Effect of Patient Centering on Patient Dose and Image Noise in Chest CT

Kaasalainen, Touko; Palmu, Kirsi; Reijonen, Vappu; Kortesniemi, Mika

doi:10.2214/ajr.13.12028

Cited by 88 publications

(92 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…8,9,14 Another trend observed was the increased sensitivity of the 0°localizer angle to phantom movement compared with 90°localizer angle, supporting previous research. 9 One would expect the 0°localizer angle to be more sensitive to vertical movement as the projected area of the phantom changes, and correspondingly, the 90°localizer angle to be more sensitive to horizontal movement. This was confirmed, although when accounting for all vertical and horizontal movement, greater variations in the CTDIvol were observed for the 0°source angle acquisitions.…”

Section: Discussionsupporting

confidence: 83%

“…9,14 This can be explained in terms of the phantom moving towards the X-ray source, thus having a greater magnification in the projection image and being interpreted by the scanner as a larger body requiring a higher tube current. 14 The CTDIvol shows little dependence on table height for the 90°l ocalizer plane, as although the phantom is moving vertically in these radiographs, its projected size remains largely unchanged.…”

Section: Resultsmentioning

confidence: 99%

“…This resulted in a mean dose increase of 33%, calculated via the change in tube current required to achieve a consistent image noise. 8 Another study calculated vertical miscentring in 112 patients, finding a median error of 25-35 mm for different patient groups, 9 while a third investigation found that patient centring was incorrect in 60 of 63 scans assessed. 10 Incorrect TCM definition resulting from miscentring may be confounded by the apparent change in body morphology resulting from images taken using a 0°, anteroposterior (AP) source angle, and a 180°, posteroanterior (PA) source angle, both of which are commonly used clinically ( Figure 1).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Investigating the CT localizer radiograph: acquisition parameters, patient centring and their combined influence on radiation dose

Lambert

Kumar²,

Chen³

et al. 2015

BJR

View full text Add to dashboard Cite

Objective: To systematically investigate the effect of CT localizer radiograph acquisition on the tube current modulation and thus radiation dose of the subsequent diagnostic scan. Methods: Localizer radiographs of an abdominal section CT phantom were taken, and the resulting volume CT dose index (CTDIvol) for the diagnostic scan was recorded. Variables included tube potential, the phantom's alignment within the CT scanner gantry in both the vertical and horizontal directions and the X-ray source angle at which the localizer was acquired. Results: Diagnostic scan CTDIvol decreased with increasing tube potential. Vertical (table height) movement was found to affect radiation dose more than horizontal movement, with 650 mm table movement resulting in a standard deviation in the diagnostic scan CTDIvol of 4.4 mGy, compared with 2.5 mGy with 6 50 mm horizontal movement. Correspondingly, localizer angles of 90°or 270°(3 o'clock and 9 o'clock X-ray source positions) were less sensitive overall to alignment errors, with a standard deviation of 2.5 mGy, compared with a 0°or 180°angle, which had a standard deviation of 3.8 mGy. Conclusion: To achieve a consistently optimized radiation dose, the localizer protocol should be paired with the diagnostic acquisition protocol. A final acquisition angle of 90°should be used when possible to minimize dose variation resulting from alignment errors. Advances in knowledge: Localizer parameters that affect radiation output were identified for this scanner system. The importance of tube potential and acquisition angle was highlighted.Radiation exposure from medical imaging remains in the public awareness and has spurred the adoption of several technologies to minimize CT dose.

show abstract

Section: Discussionsupporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Investigating the CT localizer radiograph: acquisition parameters, patient centring and their combined influence on radiation dose

Lambert

Kumar²,

Chen³

et al. 2015

BJR

View full text Add to dashboard Cite

show abstract

“…Reasons are changes in tube current-time product (e. g. by affecting the function of the automatic exposure control system), an increase of radiation dose absorbed by sensitive surface tissues, or an altered projection of organs onto the bowtie filter [24,27]. It was shown that already relatively small aberrations in vertical position of 2 -6 cm may result in dose increases of up to 51 % [25,26]. As patient centering is a user-specific factor and therefore controllable, we performed an in-service training for our radiographers pointing out the importance of proper patient positioning and the need to refresh their skills.…”

mentioning

confidence: 99%

“…However, a mean working experience of 8.32 years indicates that most radiographers involved in the study were well versed. (2) We used scanners from a single vendor, which may have affected dose values as, for example, tube current modulation techniques and bowtie filters vary among different vendors [25]. (3) In some patients alerts may have been caused by more than one source or an interaction of several causes (e. g. high BMI and off-centering).…”

mentioning

confidence: 99%

Implementation of Dose Monitoring Software in the Clinical Routine: First Experiences

Heilmaier

Zuber

Bruijns

et al. 2015

Fortschr Röntgenstr

View full text Add to dashboard Cite

Purpose: Radiation exposure of the public as a result of medical imaging has significantly increased during the last decades. To have a tool to register and control patient dose exposure, we implemented dose monitoring software at our institution and first connected our computed tomography (CT) scanners. Materials and Methods: CT dose data from July 2014 to February 2015 was retrospectively analyzed using dose monitoring software. We evaluated a number of scans above predefined dose thresholds ("alerts"), assessed reasons for alerts and compared data of two CT scanners, one located close to the emergency room ("emergency CT scanner") and one mainly used on an outpatient basis ("clinical routine CT scanner"). To check for statistically significant differences between scanners, chi-square-tests were performed. Results: A total of 8883 scans were acquired (clinical routine CT scanner, n = 3415; emergency CT scanner, n = 5468) during which 316 alerts were encountered (alert quota, 4 %). The overall alert quota ranged from 2 -5 % with significantly higher values for the clinical routine CT scanner. Reasons for alerts were high BMI (51 %), patient offcentering (24 %), scan repetition (11 %), orthopedic hardware (9 %), or other (5 %). Scan repetition was necessary significantly more often with the emergency CT scanner (p = 0.019), while high BMI, off-centering and orthopedic hardware were more frequently seen with the clinical routine CT scanner (for all, p < 0.05). There was a good correlation between high body weight and dose above threshold (r = 0.585).

show abstract

Impact of patient centering in CT on organ dose and the effect of using a positioning compensation system: Evidence from OSLD measurements in postmortem subjects

Barreto

Lamoureux

Olguín

et al. 2019

J Applied Clin Med Phys

View full text Add to dashboard Cite

The purpose of this study was to investigate the frequency and impact of vertical mis‐centering on organ doses in computed tomography (CT) exams and evaluate the effect of a commercially available positioning compensation system (PCS). Mis‐centering frequency and magnitude was retrospectively measured in 300 patients examined with chest‐abdomen‐pelvis CT. Organ doses were measured in three postmortem subjects scanned on a CT scanner at nine different vertical table positions (maximum shift ± 4 cm). Organ doses were measured with optically stimulated luminescent dosimeters inserted within organs. Regression analysis was performed to determine the correlation between organ doses and mis‐centering. Methods were repeated using a PCS that automatically detects the table offset to adjust tube current output accordingly. Clinical mis‐centering was >1 cm in 53% and 21% of patients in the vertical and lateral directions, respectively. The 1‐cm table shifts resulted in organ dose differences up to 8%, while 4‐cm shifts resulted in organ dose differences up to 35%. Organ doses increased linearly with superior table shifts for the lung, colon, uterus, ovaries, and skin (R2 = 0.73–0.99, P < 0.005). When the PCS was utilized, organ doses decreased with superior table shifts and dose differences were lower (average 5%, maximum 18%) than scans performed without PCS (average 9%, maximum 35%) at all table shifts. Mis‐centering occurs frequently in the clinic and has a significant effect on patient dose. While accurate patient positioning remains important for maintaining optimal imaging conditions, a PCS has been shown to reduce the effects of patient mis‐centering.

show abstract

Effect of Patient Centering on Patient Dose and Image Noise in Chest CT

Abstract: Regardless of patient size, most patients in this study were positioned too low, which negatively affected both patient dose and image noise. Miscentering was more pronounced in smaller pediatric patients.

Cited by 88 publications

References 23 publications

Investigating the CT localizer radiograph: acquisition parameters, patient centring and their combined influence on radiation dose

Investigating the CT localizer radiograph: acquisition parameters, patient centring and their combined influence on radiation dose

Implementation of Dose Monitoring Software in the Clinical Routine: First Experiences

Impact of patient centering in CT on organ dose and the effect of using a positioning compensation system: Evidence from OSLD measurements in postmortem subjects

Contact Info

Product

Resources

About