Use Of Digital Subtraction Research Articles

Superiority of Digital Subtraction for Analysis of Simultaneously-Acquired Dual-Radiopharmaceutical Parathyroid Scintigraphy

With dual-radiopharmaceutical (DR) parathyroid scintigraphy, imaging with 99mTcO4-or 123I-NaI is combined with 99mTc-sestamibi scintigraphy for localization of parathyroid adenomas. The set images are then either visually compared or digitally subtracted to aid in interpretation. While both EANM and SNMMI guidelines recommend use of digital subtraction over visual interpretation alone, to date, the few formal comparisons performed have not demonstrated superiority. The purpose of this investigation is to rigorously assess the added value of digital subtraction over visual interpretation alone using simultaneously-acquired 123I-NaI and 99mTc-sestamibi images. Materials: 90 consecutive patients with DR parathyroid scintigraphy for primary hyperparathyroidism who underwent successful parathyroidectomy were included. DR planar acquisition was performed 15 minutes post injection using 10% dual energy windows. Digital subtraction was subsequently performed using commercially available software. Images were independently reviewed by 3 nuclear medicine trainees and 2 experienced nuclear medicine physicians with and without digital subtraction. Results were compared with surgical and histopathologic findings, which served as ground truth. Results: 90 patients had a total of 91 confirmed parathyroid lesions. All 5 readers had significantly greater sensitivity with digital subtraction compared with visual interpretation alone while specificity was not significantly diminished. Area under the ROC curve was significantly greater with digital subtraction in 3 of 5 readers. Agreement was greater among trainees and experienced physicians when using digital subtraction. Conclusion: Using an optimized DR planar co-imaging technique, digital subtraction significantly improved inter-observer agreement and confidence of interpretation and increased sensitivity, without diminishing specificity.

Risco da exposição à radiaç ão ionizante durante procedimentos endovasculares

ObjectivesThe resource to endovascular procedures has become progressively more frequent and has increased concerns regarding the deleterious effects from radiation exposure. The purpose of this investigation is to evaluate and quantify scattered radiation exposure to which the patient and the surgical team are exposed, produced by a portable C-arm radioscopy unit during its use in the operating theatre. Material and methodsRadiation dose was measured in a controlled operating room with reproduction of usual conditions experienced during endovascular procedures in our operating theatre. A 15cm polimetilmetacrilate phantom was used as a geometrical simulation of the thorax. The scattered radiation was measured in several positions which were determined according to the usual distribution of the surgical and anesthesiological team in the room and at several heights. Radiation quantification was accomplished with resource to a portable radiation monitor RaySafe Xi Survey Detector, adjusting dose rate in mGy/s. Additionally, a RaySafe Xi R/F detector was used to measure the skin entrance exposure of the simulated patient. Readings were taken in pulsed fluoroscopy mode at a frequency of 4 frames per second (fps), digital subtraction mode and roadmap mode. The different magnifications available (Mag 1, 2 and 3) were also combined with each of these modes. In all situations, x-ray unit radiation dose was setted on level 3 which usually provides the best quality images with automatic real-time control of contrast and brightness. ResultsData analysis determined the distribution of scattered radiation among all elements of the surgical team. Maximum level of exposures was found at a height of 120cm in digital subtraction and roadmap modes. In this setting, surgical team scattered radiation exposure rates relative to patient skin entrance exposure rates were 0.47% for the surgeon, 0.21% for the anesthesiologist, 0.32% for the first assistant and 0.13% for the instrumenting nurse. The use of digital subtraction and roadmap increased levels of radiation exposure to patient and surgical team 5 times in comparison to pulsed fluoroscopy mode at 4fps. When personal radiation protection shielding was used, radiation levels were considerably inferior. ConclusionsProximity to the radiation x-ray tube increases significantly the amount of scattered radiation received. With the use of personal radiation shielding, the exposure is considerably lower and recommended radiation dose limits are not exceeded.

Implante de filtro de veia cava com uso de dióxido de carbono como meio de contraste: série de casos

OBJETIVO: Avaliar o resultado do implante de filtro em veia cava inferior empregando angiografia digital por subtração com dioxide de carbono (CO2) como meio de contraste. MÉTODOS: No período de abril de 2010 a fevereiro de 2011, sete pacientes foram submetidos ao implante de filtro na veia cava inferior, utilizando-se CO2 como meio de contraste em subtração digital. Os pacientes apresentaram como critério de inclusão trombose venosa profunda no setor ilíaco-femoral e contraindicação à anticoagulação. RESULTADOS: Foi obtido sucesso técnico em todos os casos, com adequada visualização da veia cava e veias renais, não havendo complicações relacionadas ao uso do CO2 ou ao procedimento. CONCLUSÃO: O implante de filtro de veia cava utilizando o CO2 como meio de contraste é segura e efetiva em pacientes portadores de alergia ao contraste iodado ou com insuficiência renal não dialítica.

Cervical Spine: Case Presentation, Complications, and Their Prevention

Objective. A number of case presentations of catastrophic outcomes after cervical epidural injections have occurred after both interlaminar and transforaminal injection techniques. Practitioners in pain medicine need guidance to avoid these complications Design. A systematic search of the MEDLINE database, electronically available pain journals, and recent pain and spine meeting abstracts was searched for articles relevant to cervical spine interventional procedure complications. Results. A representative case of cervical radicular pain is presented to illustrate key differences of radicular pain presenting in the cervical area from those in the lumbar area Although cervical interlaminar epidural complications more likely involve direct neurological trauma to the spinal cord or spinal nerve, the mechanism for injury after transforaminal epidural corticosteroid injections is less clear. Many investigators hypothesize that particulate steroids may be the primary cause, in that these particles may occlude segmental medullary feeding arteries that reinforce the longitudinal anterior spinal artery supply to the spinal cord. Anatomical nomenclature of spinal cord blood supply and variants of normal are presented. Conclusions. Specific examples of potential injury avoidance strategies are discussed, including: 1) the use of nonparticulate steroid preparations; 2) needle bevel/size and other technical considerations; 3) preprocedural planning and sedation considerations; 4) test dosing with local anesthetics; and 5) imaging considerations, including the use of digital subtraction to better define angiographic patterns. Recommendations for the conduct of cervical epidural injection procedures are discussed.

A method for quantifying positional change of the condyle on lateral tomograms by means of digital subtraction.

A method is described for quantifying the positional change of the condyle on lateral tomograms of the temporomandibular joint (TMJ) by use of digital subtraction. This method permits rotational and translational changes of condylar reference points for easy measurement. Accuracy was evaluated in vitro using both TMJs of two dry human skulls and in vivo with seven volunteers. The average absolute error of the angle of rotation in vitro was 0.67 degrees. For the anterior-posterior element of translation the average absolute error was 0.07 mm, and for the superior-inferior element of translation it was 0.06 mm. From these results, we could conclude that the method provides clinically acceptable measurement accuracy. To verify the usefulness of the method, a clinical application is presented.

Detection of simulated osteoporosis in human anterior maxillary alveolar bone with digital subtraction

The purpose of this in vitro study was to examine radiographic changes in human anterior maxillary alveolar bone during simulated osteoporosis (decalcification) and to determine the minimal amount of generalized decalcifications that can be detected under optimal radiographic conditions with the use of digital subtraction. Five samples of human anterior maxillary alveolus were progressively decalcified at timed intervals with 0.1 N hydrochloric acid solutions, and the percentage of calcium lost during each interval was quantified with calcium assays. Sets of four radiographs were exposed at 70 kVp initially and after each decalcification interval. The radiographs were digitized and digitally filtered, and bone profiles (scan lines) were generated between selected points on lead markers. To further reduce corrupting film-grain noise each set of four profiles were superimposed and averaged on a pixel-by-pixel basis. The averaged profile from each stage of decalcification was subtracted from the averaged initial profile on a pixel-by-pixel basis, and the mean profile intensity change for each decalcification stage calculated. Statistical analysis was performed with repeated measures analysis of variance. Results indicate that generalized decalcification less than or equal to 5.3% was detected in all samples of human anterior maxillae with the use of digital subtraction.

Detection of simulated osteoporosis in dog alveolar bone with the use of digital subtraction

The purpose of this in vitro study was to examine radiographic changes in dog alveolar bone during simulated osteoporosis (decalcification) and to determine the minimal amount of generalized bone loss that can be detected under optimal radiographic conditions with the use of digital subtraction. Five samples of dog maxillary alveolus were progressively decalcified at timed intervals with 0.1 N hydrochloric acid solutions. The percentage of calcium lost during each interval was quantified with calcium assays. Sets of four radiographs from each sample were exposed at 30 kVp and 50 kVp initially and after each decalcification interval. The radiographs were digitized and bone profiles (scan lines) were generated between images of lead markers. To suppress contaminating image noise each set of four profiles were superimposed and averaged on a pixel-by-pixel basis. The averaged profile from each stage of decalcification was subtracted from the averaged initial profile on a pixel-by-pixel basis, the mean profile intensity change for each decalcification stage calculated, and this mean change compared to the initial mean intensity to yield the percentage mean profile intensity change for each sample for each decalcification stage. Statistical analysis was performed with repeated measures analysis of variance. Results indicate that generalized decalcification of less than 7.5% was detected in all samples of dog maxillae with exposures of 30 kVp and that generalized decalcification of less than 19% was detected with exposures of 50 kVp.

Digital subtraction discography

Conventional cervical discography was carried out in 25 patients during the period of one year. At the same time, we employed the well known principle of digital subtraction. The results of DSD have been compared with conventional discography. In every case more informative images were obtained despite the use of lower amounts of contrast. The distribution pattern of the reduced amounts of contrast in the disc provides valuable information. In the shoulder region, great improvement in picture quality is possible. For these reasons, the use of digital subtraction for discography is justified.

The concept of apparent cardiac arrest as a prerequisite for coronary digital subtraction angiography

This study was undertaken to evaluate the possible use of digital subtraction applied after selective coronary arteriography. An identical position of the objects with and without contrast medium is an absolute requirement for the application of subtraction techniques. Because coronary arteries are in continuous motion, the subtraction technique cannot be applied without certain precautions. In our study, only images from corresponding moments in the cardiac cycle before and after contrast injection were matched for subtraction, that is, the concept of apparent cardiac arrest. To prevent variations in cardiac contractions due to varying RR intervals, heart rate was controlled by regular right atrial stimulation. Moreover, the stimulation rate and cine frequency were in synchrony, which was effected by triggering both on the frequency of the electric main alternating current (50 cycles/s). In this way, each cardiac cycle contains exactly the same number of frames at corresponding moments. A combination of the application of the concept of apparent cardiac arrest with the subtraction technique in 12 patients resulted in good quality images. Furthermore, better visualization of capillary filling with contrast material was obtained than with conventional coronary arteriography.