest were drawn over the source organs for each PET scan or on the CT for each PET/CT scan. Serial blood samples were obtained to measure (18)F-EF5 blood clearance. Bladder-wall dose was calculated based on urine activity measurements. Results: The urinary bladder received the largest radiation-absorbed dose, 0.12±0.034 mSv/MBq (mean±SD). The average effective dose equivalent and the effective dose of (18)F-EF5 were 0.021±0.003 mSv/MBq and 0.018±0.002 mSv/MBq, respectively. (18)F-EF5 was well tolerated in all subjects. Conclusions: (18)F-EF5 was demonstrated to be safe for patients, and the radiation exposure is clinically acceptable. As with any radiotracer with primary excretion in the urine, the bladder-wall dose can be minimized by active hydration and frequent voiding.     

Radiation dose and risk to the lens of the eye during CT examinations of the brain

Cataracts are the leading cause of blindness and visual disability worldwide. Of the known contributing factors to this condition, ionising radiation is considered the primary concern in a radiological context given the particular radiosensitivity of the lens of the eye. In light of the substantially increased application of computed tomography in brain imaging, an investigation of the relevent literature is warranted to assess thresholds, lens radiation doses and dose reduction techniques in respect to the cataractogenic risk of such examinations. The value and very existence of a lens dose threshold is debatable given different considerations of radiation dose, latency, opacity classifications and historical sample populations, though ICRP guidelines suggest a threshold of 0.5 Gy. Documented CT‐specific radiation doses to the eye following scans of the brain are highly variable between studies (2–130 mGy), primarily owing to discrepancies in scanning technique. These findings, when coupled with the relative ambiguity of known threshold values, present difficulties in assessing the overall risk of cataracts following serial CT examinations to the head. In the absence of definitive risk evaluations, a cautionary approach is advised. The implementation of gantry tilt along the supraorbital margin is recommended as standard practice on account of its highly effective radiation dose reduction outcomes. Organ‐based tube modulation and reductions in tube current may also be considered beneficial. Bismuth eye shielding is only advised where gantry tilting is unachievable, and in such cases, ensure careful adherence to appropriate shield placement and infection control measures.     

Patient doses in gamma-intracoronary radiotherapy: the Radiation Burden Assessment Study

PURPOSE: To determine accurately the radiation burden of both patients and staff from intracoronary radiotherapy (IRT) with (192)Ir and to investigate the importance of IRT in the patient dose compared with interventional X-rays. METHODS AND MATERIALS: The Radiation Burden Assessment Study (RABAS) population consisted of 9 patients undergoing gamma-IRT after percutaneous transluminal coronary angioplasty and 14 patients undergoing percutaneous transluminal coronary angioplasty only as the control group. For each patient, the dose to the organs and tissues from the internal and external exposure was determined in detail by Monte Carlo N-particle simulations. Patient skin dose measurements with thermoluminescence dosimeters served as verification. Staff dosimetry was performed with electronic dosimeters, thermoluminescence dosimeters, and double film badge dosimetry. RESULTS: With respect to the patient dose from IRT, the critical organs are the thymus (58 mGy), lungs (31 mGy), and esophagus (27 mGy). The mean effective dose from IRT was 8 mSv. The effective dose values from interventional X-rays showed a broad range (2-28 mSv), with mean values of 8 mSv for the IRT patients and 13 mSv for the control group. The mean dose received by the radiotherapist from IRT was 4 microSv/treatment. The doses to the other staff members were completely negligible. CONCLUSION: Our results have shown that the patient and personnel doses in gamma-IRT remain at an acceptable level. The patient dose from IRT was within the variations in dose from the accompanying interventional X-rays.     

Radiation exposure of hemophiliacs after radiosynoviorthesis with 186Re colloid

Very limited data are available in the literature on the doses of unwanted radiation that patients receive following treatment with radiosynoviorthesis (RSO). OBJECTIVE: The aim of this study was to assess the radiation exposure after RSO with (186)Re colloid in hemophiliacs. METHODS: This study involved 12 hemophiliacs who were treated for hemophilic joint disease with 14 RSOs by using (186)Re colloid. Whole-body scintigrams were performed 1, 6, and 24 hours and 3 and 7 days after RSO. Measurements, using a whole-body counter, were done immediately after scintigraphy, with the treated joint protected with a lead shield. The cumulative activity of (186)Re in the body and in the lymph nodes was calculated. The distribution of (186)Re in the body was determined by using the values for small colloids as proposed by the International Commission on Radiological Protection (ICRP) Publication 53. The computer code, OLINDA/EXM (Vanderbilt University, Nashville, TN), was used for the calculation of the internal dose. A constant distance of 1 m between the ankle joint and body organs, and of 0.33 m between the elbow or shoulder joint and body organs, was used to calculate the contribution of gamma radiation to the effective radiation dose. RESULTS: The mean effective dose received by hemophiliacs after RSO with (186)Re colloid was 28 +/- 9 microSv/MBq of the activity injected into the joint. The patients received 0.8-3.7 mSv (1.9 +/- 0.8 mSv) owing to the leakage of (186)Re from the treated joint and its retention in the body. The highest doses were established in the spleen (26.0 +/- 10.7 mGy), the liver (17.6 +/- 7.2 mGy), and red marrow (3.0 +/- 0.8 mGy). The contribution of gamma radiation to the effective dose was less than 0.1 mSv in RSO of the ankle, 0.4 mSv in the elbow, and 0.6 mSv in the shoulder-joint treatment. The activity of (186)Re in the regional lymph nodes was noted in 4 of the 14 treatments. In these cases, the estimated average dose received by individual lymph nodes was 14.7 +/- 1.9 Gy. CONCLUSIONS: RSO with (186)Re colloid is a safe treatment method. The effective dose received by patients after RSO by using (186)Re colloid is low, as are the radiation doses to the most exposed organs. If (186)Re is retained in the regional lymph nodes, the lymph node radiation dose would be high.     

Medical exposure to radiation and thyroid cancer

In 2008, the worldwide estimated age-standardised incidence rates for thyroid cancer incidence were 4.7 and 1.5 per 100 000 women and men, respectively. Thyroid cancer’s overall contribution to the worldwide cancer burden is relatively small, but incidence rates have increased over the last three decades throughout the world. This trend has been hypothesised to reflect a combination of technological advances enabling increased detection, but also changes in environmental factors, including population exposure to ionising radiation from fallout, diagnostic tests and treatment for benign and malignant conditions. Studies of the atomic bomb survivors and populations treated with radiotherapy have established radiation as a risk factor for thyroid cancer, particularly from early life exposure. About 0.62 mSv (20%) of the global annual per caput effective radiation dose comes from diagnostic medical and dental radiation for the period of 1997-2007, increased from 0.4 mSv for the years 1991-1996. This international trend of increasing population exposure to medical diagnostic sources of radiation, attributed in large part to the growing use of computed tomography scans, but also interventional radiology procedures, has raised concerns about exposure to radiosensitive organs such as the thyroid. Worldwide, medical and dental X-rays constitute the most common type of diagnostic medical exposures, but their contribution to the cumulative effective dose is relatively low, whereas computed tomography scans account for 7.9% of diagnostic radiology examinations but 47% of the collective effective dose from diagnostic radiation procedures in parts of the world. Although the radiation exposure from computed tomography scans is substantially lower than that from radiotherapy, multiple computed tomography scans could result in non-trivial cumulative doses to the thyroid. Studies are currently underway to assess the incidence of cancer in large cohorts of children who received computed tomography scans. National and international efforts have been developed to raise awareness and to standardise procedures for use of computed tomography and interventional radiology procedures in paediatric and general populations.     

Ergebnisse der Österreichischen CT-Dosisstudie 2010: Effektive Dosen der häufigsten CT-Untersuchungen und Unterschiede zwischen Anwendern

PurposeTo determine typical doses from common CT examinations of standard sized adult patients and their variability between CT operators for common CT indications.Materials and MethodsIn a nationwide Austrian CT dose survey doses from approx. 10,000 common CT examinations of adults during 2009 and 2010 were collected and ?typical“ radiation doses to the “average patient”, which turned out to have 75.6 kg body mass, calculated. Conversion coefficients from DLP to effective dose were determined and effective doses calculated according to ICRP 103. Variations of typically applied doses to the “average patient” were expressed as ratios between 90^th and 10^th percentile (inter-percentile width, IPW90/10), 1^st and 3^rd quartile (IPW75/25), and Maximum/Minimum.ResultsMedian effective doses to the average patients for standard head and neck scans were 1.8 mSv (cervical spine), 1.9 mSv (brain: trauma/bleeding, stroke) to 2.2 mSv (brain: masses) with typical variation between facilities of a factor 2.5 (IPW90/10) and 1.7 (IPW75/25). In the thorax region doses were 6.4 to 6.8 mSv (pulmonary embolism, pneumonia and inflammation, oncologic scans), the variation between facilities was by a factor of 2.1 (IPW90/10) and 1.5 (IPW75/25), respectively. In the abdominal region median effective doses from 6.5 mSv (kidney stone search) to 22 mSv (liver lesions) were found (acute abdomen, staging/metastases, lumbar spine: 9-12 mSv; oncologic abdomen plus chest 16 mSv; renal tumor 20 mSv). Variation factors between facilities were on average for abdominal scans 2.7 (IPW90/10) and 1.8 (IPW75/25).ConclusionVariations between CT operators are generally moderate for most operators, but in some indications the ratio between the minimum and the maximum of average dose to the typical standard patients exceeds a factor of 4 or even 5. Therefore, comparing average doses to Diagnostic Reference Levels (DRLs) and optimizing protocols need to be encouraged.     

The implementation of diagnostic reference levels to Australian radiology practice

At the present time, there is no national surveillance of the increasing ionising radiation dose to the population from diagnostic imaging procedures. As the number of procedures undertaken is increasing, it is expected that the population dose will also increase. A substantial component of that contribution is from multi-detector computed tomography (MDCT) systems. The Australian Radiation Protection & Nuclear Safety Agency (ARPANSA) estimates that the growth in MDCT scans, based on Medicare Benefits Schedule data, is increasing at approximately 9% per annum, with over 2 million MDCT scans being performed in 2009. The caput effective dose (mSv) from this modality is expected to be approaching 1.2 mSv per annum. If current dose-detriment models are accurate, the risk of induction of carcinogenic detriment from current MDCT scanning patterns is a significant public health issue that requires a concerted and ongoing response. For the application of ionising radiation in medicine, the International Commission on Radiological Protection recommends the conservative philosophy of Justification and Optimisation via the measurement of 'Diagnostic Reference Levels' to limit the potential overexposure of patients and decrease the overall population burden. The Australian government has commissioned ARPANSA to survey, calculate and construct representative national diagnostic reference levels for diagnostic imaging modalities that use ionising radiation. This will be achieved in close consultation with the professional organisations who represent the professionals responsible for the use of ionising radiation in diagnostic imaging.