Low-dose pulmonary CT angiography: reduced radiation exposure and iodine load at low tube kilovoltage

CT pulmonary angiography is the currently accepted standard in ruling out acute pulmonary embolism. Issues of radiation dose received by patients via CT have been extensively disputed by radiologists and reported by the media. In recent years there has been considerable research performed to find ways for reducing radiation exposure from CT. Herein, we will discuss specific measures that have been shown to be valuable for CT pulmonary angiography. The limitations and the potential benefits of reduced CT peak tube kilovoltage will be detailed as this method is capable of reducing both radiation exposure and iodine load to the patient simultaneously. We discuss some of the emerging tools, which will hopefully play a significant role in wider acceptance of low-dose CT pulmonary angiography protocols.

Patient exposure and image quality of low-dose pulmonary computed tomography angiography: comparison of 100- and 80-kVp protocols

OBJECTIVE: Measures to reduce radiation exposure and injected iodine mass are becoming more important with the widespread and often repetitive use of pulmonary CT angiography (CTA) in patients with suspected pulmonary embolism. In this retrospective study, we analyzed the capability of 2 low-kilovoltage CTA-protocols to achieve these goals. MATERIALS AND METHODS: Ninety patients weighing less than 100 kg were examined by a pulmonary CTA protocol using either 100 kVp (group A) or 80 kVp (group B). Volume and flow rate of contrast medium were reduced in group B (75 mL at 3 mL/s) compared with group A (100 mL at 4 mL/s). Attenuation was measured in the central and peripheral pulmonary arteries, and the contrast-to-noise ratios (CNR) were calculated. Entrance skin dose was estimated by measuring the surface dose in an ovoid-cylindrical polymethyl methacrylate chest phantom with 2 various dimensions corresponding to the range of chest diameters in our patients. Quantitative image parameters, estimated effective dose, and skin dose in both groups were compared by the t test. Arterial enhancement, noise, and overall quality were independently assessed by 3 radiologists, and results were compared between the groups using nonparametric tests. RESULTS: Mean attenuation in the pulmonary arteries in group B (427.6 +/- 116 HU) was significantly higher than in group A (342.1 +/- 87.7 HU; P < 0.001), whereas CNR showed no difference (group A, 20.6 +/- 7.3 and group B, 22.2 +/- 7.1; P = 0.302). Effective dose was lower by more than 40% with 80 kVp (1.68 +/- 0.23 mSv) compared with 100 kVp (2.87 +/- 0.88 mSv) (P < 0.001). Surface dose was significantly lower at 80 kVp compared with 100 kVp at both phantom dimensions (2.75 vs. 3.22 mGy; P = 0.027 and 2.22 vs. 2.73 mGy; P = 0.005, respectively). Image quality did not differ significantly between the groups (P = 0.151). CONCLUSIONS: Using 80 kVp in pulmonary CTA permits reduced patient exposure by 40% and CM volume by 25% compared with 100 kVp without deterioration of image quality in patients weighing less than 100 kg.

Detection of urinary stones at reduced radiation exposure: a phantom study comparing computed radiography and a low-dose digital radiography linear slit scanning system

OBJECTIVE: In this experimental study we assessed the diagnostic performance of digital linear slit scanning radiography compared with computed radiography (CR) for the detection of urinary calculi in an anthropomorphic phantom imitating patients weighing approximately 58-88 kg. CONCLUSION: Compared with CR, linear slit scanning radiography is superior for the detection of urinary stones and may be used for pretreatment localization and follow-up at a lower patient exposure.

Peri-operative adrenocortical response to low-dose (1 microg) ACTH and relation to postoperative complications in patients undergoing elective abdominal surgery

BACKGROUND: To test the hypothesis that reduced responsiveness to adrenocorticotropin (ACTH) stimulation before elective major abdominal surgery is associated with an increased incidence of postoperative complications. METHODS: A low-dose (1 microg) ACTH test was performed the day before surgery, during the operation, on the first postoperative day, and before discharge from the hospital in 77 patients undergoing major abdominal surgery (age 62 [47;69] yrs [median, quartiles]; 30 female). Thirty-one patients undergoing minor, non-abdominal surgery (mostly inguinal hernia repair) (age 57 [40;66] yrs; 14 female) served as controls with minor surgical stress. A stimulated plasma cortisol concentration >or=500 nmol/l or an increment of >or=200 nmol/l in response to 1 microg ACTH was defined as normal. Scores for surgical stress and comprehensive risk, postoperative complications, and length of hospital stay (LOS) were assessed. RESULTS: On the day before major abdominal surgery, basal and stimulated plasma cortisol were 242 (165;299) nmol/l and 497 (404;568) nmol/l, respectively. Eighteen (23%) patients had an abnormal ACTH test, and 7 of these (39%) had complications versus 25 (42%) of the 59 patients with normal ACTH tests (P = .992). Surgical stress, comprehensive risk, and intra- and postoperative basal cortisol levels were higher and the response to ACTH stimulation smaller in patients with major abdominal compared to minor surgery. The peri-operative course of ACTH responses was not associated with complications or LOS in abdominal surgery patients. CONCLUSION: In patients scheduled for abdominal surgery, pre-operatively reduced adrenal response to stimulation with 1 microg ACTH is common but not associated with postoperative complications.

Impact of a 4th generation iterative reconstruction technique on image quality in low-dose computed tomography of the chest in immunocompromised patients

PURPOSE To determine the image quality of an iterative reconstruction (IR) technique in low-dose MDCT (LDCT) of the chest of immunocompromised patients in an intraindividual comparison to filtered back projection (FBP) and to evaluate the dose reduction capability. MATERIALS AND METHODS 30 chest LDCT scans were performed in immunocompromised patients (Brilliance iCT; 20-40 mAs; mean CTDIvol: 1.7 mGy). The raw data were reconstructed using FBP and the IR technique (iDose4™, Philips, Best, The Netherlands) set to seven iteration levels. 30 routine-dose MDCT (RDCT) reconstructed with FBP served as controls (mean exposure: 116 mAs; mean CDTIvol: 7.6 mGy). Three blinded radiologists scored subjective image quality and lesion conspicuity. Quantitative parameters including CT attenuation and objective image noise (OIN) were determined. RESULTS In LDCT high iDose4™ levels lead to a significant decrease in OIN (FBP vs. iDose7: subscapular muscle 139.4 vs. 40.6 HU). The high iDose4™ levels provided significant improvements in image quality and artifact and noise reduction compared to LDCT FBP images. The conspicuity of subtle lesions was limited in LDCT FBP images. It significantly improved with high iDose4™ levels (> iDose4). LDCT with iDose4™ level 6 was determined to be of equivalent image quality as RDCT with FBP. CONCLUSION iDose4™ substantially improves image quality and lesion conspicuity and reduces noise in low-dose chest CT. Compared to RDCT, high iDose4™ levels provide equivalent image quality in LDCT, hence suggesting a potential dose reduction of almost 80%.

Ultra-low-dose dual-source CT coronary angiography with high pitch: diagnostic yield of a volumetric planning scan and effects on dose reduction and imaging strategy

OBJECTIVE To evaluate the role of an ultra-low-dose dual-source CT coronary angiography (CTCA) scan with high pitch for delimiting the range of the subsequent standard CTCA scan. METHODS 30 patients with an indication for CTCA were prospectively examined using a two-scan dual-source CTCA protocol (2.0 × 64.0 × 0.6 mm; pitch, 3.4; rotation time of 280 ms; 100 kV): Scan 1 was acquired with one-fifth of the tube current suggested by the automatic exposure control software [CareDose 4D™ (Siemens Healthcare, Erlangen, Germany) using 100 kV and 370 mAs as a reference] with the scan length from the tracheal bifurcation to the diaphragmatic border. Scan 2 was acquired with standard tube current extending with reduced scan length based on Scan 1. Nine central coronary artery segments were analysed qualitatively on both scans. RESULTS Scan 2 (105.1 ± 10.1 mm) was significantly shorter than Scan 1 (127.0 ± 8.7 mm). Image quality scores were significantly better for Scan 2. However, in 5 of 6 (83%) patients with stenotic coronary artery disease, a stenosis was already detected in Scan 1 and in 13 of 24 (54%) patients with non-stenotic coronary arteries, a stenosis was already excluded by Scan 1. Using Scan 2 as reference, the positive- and negative-predictive value of Scan 1 was 83% (5 of 6 patients) and 100% (13 of 13 patients), respectively. CONCLUSION An ultra-low-dose CTCA planning scan enables a reliable scan length reduction of the following standard CTCA scan and allows for correct diagnosis in a substantial proportion of patients. ADVANCES IN KNOWLEDGE Further dose reductions are possible owing to a change in the individual patient's imaging strategy as a prior ultra-low-dose CTCA scan may already rule out the presence of a stenosis or may lead to a direct transferal to an invasive catheter procedure.

Detection of chest trauma with whole-body low-dose linear slit digital radiography: a multireader study

The objective of our study was to compare the performance of low-dose linear slit digital radiography (DR) with computed radiography (CR) for the detection of trauma sequelae in the chest including rib fractures, pneumothorax, and lung contusion.

Impact of daclizumab, low-dose cyclosporine, mycophenolate mofetil and steroids on renal function after kidney transplantation

Early and long-term use of cyclosporine A (CsA) leads to increased risks of renal toxicity. We hypothesized that administration of daclizumab in combination with mycophenolate mofetil (MMF) allows a relevant reduction in the dose of CsA.

Nonlinear three-dimensional noise filter with low-dose CT angiography: effect on the detection of small high-contrast objects in a phantom model

To study the effect of a nonlinear noise filter on the detection of simulated endoleaks in a phantom with 80- and 100-kVp multidetector computed tomographic (CT) angiography.

State of the art low-dose CT angiography of the body

This review summarizes current evidence based on pertinent literature on low-dose computed tomography angiography (CTA) of the body. Various strategies for optimizing CTA protocols with the aim to lower the radiation dose while maintaining the diagnostic accuracy of the examination are summarized. To date, various publications have demonstrated that CTA of the body can be performed at a low radiation dose while providing high quality information. Nevertheless, a number of questions still need to be answered, including the optimal combination of tube voltage and tube current settings, as well as the appropriate protocol parameters in relation to the body physiognomy and the specific body region imaged.

Low-dose recombinant factor VIIa for massive bleeding: A single centre observational cohort study with 73 patients

recombinant activated factor VII (rFVIIa) is used off-label for massive bleeding. There is no convincing evidence of the benefits of this practice and the minimal effective dose is unknown. The aim of the study was to evaluate our in-house guideline recommending a low dose of 60 μg/kg for off-label use of rFVIIa.

Low-Dose Temporal Bone CT in Infants and Young Children: Effective Dose and Image Quality

The temporal bone is ideal for low-dose CT because of its intrinsic high contrast. The aim of this study was to retrospectively evaluate image quality and radiation doses of a new low-dose versus a standard high-dose pediatric temporal bone CT protocol and to review dosimetric data from the literature.

High Dose-Rate Versus Low Dose-Rate Brachytherapy for Lip Cancer

To analyze the outcome after low-dose-rate (LDR) or high-dose-rate (HDR) brachytherapy for lip cancer.