Mobile CT Scanner Research Articles

Technical Note: Confirming the prescribed angle of CT localizer radiographs and c-arm projection acquisitions.

Accurate CT radiograph angle is not usually important in diagnostic CT. However, there are applications in radiation oncology and interventional radiology in which the orientation of the x-ray source and detector with respect to the patient is clinically important. The authors present a method for measuring the accuracy of the tube/detector assembly with respect to the prescribed tube/detector position for CT localizer, fluoroscopic, and general radiograph imaging using diagnostic, mobile, and c-arm based CT systems. A mathematical expression relating the x-ray projection of two metal BBs is related to gantry angle. Measurement of the BBs at a prescribed gantry (i.e., c-arm) angle can be obtained and using this relation the prescribed versus actual gantry angle compared. No special service mode or proprietary information is required, only access to projection images is required. Projection images are available in CT via CT localizer radiographs and in the interventional setting via fluorography. The technique was demonstrated on two systems, a mobile CT scanner and a diagnostic CT scanner. The results confirmed a known issue with the mobile scanner and accurately described the CT localizer angle of the diagnostic system tested. This method can be used to quantify gantry angle, which is important when projection images are used for procedure guidance, such as in brachytherapy and interventional radiology applications.

Palliative Care: A Core Competency for Stroke Neurologists.

The past 2 decades have seen remarkable advances in our abilities to treat and prevent stroke. Better vascular risk factor control has led to a decrease in stroke incidence by 50% since the early 90s.1 Improvements in acute stroke care, especially at specialized centers, have led to a decline in overall stroke mortality. Over the past decade, stroke death rate in the United States decreased by one third, and stroke has moved from the third to the fifth leading cause of mortality.2 If a patient with an acute ischemic stroke presents early enough to the hospital, systems should be in place to appropriately administer tissue-type plasminogen activator within less than an hour of arrival, thereby often doubling their chances of achieving future independence.3,4 Some patients may continue on to the angio-suite for mechanical clot retrieval; those who do are twice more likely to be independent at 3 months.5–7 Despite these remarkable advances, only around 5% to 7% of patients with acute ischemic stroke receive tissue-type plasminogen activator.8,9 Mechanical thrombectomy is reserved for an even smaller proportion. Although community education may increase the proportion of patients calling for help sooner10 and mobile CT scanners and prehospital treatment may shorten the time and increase the proportion of patients receiving tissue-type plasminogen activator,11 for most patients, stroke remains disabling and often deadly. For these reasons, palliative care remains an important part of the stroke care that we deliver, especially for patients with severe stroke. Here we provide a contemporary review of the literature and offer some recommendations on how stroke providers may integrate palliative care into the care of their patients with severe ischemic or hemorrhagic stroke, focusing on early interactions. Stroke palliative care is fundamental to high-quality stroke care …

Dosimetric characterization and image quality evaluation of the AIRO mobile CT scanner.

Radiation dose and image quality from a recently introduced mobile CT imaging system are presented. Radiation dose was measured using a conventional 100 mm pencil ionization chamber and CT polymethylmetacrylate (PMMA) body and head phantoms. Image quality was evaluated with a CATPHAN 500 phantom. Spatial resolution, low contrast resolution, Modulation Transfer Function (MTF), and Normalized Noise Power Spectrum (NNPS) were analyzed. Radiation dose and image quality were compared to those from a multi-detector CT scanner (Siemens Sensation 64). Under identical technique factors radiation dose (mGy/mAs) from the AIRO mobile CT system (AIRO) is higher than that from a 64 slice CT scanner. Based on MTF analysis, both Soft and Standard filters of the AIRO system lost resolution quickly compared to the Sensation 64 slice CT. The Siemens scanner had up to 7 lp/cm for the head FOV and H40 kernel and up to 5 lp/cm at body FOV for the B40f kernel. The Standard kernel in the AIRO system was evaluated to have 3 lp/cm and 4 lp/cm for the body and head FOVs respectively. NNPS of the AIRO shows low frequency noise due to ring-like artifacts which may be caused by detector calibration or lack of artifact reducing image post-processing. Due to a higher dose in terms of mGy/mAs at both head and body FOV, the contrast to noise ratio is higher in the AIRO system than in the Siemens scanner. However detectability of the low contrast objects is poorer in the AIRO due to the presence of ring artifacts in the location of the targets.

SU‐E‐I‐21: Dosimetric Characterization and Image Quality Evaluation of the AIRO Mobile CT Scanner

Purpose:The AIRO Mobile CT system was recently introduced which overcomes the limitations from existing CT, CT fluoroscopy, and intraoperative O‐arm. With an integrated table and a large diameter bore, the system is suitable for cranial, spine and trauma procedures, making it a highly versatile intraoperative imaging system. This study is to investigate radiation dose and image quality of the AIRO and compared with those from a routine CT scanner.Methods:Radiation dose was measured using a conventional 100mm pencil ionization chamber and CT polymethylmetacrylate (PMMA) body and head phantoms. Image quality was evaluated with a CATPHAN 500 phantom. Spatial resolution, low contrast resolution (CNR), Modulation Transfer Function (MTF), and Normalized Noise Power Spectrum (NNPS) were analyzed.Results:Under identical technique conditions, radiation dose (mGy/mAs) from the AIRO mobile CT system (AIRO) is higher than that from a 64 slice CT scanner. MTFs show that both Soft and Standard filters of the AIRO system lost resolution quickly compared to the Sensation 64 slice CT. With the Standard kernel, the spatial resolutions of the AIRO system are 3lp/cm and 4lp/cm for the body and head FOVs, respectively. NNPSs show low frequency noise due to ring‐like artifacts. Due to a higher dose in terms of mGy/mAs at both head and body FOV, CNR of the AIRO system is higher than that of the Siemens scanner. However detectability of the low contrast objects is poorer in the AIRO due to the presence of ring artifacts in the location of the targets.Conclusion:For image guided surgery applications, the AIRO has some advantages over a routine CT scanner due to its versatility, large bore size, and acceptable image quality. Our evaluation of the physical performance helps its future improvements.

TU‐E‐110‐04: Tetrahedron Beam Computed Tomography

Purpose: The image quality of cone beam CT (CBCT) is significantly inferior to that of diagnostic CT systems. The major problems of CBCT systems include excessive scatter, inferior detector performance, data truncation and approximate cone reconstruction. Its inferior image quality hinders the implementation of advanced IGRT treatment techniques, such as online and offline adaptive radiation treatment (ART). We are developing a novel tetrahedron beam computed tomography (TBCT) system which can significantly improve online image quality, thereby increasing the precision of radiation treatments.Method: A multiple pixel x‐ray source may allow novel imaging systems with improved image quality, reduced x‐ray exposure and lower cost. With a single rotation, the volumes enclosed by a cone (pyramid) and tetrahedron are exactly the same. Hence a volumetric CT scan can also be achieved by rotating a tetrahedron, which is formed by a linear x‐ray source array and a linear detector array orthogonal to each other. In TBCT, scatter photons are mostly rejected thanks to the fan beam geometry. Image quality is further improved by the use of a high quality solid‐state CT detector. Approximate FDK cone reconstruction artifacts can be mitigated using iterative image reconstruction algorithms. Results: A TBCT benchtop system has been developed using a 75 pixel x‐ray tube and an in‐house developed CT detector array. An iterative image reconstruction algorithm has been developed. The system produced excellent CT images which are superior to that of commercial CBCT scanners and close to that of diagnostic CT scanners.Conclusion: TBCT is able to produce image quality close to that of diagnostic CT scanners. Clinical implementation of TBCT in IGRT can improve the precision of radiation treatments. Due to its superior image quality and compact geometry, c‐arm TBCT can also possibly be used as low‐cost, mobile diagnostic CT scanners.

SU‐C‐301‐04: Development of Iterative Image Reconstruction Algorithm for TBCT System

Purpose: Tetrahedron Beam Computed Tomography (TBCT) circumvents some problems of cone beam CT (CBCT) but still shares the same approximate reconstruction artifact with FDK algorithm. Recently, iterative image reconstruction has been widely employed in diagnostic CT scanners in order to suppress noise and reduce imaging dose. In this study we developed an iterative TBCT image reconstruction algorithm which is able to mitigate the cone beam reconstruction artifact as well as reduce image noise. Methods: Simultaneous algebraic reconstruction technique (SART) image reconstruction algorithms were developed based on our TBCT benchtop geometry. The algorithms were tested using both numerical and physical phantoms. The projection matrix was calculated using a distance driven method. Noise levels in reconstructed images were quantified. The approximate image reconstruction artifact at larger cone angle was evaluated. Results: With the same numerical and real scanned projection data, SART algorithm produces similar spatial resolution as the FDK algorithm. The cone artifact was significantly reduced as compared with FDK algorithm. The noise levels were reduced 16–20% by the iterative algorithm at different regions of the images. Conclusions: Iterative reconstruction algorithm further improves the image quality of the TBCT system. TBCT system with SART image reconstruction algorithm potentially may be used as a mobile CT scanner for diagnostics.This work is partially supported by NIH grant 1R21CA130330‐01A1 and DOD Prostate Cancer Research Program W81XWH‐07‐0083.

Vergleich der Bildqualität zweier unterschiedlicher mobiler 3-dimensionaler Röntgen-C-Bögen mit einem konventionellen CT bei der Darstellung relevanter Strukturen am knöchernen Becken

This study evaluated the image quality of two different cone beam CT scanners used in the operation theatre in pelvic trauma surgery in relation to their radiation dosage. Furthermore, the assumption that a higher dosage would result in better image quality was analysed by using the different acquisition scanner modes. We scanned the acetabulum (n=4) and iliosacral joints (n=4) of two human cadavers with a conventional CT and with two mobile cone beam CT scanners (Siemens Arcadis Orbic 3D and Ziehm Vision Vario 3D). With the two cone beam CT scanners (3D-BV), we used 6 different acquisition modes with different radiation dosages. The axial views of all scans were exported and blinded. Subsequently, the images were evaluated by 7 medical doctors with regard to identifiability of cortical structures (acetabular joint, fovea capitis femoris, cortical bone of the femur head, iliosacral joint, and sacral foramina), and the quality of the cancellous structure of the femur head. The evaluation was performed on axial views by using a defined five-point score. The interrater quality was statistically analysed according to Cohen with the kappa coefficient. In addition, the Wilcoxon test was used to identify significances between the 21 paired results of the evaluators. For determination of the signal-to-noise ratio, a Catphan 600 reference block with two different test elements (Teflon, PMP) was used. Overall, the image quality of the conventional CT scans received the best score. Comparing the two 3D cone beams, the image quality of the Siemens Arcadis Orbic 3D in high-dosage mode received the best score (median: 2.40), the Ziehm Vision Vario 3D in low-dose mode without large patient key received the lowest score (median: 3.16). The differences in the 21 paired results of the two different acquisition modes were significant in 17 cases (p < 0.05) but the size of difference when comparing the different acquisition modes was almost always small. The interobserver agreement in one acquisition mode was low (kappa 0.008-0.134). The overall evaluation results of the same acquisition mode diverged by up to 2 score points. We noted a higher signal-to-noise ratio in the high dosage mode than in the low dosage mode. When using intraoperative 3D imaging with the cone beam CT technique for pelvic injury, image acquisition in low-dose mode is adequate in terms of signal-to-noise ratio and image quality. The image quality does not correlate linearly with a higher radiation dosage. Therefore, the pelvic trauma surgeon using this technique is encouraged to gather his own experience with low dose modes thereby reducing patient radiation exposure.

SU‐GG‐I‐11: Dose and Image Quality Evaluation of a Mobile CT Scanner for Head and Neck Imaging

Purpose: To evaluate the radiation dose delivered to patients and personnel by a mobile x‐ray CT scanner designed for bedside imaging of the head and neck, and to examine image quality under clinical conditions. Method and Materials: Computed Tomography Dose Index (CTDI) was measured using a 100 mm pencil ionization chamber and 16 cm diameter acrylic phantom over a range of acquisition parameters on a mobile CT scanner (Neurologica Ceretom, Danvers, MA). Scatter radiation was measured using the same phantom. Image quality was evaluated using the manufacturer's QA phantom and the common CATPHAN phantom. Results: At 120 kVp, CTDI‐100 measured 44.8, 83.5, and 122 mGy at 7 mA and 2, 4, and 6 seconds per rotation, respectively. At 140 kVp, commonly used for head scanning, the CTDI‐100 measured 65.3, 126.8, and 176.3 mGy at 7 mA and 2, 4, and 6 seconds per rotation, respectively. All measured doses were within 10% of the CTDI values indicated to the operator on the scanner's console. Using protective lead curtains provided with the scanner, scatter radiation was well within ALARA standards. CATPHAN images demonstrated acceptable alignment, slice width and incrementation accuracy, geometric accuracy, low contrast resolution, high contrast spatial resolution, image uniformity and CT number linearity at clinical techniques. Conclusion: When operated in “low dose” (2 seconds/rotation) mode, the radiation dose delivered by the mobile CT scanner is below or comparable to the ACR's diagnostic Reference Value (RV) for head CT dose. The “standard” (4 seconds/rotation) and “high‐quality” (6 seconds/rotation) modes deliver more radiation, with a corresponding increase in image quality. Assessment using an industry‐standard phantom produced acceptable image quality performance under clinical conditions. With proper precautions, the scanner can be safely used in most intensive care environments without additional shielding, with minimal occupational exposure.

Why the private sector must not rule the NHS

Recent revelations about the scale of Government plans to give private companies effective ‘ownership’ of NHS facilities and freedom to recruit NHS staff have caused a furore – and it’s not just traditional Labour voters who are kicking up a stink. Many people, even after 8 years of New Labour government, still instinctively reject private involvement in that most valued of public services – the NHS. Despite the enormous investment into the NHS seen in recent years, there is still a huge drive to involve the private sector in everything from building hospitals to providing staff to delivering services such as mobile CT scanners. Following a leak to a national newspaper, we have evidence of the full extent of the plans – £3 billion, and up to 15% of NHS elective care will be in private hands in the next couple of years. Add to this the plans for primary care, and we have what, from any angle, looks like a semi-private NHS.

CT-gesteuerte Resektion pulmonaler Metastasen

To evaluate the feasibility and potential use of intraoperative computed tomography (IOP CT) as guidance for video-assisted thoracic surgery (VATS). Fifteen consecutive patients with peripheral intrapulmonary nodules underwent a thoracoscopy with IOP CT. Solitary lesions were known in 6/15 patients (40 %, group II) whereas 9/15 (60 %, group I) patients had multiple lesions (n >/= 2). IOP CT was performed with the mobile CT scanner Philips Tomoscan M. Radiologists intraoperatively placed percutaneous marks of lung lesions after unsuccessful VATS by use of a lung marker set (Somatex, Teltow, Germany). VATS was performed under general anaesthesia and with double lumen endotracheal intubation for single lung ventilation. Imaging quality and imaging of pulmonary nodules were rated. IOP CT was evaluated as feasible combined with VATS. Thoracotomy was avoided in 5/15 patients where lesions could not be detected by VATS. A CT-guided biopsy was performed in two patients after an unsuccessful attempt of thoracoscopy. There were no documented side effects. First clinical results suggest that a combination of VATS and IOP CT is feasible. Thus, the number of open thoracoscopies might be decreased. Intrapulmonary lesions not detectable with VATS could be marked under CT -- guidance intraoperatively and then resected by thoracoscopy.

Bedside monitoring of CBF with xenon-CT and a mobile scanner: a novel method in neurointensive care

Combining previously independently established techniques our objective was to develop and evaluate a method for bedside qualitative assessment of cerebral blood flow in neurointensive care (NICU) patients. The CT-protocol was optimized using phantoms and comparing a mobile CT-scanner (Tomoscan-M, Philips) with two stationary CT scanners. Thirty-two per cent xenon was delivered with standard equipment (Enhancer 3000). Mean cortical flow in volunteers was 48 ml/min/100 g, with the mean vascular territorial flow varying between 45 and 66 ml/min/100 g. The potential clinical usefulness was illustrated in three patients with vasospasm following subarachnoid haemorrhage. Our conclusion is that quantitative bedside measurements of CBF can be repeatedly performed in an easy and safe way in a standard NICU-setting, using xenon-inhalation and a mobile CT-scanner. The method is useful for the decision-making, and is a good example of how the quality of multi-modality monitoring in the NICU can be developed and further diversified.

Lung Cancer Screening Using Low-Dose High-Resolution CT Scanning in a High-Risk Workforce: 3,500 Nuclear Fuel Workers in Three US States

Past and present nuclear fuel workers with demonstrated or potential exposure to lung carcinogens (eg, asbestos, radiation, and/or beryllium) have been screened for early lung cancer with a low-dose (LD) mobile CT scanner at three sites in the states of Kentucky, Ohio, and Tennessee. The age the of subjects was ≥ 45 or 50 years, depending on the duration of smoking and/or occupational exposure. Those with evidence of asbestos-related disease or be sensitization were eligible at any age or with any smoking history.

Providing Optimal Radiology Service in the Severe Acute Respiratory Syndrome Outbreak: Use of Mobile CT

Severe acute respiratory syndrome (SARS) is a serious atypical pneumonia caused by a novel pathogen. We describe our experience using a mobile CT scanner in an improvised isolation ward with life-support systems, portable lead shielding, and strict barrier nursing. This scanner was used exclusively for patients with SARS and patients with other illnesses who were also thought to have SARS. This arrangement freed the other CT scanners in the main department for non-SARS patients. In 5 weeks, 90 studies were performed; no cases of cross infection of health care workers were reported. Mobile CT may be used to provide dedicated radiology services to seriously ill patients requiring strict isolation during an infectious disease outbreak.

Intraoperative computer tomography control within the scope of maxillofacial traumatology using a mobile scanner

Advances in intra-operative imaging and the development of new minimally invasive techniques are having an ever greater impact on modern surgery. Mobile CT scanners in the operating room is a new technique that permits image-guided surgery, and helps minimize postoperative complications. We report on our initial experience with intraoperative CT scanning during surgery on patients suffering lateral midface trauma. A mobile CT unit, the Tomoscan M (Philips, Utrecht, Netherlands) set up in the operating room, was evaluated in 6 patients with zygomatic bone fractures. The patients were placed on the CT scanner table, which is detachable from the gantry. The unit is powered by batteries charged from an ordinary ring mains supply via a conventional plug. The CT images obtained were of good quality in all cases. No technical problems were observed during surgery. Using repeat CT scans, the procedure also permits accurate intraoperative monitoring of the anatomical repositioning of the bone fragments, and accurate implantation. No intraoperative or early postoperative complications were observed. This new technical aid ensures highly accurate reduction of the bone fragments, and minimizes the need for reoperation. High-quality intraoperative imaging with surgical navigation increase surgical outcome, and expand the spectrum of minimally invasive surgery.

CT-directed robotic biopsy testbed: user interface and coordinate transformations

CT-guided percutaneous biopsy is a widely accepted practice in the medical field. Because efficient and safe CT-guided percutaneous interventions require accurate needle placement, there are limitations to the accuracy obtainable using free-hand techniques, particularly for small or deeply situated target areas. In addition, CT-directed percutaneous biopsy can be tedious and time consuming, since frequent re-imaging may be required. As a demonstration platform, we are developing a robotic biopsy testbed incorporating a mobile CT scanner, a small “needle driver” robot, and a localizer. This testbed will be used to compare robotically assisted biopsy to the current manual technique. The testbed will also allow us to investigate software architectures for integrating various hardware and software components. This testbed is the first step in developing the robotically assisted biopsy system of the future. In this paper, we present the overall concept and then provide details about the user interface and coordinate transformations.

Screening for Lung Cancer with a Mobile CT Scanner.

In Japan, lung cancers cause more deaths than any other cancer. Since curable early cases are hard to detect with conventional chest radiography, this