Comparing the supine and erect pelvis radiographic examinations: an evaluation of anatomy, image quality and radiation dose

Abstract

Objectives: Pelvis radiographs are usually acquired supine despite standing imaging reflecting functional anatomy. We compared the supine and erect radiographic examinations for anatomical features, radiation dose and image quality. Methods: Sixty patients underwent pelvis radiography in both supine and erect positions at the same examination appointment. Measures of body mass index and sagittal diameter were obtained. Images were evaluated using visual grading analysis and pelvic tilt was compared. Dose-area-product (DAP) values were recorded and inputted into the CalDose_X software to estimate effective dose (ED). The CalDose_X software allowed comparisons using data from the erect and supine sex-specific phantoms (MAX06 & FAX06). Results: Patient sagittal diameter was greater on standing with an average 20.6% increase at the iliac crest (median 30.0, interquartile range [26.0 to 34.0] cm), in comparison to the supine position [24.0 (22.3 to 28.0) cm; p < 0.001]. 57 (95%) patients had posterior pelvic tilt on weight-bearing. Erect image quality was significantly decreased with median image quality scores of 78% (69 to 85) compared to 87% for the supine position [81 to 91] (p < 0.001). In the erect position the ED was 47% higher [0.17 (0.13 to 0.33) mSv versus 0.12 (0.08 to 0.18) mSv (p < 0.001)], influenced by the increased sagittal diameter. 42 (70%) patients preferred the standing examination. Conclusion: Patient diameter and pelvic tilt were altered on weightbearing. Erect images demonstrated an overall decrease in image quality with a higher radiation dose. Optimal acquisition parameters are required for erect pelvis radiography as the supine technique is not directly transferable.

Pelvic tilt from supine to standing in patients with symptomatic acetabular retroversion of the hip

“…A study of 60 normal controls using the pubic symphysis to sacrococcygeal distance (PSSC), a surrogate for PT which gives measurements in millimetres rather than degrees, 31 demonstrated a posterior change in PT when moving from supine to standing similar in magnitude to the studies of hip dysplasia patients which chose this measurement. 18,19…”

“…Positional changes in PT have previously been reported in patients with developmental dysplasia of the hip (DDH), 16-20 undiagnosed hip pain, 21,22 and awaiting total hip arthroplasty (THA), 23 but have not yet been studied in patients with acetabular retroversion. It should be noted that the original descriptions of acetabular retroversion were based on supine anteroposterior (AP) pelvis radiographs and analysis of the axial sections of CT scans.…”

“…12 Functional acetabular retroversion has been associated with PT, 13 and the effect of PT on the interpretation of radiological parameters, in particular the assessment of acetabular retroversion, has been clearly illustrated. 14,15 Positional changes in PT have previously been reported in patients with developmental dysplasia of the hip (DDH), [16][17][18][19][20] undiagnosed hip pain, 21,22 and awaiting total hip arthroplasty (THA), 23 but have not yet been studied in patients with acetabular retroversion. It should be noted that the original descriptions of acetabular retroversion were based on supine anteroposterior (AP) pelvis radiographs and analysis of the axial sections of CT scans.…”

Osteoarthritis of the hip: is radiography still needed?

“…The pelvic AP radiograph should also be used to assess FAI-associated features since pelvic positioning can be controlled on the AP pelvic radiograph but not on the AP hip radiograph [44]. There is no clear consensus whether the JSW is better evaluated on weight-bearing (WB) or non-weight-bearing (nWB) AP pelvic radiographs [45][46][47][48]. The WB radiograph evaluates the pelvis in its anatomical position with a decrease in acetabular coverage and increase in posterior pelvic tilt in comparison to the nWB pelvic radiograph [49].…”

A influência da lei do inverso do quadrado da distância nos indicadores de exposição e qualidade de imagem para exames radiográficos de pelve

“…Os indicadores de exposição (IE) inerentes à ID podem fornecer ao profissional da radiologia uma estimativa de dose que atingiu o detector. Embora o IE não se relacione diretamente com a dose no paciente, ainda que o valor de referência esteja em conformidade com os definidos pelo fabricante, indicando que a exposição no detector foi alcançada (AAPM, 2015;Flintham et al, 2021). Além disso, segundo a Associação Americana de Físicos em Medicina (AAPM), o avanço da tecnologia digital na radiologia trouxe benefícios significativos, incluindo a capacidade de ajustar o contraste radiográfico (CR) na imagem digital (ID) por meio de técnicas de pós-processamento (Shepard et al, 2009).…”