Reduced Contrast Medium Dose Research Articles

CT imaging using variable helical pitch scanning for lower extremity arterial disease: Reduced contrast medium dose, improved image quality and diagnostic accuracy

ObjectivesThis study aimed to explore the feasibility of reducing contrast medium (CM) volume, improving image quality and diagnostic accuracy using variable helical pitch (VHP) scanning for patients with lower extremity arterial disease (LEAD). Materials and MethodsEighty patients who underwent lower extremity CT angiography (CTA) were prospectively enrolled and randomly assigned to either the VHP group (n = 40) or the conventional group (n = 40). Quantitative parameters and qualitative scores were compared between the two groups. Additionally, out of these patients, 72 arteries from 18 patients had DSA as the reference standard, and the diagnostic accuracy for the degree of vessel stenosis was assessed and compared. ResultsIn the VHP group, the contrast volume was significantly lower than in the conventional group (79.55 ± 11.87 mL vs. 89.63 ± 10.03 mL, p < 0.001), showing a reduction of 12.7 %. For all image quality characteristics, scores in VHP group were significantly superior to those in the conventional groups (all p < 0.05). Quantitative analysis revealed that images from the VHP group exhibited superior CT enhancement, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in the anterior tibial arteries (ATA) and dorsali pedis arteries (DPA) compared to the conventional group (all p < 0.001). Moreover, segment-based analysis showed the VHP group had significantly higher positive predictive value (PPV) and accuracy than the conventional group (PPV: 100 % vs. 76.19 %, p = 0.01; accuracy: 100 % vs. 84.38 %, p = 0.01, respectively). ConclusionsThe implementation of the VHP protocol led to a 12.7% decrease in contrast medium dosage compared to the conventional lower extremity CTA scanning protocol. Furthermore, it improved image quality and diagnostic accuracy, particularly for arteries below the knee.

Performance evaluation of using shorter contrast injection and 70 kVp with deep learning image reconstruction for reduced contrast medium dose and radiation dose in coronary CT angiography for children: a pilot study.

Iterative reconstruction algorithms are often used to reduce image noise in low-dose coronary computed tomography angiography (CCTA) but encounter limitations. The newly introduced deep learning image reconstruction (DLIR) algorithm may provide new opportunities. We assessed the image quality and diagnostic performance of DLIR in low radiation dose and contrast medium dose CCTA of pediatric patients with 70 kVp and a shortened injection protocol. This was a prospective study. A total of 27 consecutive arrhythmic pediatric patients were enrolled in the study group and underwent CCTA using a prospective ECG-triggered single-beat protocol: tube voltage 70 kVp, automatic tube current modulation for a noise index (NI) of 22, and contrast dose of 0.4-0.6 mL/kg. Images were reconstructed with DLIR. They were compared with 27 matched patients in the control group scanned with 80 kVp, a lower NI setting (NI =19), and a higher contrast dose (0.8-1.2 mL/kg). The images in the control group were reconstructed using the adaptive statistical iterative reconstruction (ASIR-V) algorithm. The image contrast, image quality, and diagnostic confidence were assessed by 2 experienced radiologists using a 5-point scale (1: nondiagnostic and 5: excellent). The CT value and standard deviation of the aorta and perivascular tissue were measured, and the contrast-to-noise ratio (CNR) for the aorta was calculated. The contrast medium and radiation doses were compared. The study and control groups had similar image contrast scores (4.75±0.57 vs. 4.78±0.42), image quality scores (3.67±0.47 vs. 3.44±0.51), and diagnostic confidence (4.74±0.44 vs. 4.74±0.45) (all P>0.05). There was an adequate enhancement in the aorta (614.74±127.73 vs. 705.89±111.20 HU) and similar CNR (20.34±4.64 vs. 20.99±4.14) in both groups. The image noise of the study group was lower in the aorta (30.61±3.88 vs. 34.77±3.49) and similar in perivascular tissue (27.66±6.24 vs. 27.55±3.33) compared with the control group. The study group reduced the total contrast medium dose by 53% to 15.07±3.68 mL and radiation dose by 36% to 0.57±0.31 mSv. The DLIR algorithm in CCTA for children using 70 kVp tube voltage with a shortened contrast medium injection protocol maintains image quality and diagnostic confidence while significantly reducing contrast medium dose and radiation dose compared with the use of the conventional CCTA protocol.

Reducing contrast medium dose with low photon energy images in renal dual-energy spectral CT angiography and adaptive statistical iterative reconstruction (ASIR)

To evaluate the value of using low energy (keV) images in renal dual-energy spectral CT angiography (CTA) and adaptive statistical iterative reconstruction (ASIR) to reduce contrast medium dose. 40 patients with renal CTA on a Discovery CT750HD were randomly divided into two groups: 20 cases (Group A) with 600 mgI kg-1 and 20 cases (Group B) with 300 mgI kg-1. The scan protocol for both groups was: dual-energy mode with mA selection for noise index of 10 HU, pitch 1.375:1, rotating speed 0.6 s/r. Images were reconstructed at 0.625 mm thickness with 40%ASIR, Group A used the conventional 70keV monochromatic images, and Group B used monochromatic images from 40 to 70 keV at 5 keV interval for analysis. The CT values and standard deviation (SD) values of the renal artery and erector spine in the plain and arterial phases were measured with the erector spine SD value representing image noise. The enhancement degree of the renal artery (ΔCT = CT(arterial) -CT(plain)), signal-to-noise ratio (SNR=CTrenal-artery/SDrenal-artery) and contrast-to-noise ratio (CNR=(CTrenal-artery-CTerector spine)/SDerector-spine) were calculated. The single factor analysis of variance was used to analyze the difference of ΔCT, SNR and CNR among image groups with p < 0.05 being statistically significant. The subjective image scores of the groups were assessed blindly by two experienced physicians using a 5-point system and the score consistency was compared by the κ test. Contrast medium dose in the 300 mgI kg-1 group was reduced by 50% compared with the 600 mgI kg-1 group, while radiation dose was similar between the two groups. The subjective scores were 4.00 ± 0.65, 4.50 ± 0.60 and 3.70 ± 0.80 for images at 70 keV (600 mgI kg-1 group), 40 keV (300 mgI kg-1 group) and 45 keV (300 mgI kg-1 group), respectively with good consistency between the two reviewers (p > 0.05). The 40 keV images in the 300 mgI kg-1 group had similar ΔCT (469.77 ± 86.95 HU vs 398.54 ± 73.68 HU) and CNR (15.52 ± 3.32 vs 18.78 ± 6.71) values as the 70 keV images in the 600 mgI kg-1) group but higher SNR values (30.19 ± 4.41 vs 16.91 ± 11.12, p < 0,05). Contrast dose may be reduced by 50% while maintaining image quality by using lower energy images combined with ASIR in renal dual-energy CTA. Combined with ASIR and energy spectrum, can reduce the amount of contrast dose in renal CTA.

Computed Tomography Angiography of the Aorta-Optimization of Automatic Tube Voltage Selection Settings to Reduce Radiation Dose or Contrast Medium in a Prospective Randomized Trial.

The aim of this study was to compare the image quality of low-kV protocols with optimized automatic tube voltage selection (ATVS) settings to reduce either radiation dose or contrast medium (CM) with that of a reference protocol for computed tomography angiography (CTA) of the thoracoabdominal aorta. In this institutional review board-approved, single-center, prospective randomized controlled trial, 126 patients receiving CTA of the aorta were allocated to one of three computed tomography protocols: (A) reference protocol at 120 kVp and standard weight-adapted CM dose; (B) protocol at 90 kVp, reduced radiation and standard CM dose; and (C) protocol at 90 kVp, standard radiation and reduced CM dose. All three protocols were performed on a third-generation dual-source computed tomography scanner using the semimode of the ATVS system. The image-task-dependent optimization settings of the ATVS (slider level) were adjusted to level 11 (high-contrast task) for protocols A and B and level 3 (low-contrast task) for protocol C. Radiation dose parameters were assessed. The contrast-to-noise ratios (CNRs) of protocols B and C were tested for noninferiority compared with A. Subjective image quality was assessed using a 5-point Likert scale. Size-specific dose estimate was 34.3% lower for protocol B compared with A (P < 0.0001). Contrast medium was 20.2% lower for protocol C compared with A (P < 0.0001). Mean CNR in B and C was noninferior to protocol A (CNR of 30.2 ± 7, 33.4 ± 6.7, and 30.5 ± 8.9 for protocols A, B, and C, respectively). There was no significant difference in overall subjective image quality among protocols (4.09 ± 0.21, 4.03 ± 0.19, and 4.08 ± 0.17 for protocols A, B, and C, respectively; P = 0.4). The slider settings of an ATVS system can be adjusted to optimize either radiation dose or CM at noninferior image quality in low-kV CTA of the aorta. This optimization could be used to extend future ATVS algorithms to take clinical risk factors like kidney function of individual patients into account.

Can iterative reconstruction algorithms replace tube loading compensation in low kVp hepatic CT? Subjective versus objective image quality.

BackgroundHepatic computed tomography (CT) with decreased peak kilovoltage (kVp) may be used to reduce contrast medium doses in patients at risk of contrast-induced acute kidney injury (CI-AKI); however, it increases image noise. To preserve image quality, noise has been controlled by X-ray tube loading (mAs) compensation (TLC), i.e. increased mAs. Another option to control image noise would be to use iterative reconstructions (IR) algorithms without TLC (No-TLC). It is unclear whether this may preserve image quality or only reduce image noise.PurposeTo evaluate image quality of 80 kVp hepatic CT with TLC and filtered back projection (FBP) compared with 80 kVp with No-TLC and IR algorithms (SAFIRE 3 and 5) in patients with eGFR <45 mL/min.Material and MethodsForty patients (BMI 18–32 kg/m2) were examined with both protocols following injection of 300 mg I/kg. Hepatic attenuation, image noise, enhancement, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and subjective image quality were evaluated for each patient.ResultsComparing TLC/FBP with No-TLC/IR-S5, there were no significant differences regarding hepatic attenuation, image noise, enhancement, SNR and CNR: 114 vs. 115 HU, 14 vs. 14 HU, 55 vs. 57 HU, 8.0 vs. 8.4, and 3.8 vs. 4.0 in median, respectively. No-TLC/IR-S3 resulted in higher image noise and lower SNR and CNR than TLC/FBP. Subjective image quality scoring with visual grading showed statistically significantly inferior scores for IR-S5 images.ConclusionCT of 80 kVp to reduce contrast medium dose in patients at risk of CI-AKI combined with IR algorithms with unchanged tube loading to control image noise does not provide sufficient diagnostic quality.

Venous-phase chest CT with reduced contrast medium dose: Utilization of spectral low keV monoenergetic images improves image quality

PurposeIntravenous contrast administration is crucial in many CT examinations but also poses a potential risk to the patient. Monoenergetic images (MonoE) of dual-energy CT systems can virtually increase iodine attenuation and might improve image quality (IQ) if contrast dose is reduced. In this study, we investigated the influence of MonoE on lymph node (LN) delineation and IQ in chest CT examinations with significantly reduced contrast dose (50 %) of a novel dual-layer CT (DLCT). Method30 patients with clinically indicated reduced contrast dose underwent venous-phase chest DLCT scans. Conventional polyenergetic (PolyE) and MonoE images at 40 keV were calculated. The contrast difference of hilar lymph nodes (LN-CD) to the adjacent right pulmonary artery, their signal-to-noise (SNR) and contrast-to-noise-ratio (CNR) were determined. Subjective IQ was evaluated by 2 readers with respect to LN delineation and overall contrast enhancement (CE) using a 5-point-Likert-scale. ResultsLN-CD, SNR and CNR were significantly higher in MonoE than in PolyE images (LN-CD 92.3 ± 37.9 vs. 33.1 ± 14.5 HU, SNR 8.4 ± 3.4 vs. 4.0 ± 1.2, CNR 9.2 ± 6.3 vs. 2.6 ± 1.5; all p < 0.01). The LN delineation (3.7 ± 0.9 vs.1.8 ± 0.7; p < 0.01) and the CE (3.9 ± 0.7 vs. 2.3 ± 0.7; p < 0.01) were rated significantly better for MonoE than for PolyE images. There was no MonoE examination classified as non-diagnostic. ConclusionsSubjective and objective IQ parameters can be significantly improved for venous-phase chest CT examinations with reduced contrast doses by utilization of low-keV MonoE reconstructions. All MonoE images provided sufficient overall CE and therefore reduced contrast doses might be considered in a wider range of DLCT examinations and patients.

80-kVp hepatic CT to reduce contrast medium dose in azotemic patients: a feasibility study.

Background Low peak kilovoltage (kVp) computed tomography (CT) may be used to reduce contrast medium doses in patients at risk of contrast medium-induced acute kidney injury if image noise can be controlled by increasing X-ray tube loading (mAs). Purpose To evaluate objective and subjective image quality in 80-kVp CT with reduced contrast medium dose and compensated mAs for unchanged image noise in patients with estimated glomerular filtration rate &lt;45 mL/min compared with the standard 120-kVp protocol. Material and Methods 80-kVp CT with 300 mg I/kg in 40 patients (body mass index 18–32 kg/m2, glomerular filtration rate &lt;45 mL/min) and 120-kVp CT with 500 mg I/kg in 40 patients (body mass index = 17–30 kg/m2, glomerular filtration rate ≥45 mL/min) was compared on mean hepatic attenuation, image noise, contrast medium enhancement, signal-to-noise ratio, contrast-to-noise ratio, effective radiation dose, and subjective image quality. Results There were no significant differences regarding median hepatic post-contrast attenuation, image noise, contrast medium enhancement, signal-to-noise ratio, contrast-to-noise ratio, or effective dose between the 80-kVp and 120-kVp cohorts: 114/110 HU; 14/14 HU; 57/53 HU; 8.0/7.4; 3.8/3.5; and 5.3/5.9 mSv, respectively. However, subjective image visual grading showed statistically significantly inferior scores for 80 kVp for six of eight items. After exclusion of seven inferior examinations not caused by the chosen kVp technique, only three items showed inferior scores for 80 kVp. Only 5% of gradings regarding overall image quality were &lt;3 of 5 points. Conclusion Despite lower subjective image quality, objective data indicate that 80-kVp CT with reduced contrast medium doses and compensated mAs may have the potential to provide satisfactory diagnostic quality in patients with body mass index &lt;30 kg/m2, which could benefit patients at risk of contrast medium-induced acute kidney injury.

Advanced Virtual Monochromatic Images from Dual Source Dual-Energy CT for a Reduction in the Contrast Medium Dose (389 mgI/kg) in Multiphase Liver CT: Evaluation of Image Quality and Focal Lesion Conspicuity

Background: Low-energy advanced virtual monochromatic images (VMIs) from dual source dual-energy CT (DSCT) could be applied to reduce contrast medium dose due to superior iodine contrast-to-noise ratios (CNRs). Objectives: To investigate feasibility of advanced VMIs from DSCT to reduce contrast medium dose in multiphase liver CT without impairing image quality and conspicuity of focal hepatic lesions (FHLs). Patients and Methods: Ninety-four patients with 110 FHLs underwent follow-up CT twice prospectively with different protocols: protocol A, conventional 100 kVp and 555 mgI/kg; protocol B, dual-energy mode and 389 mgI/kg. The signal-to-noise ratio (SNR) and lesion-to-liver CNR were compared between the VMIs (40 - 120 keV, 10-keV interval) reconstructed using advanced image-based algorithm and conventional images. Two radiologists qualitatively evaluated VMIs, compared with the 100 kVp images, using a six-point scale. Results: The SNRs of pancreas, aorta, portal and hepatic vein were similar to those at 100 kVp images (P > 0.05) at 40-50 keV images during late arterial phase (LAP) and at 40-60 keV images during portal venous phase (PVP) except for the SNRs of aorta and veins at 40 keV images which were significantly higher (P 0.05) during LAP. The CNR of 58 hypovascular FHLs was similar at 40 - 120 keV images (P > 0.05) during PVP. Among the VMIs, 50 keV and 50 - 60 keV images received the highest scores (P < 0.0315 and P < 0.0041) by both reviewers during LAP and PVP, respectively. Conclusion: Advanced 50 - 60 keV images from DSCT allowed contrast dose reduction by 30% in multiphase liver CT without impairing image quality and conspicuity of FHLs, compared with the conventional 100 kVp images with 555 mgI/kg.

Dual source abdominal computed tomography: the effect of reduced X-ray tube voltage and intravenous contrast media dosage in patients with reduced renal function.

X-ray tube voltage (kVp) reduction increases intravenous contrast medium (CM) attenuation at computed tomography (CT), but tube output limits its use in large patients. To evaluate the feasibility and image quality of reducing CM dose by low kVp and using dual X-ray source at liver CT. Patients with estimated glomerular filtration rate (eGFR) < 45 mL/min (n = 43) aged 60-91 years (75 ± 7.7), weighing 42-114 kg (75 ± 15) were prospectively scanned using a reduced CM dose of 0.25 or 0.3 g iodine (I)/kg with 70 or 80 kVp respectively, using either single-source or dual-source CT depending on patient size. Liver contrast-to-noise ratio (CNR), liver noise, and muscle noise were quantitatively compared with those of 43 consecutive patients aged > 65 years with eGFR > 45 mL/min scanned using a standard abdominal protocol at 120 kVp after receiving 0.5 gI/kg. There was no statistically significant difference in CNR, liver noise, or muscle noise at reduced CM protocols compared to the standard protocol: CNR was 4.6 (95% CI = 4.2-5.0) vs. 5.0 (95% CI = 4.5-5.5), liver noise was 11.1 (95% CI = 10.7-11.6) vs. 11.0 (95% CI = 10.5-11.6), muscle noise was 11.7 (95% CI = 11.2-12.1) vs. 10.8 (95% CI = 10.1-11.4). The mean SSDE was 70% higher with the reduced CM protocol. CM dosage can be reduced by 40-50% with maintained measured noise and CNR in patients with BMIs of 15-36 kg/m2 by lowering the tube voltage and dual-source CT scanning of the liver.

Low-voltage (80-kVp) abdominopelvic computed tomography allows 60% contrast dose reduction in patients at risk of contrast-induced nephropathy

PurposeThe purpose of this study was to evaluate the quality of image in abdominopelvic late phase computed tomography (CT) with a low tube voltage plus low dose contrast medium (CM) protocol (80-kVp, 60% CM). A compared with the conventional protocol (120-kVp, 100% CM) B in the same patients. Material and methodsThis study included with 22 patients {36 to 77 kg (mean: 55.5 kg)} who had renal insufficiency and had experience of performance conventional CT without renal insufficiency during pre-18 months. The CT value of the portal vein, liver parenchyma, abdominal aorta, psoas muscle was measured. The estimated mean CNR (contrast-to-noise ratios), FOM (figure of merit), DLP (dose length product) and ED (effective dose) were compared between protocol A and B. Moreover, two radiologists assessed the visual quality of the CT images. ResultsThe mean DLP and ED in the protocol B was about 50% lower than that in the protocol A (p < 0.01). The mean CT value of the portal vein and abdominal aorta in the protocol B were significantly higher than that in the protocol A (p < 0.01). All of the FOM in the protocol B was significantly higher than that in the protocol A (p < 0.01). However, there was no significant difference in the mean CNR and visual quality between protocol A and B. ConclusionPerformance of abdominopelvic CT using a low tube voltage plus reduced CM dose (80-kVp, 60% CM) achieved reduction of the radiation dose without impairing image quality in relatively light weight group. Clinical relevance/applicationIn abdominopelvic CT, protocol of low tube voltage (80-kVp) plus iodine dose reduction (60%) is able to provide the same quality of traditional protocols, also able to reducing radiation exposure (50%).

Prospective ECG-triggering cardiac CT for infants with complex congenital heart disease using low-dose contrast medium, low tube voltage, and adaptive statistical iterative reconstruction

To demonstrate the clinical value of prospective electrocardiography (ECG)-triggered cardiac computed tomography (CT) with low concentration contrast medium, low tube voltage, and adaptive statistic iterative reconstruction (ASIR) to reduce both radiation and contrast dose in examining infants with complex congenital heart disease (CHD). Forty-four consecutive infants (19 male, 25 female, age: 8.06±4.33 months, weight: 7.31±1.36kg) with complex CHD underwent prospective ECG-triggered low-dose cardiac CT using 80 kVp and 120mA. The contrast agent was iodixanol (270mg iodine/ml, Visipaque, GE Healthcare, Co. Cork, Ireland). Cardiac CT images were reconstructed with 70% ASIR. The quantitative CT image quality was assessed by image noise in adipose tissue and contrast-to-noise ratio (CNR) in the aorta. The qualitative image analysis was performed on a five-point grading scale by two independent reviewers and interobserver variability was calculated. The results of 32 CT examinations were also compared with the available surgical results for diagnostic accuracy evaluation. The effective dose was 0.55±0.10mSv for the patient population. The iodine load was 3.95±0.73g iodine. Image noise in adipose tissue was 16.24±1.42 HU and CNR in aorta was 21.90±7.10. All images were acceptable for diagnosis with an average score of 4.52±0.38 and good agreement between reviewers (kappa=0.75). Compared to the surgery results in 32 cases, CT was 97% and 88% accurate diagnosing extracardiac and intracardiac defects, respectively. Prospective ECG-triggered cardiac CT using 80 kVp, low-concentration iodinated contrast agent (270mg iodine/ml) and 70% ASIR reconstruction provides excellent image quality and accurate diagnosis for complex congenital heart disease in infants with reduced contrast medium dose and low radiation dose.

An Individually Optimized Protocol of Contrast Medium Injection in Enhanced CT Scan for Liver Imaging.

Objective To investigate the effectiveness of a new individualized contrast medium injection protocol for enhanced liver CT scan. Methods 324 patients who underwent plain and dual phase enhanced liver CT were randomly assigned to 2 groups: G1 (n = 224, individualized contrast medium injection protocol); G2 (n = 100, standard contrast medium injection with a dose of 1.5 ml/kg). CT values and ΔHU (CT values difference between plain and enhanced CT) of liver parenchyma and tumor-liver contrast (TLC) during hepatic arterial phase (HAP) and portal venous phase (PVP) and contrast medium dose were measured. The tumor conspicuity of hepatocellular carcinoma (HCC) between two groups was independently evaluated by two radiologists. Results The mean contrast medium dose of G1 was statistically lower than that of G2. There were no significantly statistical differences in CT values and ΔHU of liver parenchyma during HAP, TLC values during HAP, and PVP between two groups. The CT values and ΔHU of liver parenchyma during PVP of G2 were significantly higher than those of G1. Two independent radiologists were both in substantial conformity in grading tumor conspicuity. Conclusion Using the individually optimized injection protocol might reduce contrast medium dose without impacting on the imaging quality in enhanced liver CT.

Impact of iterative reconstructions on image noise and low-contrast object detection in low kVp simulated abdominal CT: a phantom study.

Low kilovoltage (kVp) computed tomography (CT) may be used to reduce contrast medium dose in patients at risk of contrast nephropathy, at the cost of increased image noise. To evaluate: (i) the impact of iterative reconstructions (Siemens SAFIRE) on low-contrast object detection to compensate for increased noise instead of increased tube loading when decreasing tube potential; and (ii) the change in iodine attenuation in simulated abdominal CT. A phantom was scanned at 70, 80, 100, and 120 kVp at fixed effective tube loading (170 mAsEFF) and fixed radiation dose (CTDIVOL 10 mGy). Images were reconstructed with filtered back-projection (FBP) and SAFIRE strengths S1-S5. Iodine attenuation, objective image noise, contrast-to-noise ratio (CNR), noise power spectrum (NPS), spatial resolution, and subjective detectability of low-contrast objects were evaluated. Compared with 120 kVp iodine attenuation increased by a factor 1.6 and 2.0, and image noise increased by a factor 1.9 and 2.5 at 80 and 70 kVp, respectively. Compared with FBP, SAFIRE showed objective reduction in image noise and increased CNR without loss of spatial resolution or any significant NPS alteration, with general tendency to improve subjective detectability of low-contrast objects. At 170 mAsEFF the number of discernible 1.0% contrast objects at 70 kVp/S5 and 80 kVp/S5 was similar to that at 120 kVp/FBP. With the SAFIRE algorithm image noise, CNR and detectability of low-contrast objects may be kept unchanged without increased tube loading when using low kVp settings to reduce contrast medium dose in azotemic patients.

Pituitary magnetic resonance imaging in Cushing's disease.

Adrenocorticotropin-secreting pituitary tumor represents about 10 % of pituitary adenomas and at the time of diagnosis most of them are microadenomas. Transsphenoidal surgery is the first-line treatment of Cushing's disease and accurate localization of the tumor within the gland is essential for selectively removing the lesion and preserving normal pituitary function. Magnetic resonance imaging is the best imaging modality for the detection of pituitary tumors, but adrenocorticotropin-secreting pituitary microadenomas are not correctly identified in 30-50 % of cases, because of their size, location, and enhancing characteristics. Several recent studies were performed with the purpose of better localizing the adrenocorticotropin-secreting microadenomas through the use in magnetic resonance imaging of specific sequences, reduced contrast medium dose and high-field technology. Therefore, an improved imaging technique for pituitary disease is mandatory in the suspect of Cushing's disease. The aims of this paper are to present an overview of pituitary magnetic resonance imaging in the diagnosis of Cushing's disease and to provide a magnetic resonance imaging protocol to be followed in case of suspicion adrenocorticotropin-secreting pituitary adenoma.

A pilot study of contrast medium dose reduction using low tube voltage and iterative reconstruction: computed tomography angiography of the head

This study aimed to reduce contrast medium dose without reducing the diagnostic capability of computed tomography (CT) angiography of the head. We evaluated the advanced statistical iterative reconstruction (ASiR) settings to adjust to low tube voltage CT. A syringe phantom was constructed using dilute contrast medium and was imaged at tube voltages of 80-120 kV. The iodine volumes, CT values, and image noise were measured in these images. The noise-power spectrum and modulation transfer function were measured from quality assurance phantom images that had been obtained using the tube voltage selected after considering the image noise results as described above and reconstructed using different ASiR rate settings and convolution kernels. Our results suggested that imaging at 100 kV could reduce the contrast medium dose by 14%, compared with imaging at 120 kV, and that the resulting image quality could equal that of conventional imaging by performing reconstruction at a 40% ASiR rate and detail kernel.