Determination of the weighted CT dose index in modern multi-detector CT scanners.

The aim of the present study was to (a) evaluate the underestimation in the value of the free-in-air (CTDI(air)) and the weighted CT dose index (CTDI(w)) determined with the standard 100 mm pencil chamber, i.e. the CTDI(100) concept, for the whole range of nominal radiation beam collimations selectable in a modern multi-slice CT scanner, (b) estimate the optimum length of the pencil-chamber and phantoms for accurate CTDI(w) measurements and (c) provide CTDI(w) values normalized to free-in-air CTDI for different tube-voltage, nominal radiation beam collimations and beam filtration values. The underestimation in the determination of CTDI(air) and CTDI(w) using the CTDI(100) concept was determined from measurements obtained with standard polymethyl-methacrylate (PMMA) phantoms and arrays of thermoluminescence dosimeters. The Monte Carlo N-Particle transport code was used to simulate standard CTDI measurements on a 16-slice CT scanner. The optimum pencil-chamber length for accurate determination of CTDI(w) was estimated as the minimum chamber length for which a further increase in length does not alter the value of the CTDI. CTDI(w)/CTDI(air) ratios were determined using Monte Carlo simulation and the optimum detector length for all selectable tube-voltage values and for three different values of beam filtration. To verify the Monte Carlo results, measured values of CTDI(w)/CTDI(air) ratios using the standard 100 mm pencil ionization chamber were compared with corresponding values calculated with Monte Carlo experiments. The underestimation in the determination of CTDI(air) using the 100 mm pencil chamber was less than 1% for all beam collimations. The underestimation in CTDI(w) was 15% and 27% for head and body phantoms, respectively. The optimum detector length for accurate CTDI(w) measurements was found to be 50 cm for the beam collimations commonly employed in modern multi-detector (MD) CT scanners. The ratio of CTDI(w)/CTDI(air) determined using the optimum detector length was found to be independent of beam collimation. Percentage differences between measured and calculated corresponding CTDI(w)/CTDI(air) ratios were always less than 8% for head and less than 5% for body PMMA phantoms. In conclusion, the CTDI(air) of MDCT scanners may be measured accurately with a 100 mm pencil chamber. However, the CTDI(100) concept was found to be inadequate for accurate CTDI(w) determination for the wide beam collimations commonly used in MDCT scanners. Accurate CTDI(w) determination presupposes the use of a pencil chamber and PMMA phantoms at least 50 cm long.

Clearance of technetium-99m-DTPA in pulmonary sarcoidosis.

BACKGROUND: The aim of this study was to explore the possible association of the lung clearance of 99mTc-DTPA scan with HRCT lung abnormalities and with the pulmonary function tests [PFTs] in patients with sarcoidosis. METHODS: We studied prospectively 15 patients [5 males, 10 females] of median age 46yr [range 27-67] with histologically proved sarcoidosis. HRCT scoring included the sum of the severity and extent of lymph node enlargement and parenchymal involvement. RESULTS: The mean DTPA clearance half-time [tau 1/ <40 min] was found [mean [SD]] 38.3+/-4.5min. The lymph node enlargement was found 34% and the parenchymal involvement 12%. DTPA clearance was negatively correlated with the parenchymal involvement [r= -0.651, p=0.0091]. The HRCT parenchymal abnormalities were found significantly correlated with PFTs [FVC [r= -0.65, p=0.008] and TLCO [r= -0.76, p=0.02]. CONCLUSIONS: Our data suggest a moderate association between 99mTc-DTPA scan and HRCT in pulmonary sarcoidosis. However, further studies in large scale of sarcoid patients are needed to clarify the role of this novel methodology in the evaluation and follow-up of this disorder.

Data and methods to estimate fetal dose from fluoroscopically guided prophylactic hypogastric artery balloon occlusion.

PURPOSE: To provide data for estimation of fetal radiation dose (DF) from prophylactic hypogastric artery balloon occlusion (HABO) procedures. METHODS: The Monte-Carlo-N-particle (MCNP) transport code and mathematical phantoms representing a pregnant patient at the ninth month of gestation were employed. PA, RAO 20° and LAO 20° fluoroscopy projections of left and right internal iliac arteries were simulated. Projection-specific normalized fetal dose (NFD) data were produced for various beam qualities. The effects of projection angle, x-ray field location relative to the fetus, field size, maternal body size, and fetal size on NFD were investigated. Presented NFD values were compared to corresponding values derived using a physical anthropomorphic phantom simulating pregnancy at the third trimester and thermoluminescence dosimeters. RESULTS: NFD did not considerably vary when projection angle was altered by ±5°, whereas it was found to markedly depend on tube voltage, filtration, x-ray field location and size, and maternal body size. Differences in NFD < 7.5% were observed for naturally expected variations in fetal size. A difference of less than 13.5% was observed between NFD values estimated by MCNP and direct measurements. CONCLUSIONS: Data and methods provided allow for reliable estimation of radiation burden to the fetus from HABO.

Accurate assessment of patient effective radiation dose and associated detriment risk from radiofrequency catheter ablation procedures.

BACKGROUND: Radiofrequency (RF) cardiac catheter ablation procedures may require extended fluoroscopic exposure resulting in elevated radiation risk. The aim of the present study was to accurately establish RF ablation radiation risk levels and to provide means for accurate patient risk estimation from studies performed in any electrophysiology laboratory. METHODS AND RESULTS: Fluoroscopy required during cardiac ablation was classified into 4 types identified by beam orientation and irradiated tissue: (1) posteroanterior exposure during catheter advancing from the groin to the heart, (2) posteroanterior heart exposure, (3) left anterior oblique heart exposure, and (4) right anterior oblique heart exposure. The duration of each exposure was monitored in 24 patients undergoing RF cardiac ablation. Dose per minute of fluoroscopy was measured at 15 organs/tissues for each projection with the use of anthropomorphic phantom and thermoluminescence dosimetry. The effective dose rate was 219, 144, 136, and 112 mu/min for groin-to-heart posteroanterior, posteroanterior, left anterior oblique, and right anterior oblique exposure, respectively. A typical ablation procedure results in a total effective dose of 8.3 mSv per hour of fluoroscopy. The average excess of fatal cancers was estimated to be 650 and 480 per million patients undergoing RF ablation requiring 1 hour of fluoroscopy for US and UK populations, respectively. The average risk for genetic defects was determined to be 1 per million births. CONCLUSIONS: Radiation risk from RF cardiac ablation is moderate compared with other complications, but it may highly exceed radiation risk from common radiological procedures. Efforts should be made toward minimization of patient radiation risk from RF ablation procedures.

Conceptus radiation dose and risk from cardiac catheter ablation procedures.

BACKGROUND: The aim of the current study was to estimate the conceptus radiation dose and risk associated with fluoroscopic imaging during a catheter ablation procedure for supraventricular tachycardia performed on the expectant mother. METHODS AND RESULTS: Exposure parameters and fluoroscopy times for each projection of the cardiac ablation procedure performed in 20 female patients of childbearing age were recorded. Radiation doses for a potential conceptus were estimated by using dose data obtained in anthropomorphic phantoms simulating pregnancy at the first, second, and third trimesters. Dose measurements were carried out using thermoluminescent dosimeters. For a typical examination, the average radiation dose to the conceptus was <1 mGy in all periods of gestation. Average excess fatal cancer was 14.5/10(6) unborn children irradiated during the first postconception weeks. Corresponding values for the second and third trimesters were 30 and 55.7/10(6), respectively. The risk for hereditary effects in future generations was 1.5/10(6) cases for conceptus irradiation during the first postconception weeks. Corresponding values for the second and third trimesters were 3.0 and 5.6/10(6), respectively. Formulas and dose data are presented for estimating the conceptus risk from any technique and x-ray system used for catheter ablation procedures. CONCLUSIONS: A typical catheter ablation procedure results in a very small increase in risk of harmful effects to the conceptus. However, estimation of conceptus dose from catheter ablation procedures is always needed to assess the risk to the individual developing in utero.

The effect of z overscanning on patient effective dose from multidetector helical computed tomography examinations.

z overscanning in multidetector (MD) helical CT scanning is prerequisite for the interpolation of acquired data required during image reconstruction and refers to the exposure of tissues beyond the boundaries of the volume to be imaged. The aim of the present study was to evaluate the effect of z overscanning on the patient effective dose from helical MD CT examinations. The Monte Carlo N-particle radiation transport code was employed in the current study to simulate CT exposure. The validity of the Monte Carlo simulation was verified by (a) a comparison of calculated and measured standard computed tomography dose index (CTDI) dosimetric data, and (b) a comparison of calculated and measured dose profiles along the z axis. CTDI was measured using a pencil ionization chamber and head and body CT phantoms. Dose profiles along the z axis were obtained using thermoluminescence dosimeters. A commercially available mathematical anthropomorphic phantom was used for the estimation of effective doses from four standard CT examinations, i.e., head and neck, chest, abdomen and pelvis, and trunk studies. Data for both axial and helical modes of operation were obtained. In the helical mode, z overscanning was taken into account. The calculated effective dose from a CT exposure was normalized to CTDI(free in air). The percentage differences in the normalized effective dose between contiguous axial and helical scans with pitch = 1, may reach 13.1%, 35.8%, 29.0%, and 21.5%, for head and neck, chest, abdomen and pelvis, and trunk studies, respectively. Given that the same kilovoltage and tube load per rotation were used in both axial and helical scans, the above differences may be attributed to z overscanning. For helical scans with pitch = 1, broader beam collimation is associated with increased z overscanning and consequently higher normalized effective dose value, when other scanning parameters are held constant. For a given beam collimation, the selection of a higher value of reconstructed image slice width increases the normalized effective dose. In conclusion, z overscanning may significantly affect the patient effective dose from CT examinations performed on MD CT scanners. Therefore, an estimation of the patient effective dose from MD helical CT examinations should always take into consideration the effect of z overscanning.

Film-screen magnification versus electronic magnification and enhancement of digitized contact mammograms in the assessment of subtle microcalcifications.

RATIONALE AND OBJECTIVES: To compare information drawn from magnification mammography with that extracted from electronic magnification, processing, and display of the digitized contact images. METHODS: Contact and magnification images of a mammographic statistical phantom were obtained. The magnification films versus the computer-enhanced, digitized images of the corresponding contact mammograms were separately presented to three observers. Receiver operating characteristic analysis was used to compare lesion detectability. The contact and magnification mammograms of 86 patients with subtle microcalcifications were also studied. The breast imaging reporting and data system (BI-RADS) scheme was used to compare the magnification patient films versus the corresponding digitized contact images. Differences in mammographic assessment were evaluated by using the kappa statistic. The dose to breast tissue from contact and magnification mammography was measured to evaluate dose reduction in instances where magnification mammography was to be avoided. RESULTS: Lesion detectability was found to be similar when either the digitized film image or the magnification hard-copy film was inspected. Interpretation of patient images by inspection of the contact and magnification screen-film mammograms on a view-box was in excellent agreement with that yielded by inspection of the contact image on a view-box and the computer-enhanced, digitized contact image on a display monitor. CONCLUSIONS: Electronic magnification and processing of the digitized contact image may provide valuable information concerning subtle microcalcifications, rendering magnification mammography unnecessary for many patients with such lesions.

Estimation of fetal radiation dose from computed tomography scanning in late pregnancy: depth-dose data from routine examinations.

RATIONALE AND OBJECTIVES: To provide depth-dose data for estimating fetal radiation dose from routine computed tomography (CT) examinations of the trunk. METHODS: Doses were measured during CT examinations of the thorax, upper abdomen, abdomen, and pelvis in two anthropomorphic phantoms simulating pregnant women in the second and third trimesters. Thermoluminescent dose meters were used for dose measurements. RESULTS: In CT examinations of the abdomen, doses of 30.0 to 43.6 mGy and of 29.1 to 42.0 mGy were measured at the measuring points in the phantom simulating pregnancy in the second and third trimesters, respectively. In CT examinations of the upper abdomen, pelvis, and thorax, both phantoms received lower doses of radiation. Knowledge of the normalized weighted dose index of the CT scanner and of the kVp and mAs settings of the protocol used for examination of the pregnant woman is needed to adjust the dose data found in the present study to modified protocols and different CT equipment. CONCLUSIONS: These dosimetric data may be used to guide the management of pregnant patients undergoing CT examinations of the trunk.

Embryo depth during the first trimester. Data required for embryo dosimetry.

RATIONALE AND OBJECTIVES: To provide data regarding embryo depth during the extremely radiosensitive gestational stages of organogenesis and early fetal period for use in embryo dosimetry. METHODS: Ultrasound examination was performed in 73 pregnant women at gestational age 5 to 13 weeks and in a control group of 75 nonpregnant women. Embryo skull and abdominal depth from the maternal skin surface were determined in the anteroposterior direction. Uterus depth was measured in the control group. Measurements were taken before and after voiding. Gestational age and maternal age, height, and weight were noted. Body mass index (BMI) was estimated for every woman from the formula BMI = W/H2. RESULTS: The mean embryo pre- and postvoid skull depth was 8.3 and 5.7 cm and the mean abdominal depth was 8.4 and 5.8 cm, respectively. The mean pre- and postvoid uterus depth was 9.5 and 4.7 cm. Mean abdominal depth and mean skull depth values were significantly different than mean uterus depth for full as well as for empty bladder. Embryo skull depth and abdominal depth were found to be significantly correlated with maternal BMI. Skull and abdominal dimensions were found to be significantly correlated with gestational age. CONCLUSIONS: During the first trimester, embryo depth ranges from 4 to 10 cm, depending on the individual, the status of the bladder, and the maternal BMI. For an accurate determination of embryo depth, ultrasound measurement should be performed.

Accidental embryo irradiation during barium enema examinations. An estimation of absorbed dose.

RATIONALE AND OBJECTIVES: To investigate the possibility of an embryo to receive a dose of more than 10 cGy, the threshold of malformations induction in embryos reported by the International Commission on Radiological Protection, during barium enema examinations. METHODS: Thermoluminescent dosimeters were placed in a phantom to calculate the depth-to-skin conversion coefficient needed for dose estimation at the average embryo depth in patients. Barium enema examinations were performed in 20 women of childbearing age with diagnostic problems demanding longer fluoroscopy times. Doses at 6 cm, the average embryo depth, were determined by measurements at the patients' skin followed by dose calculation at the site of interest. RESULTS: The range of doses estimated at embryo depth for patients was 1.9 to 8.1 cGy. The dose always exceeded 5 cGy when fluoroscopy time was longer than 7 minutes. CONCLUSION: The dose at the embryo depth never exceeded 10 cGy. This study indicates that fluoroscopy time should not exceed 7 minutes in childbearing-age female patients undergoing barium enema examinations.

Determination of dose-area product from panoramic radiography using a pencil ionization chamber: normalized data for the estimation of patient effective and organ doses.

The aims of the present study were (a) to investigate the potential of pencil ionization chamber to be used for the determination of dose-width product (DWP) and dose-area product (DAP) from panoramic radiographic exposures and (b) to provide data normalized to DAP for the determination of patient effective and gonadal dose from panoramic radiography performed in any laboratory. A pencil ionization chamber commonly used to measure CT dose index (CTDI) in CT scanners was employed to determine DWP for various combinations of panoramic exposure settings at the beam exit slit of a Cranex Tome panoramic x-ray unit (Soredex, Helsinki, Finland). DWP values were also measured using an array of thermoluminescence dosimeters. Reproducibility of the DWP measurement was tested. The effect of milliamperage and kilovoltage of panoramic exposures on DWP was investigated. DAP was estimated using the value of DWP measured using the pencil ionization chamber and the beam exit slit length measured using dosimetric film attached on the beam exit slit. A Rando anthropomorphic phantom appropriately loaded with thermoluminescent dosimeters (TLDs) was used to obtain organ dose and effective dose values from panoramic radiography. Reproducibility of DWP determination using the proposed method was better than 1.5%. DWP was found to be linearly related to milliamperage (r>0.999, p<0.001) and to kilovoltage raised in a power ranging from 2.18 to 2.55. DWP measured using the pencil chamber was found to be up to 11% higher than the corresponding values determined using TLD array. The panoramic exposure obtained with settings appropriate for the typical adult patient was found to result in 0.008 mSv patient effective dose, 0.0002 mGy gonadal dose, and 11.3 cGy cm2 DAP. The use of a pencil ionization chamber is proposed for the determination of DWP and DAP from panoramic radiographic exposures. Normalized data over DAP were provided for the determination of patient effective and gonadal dose from panoramic radiography.

Conceptus radiation dose assessment from fluoroscopically assisted surgical treatment of hip fractures.

Our aims in the present study were to (a) provide normalized dose data for the estimation of the conceptus dose from fluoroscopically assisted surgical treatment of hip fractures carried out during all trimesters of pregnancy and (b) estimate the conceptus radiation dose and risks associated with fluoroscopy during a typical treatment of hip fracture performed on a pregnant woman. Conceptus doses normalized to entrance surface dose (ESD) or dose area product (DAP) were obtained with the help of anthropomorphic phantoms simulating pregnancy in the three trimesters of gestation. ESD and conceptus dose measurements were carried out using thermoluminescent dosimeters. DAP to conceptus dose conversion factors were estimated for the first, second and third trimesters of gestation. Conceptus dose data normalized to ESD were also estimated to investigate whether these conversion factors may be used for procedures carried out in x-ray units not equipped with a DAP meter. Fluoroscopically assisted surgical treatments were performed in 18 women. The projections involved in these procedures are (a) posteroanterior (PA) and (b) lateral crosstable 45 degrees (LC). Radiation doses for a potential conceptus were estimated by using normalized dose data obtained in phantoms. The results consist of tabulated dose data normalized to DAP or ESD for the estimation of a conceptus dose. An important finding of this study was that the total DAP of a procedure, instead of the individual DAP values of each projection, could be used for the accurate estimation of the conceptus dose. Conceptus doses calculated using dose data normalized to ESD are about 23% higher compared to those estimated using data normalized to DAP. This discrepancy may be attributed to the contribution of scattering radiation from PA projection to ESD measurement of LC projection and vice versa. Therefore, dose data normalized to ESD do not provide accurate conceptus dose estimation. Doses normalized to DAP showed a dependence on (a) tube potential and (b) tube filtration. Data are provided to extent the doses normalized to DAP for the standard spectrum to other tube voltages and filtrations. The maximum dose for a potential conceptus was 0.425 mGy for a patient irradiated for 50 seconds during the PA projection and for 40 seconds during the LC projection. Although the total duration of fluoroscopy is usually less than 2 minutes during a typical procedure, screening time as long as 14 minutes has been reported in the literature for treatment of complex fractures. The relationship between conceptus dose and fluoroscopy time found in the current study showed that, in these cases, the radiation dose received by a conceptus may exceed 1 mGy. In conclusion, an accurate estimation of conceptus doses associated with fluoroscopically assisted surgical treatment of hip fractures can be made using the DAP normalized dose data provided in this study. Conceptus doses from a typical procedure is less than 1 mGy during all trimesters.

Pegulated liposomal doxorubicin and cisplatin given concurrently with conventional radiotherapy: a phase I dose-escalation trial for patients with squamous cell carcinoma of head and neck and lung.

This is a phase I study of concurrent chemoradiation with pegulated liposomal doxorubicin (PLDH) and cisplatin for patients with squamous non-small cell lung cancer (NSCLC) and head and neck carcinoma (SCCHN). Nine patients with NSCLC and 9 with SCCHN were recruited in two phase I dose-escalation trials. The starting dose of PLDH was 7 mg/m2 once a week and was increased by 5 mg/m2 dose increments for every 3 patients. The standard dose of cisplatin was 20 mg/m2 once a week for 6.5-7 weeks of conventional external irradiation. The total tumor dose was 64 and 70 Gy for NSCLC and SCCHN patients respectively. The maximum tolerated dose of PLDH was 12 mg/m2 for the two cohorts of patients. Grade 3 mucositis was the dose limiting toxicity for NSCLC and SCCHN patients, at the 17 mg/m2 dose level. Three chemoradiation delays of 7 days were confirmed. The median time of follow-up was 17.9 months (range 3-36 months). Four patients died due to local-regional failure combined with distant metastases (3 patients) and pericardial effusion (1 patient). In total, there were 6/18 (33%) CRs (95% confidence interval, 11-55%), and 10/18 (55%), PRs (95% confidence interval, 32-78%). The recommended phase II PLDH dose combined to cisplatin and external irradiation is 12 mg/m2/week. The incorporation of PLDH in concomitant chemoradiation regimens for future treatment of squamous cell carcinoma of the lung and head and neck is warranted.

Serum proinflammatory cytokines and its relationship to clinical parameters in lung cancer patients with reactive thrombocytosis.

Proinflammatory cytokines Interleukin-1 beta (IL-1 beta) and Interleukin-6 (IL-6) play a significant role in the pathogenetic processes related to various malignant and inflammatory conditions. Leukocytosis, thrombocytosis and increased acute phase protein levels are part of a systemic inflammatory response. In this study, we measured the concentrations of IL-1 beta, IL-6 and ferritin as well as hemoglobin, lactate dehydrogenase (LDH), C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) in 23 patients (male 15, female 8, median age 68 years) with lung cancer and reactive thrombocytosis (LCRT), in 27 (male 18, female 9, median age 64 years) with benign inflammatory lung disorder (BILD) and 18 (male 10, female 8, median age 62 years) lung cancer patients with a normal platelet count (LCNP). IL-1 beta levels were significantly higher in the three patient groups in comparison with control subjects (P < 0.001) but without significant difference among the three patient groups. IL-6 was higher in all three patients groups but only in the BILD group it was significantly higher than the control group (P < 0.05). However, no significant difference in IL-6 serum levels was found between the two lung cancer groups. CRP and LDH were significantly higher in the LCRT group in comparison with the other two patient groups (P < 0.01 and 0.001, respectively), while ferritin was higher in both lung cancer groups in comparison with the BILD group (P < 0.001). Our data suggest that in lung cancer patients, reactive thrombocytosis is part of the systemic inflammatory reaction for which IL-1 beta and IL-6 may be intermediate but not independent mediators.

Effect of dual and triple energy window scatter correction methods on image quality in liver scintigraphy.

AIM: To investigate the effect of two scatter correction methods on lesion detectability for both planar and tomographic hepatic imaging. METHODS: All planar and tomographic acquisitions involved simultaneous collection of photons in the main photopeak window (126-154 keV) and three additional windows (92-116, 116-126 and 154-164 keV). Uncorrected and corrected for scatter images were obtained from the same acquisition data. The dual energy window (DEW) and the triple energy window (TEW) scatter compensation methods were used to obtain two sets of corrected images. The DEW method was implemented with main photopeak window 126-154 keV, Compton scatter window 92-126 keV and scatter multiplier k = 0.5. A modified TEW method was also applied with main photopeak window 126-154 keV and scatter subwindows 116-126 keV and 154-164 keV. Phantoms were used to study the effect of scatter correction on contrast and signal-to-noise ratio. The observer's ability to identify lesions was studied on uncorrected and corrected for scatter patient images. RESULTS: In planar imaging, both scatter compensation methods yielded contrast enhancement. However signal to noise ratio (SNR) was degraded to 0.63 and 0.67 when DEW and TEW were applied respectively. In SPECT images, contrast was increased by a factor of 2.4 and 1.7, while SNR was degraded to 0.60 and 0.64 when DEW and TEW methods were used respectively. CONCLUSIONS: Scatter correction using DEW and TEW methods may improve observer's ability to distinguish lesions in planar (p < 0.05 for both methods) and SPECT (p < 0.05 for both methods) liver studies.

Patient dose reduction in CT examinations by optimising scanogram acquisition.

The objective was to determine the optimum settings of the scanogram performed in computed tomography (CT) examinations for scan localisation. Head, abdomen and thorax scanograms were performed on a Rando anthropomorphic phantom using various selectable combinations of tube voltage and tube current values. Thermoluminescence dosemeters were used to obtain entrance skin dose data. Effective dose was estimated using normalised organ dose data provided by the National Radiological Protection Board. One hundred and twelve head, 114 thoracic and 111 abdominal patient scanograms were obtained with lower settings than those recommended by the operator's manual. Scanogram sufficiency was assessed by four observers. Head and thoracic scanograms obtained with 80 kV/50 mA and abdominal scanograms obtained with 80 kV/75 mA were found to be acceptable, even though the operator's manual recommendation was 120 kV/100 mA. Thus, the scanogram effective dose was reduced by 72%, 84% and 88% for head, thorax and abdomen examination respectively. Effective dose from a complete CT examination may be reduced by up to 3.5% without any subsequent image quality degradation of the diagnostically important sectional images.

Hybrid cardiac imaging: insights in the dilemma of the appropriate clinical management of patients with suspected coronary artery disease.

AIM: To evaluate the potential of SPECT myocardial perfusion imaging (MPI)-computed tomography coronary angiography (CTCA) hybrid fusion imaging to improve the diagnostic performance of cardiac SPECT/MPI and CTCA alone in order to act as more accurate gate keeper to further investigation invasive or not. METHODS AND RESULTS: Twenty-five patients were subjected to SPECT/MPI and CTCA within a period of 1 month without any medical treatment modification. A fusion software package was used for cardiac SPECT-CTCA image fusion. Semiquantitative analysis was performed for cardiac SPECT, CTCA and SPECT/MPI-CTCA fusion images. Patients were classified in 2 groups according to the clinical decision for further investigation (group A), or not (group B). Statistically significant differences were observed when SPECT/MPI-CTCA fusion images were used instead of cardiac SPECT alone (p<0.05). No statistically significant differences were observed comparing CTCA alone to SPECT/MPI-CTCA fusion images (p=0.25). A mid-term follow-up (mean 3.58 ± 0.24 years) showed that all patients classified in group A based on the interpretation of SPECT MPI-CTCA fused images underwent conventional coronary angiography with further necessity for PTCA or CABG whereas absence of major or minor cardiac events was revealed for all patients of group B. CONCLUSION: In patients suspected for coronary artery disease, cardiac SPECT/MPI-CTCA fusion imaging was found to considerably alter the clinical decision for referral to further investigation derived from SPECT/MPI.

Accuracy of multislice CT angiography for the assessment of in-stent restenoses in the iliac arteries at reduced dose: a phantom study.

OBJECTIVE: We investigated the potential of low-dose CT angiography for accurate assessment of in-stent restenoses (ISRs) of the iliac artery. METHOD: A Rando anthropomorphic phantom (Alderson Research Labs, Stanford, CA), custom-made wax simulating hyperplastic tissue and a nitinol stent were used to simulate a patient with clinically relevant iliac artery ISRs. The cylindrical lumen was filled with a solution of iodine contrast medium diluted in saline, representing a patient's blood during CT angiography. The phantom was subjected to standard- and low-dose angiographic exposures using a modern multidetector (MD) CT scanner. The percentage of ISR was determined using the profile along a line normal to the lumen axis on reconstructed images of 2 and 5 mm slice thickness. Percentage ISRs derived using the standard- and low-dose protocols were compared. In a preliminary study, seven patients with stents were subjected to standard- and low-dose MDCT angiography during follow-up. The resulting images were assessed and compared by two experienced radiologists. RESULTS: The accuracy in measuring the percentage ISR was found to be better than 12% for all simulated stenoses. The differences between percentage ISRs measured on images obtained at 120 kVp/160 mAs and 80 kVp/80 mAs were below 6%. Patient image sets acquired using low-exposure factors were judged to be of satisfactory diagnostic quality. The assessment of ISR did not differ significantly between image sets acquired using the standard factors and those acquired using the low-exposure factors, although the mean reduction in patient effective dose was 48%. CONCLUSION: A reduction in exposure factors during MDCT angiography of the iliac artery is possible without affecting the accuracy in the determination of ISRs.

Occupational exposure in the electrophysiology laboratory: quantifying and minimizing radiation burden.

Fluoroscopically guided procedures in the electrophysiology room, such as radiofrequency catheter ablation and implantation of cardiac resynchronization devices, may result in high radiation exposure of electrophysiologists and assisting staff. Our aim was to provide accurate and applicable data on occupational doses to the electrophysiology laboratory personnel. We exposed fluoroscopically an anthropomorphic phantom at three projections common in electrophysiology studies. For each exposure, scattered radiation was measured at 182 sites of the cardiology room at four body levels. Effective dose values, eye lens, skin and gonadal doses to the laboratory staff were calculated. Our study has shown that a procedure requiring 40 min of fluoroscopy yields a maximum effective dose of 129 microSv and a maximum value of gonadal dose of 56.8 microSv to staff using a 0.35 mm lead-equivalent apron. A conservative estimate of the electrophysiologist's annual maximum permissible workload is 155 procedures. Staff effective dose values vary by a factor of 40 due to positioning during fluoroscopy and by a factor of 11 due to radiation protection equipment. Undercouch protective shields may reduce gonadal doses up to 98% and effective dose up to 25%. Consequently, radiation levels in the electrophysiology room are not negligible. Mitigation of occupational exposure is feasible through good fluoroscopy and working practices.

Imaging ultrasonometry of the calcaneus: dependence on calcaneal area.

The purpose of this study was (1) to investigate the dependence of broadband ultrasound attenuation (BUA) and speed of sound (SOS) measured in a circular region of interest (ROI) having a fixed size on calcaneal area and (2) to examine whether the normalization of ultrasonic variables for the area of the calcaneus provides better differentiation of diseased subjects from healthy individuals. Ultrasound variables were estimated in 169 healthy postmenopausal women (mean age 66.5 years, range 42-87 years) and 39 women with vertebral fractures (mean age 72.9 years, range 51-86 years). A minimum attenuation ROI, 15 mm in diameter, with a commercial imaging ultrasonometer was used. Significant relationships were found between both ultrasonic variables and calcaneal area (r2 = 0.06, P < 0.001 for BUA, r2 = 0.12, P < 0.0001 for SOS). Normalization of ultrasound variables (BUAn and SOSn) was based on the regression equations of the relationships among BUA, SOS, and calcaneal area. In a precision study, nine women were examined five times each to determine the errors arising from both the repositioning of the foot and selection of the calcaneal area. The reproducibility errors of BUA, SOS, BUAn, SOSn, and area were 0.87%, 0.20%, 1.07%, 0.27%, and 3.72%, respectively. Significant differences were found between the areas under the ROC curve for BUAn and BUA (area under the curve = 0.93 for BUAn versus 0.90 for BUA, P = 0.003) as well as for SOSn and SOS (area under the curve = 0.85 for SOSn versus 0.79 for SOS, P = 0.003). Normalization of ultrasound variables for calcaneal area improves the discrimination of clinical studies.