Analysis of Patients' X-ray Exposure in 146 Percutaneous Radiologic Gastrostomies.

Purpose Analysis of patient´s X-ray exposure during percutaneous radiologic gastrostomies (PRG) in a larger population. Materials and Methods Data of primary successful PRG-procedures, performed between 2004 and 2015 in 146 patients, were analyzed regarding the exposition to X-ray. Dose-area-product (DAP), dose-length-product (DLP) respectively, and fluoroscopy time (FT) were correlated with the used x-ray systems (Flatpanel Detector (FD) vs. Image Itensifier (BV)) and the necessity for periprocedural placement of a nasogastric tube. Additionally, the effective X-ray dose for PRG placement using fluoroscopy (DL), computed tomography (CT), and cone beam CT (CBCT) was estimated using a conversion factor. Results The median DFP of PRG-placements under fluoroscopy was 163 cGy*cm2 (flat panel detector systems: 155 cGy*cm2; X-ray image intensifier: 175 cGy*cm2). The median DLZ was 2.2 min. Intraprocedural placement of a naso- or orogastric probe (n = 68) resulted in a significant prolongation of the median DLZ to 2.5 min versus 2 min in patients with an already existing probe. In addition, dose values were analyzed in smaller samples of patients in which the PRG was placed under CBCT (n = 7, median DFP = 2635 cGy*cm2), or using CT (n = 4, median DLP = 657 mGy*cm). Estimates of the median DFP and DLP showed effective doses of 0.3 mSv for DL-assisted placements (flat panel detector 0.3 mSv, X-ray image converter 0.4 mSv), 7.9 mSv using a CBCT - flat detector, and 9.9 mSv using CT. This corresponds to a factor 26 of DL versus CBCT, or a factor 33 of DL versus CT. Conclusion In order to minimize X-ray exposure during PRG-procedures for patients and staff, fluoroscopically-guided interventions should employ flat detector systems with short transmittance sequences in low dose mode and with slow image frequency. Series recordings can be dispensed with. The intraprocedural placement of a naso- or orogastric probe significantly extends FT, but has little effect on the overall dose of the intervention. Due to the significantly higher X-ray exposure, the use of a CBCT as well as PRG-placements using CT should be limited to clinically absolutely necessary exceptions with strict indication. Key Points · Fluoroscopically-guided PRG placements are interventions with low X-ray exposure.. · X-ray exposure from fluoroscopy is lower using flat panel detector systems as compared to image intensifier systems.. · The concomitant placement of an oro- or nasogastric probe extends the fluoroscopy time.. · Gastric probe placement is worthwhile to prevent the premature use of the significantly radiation-intensive CT.. · The use of the C-arm CT or the CT increases the beam exposure by 26 or 33 times, respectively.. · The PRG placement using C-arm CT and CT should only be performed in exceptional cases.. Citation Format · Petersen TO, Reinhardt M, Fuchs J et al. Analysis of Patients' X-ray Exposure in 146 Percutaneous Radiologic Gastrostomies. Fortschr Röntgenstr 2017; 189: 820 - 827.

[Dose measurement in small animal radiology: how intense is the influence of distance and position of the investigator in relation to the patient?]. / Ergebnisse dosimetrischer Untersu- chungen in der Kleintierpraxis: Welchen Einfluss haben der Abstand und die Position des Untersuchers zum Patienten?

Radiation exposure of body parts of persons, needed to restrain small animal during the examination, varies depending on the distance and position in relation to the patient, the region investigated, and the exposure settings applied. The aim of the study was to quantify the effects of these factors on the ambient dose. The dosimeter was positioned with varying distance from the direct beam (from 30 to 150 cm) and on different level above the floor (55 cm, 85 cm, and 150 cm. The study consisted of two parts. In the first part a plastic water tank (thickness: 18 cm) was used as source of scatter radiation. Different exposure settings (77 kVp; 20 - 10 - 5 - 2.5 - 1.25 mAs) were applied. In the second part dose was measured during the examination of the abdomen of a large dog (thickness: 18 cm; 77 kVp, 20 mAs) and of the skull of a cat (thickness: 6 cm; 55 kVp, 20 mAs). At the level of the patient (85 cm above the floor) the dose decline relative to the distance followed a quadratic function. In the series "abdomen-dog" the mean dose values ranged from 51.6 microSv (30 cm distance) to 1.02 microSv (150 cm distance). The corresponding doses for the series "skull-cat" were 0.98 microSv and 0.02 microSv, respectively. Comparably lower doses were measured on the lines along the table, when non-irradiated parts of the body were located between the exposed patient volume and the dosimeter. At 150 cm above the floor higher doses were observed relative to the doses at the level of the table. The following conclusions can be drawn: (1.) Depending on the target volume the ambient dose varies in a wide range. (2.) An increase of the distance of only few centimetres is reducing exposure considerably. Therefore persons should make use of it whenever this is possible. (3.) Persons should stand on the short sides of the table while fixing the patient. (4.) Head and neck are relatively highly exposed. Methods to protect the thyroid gland and the eye lens are indicated. (5.) Since different exposure levels can be applied in digital radiography, the range of dose levels is rather wide. Therefore strict dose discipline (e.g. by use of exposure tables and dose indicators) is necessary to avoid continuing overexposure.

Quantification of radiation dose savings in cardiac computed tomography using prospectively triggered mode and ECG pulsing: a phantom study.

OBJECTIVE: To quantify radiation dose reduction in cardiac computed tomography (CT) using a prospectively triggered mode compared with a retrospective ECG-gated helical mode. METHODS: Absorbed organ doses in cardiac 64-row multidetector CT were quantified using an anthropomorphic male Alderson phantom with 74 thermoluminescence dosimeters. Three different imaging protocols were applied: retrospective ECG-gating, retrospective ECG-gating with additional ECG-pulsing, and a prospectively triggered mode. The measured organ doses were compared with dose estimation by a mathematical phantom. RESULTS: Compared with the retrospective ECG-gating mode, the mean relative organ doses were reduced by 44% using ECG pulsing and by 76% using the prospectively triggered mode. The range of dose savings varied from 34% to 49% using ECG pulsing and from 65% to 87% using the prospectively triggered mode. The effective dose was 16.5 mSv using retrospective gating, 9.2 mSv using retrospective gating with ECG pulsing and 4.0 mSv using the prospectively triggered mode. CONCLUSIONS: Our measurements confirm the high dose-saving potential of the prospectively triggered technique in cardiac CT. The reduction in the organ doses measured corresponds to estimates determined by the mathematical phantom. The effective dose calculated by the mathematical phantom was, in some cases, significantly lower than that calculated using the anthropomorphic phantom.