PATIENT DOSES IN WHOLE-BODY PET/CT EXAMINATIONS IN THE LARGEST TERTIARY HOSPITAL IN GREECE.

The purpose of this study was to determine the patient radiation dose in combined whole-body positron emission tomography/computed tomography (PET/CT) examinations performed in the largest tertiary hospital in Greece. Computed tomography dose index (CTDIvol), dose length product (DLP), weight, height and administered activity of 2-[18F] fluoro-2-deoxy-D-glucose values for PET/CT examinations were recorded in a sample of 1014 randomly selected patients. The mean (±standard deviation) and median (interquartile) CTDIvol values were equal to 5.5 ± 2.4 and 4.8 (2.5) mGy, respectively. The respective DLP values were 483.3 ± 212.4 and 426 (234.6) mGy·cm. For the administered activity, mean and median were equal to 363.9 ± 68.3 and 361.6 (85.6) MBq. The mean administered activity per body weight was 4.8 ± 0.6 and the median 4.8 (0.6) MBq/kg. The results of this survey are within the range of values reported in the literature and can be used as a standard of reference until national diagnostic reference levels are established for whole-body PET/CT procedures.

Evaluation of image quality and patient exposure in fluoroscopy using a phantom: Is there any clinical relevance?

OBJECTIVE: To investigate the impact of X-ray preset acquisition protocol settings on fluoroscopy image quality (IQ) and radiation exposure. MATERIALS & METHODS: A quality control (QC) phantom was imaged with a modern digital C-arm system, using various preset fluoroscopy protocols. IQ was assessed using human observers and in-house software for automated evaluation, based on contrast-to-noise ratios of details and their background. Patient radiation exposure was evaluated using the displayed Incident Air-Kerma and Kerma-Area Product values. RESULTS: Protocol selection affects radiation exposure by a factor of about 3. IQ evaluation showed that acquisition protocols produce images with quite different characteristics. The visual IQ evaluation method was time consuming and cumbersome. The automated method, utilized the visual IQ evaluation results for calibration of detection thresholds. However, it failed to reproduce these results for all images and details types. In some images, digital image processing created artifacts which affected the pixel value distributions around details in a way that could be handled only by the human vision. CONCLUSION: Manufacturers provide many preset protocols designated for specific clinical uses, which have large impact on IQ characteristics and radiation exposure. However, protocol settings' selection rationale is essentially a "black box" for the end user. Though QC phantoms are currently used for IQ evaluation, they are not appropriate for drawing firm conclusions concerning the expected performance of each protocol in clinical practice. Currently, there is no consensus on the optimum technical characteristics of preset protocols for specific procedures. More work is needed in this area.

The impact of image processing algorithms on digital radiography of patients with metalic hip implants.

OBJECTIVE: To investigate the impact of image processing algorithms on image quality of digital radiographs. This study was motivated from a case of a patient with metallic hip implant, where the anatomy around the implant was misrepresented, due to failure of the processing algorithm. MATERIALS & METHODS: A quality control phantom was imaged using a digital radiographic unit and the standard examination protocol for Pelvis anteroposterior (AP) projection. The original image was reprocessed with all available selections of Diamond View, which is a processing algorithm for optimizing image quality of different anatomic regions. The same procedure was repeated for two other examination protocols, Femur AP and Hip AP, which differ in terms of harmonization kernel and gain, and look up table settings. The whole procedure was repeated with a Pb strip, 2 cm wide and 3 mm thick, positioned close to the right phantom edge, in order to simulate a metallic hip implant. Using ImageJ a number of regions of interest (ROIs) were positioned on the phantom images and the impact of processing parameters on certain image characteristics and image quality indices was evaluated. RESULTS: Processing parameters have a strong impact on image characteristics, but in terms of image quality, differences between images with and without the implant are small. Exception is the regions in the vicinity of the implant, where larger differences, that could affect diagnosis, were observed. CONCLUSION: In case of doubt, additional processing with settings which minimize the risk of anatomic misrepresentation should be used.

The potential role of brachytherapy in the irradiation of patients with lung cancer: a systematic review

To review the use of brachytherapy as an adjuvant therapy to reduce recurrences after sublobar resections and as a palliation to patients with inoperable disease. Α review of all published studies was performed to identify the recurrence rate after brachytherapy adjuvant to sublobar resection and assess the palliation of symptoms and the complications of brachytherapy as a palliative treatment. Most of the studies that we found about brachytherapy as an adjuvant therapy to sublobar resection due to patient’s poor cardiopulmonary reserve showed that brachytherapy offered low recurrence rate with low toxicity. Ten studies concerning palliative brachytherapy showed improvement of symptoms with good tolerance and good endoscopic response rates. Literature suggests that brachytherapy for inoperable symptomatic disease can be delivered for symptom improvement with acceptable toxicity. Brachytherapy as an alternative treatment option for lung cancer needs more investigation with more prospective trials (AU)

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The potential role of brachytherapy in the irradiation of patients with lung cancer: a systematic review.

To review the use of brachytherapy as an adjuvant therapy to reduce recurrences after sublobar resections and as a palliation to patients with inoperable disease. Α review of all published studies was performed to identify the recurrence rate after brachytherapy adjuvant to sublobar resection and assess the palliation of symptoms and the complications of brachytherapy as a palliative treatment. Most of the studies that we found about brachytherapy as an adjuvant therapy to sublobar resection due to patient's poor cardiopulmonary reserve showed that brachytherapy offered low recurrence rate with low toxicity. Ten studies concerning palliative brachytherapy showed improvement of symptoms with good tolerance and good endoscopic response rates. Literature suggests that brachytherapy for inoperable symptomatic disease can be delivered for symptom improvement with acceptable toxicity. Brachytherapy as an alternative treatment option for lung cancer needs more investigation with more prospective trials.

THE IMPACT OF X-RAY UNIT TYPE USED FOR ENDOSCOPIC RETROGRADE CHOLANGIOPANCREATOGRAPHY PROCEDURES ON PATIENT DOSES.

To investigate whether the X-ray unit type used for interventional endoscopic retrograde cholangiopancreatography (ERCP) procedures may affect patient radiation doses. A total of 471 ERCP procedures performed in 4 hospitals with 4 types of X-ray units were studied. Kerma-area product (KAP), fluoroscopy time (T) and total number of radiographs acquired (F) were recorded. KAP, T and F values exhibited a great variation, ranging from 0.1 to 130.2 Gy cm2 (mean 16 Gy cm2), 0.13 to 33.7 min (mean 5.4 min) and 0 to 26 radiographs (mean 3.5), respectively. The respective mean values for the four types of X-ray units that were investigated were as follows: KAP: 17.4, 12.5, 5.6 and 36.3 Gy cm2, T: 4.7, 5.2, 3.8 and 11.5 min and F: 1.7, 7.4, 1.9 and 4.6 radiographs. The type of the X-ray unit seems to significantly affect patient radiation dose, with the C-arm delivering the lowest and the angiography unit the highest patient doses.

Patient radiation doses in various fluoroscopically guided orthopaedic procedures.

All orthopaedic fluoroscopic procedures performed using C-arm guidance were monitored for 1 y. The type of procedure, fluoroscopy time (T), kerma-area product (KAP) values and number of radiographs (F) were recorded. The two most often performed techniques were as follows: intramedullary nailing (IMN) of intertrochanteric/peritrochanteric (IP) fractures (101 cases, 49.3 %) and antergrade IMN of femur or tibia shaft (TS) fractures (28 cases, 13.7 %). For the remaining procedures, none accounted for >5 %, categorised as 'various' (76 cases, 37 %). Large variations in T, KAP and F were observed. For IMN of IP fractures, antergrade IMN of femur and TS fractures and for various procedures, respectively, median values were T--2.1, 2.2 and 0.6 min, KAP--6.3, 6.3 and 0.6 Gy cm(-2) and F--21, 2.2 and 6.7. The patient doses during fluoroscopically guided procedures are relatively low compared with other interventional procedures.

Measuring skin dose in CT examinations under complex geometries: Instruments, methods and considerations.

OBJECTIVE: To investigate skin dose in Computed Tomography (CT) and its dependence on scanning geometry. MATERIALS AND METHODS: Measurements of entrance surface air kerma (ESAK) in free air and entrance skin dose (ESD) on an anthropomorphic phantom were performed in a 64-slice CT scanner, using two different instruments: the Dose Profiler (DP) and the QED skin diode (QEDSD). Using DP and QEDSD, the ESAK rate profiles at the isocenter and at different distances from it, were measured using axial scans. Using DP and helical scans the ESAK rate profile in the Z-axis was acquired. The same profile was acquired with the QEDSD also, using many axial scans and manual table translation. ESD measurements were performed with the DP and QEDSD, in axial and helical scan mode. RESULTS: ESAK measurements with DP and QEDSD were in good agreement, for both point dose and profile measurements. The agreement was also good for ESD measurements but not for helical scans, due to variable X-ray beam overlapping and different tube angular positions at each scan start. It was observed that the ESD values at different Y-axis offsets were comparable to the respective ESAK values recorded at the same Y-axis offset distances without the phantom. CONCLUSIONS: Both DP and QEDSD were proven suitable for performing point ESD measurements. However, calculating the skin dose distribution in CT examinations is a very challenging task. A practical approach would be for CT scanners to provide a conservative estimate of the peak skin dose using the isocenter ESAK value.

Dual-energy contrast-enhanced digital mammography: Glandular dose estimation using a Monte Carlo code and voxel phantom.

PURPOSE: To estimate the mean glandular dose of contrast enhanced digital mammography, using the EGSnrc Monte Carlo code and female adult voxel phantom. METHODS: Automatic exposure control of full field digital mammography system was used for the selection of the X-ray spectrum and the exposure settings for dual energy imaging. Measurements of the air-kerma and of the half value layers were performed and a Monte Carlo simulation of the digital mammography system was used to compute the mean glandular dose, for breast phantoms of various thicknesses, glandularities and for different X-ray spectra (low and high energy). RESULTS: For breast phantoms of 2.0-8.0 cm thick and 0.1-100% glandular fraction, CC view acquisition, from AEC settings, can result in a mean glandular dose of 0.450 ± 0.022 mGy -2.575 ± 0.033 mGy for low energy images and 0.061 ± 0.021 mGy - 0.232 ± 0.033 mGy for high energy images. In MLO view acquisition mean glandular dose values ranged between 0.488 ± 0.007 mGy - 2.080 ± 0.021 mGy for low energy images and 0.065 ± 0.012 mGy - 0.215 ± 0.010 mGy for high energy images. CONCLUSION: The low kV part of contrast enhanced digital mammography is the main contributor to total mean glandular breast dose. The results of this study can be used to provide an estimated mean glandular dose for individual cases.

Radiation dose in repeated CT guided radiofrequency ablations.

OBJECTIVE: To calculate the cumulative effective and skin doses in patients that underwent repeated CT guided radiofrequency ablations (RFA). MATERIALS AND METHODS: From all patients that had undergone RFA during a five years period those which had three or more RFAs were selected. Using the CT images DICOM data, the dose length product (DLP), effective dose (E), skin dose profiles as well as the peak skin dose (PSD) were calculated, using appropriate methods and software developed for this purpose. For each patient, cumulative DLP and E were also calculated from the sum of the respective figures of each individual procedure. To calculate PSD, the skin dose profiles of each procedure were overlaid on the same Z-axis scale using anatomical landmarks for reference and the skin doses to each point were summed up. RESULTS: Five patients were studied; four had undergone 3 RFAs and one 10 RFAs. Cumulative DLP, E and PSD ranges were 5.6-22.3 Gy cm, 0.08-0.36 Sv and 0.8-3.4 Gy, respectively. Median E and PSD values per RFA were 35 mSv and 0.4 Gy, respectively. For comparison purposes it must be noted that in this CT department a routine abdomen-pelvis scan results to an E of about 10 mSv. CONCLUSIONS: Patients that undergo repeated RFAs are exposed to considerably high radiation exposure levels. When these patients are in the final stage of malignant diseases, stochastic effects may not be of major concern. However, optimization of the exposure factors and monitoring of these patients to avoid skin injuries are required.

Effective and ovarian dose in PA conventional and rotational 3D hysterosalpingography examinations.

The purpose of this study was to compare effective and ovarian doses (E and OD, respectively) in hysterosalpingography (HSG) examinations performed with conventional posterioanterior (PA) projections and rotational 3D (3D) techniques. 29 HSG examinations (11 conventional and 18 3D), were performed using a digital C-arm angiographic system. In the conventional technique, we used posterioanterior (PA) instead of an anterioposterior (AP) projection normally used according to the international literature. All information concerning exposure conditions for each patient, were recorded. Thermoluminescent dosimeters (TLDs) were attached on the skin of each patient over the ovaries. In conventional HSGs, average values were for Dose Area Product (DAP) 0.41 Gycm(2), for Effective Dose (E) 0.15 mSv and for Ovarian Dose (OD) 0.24 mGy. In 3D-HSGs, they were 14.4 Gycm(2), 2.29 mSv and 3.96 mGy correspondingly. Patient doses in 3D-HSGs are of the same order of magnitude with those reported in the literature for conventional technique. However, they are larger compared to the conventional HSG performed with the technique we use in this specific X-ray system. E and OD are much lower with our technique where PA projection and the specific C-arm system are used in comparison with the corresponding values published in the literature for the conventional technique where the AP projection is used.

Ultrasound-assisted endocavitary HDR-Ir192 brachytherapy for unresectable locally advanced uterine cervix carcinoma: retrospective analysis focusing the efficacy and tolerability

PURPOSE: To evaluate the impact of uterine cavity's ultrasound to final selected length of intracavitary tandem. The efficacy and tolerability of external beam radiation plus HDR-Ir(192) brachytherapy in our cohort of patients were also estimated. MATERIALS AND METHODS: 48 women with locally advanced unresectable uterine cervix carcinoma were treated by HDR-Ir(192) endocavitary brachytherapy between January 2007 and January 2009. The median age was 63 (range 38-74). The distribution according to Federation of Gynaecology and Obstetrics (FIGO) staging system was as follows: Stage IIB, 54.16 %; IIIA, 10.4 %; IIIB, 27.0 %; and IVA, 8.3 %. HDR intracavitary brachytherapy was given weekly, beginning at the last week of whole pelvis irradiation, with a dose of 7 Gy to point A for three to four fractions. The median overall treatment time was 50 days (range 42-73 days). The median follow-up time was 2.7 years (range 3 months to 4.9 years). Multivariate analysis was performed using the Cox regression proportional hazards model. RESULTS: The complete remission rate after radiotherapy was 93.75 % (45/48). The 5-year actuarial major complication rates (Grade 3 or above) were 6.3 % overall (2.1 % proctitis, 2.1 % cystitis and 2.1 % enteritis). Estimation of the length of uterine cavity by ultrasound helped decisively in the proper placement of the intrauterine tandem inserted. CONCLUSIONS: Prior knowledge of the length of uterine cavity can facilitate the decisions regarding the proper insertion length of the tandem. Results of cervical cancer treatment with external beam radiation and HDR intracavitary brachytherapy in our hospital are encouraging (AU)

A method for calculating the dose length product from CT DICOM images.

OBJECTIVE: The dosimetric calculations in CT examinations are currently based on two quantities: the volume weighted CT dose index (CTDI(vol)) and the dose-length product (DLP). The first quantity is dependent on the exposure factors, scan field of view, collimation and pitch factor selections, whereas the second is additionally dependent on the scan length. METHODS: In this study a method for the calculation of these quantities from digital imaging and communication in medicine (DICOM) CT images is presented that allows an objective audit of patient doses. This method was based on software that has been developed to enable the automatic extraction of the DICOM header information of each image (relating to the parameters that affect the aforementioned quantities) into a spreadsheet with embedded functions for calculating the contribution of each image to the CTDI(vol) and DLP values. The applicability and accuracy of this method was investigated using data from actual examinations carried out in three different multislice CT scanners. These examinations have been performed with the automatic exposure control systems activated, and therefore the tube current and tube loading values varied during the scans. RESULTS: The calculated DLP values were in good agreement (±5%) with the displayed values. The calculated average CDTI(vol) values were in similar agreement with the displayed CTDI(vol) values but only for two of the three scanners. In the other scanner the displayed CTDI(vol) values were found to be overestimated by about 25%. As an additional application of this method the differences among the tube modulation techniques used by the three CT scanners were investigated. CONCLUSION: This method is a useful tool for radiation dose surveys.

Multi-channel magnetoencephalogram on Alzheimer disease patients.

Magnetoencephalogram (MEG) recordings of 8 patients with advanced Alzheimer Disease (AD) and 9 normal individuals were obtained with a 122-channel whole head biomagnetometer SQUID (Superconductive Quantum Interference Device) to record the minute magnetic fields generated by the brain. The obtained MEG signals were analyzed using linear signal analysis techniques such as Fourier Transform in order to get the frequency distribution of MEG values. The obtained frequencies from all MEG sensors located outside the scalp of each subject were stored for evaluation. From this evaluation it was concluded that in patients with AD the dominant frequencies were significantly lower compared to normal individuals.

Investigation of breast dose in five screening mammography centres in Greece.

The objectives of this study were to investigate the techniques currently used for screening mammography in Greece, to estimate the mean glandular dose (MGD) for establishing a baseline radiation dose database, to analyse the effects of various factors on MGD, and to compare the results with others in the literature. Five mammographic facilities and 250 women having as a routine screening mammogram one craniocaudal (CC) and one mediolateral oblique (MLO) projection in each breast were included in the study. The parameters recorded were age, weight, compressed breast thickness (CBT), tube potential (kV), tube loading (mA s) and MLO projection angle. Large differences were observed among the different mammography facilities, mainly in terms of the tube potential setting and the MLO angle used. The average MGD per exposure was 1.4 +/- 0.6 mGy while the respective averages separately for the CC and MLO projections were 1.2 +/- 0.5 and 1.5 +/- 0.7 mGy, respectively. The average MGD values recorded in this study were below the limit of 2 mGy established for the reference medium-sized breast of 4.5 cm CBT. However, the variety of techniques observed revealed the need for a nationwide survey concerning screening mammography in Greece.

Correlation of image quality with exposure index and processing protocol in a computed radiography system.

The correlation of image quality with the exposure index (EI) and the processing protocol was investigated in a Kodak computed radiography (CR) system using clinical radiographs and a water phantom containing an aluminium and a copper step-wedge. The phantom was exposed to different dose levels and the acquired images were processed using four clinical protocols. The quality of these images was evaluated in terms of image brightness, contrast and noise. In clinical radiographs, there was no straightforward correlation of image quality with EI. In phantom images, higher EI values improved contrast and reduced noise but after a point this improvement does not justify the implied increase in patient dose. Image brightness, contrast and noise were also strongly dependent on the processing protocol. To obtain the images of satisfactory quality with the Kodak CR system, a dose slightly higher than those used in 400 relative speed screen-film systems and a processing protocol designated for the specific radiographic examination are required.

Comparison of patient doses in interventional radiology procedures performed in two large hospitals in Greece.

Purpose of the study was to determine patient doses in the most common interventional radiology (IR) procedures performed in two large Greek hospitals. A total of 164 patients who underwent 4 types of IR procedures were studied. Fluoroscopy time, total exposure time, number of frames, number of runs, radiation field size, and cumulative dose-area product (DAP) were recorded. The median DAP values for carotid arteriography and lower limb arteriography were 66 and 123 Gy cm2 for hospital 'A' and 21 and 49 Gy cm2 for hospital 'B'. For the cerebral arteriographies performed in hospital 'A', the median DAP was 116 Gy cm2, while for the hepatic embolizations performed in hospital 'B', it was 104 Gy cm2. The DAP values observed in hospital 'A' for carotid arteriography and lower limb arteriography were almost three times than those of hospital 'B'. From the data analysis, it is evident that dose optimization in hospital 'A' should be pursued through revision of the techniques used.

Radiation doses to patients undergoing standard radiographic examinations: a comparison between two methods.

The objective of the study was to derive a mathematical method for calculating the entrance surface dose (ESD) from exposure factors for all tube potentials used in clinical practice and to compare the calculated ESDs (ESD(C)) with those measured (ESD(TLD)) using thermoluminescent dosemeters (TLDs). The exposure parameters of 43 patients who underwent (a) posteroanterior (PA) and lateral (LAT) chest examination (13 patients), (b) supine abdomen (10 patients), (c) erectus abdomen (10 patients), or (d) urinary tract examination (10 patients) were recorded. Patient ESD was directly measured by TLDs and calculated from exposure factors. The differences between ESD(C) and ESD(TLD) were quite small and could be explained by the uncertainties involved in both methods, in all but the PA chest examination where the ESD(C) was about 50% larger than ESD(TLD). However, in PA chest the ESD(TLD) was close to the minimum detectable dose of TLDs, questioning the accuracy of ESD(TLD). Further investigation showed that using the high tube potential technique (130 kV) in the PA chest examination resulted in very short exposure times, in the region of 4 ms. In such short exposure times, the X-ray generator operation presented stability problems that led to loss of output linearity and consequently to false calculation of ESD. The calculation method offers a reliable and cheap alternative to the measurement of ESD by TLD, provided that the exposure times are not as short as in the PA chest examinations recorded in this study, so that the output linearity with tube current-time product (mAs) is maintained.

Optical density variations in CT films and their effect on image quality.

It was recently reported that optical density (OD) variations were observed in CT films printed with a laser camera, depending on the printing format and the frame position within the film. The purpose of the present study was to investigate if these variations are common to both laser and dry-film printers and if the different OD settings along with day-to-day and frame-to-frame variations may affect the image quality. Eight laser and five dry-film printers installed at 12 different CT facilities were tested. For each one, the SMPTE test pattern was printed on all frames of a film using the same printing format. The ODs of the 0%, 10%, 40% and 70% patches of the 11-step greyscale of the SMPTE patterns were measured with a densitometer in all frames, while all films were examined on a viewing box to assess subjectively the image quality by visual inspection of the test pattern. A wide range of OD settings and variations were recorded. Frame-to-frame variations in the same film of up to 0.19, 0.15 and 0.21 OD, were observed for contrast index (CI, the OD difference of patches 10% and 70%), speed index (SI, the OD of patch 40%) and maximum OD (OD(max), the OD of patch 0%), respectively. The variations were not always of the same magnitude, nor always followed the same pattern, even for printers of the same model. Considering all films and frames, the CI ranged from 1.26 to 1.74, the SI from 0.68 to 1.43 and the OD(max) from 2.5 to 3.11 OD, well beyond the proposed settings and tolerances of 1.55+/-0.15, 1.15+/-0.1 and 2.45+/-0.1 given in the literature for CI, SI and OD(max), respectively. Despite these large differences, the various problems that were identified in image quality from the visual inspection of the films could not be directly attributed to OD settings, as films with similar CI, SI and OD(max) presented quite different image quality levels. Therefore, for routine quality control, thorough visual inspection of the SMPTE test pattern provides all the necessary information about the imaging chain status.

Virtual bronchoscopy versus thin section computed tomography in evaluation of moderate and low grade stenoses: receiver operating characteristic curve analysis.

PURPOSE: To evaluate the impact of virtual bronchoscopy, under proper threshold settings, on observer level of confidence in the assessment of bronchial abnormalities producing stenoses < or = 75% compared to interpretation of thin section computed tomography (CT) images. MATERIAL AND METHODS: Sixty-five patients with fiberoptic bronchoscopy positive for tracheobronchial abnormalities were evaluated in a blinded observer study using a commercially available virtual endoscopy software package. The findings of virtual endoscopy were compared with those of fiberoptic bronchoscopy using receiver operating characteristic curves (ROCs) and other statistical tools. RESULTS: A total of 102 lesions were identified by fiberoptic bronchoscopy, with 44 of these producing bronchial stenoses < or = 75%. Concerning the latter lesions, for virtual bronchoscopy the areas under the ROCs were 0.93 and 0.96 for the two observers, respectively, while for thin section CT the corresponding values were 0.86 and 0.88; the differences observed were statistically significant. Contrary to thin section CT, virtual bronchoscopy did not show statistically significant differences from fiberoptic bronchoscopy regarding estimation of degree of stenosis. CONCLUSION: Virtual bronchoscopy under proper threshold settings has a statistically significant impact on observer performance where moderate and low-grade bronchial stenoses are concerned and gives an estimate of the degree of stenosis more precisely than thin section CT.