L. Bertoletti

Multidetector–row CT angiography of renal artery stenosis in 50 consecutive patients: prospective interobserver comparison with DSA

Purpose.The purpose of this study was to establish the diagnostic value of multidetector–row computed tomography (MDCT) angiography compared with digital subtraction angiography (DSA) for detection and quantification of both main and accessory renal artery stenosis in patients with secondary hypertension.Materials and methods.Fifty consecutive patients scheduled for DSA were considered candidates for MDCT angiography. In all patients, MDCT angiography of the abdominal aorta was performed before DSA. For the purpose of interpretation, the arteries were separately interpreted either with DSA or MDCT angiography in order to provide qualitative and quantitative information. For qualitative evaluation, one experienced reader graded the opacification of renal arteries as excellent, good or poor; for quantitative evaluation, MDCT and DSA were independently evaluated for the number of renal arteries and the presence, location and degree of stenosis in random order by three readers. On the basis of consensus readings, calculations of sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) for detection of degree of stenosis were made by using DSA findings as the standard of reference. Interobserver variability was also assessed.Results.With regard to qualitative analysis, arterial enhancement was considered excellent in 39 patients and good in 11. For quantitative analysis, 73 arteries were classified as normal with DSA. Although 72 of these were also classified as normal with CT angiography, one was overestimated by one grade; at DSA, 16 arteries were classified as moderately stenotic; in two arteries, there was an overestimation of one grade. Perfect correlation was achieved for the diagnosis of occlusion. In two patients, all three readers detected multiple severe stenoses on both modalities, with a “string–of–beads” appearance typical of fibromuscular dysplasia. Accessory arteries were correctly identified as such by all three readers on either DSA or MDCT. Levels of sensitivity, specificity and accuracy regarding degree of stenosis were 100%, 98.6% and 96.9%, respectively, with PPV and NPV of 97.6% and 100%, respectively. When we considered significant arterial stenosis (50%–100% luminal narrowing), sensitivity, specificity and accuracy were 100%, 97.3% and 97.8%, respectively, with a PPV and NPV of 98.2% and 97.8%, respectively. For all observers, interobserver agreement was almost perfect (k=0.81–1) for both MDCT and DSA, with a k value between 0.82 and 0.95.Conclusions.MDCT angiography is very accurate and robust, even for the assessment of renal artery stenosis, and has the potential to become a viable substitute, in most cases, for diagnostic catheter–based DSA.

MDCT of the abdominal aorta: basics, technical improvements, and clinical applications

ConclusionMultiple diagnostic techniques have been proposed for the evaluation of the abdominal aorta and iliac arteries so as to avoid the use of DSA.The development of MDCT has improved the assessment of the aorta and its branches allowing increasingly faster acquisition of thin sections. The increasing speed of the acquisition requires more attentive administration of iodinated contrast agent, at higher flow rates and with higher iodine concentration so that a homogeneous enhancement throughout the acquisition is achieved. Compared to other techniques, MDCT angiography has several advantages related to transverse data acquisition and the possibility of performing multiplanar interactive reconstructions. Furthermore, the rapid diffusion of MDCT scanners worldwide, not followed by the diffusion of high-field-strenght MR systems, enable to perform high quality MR angiography, has allowed an increasing number of CT angiography examinations to be performed.There are two major limitations of MDCT angiography in the evaluation of patients with peripheral arterial disease: the use of ionizing radiation and iodinated contrast agents. Regarding the radiation issue, it has been recently noted that it is not that important in older individuals who are the typical patients with peripheral arteriopathy, and that the radiation dose, compared with that of DSA, is significantly lower. Furthermore, as shown in other areas, it might be possible to reduce the radiation dose to the patient by optimizing the acquisition protocol. Concerning the use of iodinated contrast agents, it must be noted that several patients present with poor renal function and cannot tolerate administration of a possibly nephrotoxic agent; nevertheless, the nephrotoxicity of nonionic contrast agents has been significantly reduced as compared with ionic contrast agents and their administration can be considered safe and well tolerated, even in high-risk populations. Furthermore, the amount of iodinated contrast agent needed for MDCT angiography is significantly lower than that of single-slice spiral CT angiography, and the further increase in speed of new multidetector-row CTs will allow the use of even smaller amounts.

Computer-aided detection (CAD) in lung cancer screening at chest MDCT: ROC analysis of CAD versus radiologist performance.

To evaluate the performance of a computer-aided detection (CAD) algorithm in the detection of pulmonary nodules on high-resolution multidetector row computed tomography images in a large, homogeneous screening population, and to evaluate the effect of the system output on the performance of radiologists, using receiver operating characteristic analysis. Three radiologists with variable experience (1 to 7 y), independently read the 200 computed tomography scans and assigned each nodule candidate a confidence score (1-2-3: unlikely, probably, and definitely a nodule). CAD was applied to all scans; successively readers reevaluated all findings of the CAD, assigning, in consensus, a confidence score (1 to 3). The reference standard was established by the consensus of 2 experienced radiologists with 30 and 15 years of experience. Results were used to generate an free-response receiver operating characteristic analysis. The reference standard showed 125 nodules. Sensitivity for readers I-II-III was 57%, 68%, and 46%. A double reading resulted in an increase in sensitivity up to 75%. With CAD, sensitivity was increased to 94%, 96%, and 94% for readers I, II, and III. The area under the free-response receiver operating characteristic curve (Az) was 0.72, 0.82, 0.55, and 0.84 for readers I, II, III, and the CAD, when considering all nodules. Differences between readers I-II and CAD were not significant (P=0.9). There was a significant difference between reader III and the CAD. For nodules <6-mm Az was 0.40, 0.47, 0.14, and 0.72 for readers I, II, III, and the CAD. Differences between all readers and the CAD were significant (P<0.05). CAD can aid in daily radiologic routine detecting a substantial number of nodules unseen by radiologists. This is true for both board-certified radiologists and for less experienced readers especially in the detection of small nodules.

Volumetric evaluation of therapy response in patients with lung metastases. Preliminary results with a computer system (CAD) and comparison with unidimensional measurements

Purpose.The aim of this study was to assess the efficacy of a Computer–Aided Detection (CAD) system in the identification of lung metastases and to compare the volumetric CAD measurements with unidimensional observer measurements in the evaluation of treatment response in oncology patients.Materials and methods.Two observers (A and B) evaluated nine patients undergoing lung computed tomography (CT) just before and immediately after treatment with chemotherapy. Multislice CT scans were performed before and after the injection of contrast material with a high–resolution protocol (collimation 4x1 mm, 100 mAs, 120 kV). Response Evaluation Criteria in Solid Tumours (RECIST) criteria were used to consider the disease as stable, increased or decreased. Subsequently, target lesions (most significant lesions identified before and after chemotherapy) were evaluated with a computerised system (CAD) to establish volumetric measurements. Observers’ unidimensional measurements and CAD volumetric measurements were analysed for comparison.Results.Twenty–four nodules (diameter: 5–18 mm in the first study and 4–20 mm in the follow–up study) were included. Observers agreed in the assessment of therapy response in 21 nodules: eight were considered to have increased in size, and 13 were judged stable. Observer and CAD measurements disagreed in three nodules: two were considered stable by radiologists and increased by CAD; one was considered increased by radiologists and stable by CAD.As regards patient response, radiologists disagreed in two cases. CAD and observers did not agree in one case.Conclusions.Our preliminary data suggest that volumetric measurements can modify the diagnostic and therapeutic evaluation of oncology patients under chemotherapy.CAD volumetric measurements allow an easy and objective evaluation, reducing interobserver variability in the evaluation of chemotherapy response.

Dose reduction and image quality assessment in 64-detector row computed tomography of the coronary arteries using an automatic exposure control system.

Objective: To evaluate dose reduction and image quality in coronary 64-slice multidetector computed tomography using an automatic exposure control system (AECs). Methods: A total of 101 patients were divided into 4 groups. Tube current was 600 and 800 mAs in groups A and B and adapted at 600 and 800 quality-reference mAs using an AECs in groups C and D. Effective dose and organ-equivalent dose were evaluated. Image noise was quantified as standard deviation of air-space attenuation. Two observers assessed technical adequacy and image quality using a 4-point scale. Results: Effective dose ranged from 8.6 mSv (group C) to 15 mSv (group B) with significant dose reduction for examinations performed at 600 mAs (21.7%) and 800 mAs (29.4%). Contribution of organ-equivalent doses showed higher exposure for lungs (42%) and breast (22%). Noise was significantly higher in groups studied with AECs. Larger coronary segments resulted in higher image quality scores without differences between groups. Conclusion: Automatic exposure control systems provides images of diagnostic quality with substantial dose reduction.

MDCT assessment of lung volume in patients undergoing bronchial stenting for treatment of pulmonary emphysema: correlation with respiratory tests and personal experience

Purpose.The aid of this study was to evaluate lung volume reduction with multidetector-row computed tomography (MDCT) in patients with emphysema who have undergone endobronchial valve placement.Materials and methods.Nine patients with emphysema were studied by low-dose chest MDCT (64-slice Somatom Sensation Cardiac, Siemens) with a collimation of 64x0.6 mm and a slice thickness of 1 mm. After treatment, MDCT scans were repeated at 7 and 30 days. A single observer calculated the volume of the treated lobe and of both lungs on a dedicated console. Volume calculations were then compared with the results of lung function tests.Results.Four patients in whom MDCT showed severe emphysema of the right upper lobe (RUL) were selected for endobronchial valve insertion. Volume assessment at 30 days showed a 29% reduction in RUL volume in patient A, a 15% reduction in patient B, a <1% reduction in patient C and a 30% reduction in patient D. Correlation with lung function tests confirmed a major reduction of forced expiratory volume in 1 s (FEV1) and vital capacity (VC) and improved walking test results after 7 and 30 days.Conclusions.In patients undergoing endobronchial valve placement, MDCT with dedicated software allows for a better evaluation of volume reduction of a single lobe and of the whole lung.

Noninvasive imaging of the coronary arteries using a 64-row multidetector CT scanner: initial clinical experience and radiation dose concerns@@@Imaging non invasivo delle arterie coronarie con TC spirale a 64 strati: esperienza clinica iniziale e considerazioni dosimetriche

Purpose.We present our initial clinical experience with a recently introduced 64-detector computed tomography (64-MDCT) scanner that makes use of a periodic motion of the focal spot in the longitudinal direction (z-flying focal spot), which enables it to reach a final spatial resolution of 0.4×0.4×0.4 mm3 and a temporal resolution of 83 ms.Materials and methods.A total of 114 patients (108 men, six women; age range 36–77 years, mean 63.1 years) underwent retrospective electrocardiogram (ECG)-gated examination of the coronary arteries using a 64-MDCT scanner (Somatom Sensation 64, Siemens Medical Solutions, Germany). Acquisition parameters were the following: collimation 64×0.6 mm, 800 quality reference milliampere second (mAs), 120 kVp, 0.33-s gantry rotation time and pitch 0.2. Images were acquired in all cases after i.v. administration of 80 ml of contrast agent (Iomeron 400 mgI/dl, Bracco, Italy) + 30 ml of saline at 4 /s and delay time determined using a bolus triggering technique. Oral betablockers were administered to patients with heart rate (HR) >75 bpm. To reduce radiation exposure, an automatic exposure control system was applied in all cases to adapt tube current to patient size and anatomic shape (CARE Dose 4D, Siemens Medical Solutions, Germany). The optimal temporal window for raw data reconstruction was chosen from an initial preview of images reconstructed with different phase settings (range 0%–95% RR interval with 5% gap) at a selected anatomical level in the mid part of the right coronary artery. CT dose index volume and effective dose were quantified in all patients using dedicated software.Results.Mean HR recorded during image acquisition was 65.6±19.2 bmp (range: 44–96 bmp), and beta-blockers were administered to 16/114 patients (14.0%). Technical adequacy was achieved in all patients but two (2/114; 1.7%). In patients with HR <60 bmp, the best reconstruction intervals were identified in the end-systolic (30%–35% of the RR interval) and end-diastolic (60%–65% of the RR interval) phases; with faster HR (>80 bmp), high image quality was observed in end-systole (30%–35% of the RR interval). Mean CT dose index (CTDI) volume was 36.53±8.30 mGy per patient. In comparison with a conventional examination with fixed mAs, the use of the CARE Dose 4D system provided a 33.3% CTDI volume reduction (p<0.001). Mean effective dose was 9.5±3.4 millisievert (mSv) per patient (range 7.1–17.7).Conclusions.The 64-MDCT scanner diagnostic performance for coronary CT angiography is further improved with better spatial and temporal resolution and faster scan times; besides, initial clinical results are promising. The use of dose-reducing acquisition techniques is mandatory to limit radiation exposure to the patient.

Imaging non invasivo delle arterie coronarie con TC spirale a 64 strati: Esperienza clinica iniziale e considerazioni dosimetriche

Purpose.We present our initial clinical experience with a recently introduced 64-detector computed tomography (64-MDCT) scanner that makes use of a periodic motion of the focal spot in the longitudinal direction (z-flying focal spot), which enables it to reach a final spatial resolution of 0.4×0.4×0.4 mm3 and a temporal resolution of 83 ms.Materials and methods.A total of 114 patients (108 men, six women; age range 36–77 years, mean 63.1 years) underwent retrospective electrocardiogram (ECG)-gated examination of the coronary arteries using a 64-MDCT scanner (Somatom Sensation 64, Siemens Medical Solutions, Germany). Acquisition parameters were the following: collimation 64×0.6 mm, 800 quality reference milliampere second (mAs), 120 kVp, 0.33-s gantry rotation time and pitch 0.2. Images were acquired in all cases after i.v. administration of 80 ml of contrast agent (Iomeron 400 mgI/dl, Bracco, Italy) + 30 ml of saline at 4 /s and delay time determined using a bolus triggering technique. Oral betablockers were administered to patients with heart rate (HR) >75 bpm. To reduce radiation exposure, an automatic exposure control system was applied in all cases to adapt tube current to patient size and anatomic shape (CARE Dose 4D, Siemens Medical Solutions, Germany). The optimal temporal window for raw data reconstruction was chosen from an initial preview of images reconstructed with different phase settings (range 0%–95% RR interval with 5% gap) at a selected anatomical level in the mid part of the right coronary artery. CT dose index volume and effective dose were quantified in all patients using dedicated software.Results.Mean HR recorded during image acquisition was 65.6±19.2 bmp (range: 44–96 bmp), and beta-blockers were administered to 16/114 patients (14.0%). Technical adequacy was achieved in all patients but two (2/114; 1.7%). In patients with HR <60 bmp, the best reconstruction intervals were identified in the end-systolic (30%–35% of the RR interval) and end-diastolic (60%–65% of the RR interval) phases; with faster HR (>80 bmp), high image quality was observed in end-systole (30%–35% of the RR interval). Mean CT dose index (CTDI) volume was 36.53±8.30 mGy per patient. In comparison with a conventional examination with fixed mAs, the use of the CARE Dose 4D system provided a 33.3% CTDI volume reduction (p<0.001). Mean effective dose was 9.5±3.4 millisievert (mSv) per patient (range 7.1–17.7).Conclusions.The 64-MDCT scanner diagnostic performance for coronary CT angiography is further improved with better spatial and temporal resolution and faster scan times; besides, initial clinical results are promising. The use of dose-reducing acquisition techniques is mandatory to limit radiation exposure to the patient.

Volumetric evaluation of therapy response in patients with lung metastases. Preliminary results with a computer system (CAD) and comparison with unidimensional measurements@@@Valutazione volumetrica della risposta alla terapia in pazienti con metastasi polmonari. Prime esperienze con un sistema di misurazione computerizzato (CAD) e confronto con misurazioni unidimensionali

Purpose.The aim of this study was to assess the efficacy of a Computer–Aided Detection (CAD) system in the identification of lung metastases and to compare the volumetric CAD measurements with unidimensional observer measurements in the evaluation of treatment response in oncology patients.Materials and methods.Two observers (A and B) evaluated nine patients undergoing lung computed tomography (CT) just before and immediately after treatment with chemotherapy. Multislice CT scans were performed before and after the injection of contrast material with a high–resolution protocol (collimation 4x1 mm, 100 mAs, 120 kV). Response Evaluation Criteria in Solid Tumours (RECIST) criteria were used to consider the disease as stable, increased or decreased. Subsequently, target lesions (most significant lesions identified before and after chemotherapy) were evaluated with a computerised system (CAD) to establish volumetric measurements. Observers’ unidimensional measurements and CAD volumetric measurements were analysed for comparison.Results.Twenty–four nodules (diameter: 5–18 mm in the first study and 4–20 mm in the follow–up study) were included. Observers agreed in the assessment of therapy response in 21 nodules: eight were considered to have increased in size, and 13 were judged stable. Observer and CAD measurements disagreed in three nodules: two were considered stable by radiologists and increased by CAD; one was considered increased by radiologists and stable by CAD.As regards patient response, radiologists disagreed in two cases. CAD and observers did not agree in one case.Conclusions.Our preliminary data suggest that volumetric measurements can modify the diagnostic and therapeutic evaluation of oncology patients under chemotherapy.CAD volumetric measurements allow an easy and objective evaluation, reducing interobserver variability in the evaluation of chemotherapy response.

Valutazione volumetrica della risposta alla terapia in pazienti con metastasi polmonari. Prime esperienze con un sistema di misurazione computerizzato (CAD) e confronto con misurazioni unidimensionali

Purpose.The aim of this study was to assess the efficacy of a Computer–Aided Detection (CAD) system in the identification of lung metastases and to compare the volumetric CAD measurements with unidimensional observer measurements in the evaluation of treatment response in oncology patients.Materials and methods.Two observers (A and B) evaluated nine patients undergoing lung computed tomography (CT) just before and immediately after treatment with chemotherapy. Multislice CT scans were performed before and after the injection of contrast material with a high–resolution protocol (collimation 4x1 mm, 100 mAs, 120 kV). Response Evaluation Criteria in Solid Tumours (RECIST) criteria were used to consider the disease as stable, increased or decreased. Subsequently, target lesions (most significant lesions identified before and after chemotherapy) were evaluated with a computerised system (CAD) to establish volumetric measurements. Observers’ unidimensional measurements and CAD volumetric measurements were analysed for comparison.Results.Twenty–four nodules (diameter: 5–18 mm in the first study and 4–20 mm in the follow–up study) were included. Observers agreed in the assessment of therapy response in 21 nodules: eight were considered to have increased in size, and 13 were judged stable. Observer and CAD measurements disagreed in three nodules: two were considered stable by radiologists and increased by CAD; one was considered increased by radiologists and stable by CAD.As regards patient response, radiologists disagreed in two cases. CAD and observers did not agree in one case.Conclusions.Our preliminary data suggest that volumetric measurements can modify the diagnostic and therapeutic evaluation of oncology patients under chemotherapy.CAD volumetric measurements allow an easy and objective evaluation, reducing interobserver variability in the evaluation of chemotherapy response.