Examinations for creating an image of unacquired dose from the images of two types of dose in digital radiography.

BACKGROUND: Digital radiography (DR) is grayscale adjustable and it can be unclear whether an acquired DR image is captured with the minimum radiation dose required. It is necessary to make an image of the amount of noise when taken at a lower dose than the acquired image, without increased exposure. OBJECTIVE: To examine whether an image of unacquired dose can be created from two types of dose DR images acquired using a phantom. METHODS: To create an additive image from two images of different doses, the pixel value of one image is multiplied by a coefficient and added to the other. The normalized noise power spectra (NNPS) of the normal image and the additive image with the same signal-to-noise ratio (SNR) are compared. The image noise of the unacquired doses is estimated from the graph changes of the pixel values and standard deviations of two images. The error between the SNR of the image obtained by changing the dose and the estimated SNR is measured. We propose a multiplication coefficient calculation formula that theoretically adjusts the additive image to the target SNR. The SNR error of the image created based on this formula is measured. RESULTS: The NNPS curves of the additive and normal images show a difference on the high frequency side. According to the statistics considering the preset of mAs value, there is no significant difference at 85%. The SNR estimation error is approximately 1%. The SNR error of the additive image created based on the formula is approximately 5%. CONCLUSION: The noise of the image of unacquired dose can be estimated, and the additive image adjusted to this value can be considered equivalent to the image taken at the actual dose.

[Improvement of SNR When Adding X-ray Images with Different SNRs].

Some radiologic patient positioning techniques that can be used for X-ray examinations can be difficult to apply. One method involves using ultra-low-dose X-ray images to confirm positioning. These positioning images are typically discarded and not used for diagnosis. The purpose of this study was to improve the signal-to-noise ratio (SNR) in diagnostic imaging by including these ultra-low-dose positioning images rather than discarding them. To add two images together, we devised a method in which one image is multiplied by the coefficient calculated from its SNR before the addition. The images were dichotomized into a high SNR group and a low SNR group. The images in the high SNR group and the low SNR group were summed. When doing so, the images of the low SNR group were multiplied. There was one maximum SNR point while the SNR was being changed. The maximum SNR of the synthesized images was equal to the value of the square root of the sum of the squares of the two images. The multiplication coefficient, in the case of the maximum SNR, was near 1 when an image agreed with the Poisson distribution; when it did not, it was far from 1. The difference between the calculated values of the hypothetical measurement of the multiplication coefficient was small. In this study, we showed that improving SNR of a diagnostic image could be achieved by adding a positioning image. The multiplication coefficient in the case of the SNR maximum of a synthesized image is calculable. The measurement of a Wiener spectrum is needed for noise evaluation. There can be problems where there is motion after a positioning image is exposed.

Whole-Body Clinical Applications of Digital Tomosynthesis.

With flat-panel detector mammography, radiography, and fluoroscopy systems, digital tomosynthesis (DT) has been recently introduced as an advanced clinical application that removes overlying structures, enhances local tissue separation, and provides depth information about structures of interest by providing high-quality tomographic images. DT images are generated from projection image data, typically using filtered back-projection or iterative reconstruction. These low-dose x-ray projection images are easily and swiftly acquired over a range of angles during a single linear or arc sweep of the x-ray tube assembly. DT is advantageous in a variety of clinical contexts, including breast, chest, head and neck, orthopedic, emergency, and abdominal imaging. Specifically, compared with conventional mammography, radiography, and fluoroscopy, as a result of reduced tissue overlap DT can improve detection of breast cancer, pulmonary nodules, sinonasal mucosal thickening, and bone fractures and delineation of complex anatomic structures such as the ostiomeatal unit, atlantoaxial joint, carpal and tarsal bones, and pancreatobiliary and gastrointestinal tracts. Compared with computed tomography, DT offers reduced radiation exposure, better in-plane resolution to improve assessment of fine bony changes, and less metallic artifact, improving postoperative evaluation of patients with metallic prostheses and osteosynthesis materials. With more flexible patient positioning, DT is also useful for functional, weight-bearing, and stress tests. To optimize patient management, a comprehensive understanding of the clinical applications and limitations of whole-body DT applications is important for improvement of diagnostic quality, workflow, and cost-effectiveness. Online supplemental material is available for this article. (©)RSNA, 2016.

Much caution does no harm! Organophosphate poisoning often causes pancreatitis.

Organophosphate poisoning (OP) results in various poisoning symptoms due to its strong inhibitory effect on cholinesterase. One of the occasional complications of OP is pancreatitis. A 62-year-old woman drank alcohol and went home at midnight. After she quarreled with her husband and drank 100 ml of malathion, a parasympathomimetic organophosphate that binds irreversibly to cholinesterase, she was transported to our hospital in an ambulance. On admission, activated charcoal, magnesium citrate, and pralidoxime methiodide (PAM) were used for decontamination after gastric lavage. Abdominal computed tomography detected edema of the small intestine and colon with doubtful bowel ischemia, and acute pancreatitis was suspected. Arterial blood gas analysis revealed severe lactic acidosis. The Ranson score was 6 and the APACHE II (Acute Physiology and Chronic Health Evaluation) score was 14. Based on these findings, severe acute pancreatitis was diagnosed. One day after admission, hemodiafiltration (HDF) was started for the treatment of acute pancreatitis. On the third hospital day, OP symptoms were exacerbated, with muscarinic manifestations including bradycardia and hypersalivation and decreased plasma cholinesterase activity. Atropine was given and the symptoms improved. The patient's general condition including hemodynamic status improved. Pancreatitis was attenuated by 5 days of HDF. Ultimately, it took 14 days for acute pancreatitis to improve, and the patient discharged on hospital day 32. Generally, acute pancreatitis associated with OP is mild. In fact, one previous report showed that the influence of organophosphates on the pancreas disappears in approximately 72 hours, and complicated acute pancreatitis often improves in 4-5 days. However, it was necessary to treat pancreatitis for more than 2 weeks in this case. Therefore, organophosphate-associated pancreatitis due to malathion is more severe. Although OP sometime causes severe necrotic pancreatitis or pancreatic pseudocysts, it was thought that the present patient had a good clinical course without these complications due to the appropriate intensive care including nafamostat, antibiotics, fluid resuscitation, and HDF. In conclusion, OP-associated pancreatitis requires careful assessment because it may be aggravated, as in this case.

Dual-energy subtraction radiography improves laryngeal delineation in patients with moderate to severe cervical spondylosis.

PURPOSE: To investigate the feasibility of dual-energy subtraction (DES) in patients with moderate-severe cervical spondylosis for improving delineation of the larynx on flat panel detector (FPD) radiography. MATERIALS AND METHODS: For 118 patients, we graded conventional/DES anterior-posterior views for delineation of the vocal cords, subglottis, and pyriform sinus using a 5-point scale and lateral views from conventional laryngeal FPD radiography to determine cervical spondylosis severity on a scale from 0 (none) to 3 (severe). We compared the delineation of each anatomical structure in both groups of grades 0-1 and grades 2-3 of spondylosis severity between conventional and DES methods and the improved delineation rate for each anatomical structure by DES compared to the conventional method between both groups. RESULTS: With DES, the delineation of each anatomical structure was significantly better than with conventional radiography for both groups (P < 0.0001). The improved delineation rate of the vocal cord and subglottis using DES was significantly higher in grades 2-3 than in grades 0-1 (P < 0.05), although there was no significant difference in the delineation rate of the pyriform sinus between the groups (P = 0.847). CONCLUSION: DES provides better delineation of the laryngeal anatomy than conventional FPD radiography predominantly in patients with moderate-severe cervical spondylosis.

Detection of paranasal sinus opacification with digital tomosynthesis radiography: a clinical pilot study.

OBJECTIVE: We investigated the diagnostic accuracy of digital tomosynthesis (DT) radiography for detecting sinus opacification. METHODS: For 31 adult patients with signs suggestive of sinusitis who underwent both sinus multi-detector-row computed tomography and DT, 2 readers independently assessed opacification in the maxillary, ethmoid, frontal, and sphenoid sinuses by DT and in consensus determined the presence of opacification in each sinus by multi-detector-row computed tomography as a reference. We assessed the diagnostic accuracy of DT and interreader agreement with DT using Cohen κ statistics. RESULTS: For the maxillary, ethmoid, frontal, and sphenoid sinuses, opacification was identified in 81.7%, 75.9%, 59.3%, and 40.7%; the sensitivity/specificity for detecting opacification by DT were 93.9/72.7%, 79.5/71.4%, 93.8/72.7%, and 90.9/75.0% for reader 1 and 95.9/100.0%, 95.5/92.9%, 100.0/81.8%, and 81.8/75.0% for reader 2; the interreader agreement was 0.79, 0.42, 0.67, and 0.63, respectively. CONCLUSIONS: Digital tomosynthesis allows relatively accurate detection of sinus opacification with substantial interreader agreement for all the sinuses except the ethmoid sinuses.

Radiation dose of digital tomosynthesis for sinonasal examination: comparison with multi-detector CT.

OBJECTIVE: Using an anthropomorphic phantom, we have investigated the feasibility of digital tomosynthesis (DT) of flat-panel detector (FPD) radiography to reduce radiation dose for sinonasal examination compared to multi-detector computed tomography (MDCT). MATERIALS AND METHODS: A female Rando phantom was scanned covering frontal to maxillary sinus using the clinically routine protocol by both 64-detector CT (120 kV, 200 mAs, and 1.375-pitch) and DT radiography (80 kV, 1.0 mAs per projection, 60 projections, 40° sweep, and posterior-anterior projections). Glass dosimeters were used to measure the radiation dose to internal organs including the thyroid gland, brain, submandibular gland, and the surface dose at various sites including the eyes during those scans. We compared the radiation dose to those anatomies between both modalities. RESULTS: In DT radiography, the doses of the thyroid gland, brain, submandibular gland, skin, and eyes were 230 ± 90 µGy, 1770 ± 560 µGy, 1400 ± 80 µGy, 1160 ± 2100 µGy, and 112 ± 6 µGy, respectively. These doses were reduced to approximately 1/5, 1/8, 1/12, 1/17, and 1/290 of the respective MDCT dose. CONCLUSION: For sinonasal examinations, DT radiography enables dramatic reduction in radiation exposure and dose to the head and neck region, particularly to the lens of the eye.

Postoperative follow-up of olecranon fracture by digital tomosynthesis radiography.

Digital tomosynthesis with flat-panel detector radiography is a novel application that allows easy, swift volume data acquisition of any anatomical site of interest with arbitrary patient posture. A single sweep of the X-ray tube provides multiple tomographic images of high resolution. We present the first patient with olecranon fracture who underwent internal fixation and 1-year postoperative follow-up with tomosynthesis. The minimal metallic artifact by this modality successfully provided detailed information regarding the healing process of the fracture.

Dual-energy subtraction imaging for diagnosing vocal cord paralysis with flat panel detector radiography.

OBJECTIVE: To investigate the clinical feasibility of dual energy subtraction (DES) imaging to improve the delineation of the vocal cord and diagnostic accuracy of vocal cord paralysis as compared with the anterior-posterior view of flat panel detector (FPD) neck radiography. MATERIALS AND METHODS: For 122 consecutive patients who underwent both a flexible laryngoscopy and conventional/DES FPD radiography, three blinded readers retrospectively graded the radiographs during phonation and inspiration on a scale of 1 (poor) to 5 (excellent) for the delineation of the vocal cord, and in consensus, reviewed the diagnostic accuracy of vocal cord paralysis employing the laryngoscopy as the reference. We compared vocal cord delineation scores and accuracy of vocal cord paralysis diagnosis by both conventional and DES techniques using kappa statistics and assessing the area under the receiver operating characteristic curve (AUC). RESULTS: Vocal cord delineation scores by DES (mean, 4.2 +/- 0.4) were significantly higher than those by conventional imaging (mean, 3.3 +/- 0.5) (p < 0.0001). Sensitivity for diagnosing vocal cord paralysis by the conventional technique was 25%, whereas the specificity was 94%. Sensitivity by DES was 75%, whereas the specificity was 96%. The diagnostic accuracy by DES was significantly superior (kappa = 0.60, AUC = 0.909) to that by conventional technique (kappa = 0.18, AUC = 0.852) (p = 0.038). CONCLUSION: Dual energy subtraction is a superior method compared to the conventional FPD radiography for delineating the vocal cord and accurately diagnosing vocal cord paralysis.

Optimizing parameters for flat-panel detector digital tomosynthesis.

Digital tomosynthesis is a novel technique that allows easy and swift volume data acquisition in selected regions of the body. However, many radiologists and technologists are unfamiliar with this technique and the potential artifacts related to data acquisition. Digital tomosynthesis requires a single linear sweep of the x-ray tube assembly with corresponding tomographic reconstruction of large-area flat-panel detector radiographic data. Standard acquisition parameters include sweep angle, sweep direction, patient barrier-object distance, number of projections, and total radiation dose. Potential acquisition-related artifacts include blurring-ripple, ghost artifact-distortion, poor spatial resolution, image noise, and metallic artifact. A comprehensive understanding of the relationships between acquisition parameters and potential associated artifacts is critical to optimizing acquisition technique and avoiding misinterpretation of artifacts. Sweep direction should be chosen on the basis of the anatomy of interest and the purpose of the examination so as to reduce the influence of blurring-ripple, ghost artifact-distortion, and metallic artifact. Adjusting the sweep angle, number of projections, and radiation dose will optimize depth resolution, avoid ripple in the sections of interest, and reduce unnecessary radiation exposure without compromising image quality. Thus, it is important that the radiologist and technologist establish appropriate protocols for different examination types to allow optimal utilization of this novel imaging technique.