Multi-detector Row Computed Tomography Systems Research Articles

Effective Dose Measurements of the Latest-Generation Angiographic System in Patients with Acute Stroke: A Comparison with the Newest Multidetector CT Generation.

Patients with acute ischemic stroke are increasingly triaged with one-stop management approaches, resulting in baseline imaging with a flat detector CT scanner. This study aimed to estimate the effective dose to a patient of a novel cervical and intracranial flat detector CT angiography and a flat detector CT perfusion protocol and to compare it with the effective dose of analogous multidetector row CT protocols. We estimated the effective dose to the patient according to the International Commission on Radiological Protection 103 using an anthropomorphic phantom with metal oxide semiconductor field effect transistor dosimeters. Placement was according to the organ map provided by the phantom manufacturer. We used 100 measurement points within the phantom, and 18 metal oxide semiconductor field effect transistor dosimeters were placed on the surface of the phantom. All protocols followed the manufacturer's specifications, and patient positioning and collimation were performed as in routine clinical practice. Measurements were obtained on the latest-generation angiography and multidetector row CT systems with identical placement of the metal oxide semiconductor field effect transistor dosimeters. The estimated effective doses of the investigated perfusion protocols were 4.52 mSv (flat detector CT perfusion without collimation), 2.88 mSv (flat detector CT perfusion with collimation), and 2.17 mSv (multidetector row CT perfusion). A novel protocol called portrait flat detector CT angiography that has a z-axis coverage area comparable with that of multidetector row CT angiography had an estimated effective dose of 0.91 mSv, while the dose from multidetector row CT was 1.35 mSv. The estimated effective dose to the patient for flat detector CT perfusion and angiography on a modern biplane angiography system does not deviate substantially from that of analogous multidetector row CT protocols.

Scientific Research Group Report: Nationwide Survey on Radiation Exposure of Pediatric CT Examination in Japan (2018)

To understand the latest pediatric computed tomography (CT) exposure required for the revision of national DRLs. A questionnaire was sent to 409 facilities where the members of the Japanese Society of Radiological Technology and the Japanese Society of Pediatric Radiology are enrolled. We investigated the imaging conditions, CTDIvol, and DLP of the pediatric head, chest, and abdominal CT examinations. In all, 43 facilities (11%) responded to our survey. multi detector-row CT (MDCT) systems were available in all surveyed facilities. More than 98% of the MDCT systems had more than 64 detector rows. The CTDIvol of all CT protocols was lower than the NDRL due to the progress of updating to MDCTs with radiation exposure reduction functions such as an iterative reconstruction, but the DLP of head and abdominal CT protocols of some age group were higher than NDRL. It is necessary to review the imaging protocol with the attending physician and radiologist and consider further optimization of medical exposure.

Radiation Dose and Image Quality Assessment of the Bolus Timing Method for CT Angiography

Background: Bolus timing monitoring scans used for computed tomography angiography (CTA) repetitively expose the same region of the body to radiation with a view to determining the appropriate threshold attenuation level of the contrast material (CM). Therefore, for an effective CT scan, it is necessary to minimize repetitive radiation exposures from bolus timing. Objectives: This study aims to effectively identify and reduce the radiation dose needed for repetitive monitoring scans utilized in CT involving the bolus timing method. Patients and Methods: To investigate the currently employed protocols and the number of monitoring scans in bolus timing CT studies, 983 patients (581 males and 402 females; mean age 62.7) were retrospectively analyzed from October 1, 2013 to March 31, 2014. To identify the appropriate kVp and mA change in the hounsfield unit (HU) and measure the contrast-to-noise ratio (CNR) and the signal-to-noise ratio (SNR) in the bolus timing method, a 2 mL syringe containing CM diluted with saline at a ratio of 1 to 300 was inserted into cavities of a CT dose index (CTDI) head phantom and scanned with a 64-section multi-detector row CT system. The dose variation was analyzed using results from the ionization chamber and CTDI. Results: This retrospective analysis of bolus-timing CT studies found that patients underwent an average of 4.5 to 5.4 monitoring scans. Furthermore, while the HU value of the mixed CM syringe in the central CTDI head phantom cavity was inversely proportional to mA, the decrease in the HU value became weaker at a value of 50 mA with 100 kVp and at 30 mA with 120 kVp. Here, the CNR (Pearson correlation r = 0.983, Kendall’s t = 0.978, P < 0.000) became slightly higher with an increase in mA at 100 kVp compared to 120 kVp, whereas the SNR (Pearson correlation r = 0.997, Kendall’s t = 1.0, P < 0.000) became similar to 100 kVp. Conclusion: It is recommended that minimum level of radiation (100 kVp, 50 mA; 120 kVp, 30 mA) at which the HU value at the trigger threshold is not significantly different from that of the actual helical scans should be used to minimize the radiation dose caused by repetitive monitoring scans in the bolus timing method.

SU‐E‐I‐49: Influence of the Phantom Length in Computed Tomography Dose Profile Dosimetry

Purpose: We measured the computed tomography (CT) dose profile with CT dose phantom for several X‐ray beam widths on 64‐slice, and 320‐slice multi detector‐row CT (MDCT) using micro ionization chamber, and assessed the association of the CTDI100 value with CT dose phantom length. Methods: The CT dose profile (CTDP) was measured as Dm using radiation monitor (Model 9015, Radcal, Monrovia, CA) with micro ionization chamber (10X5‐0.18, Radcal, Monrovia, CA) which have an active length of 19 mm and a 0.18 cm3 active area on 64‐slice MDCT (Aquilion CX, Toshiba Medical Systems, Tochigi, Japan), and 320‐slice MDCT (Aquilion One, Toshiba Medical Systems, Tochigi, Japan). The MDCT systems were used with a tube voltage of 120 kV, tube current of 100 mA, rotation time of 1 second, and nominal X‐ray beam widths of 4, 12, 32, and 160 mm (4*1 mm, 4*3 mm, 64*0.5 mm, and 320*0.5 mm axial slice acquisitions, respectively). A micro ionization chamber was placed in the center of the single CT dose phantom, and we acquired several axial scans as 5 mm increments of phantom length. Then two, and three coupled dose phantom were placed together to simulate a 300‐mm‐long, and 450‐mm‐long phantom. We acquired several axial scans in similar method. Results: The observed percent increase of the Dm with extended length from 150 mm to 300 mm of the CT dose phantom was 120 % at range from −60 to 60 mm. However, it was greatly increased toward peripheral area of the DP. With extended length from 300 mm to 450 mm of CT dose phantom, the observed percent increase of the Dm was slightly increased. There was no difference in the form of the CTDP between 300‐mm‐long phantom and 450‐mm‐long phantom. Conclusion: In upward of the 300‐mm‐long CT dose phantom, there is no difference in the form of the CTDP.

Two cases of absence of the celiac trunk highlighted using MDCT angiography

Usually the celiac trunk divides into three branches: left gastric artery, common hepatic artery, and splenic artery. The anatomical variations of the branching pattern are quite common. On a series of 1,500 cases examined by multidetector‐row computed tomography (MDCT) (64‐slice MDCT system; SOMATOM Sensation, Siemens Medical Solutions, Forchheim, Germany), we highlighted two cases of absence of the celiac trunk. The left gastric, splenic, and common hepatic arteries arising independently from the abdominal aorta. This anatomical variation of the unpaired branches of the abdominal aorta are due to developmental changes in the ventral segmental arteries. Knowledge of the anatomical variations of the celiac trunk is essential for clinical practice.

Bronchoscopy versus multi-detector computed tomography in the diagnosis of congenital vascular ring

Vascular rings are congenital vascular anomalies of the aortic arch complex which cause compression of the trachea and/or oesophagus. A variety of investigations may lead to diagnosis of these anomalies, including bronchoscopy and computed tomography. During the latter, image acquisition and processing use the multi-detector row technique and new reconstruction algorithms, producing high-resolution images which can be visualised as complex, three-dimensional renditions. This study aimed to assess and compare the roles of bronchoscopy and multi-detector row computed tomography in the diagnosis of congenital vascular ring. We included infants and children below the age of 16 years who presented with congenital vascular ring. All patients underwent rigid bronchoscopy under general anaesthesia, with spontaneous respiration. All computed tomography scans were obtained using a 16 multi-detector row computed tomography system, followed by data reconstruction on a three-dimensional workstation. Ten patients with congenital vascular ring were identified (six boys and four girls). Fifty per cent of cases presented within the first year of life. Double aortic arch was the most common anomaly (40 per cent). Bronchoscopy detected external tracheal compression in nine cases (90 per cent). Associated airway lesions were detected endoscopically in three cases. In contrast, multi-detector row computed tomography detected the vascular ring in all cases, with accurate detection of the compressing vessel; however, it did not detect any associated airway lesions. Bronchoscopy and radiological evaluation are essential for the diagnosis and pre-operative evaluation of congenital vascular ring. Multi-detector row computed tomography can provide more information about the nature of the disease, and can facilitate better communication between clinicians, compared with conventional computed tomography.

P-007 Initial experience with a combined multi-detector row CT and a biplane angiography suite with a single interactive table for the evaluation and treatment of vascular disease involving the head and neck

Introduction and purposeThe purpose of this study is to present our initial experience with the usefulness of a combined multi-detector row CT and biplane angiographic system with a single interactive...

Pushing the Envelope

Multidetector row computed tomography (MDCT) has been used for cardiothoracic imaging since the advent of 4-slice computed tomography (CT) in 1999. Available since 2004, 64-slice CT systems are currently considered a prerequisite for successfully integrating cardiothoracic CT into routine clinical algorithms. Developments are ongoing that aim to solve the remaining challenges of cardiothoracic CT. In this review article, we focus on 3 aspects that have significantly influenced the design of newer CT scanners. (1) A faster scan speed enables coverage of the cardiothoracic anatomy in shorter scan times, which is beneficial for patients with limited ability to cooperate and opens new clinical possibilities. A coveted goal for cardiac CT is a "snapshot image" of the entire heart in 1 cardiac cycle, which can be obtained by using MDCT systems with area detectors or dual-source CT systems with electrocardiogram (ECG)-triggered high-pitch spiral. (2) Techniques to reduce the radiation dose to the patient, such as ECG-controlled dose modulation, ECG-triggered sequential CT, low kV scanning, and iterative reconstruction, have gained considerable attention as a consequence of the ongoing discussion of radiation exposure by CT. (3) New developments aim to establish a role for CT in the functional imaging of the lung and of the heart beyond the mere visualization of anatomy. Evaluation of the first-pass enhancement of the myocardium, with single-energy or with dual-energy data acquisition, and cardiac perfusion examinations may have the potential to enhance the application spectrum of cardiac CT by providing the means to determine the hemodynamic relevance of coronary artery stenosis.

Sémiologie des atteintes du cœur droit en pathologie pulmonaire

Numerous respiratory disorders may be responsible for right heart dysfunction, frequently suboptimally assessed in routine clinical practice. Multidetector-row CT systems with fast scanning capabilities can acquire images of the thorax with reduced cardiac motion artifacts, enabling improved evaluation of the heart. Moreover, the introduction of fast rotation speed and dedicated cardiac reconstruction algorithms exploiting the multislice acquisition scheme of the data has opened the possibility of integrating right cardiac functional information into a diagnostic CT scan of the chest, without or with ECG gating.

Ultra-low-dose computed tomography system with a flat panel detector: assessment of radiation dose reduction and spatial and low contrast resolution

The aim of this study was to introduce a prototype cone-beam computed tomography system equipped with a flat panel detector (FPD-CT system) and measure its radiation dose and spatial and lowcontrast resolution. A patient was rotated in a sitting position, and cone beam data were acquired with the flat panel detector from a fixed X-ray tube. Absorbed dose, spatial and low-contrast resolution, and variation in the CT attenuation value were assessed quantitatively in the acrylic phantom. The visibility of normal blood vessels in clinical images of seven patients was analyzed qualitatively by five board-certified radiologists. These quantitative and qualitative data were compared between the FPD-CT system and multidetector row CT (MDCT). Minimal low-contrast sensitivity and a moderate spatial resolution were demonstrated in images of central lung fields acquired by FPD-CT. The absorbed dose in the FPD-CT system decreased to approximately 2.5% of the dose in the MDCT system. Considering crossover structures in normal blood vessels and bronchi in the central areas of lung fields, this result implies that fairly acceptable spatial resolution can be realized with FPD-CT for detection and frequent follow-up of pulmonary abnormalities in the central lung fields.

Integrated assessment of coronary anatomy and myocardial perfusion using a retractable SPECT camera combined with 64-slice CT: initial experience

We evaluated a prototype SPECT system integrated with multidetector row CT (MDCT) for obtaining complementary information on coronary anatomy and hemodynamic lesion significance. Twenty-five consecutive patients with known or suspected coronary artery disease (CAD) underwent routine SPECT myocardial perfusion imaging (MPI). All patients also underwent repeat MPI with a mobile SPECT unit which could be attached to a 64-slice MDCT system. Coronary CT angiography (cCTA) was performed without repositioning the patient. Investigational MPI was compared with routine MPI for detection of myocardial perfusion defects (PD). Two observers diagnosed presence or absence of CAD based on MPI alone, cCTA alone, and based on combined MPI and cCTA with fused image display. In 22/24 patients investigative MPI corresponded with routine MPI (r = 0.80). Stenosis >or= 50% at cCTA was detected in 6/24 patients. Six out of 24 patients had PD at regular MPI. Three of these six patients had no significant stenosis at cCTA. Three out of 19 patients with normal MPI studies had significant stenosis at cCTA. Our initial experience indicates that the integration of SPECT MPI with cCTA is technically feasible and enables the comprehensive evaluation of coronary artery anatomy and myocardial perfusion with a single instrumental setup.

Technical principles of dual source CT

During the past years, multi-detector row CT (MDCT) has evolved into clinical practice with a rapid increase of the number of detector slices. Today's 64 slice CT systems allow whole-body examinations with sub-millimeter resolution in short scan times. As an alternative to adding even more detector slices, we describe the system concept and design of a CT scanner with two X-ray tubes and two detectors (mounted on a CT gantry with a mechanical offset of 90°) that has the potential to overcome limitations of conventional MDCT systems, such as temporal resolution for cardiac imaging. A dual source CT (DSCT) scanner provides temporal resolution equivalent to a quarter of the gantry rotation time, independent of the patient's heart rate (83 ms at 0.33 s rotation time). In addition to the benefits for cardiac scanning, it allows to go beyond conventional CT imaging by obtaining dual energy information if the two tubes are operated at different voltages. Furthermore, we discuss how both acquisition systems can be used to add the power reserve of two X-ray tubes for long scan ranges and obese patients. Finally, future advances of DSCT are highlighted.

Preoperative assessment of hilar cholangiocarcinoma using multidetector-row CT: correlation with histopathological findings

Our aim was to investigate the diagnostic reliability of multidetector-row computed tomography (MDCT) for preoperative assessment of local tumoral spread in hilar cholangiocarcinoma. MATEIRALS AND METHODS: Thirteen of 30 consecutive patients with hilar cholangiocarcinoma who underwent surgery, excluding 17 patients who underwent biliary drainage or preoperative portal embolization, were retrospectively evaluated. Using MDCT systems of 4 detector rows or 16 detector rows, plain and dynamic contrast-enhanced images of three phases were obtained. Extent of tumor spread and lymph node metastasis were assessed with MDCT and compared with histopathological findings. The Bismuth-Corlette classification of hilar cholangiocarcinoma with MDCT were type I, 1 patient; type IIIa, 3 patients; type IIIb, 4 patients; and type IV, 5 patients; those with histopathological findings were type I, 1 patient; type IIIa, 2 patients; type IIIb, 4 patients; and type IV, 6 patients. One patient diagnosed as type IIIa with MDCT was pathologically diagnosed as type IV. Accuracy of MDCT in tumoral spread was 92.3%, although that of lymph node metastasis was 54%. MDCT is likely to play an important role in evaluation of focal lesion spread especially in intrapancreatic tumor invasion, although a greater number of cohort cases are necessary to clearly define its role.

Artefact misinterpretation on CT images of the head

In most radiology departments, axial computed tomography (CT) is the standard acquisition mode for routine head examinations. Historically, this practice involved the use of singledetector row machines, and has persisted even with the advent of helical and multidetector row CT systems. Artefacts seen using multidetector row CT systems have been shown to be substantially fewer than a single-detector row machines, and those that were identified were associated with helical scanning. However, artefacts can be seen if the axial scanning mode is used on a multidetector row CT system when one of the detector rows is faulty. It is important for radiologists, CT radiographers, and physicists to be aware of these as they can mimic disease and cause misinterpretation. We report the cases of three patients who underwent emergency head CT examinations that showed artefacts misinterpreted initially as pathological lesions by the radiologist, necessitating further investigations. Although there has been a report of an unknown substance on the collimator assembly causing hypoattenuating artefacts, prior to the present series, there have been no reports of contrast medium spill on the detector and optic assembly causing artefacts.

The reliability of computed tomography (CT) values and dimensional measurements of the oropharyngeal region using cone beam CT: comparison with multidetector CT

To evaluate the reliability of cone beam CT (CBCT) values and dimensional measurements of oropharyngeal air spaces as compared with those of multidetector row CT (MDCT). A soft tissue equivalent phantom with different sized holes was used. The phantom was scanned using CBCT and MDCT. In addition, a volunteer was examined using both methods for clinical comparison. The CT data were retrieved to a personal computer and treated using image processing software for three-dimensional rendering and dimensional measurements. The CT values of air, water and soft tissues were measured experimentally and the CT values of air, fat and muscle were measured in a clinical case. The diameter of each hole drilled in the phantom was measured on CBCT and MDCT images using the software tool and digimatic callipers. The CBCT values were quite different from the Hounsfield units obtained with a typical MDCT system. The standard deviations were almost ten times larger with CBCT. In vivo assessment showed that the CBCT values for fat had a wide range that partially overlapped the values for muscle. The measurement of distances greater than 4 mm was consistent for all methods. The difference for holes was less than 0.2 mm. The phantom study showed that CBCT provides limited quantitative CT values for each pixel on sliced images for differentiating air, water and soft tissues. However, the measurement of air spaces with CBCT was quite accurate.

WE-D-332-01: Advances in Sub-Second CT Scanning with a 64-Row Amorphous Silicon Flat Panel Imager

Purpose: To increase the data acquisition speed and detection limits of amorphous silicon flat panels for use in a low cost multidetector‐row CT (MDCT) scanner with diagnostic image quality. Method and Materials: A bench‐top sub‐second flat panel (FP) multidetector‐row CTsystem has been developed using three 64‐row FP detectors. Each FP is 30 cm × 3.3 cm in active area with 576 × 64 pixels that are 0.52 mm per side. A high degree of parallel processing is used to speed the data acquisition from the panels. Dynamic gain operation of the ASIC readout amplifiers has been used to improve noise performance over the previous fixed gain mode. The system has been tested with various detachable scintillators and scans of performance and anthropomorphic phantoms are compared with their diagnostic MDCT scans. Results: The 64‐row FP MDCT system can achieve full rotation 660 projection scans in 1 seconds. A 0.3 second partial rotation scan can be achieved with 32 rows by row binning. The image quality of 20 cm diameter performance phantom scans is comparable to a commercial MDCT scanner with similar technique/dose. Medium sized body scans are nearly comparable except for slight artifacts due to panel overlaps and lag. Large body phantom scans have improved with increased dynamic range provided by the readout ASICs dynamic gain mode. Conclusion: The results indicate the potential for FP MDCT to be used as a less expensive and less complex alternative to crystalline silicon detectors on MDCT scanners. There is pressure to increase the number of MDCT rows beyond 64 in cardiac imaging to achieve single organ coverage in one scan rotation. The use of larger area FP detectors to achieve greater than 256 rows exists and the sub second speed can be achieved with compensations and a high degree of parallel processing.

SU‐FF‐I‐31: Sub‐Second CT Scanner with a 64‐Row Amorphous Silicon Flat Panel

Purpose: To increase the data acquisition speed and detection limits of amorphous silicon flat panels for use in a low cost multidetector‐row CT (MDCT) scanner with diagnostic image quality. Methods and Materials: A bench‐top sub‐second flat panel (FP) multidetector‐row CT system has been developed using three 64‐row FP detectors. Each FP is 30 cm × 3.3 cm in active area with 576 × 64 pixels that are 0.52 mm per side. A high degree of parallel processing is used to speed the data acquisition from the panels. The FPs are overlapped slightly enabling a scan diameter of 50 cm and slice volumes up to 20 mm. The system has been tested with various detachable scintillators and scans of performance and anthropomorphic phantoms are compared with their diagnostic MDCT scans. Results: The FP MDCT system can achieve full rotation 600 projection scans in 0.5 seconds with 32 rows and 0.6 second partial rotation scans with 64 rows. The image quality of 20 cm diameter performance phantom scans is comparable to a commercial MDCT scanner with similar technique/dose. Medium sized body scans are nearly comparable except for artifacts due to the panel overlaps and lag. Thus far, large body phantom scans are less comparable due to the additional dynamic range requirement, which are not optimized with the current ASIC amplifiers. Conclusion: The results indicate the potential for FP MDCT to be used as a less expensive and less complex alternative to crystalline silicon detectors on MDCT scanners. There is pressure to increase the number of MDCT rows beyond 64 in cardiac imaging to achieve single organ coverage in one scan rotation. The use of larger area FP detectors to achieve greater than 256 rows exists and the sub second speed can be achieved with compensations and a high degree of parallel processing.

Dose Reduction in CT while Maintaining Diagnostic Confidence: Diagnostic Reference Levels at Routine Head, Chest, and Abdominal CT—IAEA-coordinated Research Project

To measure radiation doses for computed tomography (CT) of the head, chest, and abdomen and compare them with the diagnostic reference levels, as part of the International Atomic Energy Agency Research coordination project. The local ethics committees of all participating institutions approved the study protocol. Written informed consent was obtained from all patients. All scanners were helical single-section or multi-detector row CT systems. Six hundred thirty-three patients undergoing head (n = 97), chest (n = 243), or abdominal (n = 293) CT were included. Collected data included patient height, weight, sex, and age; tube voltage and tube current-time product settings; pitch; section thickness; number of sections; weighted or volumetric CT dose index; and dose-length product (DLP). The effective dose was also estimated and served as collective dose estimation data. Mean volumetric CT dose index and DLP values were below the European diagnostic reference levels: 39 mGy and 544 mGy . cm, respectively, at head CT; 9.3 mGy and 348 mGy . cm, respectively, at chest CT; and 10.4 mGy and 549 mGy . cm, respectively, at abdominal CT. Estimated effective doses were 1.2, 5.9, and 8.2 mSv, respectively. Comparison of CT results with diagnostic reference levels revealed the need for revisions, partly because the newer scanners have improved technology that facilitates lower patient doses.

Multi–Detector Row CT Systems and Image-Reconstruction Techniques

The introduction in 1998 of multi-detector row computed tomography (CT) by the major CT vendors was a milestone with regard to increased scan speed, improved z-axis spatial resolution, and better utilization of the available x-ray power. In this review, the general technical principles of multi-detector row CT are reviewed as they apply to the established four- and eight-section systems, the most recent 16-section scanners, and future generations of multi-detector row CT systems. Clinical examples are used to demonstrate both the potential and the limitations of the different scanner types. When necessary, standard single-section CT is referred to as a common basis and starting point for further developments. Another focus is the increasingly important topic of patient radiation exposure, successful dose management, and strategies for dose reduction. Finally, the evolutionary steps from traditional single-section spiral image-reconstruction algorithms to the most recent approaches toward multisection spiral reconstruction are traced.

Three-dimensional treatment planning using electrocardiographically gated multi-detector row CT

Purpose Information concerning the amount and nature of target motion is essential for the determination of internal margin size. However, there are few published reports outlining the motion with heart and aortic pulsation. We introduce a method for three-dimensional radiation treatment planning (3D-RTP) by using electrocardiographically (ECG) gated spiral scanning with a four-section CT system. We describe a new approach to visualize internal organ motion resulting from cardiac motion with ECG gated multidetector row CT. Methods and materials Five patients with lung or liver tumors were studied with a multidetector row CT system under shallow inspiration breath-holding. With retrospective ECG gating, only data acquired within a predefined interval of the cardiac cycle are used for image reconstruction. All reconstructed image data at diastolic and systolic phases of the cardiac cycle were transferred to the 3D-RTP system. The shift of the internal organs between the cardiac cycles was evaluated. Results Cardiac contraction influences anterior thorax, pulmonary peripheral vessels, and liver position, in addition to locations near the heart. Apparent movements more than 5 mm between diastolic and systolic phases were observed in the left ventricle, right atrium, and superior vena cava. Two-phase imaging was useful for showing the movement of internal organs during cardiac contraction under breath-holding. Conclusion Spatial information using ECG-gated CT has the potential to determine the planning target volume of moving lung and liver tumors more precisely than conventional CT planning.