Accuracy of low-dose computed tomography (CT) for detecting and characterizing the most common CT-patterns of pulmonary disease

Purpose

To assess the ability of low-dose CT to detect and characterize the most common CT patterns of pulmonary disease.

Methods and materials

Sixty patients with nodules, consolidations or interstitial disease were scanned using a low-dose (128 mm × 0.6 mm, 40 reference mAs, 120 kVp) and standard-dose CT protocol (150 reference mAs, 120 kVp). Two radiologists with 3 and 10 years of thoracic imaging experience searched both exams in consensus for the most commonly observed CT patterns according to the Fleischner Society criteria, which consisted of 46 different subgroups of ground-glass opacities, nodules, interstitial and airspace diseases. The standard of reference was established by consensus of a panel of two experienced chest radiologists (9 and 12 years of experience).

Results

The lung segments (1080) showed 813 nodules, 596 ground-glass opacities, 74 airspace and 575 interstitial diseases and 64 normal segments. In particular, air-space disease and nodules were unaffected by the increase in noise. However, the sensitivity to detect ground-glass opacities, ground-glass nodules and interstitial opacities decreased significantly, from 89% to 77%, 86% to 68% and 91% to 71%, respectively (all p-values < 0.00001). Using iterative reconstruction instead of the applied filtered back projection sensitivity for ground-glass nodules rose to the sensitivity of standard-dose CT in an additional phantom study.

Conclusion

A low-dose CT of 40 mAs/120 kVp is feasible for detecting solid nodules, airspace, airways and pleural disease. For diagnosing pathologies consisting of ground-glass opacities or interstitial opacities, higher tube current or iterative reconstruction is required.     

Using low tube voltage (80kVp) quadruple phase liver CT for the detection of hepatocellular carcinoma: two-year experience and comparison with Gd-EOB-DTPA enhanced liver MRI

Purpose

To validate the diagnostic performance of quadruple phase low tube voltage liver CT through the comparison with Gd-EOB-DTPA enhanced liver MRI for the detection of HCC.

Materials and methods

Non-obese patients (38 men, eight women) with 68 HCCs underwent quadruple-phase CT at 16 MDCT (using low tube voltage, 80 kVp; moderately high tube current, 280 mAs) and Gd-EOB-DTPA-enhanced 3 T MRI. Three observers independently and randomly reviewed the CT and MR images on a tumor-by-tumor basis. The diagnostic accuracy of these techniques for detecting HCC was assessed using alternative free-response receiver operating characteristic analysis. Sensitivity and positive predictive values were evaluated. The mean effective doses for the low dose CT were also evaluated.

Results

The areas under the ROC curves were 0.963, 0.959, and 0.941 for low dose CT and 0.981, 0.982, and 0.976 for MRI. Differences in Az of the two techniques for each observer were not statistically significant (P > .05). Differences in sensitivity and positive predictive values between the two techniques for each observer were not also statistically significant: sensitivity (86.8%, 82.4%, 85.3% for CT and 95.6%, 94.1%, 91.2% for MRI) and positive predictive values (92.2%, 90.3%, 89.2% for CT and 92.9%, 92.8%, 92.5% for MRI). Six HCCs (8.8%) in five patients were observed only on hepatobiliary phase of MRI, and all were smaller than 1.5 cm. The mean effective dose for CT was approximately 10.2 mSv.

Conclusions

Quadruple-phase low-dose liver CT (80 kVp, 280 mAs) had relatively good diagnostic performance for detecting HCC in non-obese patients. Because no significant difference was observed between low-dose CT and MRI, the use of low-dose liver CT can be justified based on its reduced radiation effects.     

Reducing the radiation dose for low-dose CT of the paranasal sinuses using iterative reconstruction: feasibility and image quality

Purpose

To evaluate image quality of dose-reduced CT of the paranasal-sinus using an iterative reconstruction technique.

Methods

In this study 80 patients (mean age: 46.9 ± 18 years) underwent CT of the paranasalsinus (Siemens Definition, Forchheim, Germany), with either standard settings (A: 120 kV, 60 mAs) reconstructed with conventional filtered back projection (FBP) or with tube current–time product lowering of 20%, 40% and 60% (B: 48 mAs, C: 36 mAs and D: 24 mAs) using iterative reconstruction (n = 20 each). Subjective image quality was independently assessed by four blinded observers using a semiquantitative five-point grading scale (1 = poor, 5 = excellent). Effective dose was calculated from the dose-length product. Mann–Whitney-U-test was used for statistical analysis.

Results

Mean effective dose was 0.28 ± 0.03 mSv(A), 0.23 ± 0.02 mSv(B), 0.17 ± 0.02 mSv(C) and 0.11 ± 0.01 mSv(D) resulting in a maximum dose reduction of 60% with iterative reconstruction technique as compared to the standard low-dose CT. Best image quality was observed at 48 mAs (mean 4.8; p < 0.05), whereas standard low-dose CT (A) and maximum dose reduced scans (D) showed no significant difference in subjective image quality (mean 4.37 (A) and 4.31 (B); p = 0.72). Interobserver agreement was excellent (κ values 0.79–0.93).

Conclusion

As compared to filtered back projection, the iterative reconstruction technique allows for significant dose reduction of up to 60% for paranasal-sinus CT without impairing the diagnostic image quality.     

Comparison of adaptive statistical iterative and filtered back projection reconstruction techniques in brain CT

Purpose

To compare image quality and visualization of normal structures and lesions in brain computed tomography (CT) with adaptive statistical iterative reconstruction (ASIR) and filtered back projection (FBP) reconstruction techniques in different X-ray tube current–time products.

Materials and methods

In this IRB-approved prospective study, forty patients (nineteen men, twenty-one women; mean age 69.5 ± 11.2 years) received brain scan at different tube current–time products (300 and 200 mAs) in 64-section multi-detector CT (GE, Discovery CT750 HD). Images were reconstructed with FBP and four levels of ASIR-FBP blending. Two radiologists (please note that our hospital is renowned for its geriatric medicine department, and these two radiologists are more experienced in chronic cerebral vascular disease than in neoplastic disease, so this research did not contain cerebral tumors but as a discussion) assessed all the reconstructed images for visibility of normal structures, lesion conspicuity, image contrast and diagnostic confidence in a blinded and randomized manner. Volume CT dose index (CTDI_vol) and dose-length product (DLP) were recorded. All the data were analyzed by using SPSS 13.0 statistical analysis software.

Results

There was no statistically significant difference between the image qualities at 200 mAs with 50% ASIR blending technique and 300 mAs with FBP technique (p > .05). While between the image qualities at 200 mAs with FBP and 300 mAs with FBP technique a statistically significant difference (p < .05) was found.

Conclusion

ASIR provided same image quality and diagnostic ability in brain imaging with greater than 30% dose reduction compared with FBP reconstruction technique.     

Lung cancer screening with CT: Evaluation of radiologists and different computer assisted detection software (CAD) as first and second readers for lung nodule detection at different dose levels

Objectives

To find the best pairing of first and second reader at highest sensitivity for detecting lung nodules with CT at various dose levels.

Materials and methods

An anthropomorphic lung phantom and artificial lung nodules were used to simulate screening CT-examination at standard dose (100 mAs, 120 kVp) and 8 different low dose levels, using 120, 100 and 80 kVp combined with 100, 50 and 25 mAs. At each dose level 40 phantoms were randomly filled with 75 solid and 25 ground glass nodules (5–12 mm). Two radiologists and 3 different computer aided detection softwares (CAD) were paired to find the highest sensitivity.

Results

Sensitivities at standard dose were 92%, 90%, 84%, 79% and 73% for reader 1, 2, CAD1, CAD2, CAD3, respectively. Combined sensitivity for human readers 1 and 2 improved to 97%, (p1 = 0.063, p2 = 0.016). Highest sensitivities – between 97% and 99.0% – were achieved by combining any radiologist with any CAD at any dose level. Combining any two CADs, sensitivities between 85% and 88% were significantly lower than for radiologists combined with CAD (p < 0.03).

Conclusions

Combination of a human observer with any of the tested CAD systems provide optimal sensitivity for lung nodule detection even at reduced dose at 25 mAs/80 kVp.     

Reduced-dose chest CT with 3D automatic exposure control vs. standard chest CT: quantitative assessment of emphysematous changes in smokers' lung parenchyma

Objectives

To determine the capability of reduced-dose chest CT with three-dimensional (3D) automatic exposure control (AEC) on quantitative assessment of emphysematous change in smoker’ lung parenchyma, compared to standard chest CT.

Methods

Twenty consecutive smoker patients (mean age 62.8 years) underwent CT examinations using a standard protocol (150 mAs) and a protocol with 3D-AEC. In this study, the targeted standard deviations number was set to 160. For quantitative assessment of emphysematous change in lung parenchyma in each subject using the standard protocol, a percentage of voxels less than −950 HU in the lung (%LAA₋₉₅₀) was calculated. The 3D-AEC protocol's %LAA was computed from of voxel percentages under selected threshold CT value. The differences of radiation doses between these two protocols were evaluated, and %LAAs₋₉₅₀ was compared with the 3D-AEC protocol %LAAs.

Results

Mean dose length products were 780.2 ± 145.5 mGy cm (standard protocol), and 192.0 ± 95.9 (3D-AEC protocol). There was significant difference between them (paired Student's t test, p < 0.00001). Meanwhile, only setting −960 HU yielded no significant difference (paired Student's t test, p = 0.32) between %LAAs₋₉₅₀ and 3D-AEC protocol %LAAs. In adopting the feasible threshold CT values of the 3D-AEC protocol, the 3D-AEC protocol %LAAs were significantly correlated with %LAAs₋₉₅₀ (r = 0.98, p < 0.001) and limits of agreement from Bland–Altman analysis was 0.52 ± 4.3%.

Conclusions

Changing threshold CT values demonstrated that reduced-dose chest CT with 3D-AEC can substitute for the standard protocol in assessments of emphysematous change in smoker’ lung parenchyma.     

Time-resolved CT angiography in aortic dissection

Objectives

We performed this study to assess feasibility and additional diagnostic value of time-resolved CT angiography of the entire aorta in patients with aortic dissection.

Materials and methods

14 consecutive patients with known or suspected aortic dissection (aged 60 ± 9 years) referred for aortic CT angiography were scanned on a dual-source CT scanner (Somatom Definition Flash; Siemens, Forchheim, Germany) using a shuttle mode for multiphasic image acquisition (range 48 cm, time resolution 6 s, 6 phases, 100 kV, 110 mAs/rot). Effective radiation doses were calculated from recorded dose length products. For all phases, CT densities were measured in the aortic lumen and renal parenchyma. From the multiphasic data, 3 phases corresponding to a triphasic standard CT protocol, served as a reference and were compared against findings from the time-resolved datasets.

Results

Mean effective radiation dose was 27.7 ± 3.5 mSv. CT density of the true lumen peaked at 355 ± 53 HU. Compared to the simulated triphasic protocol, time-resolved CT angiography added diagnostic information regarding a number of important findings: the enhancement delay between true and false lumen (n = 14); the degree of membrane oscillation (n = 14); the perfusion delay in arteries originating from the false lumen (n = 9). Other additional information included true lumen collapse (n = 4), quantitative assessment of renal perfusion asymmetry (n = 2), and dynamic occlusion of aortic branches (n = 2). In 3/14 patients (21%), these additional findings of the multiphasic protocol altered patient management.

Conclusions

Multiphasic, time-resolved CT angiography covering the entire aorta is feasible at a reasonable effective radiation dose and adds significant diagnostic information with therapeutic consequences in patients with aortic dissection.     

Patterns of pulmonary tuberculosis on FDG-PET/CT

Objective

This study aims to describe patterns of pulmonary tuberculosis (TB) on FDG-PET/CT.

Methods

All patients with a diagnosis of TB and who underwent FDG-PET/CT between January 2009 and June 2010 were included. Clinical, biological and imaging data were reviewed. TB was proven either on bacteriological or histopathological studies (n = 13) or on a clinical and imaging basis (n = 3).

Results

Sixteen patients (11 men; median age 56, range 22–84 years) were included. Two distinct patterns were identified. In the lung pattern (9/16), patients had predominantly pulmonary symptoms (6/9 patients, 67%) with a parenchymal involvement: uptakes on lung consolidation ± cavitation surrounded by micronodules. Mediastino-hilar lymph nodes were slightly enlarged (15 mm, 10–27) with moderate uptake (3.9, 2.5–13.4). In the lymphatic pattern (7/16), patients had predominantly systemic symptoms (5/7 cases, 71%) and all had extra-thoracic involvement. Mediastino-hilar lymph nodes were more enlarged (30 mm, 18–35, p = 0.03) and with higher uptake (6.8, 5.7–16.8, p = 0.034) than in the lung pattern.

Conclusion

We identified two distinct patterns of pulmonary TB on FDG-PET/CT. The lung pattern related to a restricted and slight hypermetabolic infection and the lymphatic pattern related to a systemic and intense infection. Combined interpretation of PET and CT findings improves the specificity of images, especially for the lung pattern.     

Pulmonary nodules: effect of adaptive statistical iterative reconstruction (ASIR) technique on performance of a computer-aided detection (CAD) system-comparison of performance between different-dose CT scans

Purpose

To evaluate the effects of ASIR on CAD system of pulmonary nodules using clinical routine-dose CT and lower-dose CT.

Materials and methods

Thirty-five patients (body mass index, 22.17 ± 4.37 kg/m²) were scanned by multidetector-row CT with tube currents (clinical routine-dose CT, automatically adjusted mA; lower-dose CT, 10 mA) and X-ray voltage (120 kVp). Each 0.625-mm-thick image was reconstructed at 0%-, 50%-, and 100%-ASIR: 0%-ASIR is reconstructed using only the filtered back-projection algorithm (FBP), while 100%-ASIR is reconstructed using the maximum ASIR and 50%-ASIR implies a blending of 50% FBP and ASIR. CAD output was compared retrospectively with the results of the reference standard which was established using a consensus panel of three radiologists. Data were analyzed using Bonferroni/Dunn's method. Radiation dose was calculated by multiplying dose-length product by conversion coefficient of 0.021.

Results

The consensus panel found 265 non-calcified nodules ≤30 mm (ground-glass opacity [GGO], 103; part-solid, 34; and solid, 128). CAD sensitivity was significantly higher at 100%-ASIR [clinical routine-dose CT, 71% (overall), 49% (GGO); lower-dose CT, 52% (overall), 67% (solid)] than at 0%-ASIR [clinical routine-dose CT, 54% (overall), 25% (GGO); lower-dose CT, 36% (overall), 50% (solid)] (p < 0.001). Mean number of false-positive findings per examination was significantly higher at 100%-ASIR (clinical routine-dose CT, 8.5; lower-dose CT, 6.2) than at 0%-ASIR (clinical routine-dose CT, 4.6; lower-dose CT, 3.5; p < 0.001). Effective doses were 10.77 ± 3.41 mSv in clinical routine-dose CT and 2.67 ± 0.17 mSv in lower-dose CT.

Conclusion

CAD sensitivity at 100%-ASIR on lower-dose CT is almost equal to that at 0%-ASIR on clinical routine-dose CT. ASIR can increase CAD sensitivity despite increased false-positive findings.     

Cost reduction in abdominal CT by weight-adjusted dose

Aim

To analyze the influence of contrast dose adjusted by weight vs. fixed contrast dose in the attenuation and cost of abdominal computed tomography (CT).

Materials and methods

A randomised, consecutive, parallel group study was conducted in 151 patients (74 men and 77 women, age range 22–67 years), studied with the same CT helical protocol. A dose at 1.75 ml/kg was administered in 101 patients while 50 patients had a fixed dose of 120 ml of same non-ionic contrast material (320 mg/ml). Mean enhancements were measured at right hepatic lobe, superior abdominal aorta and inferior cava vein. Statistical analysis was weight-stratified (<60, 61–70, 71–80 and >81 kg).

Results

Aortic attenuation was significantly superior (p < 0.05) in the dose adjusted by weight group than in the fixed dose group. Patients who weighed >61 kg in dose-adjusted group, presented higher hepatic attenuation, being statistically significant in those >81 kg (p < 0.01). In dose-adjusted group, there was a savings of €4.1 per patient in patients weighing <80 kg. In patients weighing >80 kg, there was an over cost of €10.7 per patient.

Conclusions

An injection volume of 1.75 ml/kg offers an optimal diagnostic quality with a global savings of €1.34 per patient.     

Reducing radiation in CT urography for hematuria: Effect of using 100 kilovoltage protocol

Objective

To compare 128-slice multidetector computed tomography (MDCT) at 100 kVp and 120 kVp for image quality and radiation dose.

Materials and methods

Our study had approval of our institutional review board. We retrospectively selected 25 patients who underwent CT urography for the evaluation of hematuria. The CT scans were taken with 128-slice MDCT, with three phases (precontrast, nephrographic, and excretory), using an automatic tube current modulation with reference tube level of 180 mA s and tube voltages of either 100 kVp (n = 14, mean age 26.71) or 120 kVp (n = 11, mean age 25.54). The signal-to-noise-ratio (SNR) and contrast-to-noise-ratio (CNR) of the urinary tract, the subjective image quality of the urinary tract evaluated with a five point scale by two radiologists and the effective dose calculated on the basis of dose-length-product (DLP) and volume-CT-dose-index (CTDIvol) were compared between the groups with Student's t test or Mann–Whitney U test.

Results

There was no significant difference in the SNR (p = 0.358), CNR (p = 0.303) and the subjective image quality (p = 0.486) between the two protocols. The mean CTDIvol, DLP and the effective dose in the 100 kVp protocol were significantly lower than the 120 kVp protocol (p = 0.000, 0.000).

Conclusion

CT urography using 100 kVp protocol resulted in reduction of radiation dose without loss of objective or subjective image quality.     

Routine chest and abdominal high-pitch CT: an alternative low dose protocol with preserved image quality

Objective

To investigate the radiation dose and image quality of the high-pitch dual source computer tomography (DSCT) for routine chest and abdominal scans.

Methods

130 consecutive patients (62 female, 68 male, median age 55 years) were included. All patients underwent 128-slice high-pitch DSCT (chest n = 99; abdomen n = 84) at a pitch of 3.2. Two observers independently rated image quality using a 4-point score (1: excellent to 4: non-diagnostic). Image noise was measured and operational radiation dose quantities were recorded. An additional group of 132 patients (chest, n = 80; abdomen n = 52) scanned with standard-pitch CT matched for age, gender, and body mass index (BMI) served as control group.

Results

Interobserver agreement for image quality rating was good (k = 0.74). Subjective image quality of high-pitch CT was diagnostic in all patients (median score chest; 2, median score abdomen: 2). Image noise of high-pitch CT was comparable to standard-pitch for the chest (p = 0.32) but increased in the abdomen (p < 0.0001). For high-pitch CT radiation dose was 4.4 ± 0.9 mSv (chest) and 6.5 ± 1.2 mSv (abdomen). These values were significantly lower compared to standard-pitch CT (chest: 5.5 ± 1.2 mSv; abdomen: 11.3 ± 3.8 mSv).

Conclusion

Based on the technical background high-pitch dual source CT may serve as an alternative scan mode for low radiation dose routine chest and abdominal CT.     

Growth rate of lung cancer recognized as small solid nodule on initial CT findings

Introduction

To study the characteristics of lung cancer, appearing as small solid nodules on initial computed tomography (CT) findings, and to determine an appropriate follow-up duration so as to differentiate between malignancy and benign tumor.

Methods

We analyzed the records of 34 patients who had undergone surgical resection of lung cancer, which appeared as small solid nodules on initial CT findings. We studied the CT findings, volume doubling times (VDT), follow-up durations, pathological and clinical findings.

Results

VDT is classified as follows: (1) slow growth group (SGG), with a VDT of more than 700 days and (2) rapid growth group (RGG), with a VDT of less than 700 days. The median VDT of the SGG was 1083 days, and the RGG was 256 days (p < 0.01). The median duration for follow-up of the SGG was 1218 days, and 179 days for the RGG. A statistical difference was noted in the follow-up durations (p < 0.01). There were no statistical differences in the preoperative thin-section CT (TSCT) findings, or in the pathological findings. The RGG included more patients with smoking histories. The CT findings of RGG tended to reveal changed in base lung field such as emphysema, and lung fibrosis.

Conclusions

Generally, lung cancer appearing as small solid nodules on initial CT findings grew rapidly, but there were some cases which displayed slow growth patterns. These cases required follow up for over two years, before diagnosis was possible. We concluded the appropriate maximum followup duration is three years.     

Intermodality comparison between 3D perfusion CT and 18F-FDG PET/CT imaging for predicting early tumor response in patients with liver metastasis after chemotherapy: Preliminary results of a prospective study

Objectives

To evaluate the feasibility of 3D perfusion CT for predicting early treatment response in patients with liver metastasis from colorectal cancer.

Methods

Seventeen patients with colon cancer and liver metastasis were prospectively enroled to undergo perfusion CT and 18F-FDG-PET/CT before and after one-cycle of chemotherapy. Two radiologists and three nuclear medicine physicians measured various perfusion CT and PET/CT parameters, respectively from the largest hepatic metastasis. Baseline values and reduction rates of the parameters were compared between responders and nonresponders. Spearman correlation test was used to correlate perfusion CT and PET/CT parameters, using RECIST criteria as reference standard.

Results

Nine patients responded to treatment, eight patients were nonresponders. Baseline SUV_mean30 on PET/CT, reduction rates of 30% metabolic volume and 30% lesion glycolysis (LG₃₀) on PET/CT and blood flow (BF) and flow extraction product (FEP) on perfusion CT after chemotherapy were significantly different between responders and nonresponders (P = 0.008–0.046). Reduction rates of BF (correlation coefficient = 0.630) and FEP (correlation coefficient = 0.578) significantly correlated with that of LG₃₀ on PET/CT (P < 0.05).

Conclusion

CT perfusion parameters including BF and FEP may be used as early predictors of tumor response in patients with liver metastasis from colorectal cancer.     

Iterative reconstruction reduces abdominal CT dose

Objective

In medical imaging, lowering radiation dose from computed tomography scanning, without reducing diagnostic performance is a desired achievement. Iterative image reconstruction may be one tool to achieve dose reduction. This study reports the diagnostic performance using a blending of 50% statistical iterative reconstruction (ASIR) and filtered back projection reconstruction (FBP) compared to standard FBP image reconstruction at different dose levels for liver phantom examinations.

Methods

An anthropomorphic liver phantom was scanned at 250, 185, 155, 140, 120 and 100 mA s, on a 64-slice GE Lightspeed VCT scanner. All scans were reconstructed with ASIR and FBP. Four readers evaluated independently on a 5-point scale 21 images, each containing 32 test sectors. In total 672 areas were assessed. ROC analysis was used to evaluate the differences.

Results

There was a difference in AUC between the 250 mA s FBP images and the 120 and 100 mA s FBP images. ASIR reconstruction gave a significantly higher diagnostic performance compared to standard reconstruction at 100 mA s.

Conclusion

A blending of 50–90% ASIR and FBP may improve image quality of low dose CT examinations of the liver, and thus give a potential for reducing radiation dose.     

Treatment response assessment of radiofrequency ablation for hepatocellular carcinoma: usefulness of virtual CT sonography with magnetic navigation

Purpose

Virtual CT sonography using magnetic navigation provides cross sectional images of CT volume data corresponding to the angle of the transducer in the magnetic field in real-time. The purpose of this study was to clarify the value of this virtual CT sonography for treatment response of radiofrequency ablation for hepatocellular carcinoma.

Patients and methods

Sixty-one patients with 88 HCCs measuring 0.5–1.3 cm (mean ± SD, 1.0 ± 0.3 cm) were treated by radiofrequency ablation. For early treatment response, dynamic CT was performed 1–5 days (median, 2 days). We compared early treatment response between axial CT images and multi-angle CT images using virtual CT sonography.

Results

Residual tumor stains on axial CT images and multi-angle CT images were detected in 11.4% (10/88) and 13.6% (12/88) after the first session of RFA, respectively (P = 0.65). Two patients were diagnosed as showing hyperemia enhancement after the initial radiofrequency ablation on axial CT images and showed local tumor progression shortly because of unnoticed residual tumors. Only virtual CT sonography with magnetic navigation retrospectively showed the residual tumor as circular enhancement. In safety margin analysis, 10 patients were excluded because of residual tumors. The safety margin more than 5 mm by virtual CT sonographic images and transverse CT images were determined in 71.8% (56/78) and 82.1% (64/78), respectively (P = 0.13). The safety margin should be overestimated on axial CT images in 8 nodules.

Conclusion

Virtual CT sonography with magnetic navigation was useful in evaluating the treatment response of radiofrequency ablation therapy for hepatocellular carcinoma.     

CT fluoroscopy-guided vs. multislice CT biopsy mode-guided lung biopsies: accuracy, complications and radiation dose

Background

The aim of this retrospective study was to compare the diagnostic accuracy, the frequency of complications, the duration of the interventions and the radiation doses of CT fluoroscopy (CTF) guided biopsies of lung lesions with those of multislice CT (MS-CT) biopsy mode-guided biopsies.

Methods

Data and images from 124 consecutive patients undergoing CTF-guided lung biopsy (group A) and 132 MS-CT-biopsy mode-guided lung biopsy (group B) were reviewed. CTF-guided biopsies were performed on a Siemens Emotion 6 CT scanner with intermittent or continuous CT-fluoroscopy, MS-CT biopsy mode-guided biopsies were performed on a Siemens Emotion 16 CT scanner. All biopsies were performed with a coaxial needle technique.

Results

The two groups (A vs. B) did not differ significantly regarding sensitivity (95.5% vs. 95.9%), specificity (96.7% vs. 95.5%), negative predictive value (87.9% vs. 84%) or positive predictive value (98.8% vs. 98.9%). Pneumothorax was observed in 30.0% and 32.5% of the patients, respectively. Chest tube placement was necessary in 4% (group A) and 13% (group B) of the patients. The duration of the intervention was significantly longer in group A (median 37 min vs. 32 min, p = 0.04). The mean CT dose index (CTDI) was 422 in group A and 36.3 in group B (p < 0.001).

Conclusion

Compared to CTF-guided biopsies, chest biopsies using the MS-CT biopsy mode show dramatically lower CTDI levels. Although the diagnostic yield of the procedures do not differ significantly, biopsies using the MS-CT-biopsy mode have a three-fold higher rate of chest tube placement.     

Radiation dose of cardiac dual-source CT: the effect of tailoring the protocol to patient-specific parameters

Objective

To determine the radiation doses and image quality of different dual-source computed tomography coronary angiography (CTCA) protocols tailored to the heart rate (HR) and body mass index (BMI) of the patients.

Materials and methods

Two hundred consecutive patients (68 women; mean age 61 ± 9 years) underwent either helical CTCA with retrospective ECG-gating or sequential CT with prospective ECG-triggering: 50 patients (any BMI, any HR) were examined with a standard, non-tailored protocol (helical CTCA, 120 kV, 330 mAs), whereas the other 150 patients were examined with a tailored protocol: 40 patients (group A, BMI ≤ 25 kg/sqm, HR ≤ 70 bpm) with sequential CTCA (100 kV, 190 mAs_ref), 43 patients (group B, BMI ≤ 25 kg/sqm, HR > 70 bpm) with helical CTCA (100 kV, 220 mAs), 28 patients (group C, BMI > 25 kg/sqm, HR ≤ 70 bpm) with sequential CTCA (120 kV, 330 mAs_ref), and 39 patients (group D, BMI > 25 kg/sqm, HR > 70 bpm) with helical CTCA (120 kV, 330 mAs). The effective radiation dose estimates were calculated from the dose-length-product for each patient. Image quality was classified as being diagnostic or non-diagnostic in each coronary segment.

Results

Image quality was diagnostic in 2403/2460 (98%) and non-diagnostic in 57/2460 (2%) of all coronary segments. No significant differences in image quality were found among all five CTCA protocols (p = 0.78). The non-tailored helical CTCA protocol was associated with a radiation dose of 9.0 ± 1.0 mSv, being significantly higher compared to that using sequential CTCA (group A: 1.3 ± 0.3 mSv, p < 0.001; group C: 2.9 ± 0.6 mSv, p < 0.001), and helical CTCA at reduced tube voltage and tube current (group B: 4.2 ± 0.6 mSv, p < 0.01). No significant differences were found compared to the non-tailored CTCA protocol in patients with HR > 70 bpm (group D: 8.5 ± 0.9 mSv, p = 0.51).

Conclusions

Dual-source CTCA is associated with radiation doses ranging between 1.3 and 9.0 mSv, depending on the protocol used. Tailoring of the CTCA protocol to the HR and BMI of the individual patient results in dose reductions of up to 86%, while maintaining a diagnostic image quality of the examination.     

Image quality and radiation dose of low dose coronary CT angiography in obese patients: Sinogram affirmed iterative reconstruction versus filtered back projection

Purpose

To investigate the image quality and radiation dose of low radiation dose CT coronary angiography (CTCA) using sinogram affirmed iterative reconstruction (SAFIRE) compared with standard dose CTCA using filtered back-projection (FBP) in obese patients.

Materials and methods

Seventy-eight consecutive obese patients were randomized into two groups and scanned using a prospectively ECG-triggered step-and-shot (SAS) CTCA protocol on a dual-source CT scanner. Thirty-nine patients (protocol A) were examined using a routine radiation dose protocol at 120 kV and images were reconstructed with FBP (protocol A). Thirty-nine patients (protocol B) were examined using a low dose protocol at 100 kV and images were reconstructed with SAFIRE. Two blinded observers independently assessed the image quality of each coronary segment using a 4-point scale (1 = non-diagnostic, 4 = excellent) and measured the objective parameters image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Radiation dose was calculated.

Results

The coronary artery image quality scores, image noise, SNR and CNR were not significantly different between protocols A and B (all p > 0.05), with image quality scores of 3.51 ± 0.70 versus 3.55 ± 0.47, respectively. The effective radiation dose was significantly lower in protocol B (4.41 ± 0.83 mSv) than that in protocol A (8.83 ± 1.74 mSv, p < 0.01).

Conclusion

Compared with standard dose CTCA using FBP, low dose CTCA using SAFIRE can maintain diagnostic image quality with 50% reduction of radiation dose.     

Quantification of left and right ventricular function and myocardial mass: comparison of low-radiation dose 2nd generation dual-source CT and cardiac MRI

Objective

To prospectively evaluate the accuracy of left and right ventricular function and myocardial mass measurements based on a dual-step, low radiation dose protocol with prospectively ECG-triggered 2nd generation dual-source CT (DSCT), using cardiac MRI (cMRI) as the reference standard.

Materials and methods

Twenty patients underwent 1.5 T cMRI and prospectively ECG-triggered dual-step pulsing cardiac DSCT. This image acquisition mode performs low-radiation (20% tube current) imaging over the majority of the cardiac cycle and applies full radiation only during a single adjustable phase. Full-radiation-phase images were used to assess cardiac morphology, while low-radiation-phase images were used to measure left and right ventricular function and mass. Quantitative CT measurements based on contiguous multiphase short-axis reconstructions from the axial CT data were compared with short-axis SSFP cardiac cine MRI. Contours were manually traced around the ventricular borders for calculation of left and right ventricular end-diastolic volume, end-systolic volume, stroke volume, ejection fraction and myocardial mass for both modalities. Statistical methods included independent t-tests, the Mann–Whitney U test, Pearson correlation statistics, and Bland–Altman analysis.

Results

All CT measurements of left and right ventricular function and mass correlated well with those from cMRI: for left/right end-diastolic volume r = 0.885/0.801, left/right end-systolic volume r = 0.947/0.879, left/right stroke volume r = 0.620/0.697, left/right ejection fraction r = 0.869/0.751, and left/right myocardial mass r = 0.959/0.702. Mean radiation dose was 6.2 ± 1.8 mSv.

Conclusions

Prospectively ECG-triggered, dual-step pulsing cardiac DSCT accurately quantifies left and right ventricular function and myocardial mass in comparison with cMRI with substantially lower radiation exposure than reported for traditional retrospective ECG-gating.