Relevance of open magnetic resonance imaging position (sitting and standing) to quantify pelvic organ prolapse in women

Anatomical changes in the male pelvis between the supine and upright positions-A feasibility study for prostate treatments in the upright position

Treating and imaging patients in the upright orientation is gaining acceptance in radiation oncology and radiology and has distinct advantages over the recumbent position. An IRB approved study to investigate the positions and orientations of the male pelvic organs between the supine and upright positions was conducted. The study comprised of scanning 15 male volunteers (aged 55-75 years) on a 0.6 T Fonar MRI scanner in the supine and upright positions with a full bladder and in the upright position with an empty bladder. The Pelvic study revealed that in the upright position the 1. Position and shape of the prostate are not impacted significantly by bladder fill. 2. Distance between the sacrum and the anterior bladder wall is significantly smaller. 3. Anterior-Posterior length and the bladder width is significantly larger. 4. Seminal vesicles are pushed down by the bladder. 5. Top of the penile bulb is further away from the apex of the prostate. These observed differences could positively impact upright prostate treatments by 1. Reducing the risk of small bowel approximating the treatment volume. 2. Prostate treatments can be done with a reduced focus on bladder fill. 3. Radiation beams for treating intermediate risk prostrate can be made smaller or a larger portion of the seminal vesicles can be treated with the same beam size than typically used for supine treatments. 4. Reducing the average dose to the penile bulb.

Pelvic inclination correction system for magnetic resonance imaging analysis of pelvic organ prolapse in upright position

INTRODUCTION AND HYPOTHESIS

Pelvic organ prolapse quantification by means of upright magnetic resonance imaging (MRI) is a promising research field. This study determines the angle for the pelvic inclination correction system (PICS) for upright patient position, which is hypothesized to deviate from the supine PICS angle. The necessity of different PICS angles for various patient positions will also be discussed.

METHODS

Magnetic resonance scans of 113 women, acquired in an upright patient position, were used to determine the upright PICS angle, defined as the angle between the sacrococcygeal-inferior pubic point (SCIPP) line and the horizontal line. The difference and correlation between the upright and supine PICS angles were calculated using the paired Student's t-test and the Pearson's correlation coefficient (r) respectively. The effect of the difference between the upright and supine PICS angle on the measured pelvic organ extent was calculated using goniometry.

RESULTS

The mean (interquartile range) PICS angles were 29° (26-35°) for the upright and 33° (30-37°) for the supine patient position. They were significantly different (p<0.001) and very strongly correlated (r = 0.914, p<0.001). The 4° difference between the average upright and supine PICS angle results in an average underestimation of the measured cervix height of approximately 0.5 cm for patients scanned in upright position.

CONCLUSIONS

The PICS angle for the upright patient position is 29°. The use of a dedicated PICS angle for different patient positions allows for more accurate pelvic organ extent analysis in patients with prolapse.

Considerations for Upright Particle Therapy Patient Positioning and Associated Image Guidance

Particle therapy is a rapidly growing field in cancer therapy. Worldwide, over 100 centers are in operation, and more are currently in construction phase. The interest in particle therapy is founded in the superior target dose conformity and healthy tissue sparing achievable through the particles’ inverse depth dose profile. This physical advantage is, however, opposed by increased complexity and cost of particle therapy facilities. Particle therapy, especially with heavier ions, requires large and costly equipment to accelerate the particles to the desired treatment energy and steer the beam to the patient. A significant portion of the cost for a treatment facility is attributed to the gantry, used to enable different beam angles around the patient for optimal healthy tissue sparing. Instead of a gantry, a rotating chair positioning system paired with a fixed horizontal beam line presents a suitable cost-efficient alternative. Chair systems have been used already at the advent of particle therapy, but were soon dismissed due to increased setup uncertainty associated with the upright position stemming from the lack of dedicated image guidance systems. Recently, treatment chairs gained renewed interest due to the improvement in beam delivery, commercial availability of vertical patient CT imaging and improved image guidance systems to mitigate the problem of anatomical motion in seated treatments. In this review, economical and clinical reasons for an upright patient positioning system are discussed. Existing designs targeted for particle therapy are reviewed, and conclusions are drawn on the design and construction of chair systems and associated image guidance. Finally, the different aspects from literature are channeled into recommendations for potential upright treatment layouts, both for retrofitting and new facilities.

Magnetic resonance imaging evaluation of pelvic floor structure during pregnancy

OBJECTIVE

Among the various risk factors of pelvic floor disorders, pregnancy has been reported to affect the pelvic floor structure; however, not all these effects have been understood yet. The aim of this study is to elucidate how pregnancy affects pelvic floor structure via magnetic resonance imaging (MRI).

STUDY DESIGN

We conducted a retrospective study between January 2010 and December 2019 to extract clinical records of pregnant and non-pregnant women, who underwent MRI for obstetrical diseases and ovarian benign tumors, respectively. The data on age, body mass index (BMI), complications, gravida, parity, gestational age, and obstetrical history were collected, and pubo-coccygeal line (PCL), pubo-rectal line (PRL), and M line (ML) on their MR images were measured. Statistical analyses were performed with Wilcoxon test, chi-square test, and Kruskal-Wallis test with Steel-Dwass post hoc test as appropriate. Statistical significance was set at P < 0.05.

RESULTS

We analyzed the reports of 56 (pregnancy group) and 106 women (non-pregnancy group). There was no significant difference in age or BMI, while the obstetric history was significantly different between these groups. Median PCL, PRL, and ML in the pregnancy group were significantly longer than those in the non-pregnancy group (114.1 mm vs. 110.0 mm, P = 0.018; 48.6 mm vs. 41.6 mm, P < 0.0001 and 21.7 mm vs. 10.0 mm, p < 0.0001. respectively). The subgroup analysis of the effect of pregnancy and vaginal delivery (VD) history on changes in these lines revealed that pregnancy-induced PRL increase tended to recover to the reference level of "non-pregnant without VD," but ML increase did not fully recover.

CONCLUSION

MRI revealed a strong effect of pregnancy on pelvic floor structure.

MR defecography technique: recommendations of the society of abdominal radiology's disease-focused panel on pelvic floor imaging

PURPOSE

To develop recommendations for magnetic resonance (MR) defecography technique based on consensus of expert radiologists on the disease-focused panel of the Society of Abdominal Radiology (SAR).

METHODS

An extensive questionnaire was sent to a group of 20 experts from the disease-focused panel of the SAR. The questionnaire encompassed details of technique and MRI protocol used for evaluating pelvic floor disorders. 75% agreement on questionnaire responses was defined as consensus.

RESULTS

The expert panel reached consensus for 70% of the items and provided the basis of these recommendations for MR defecography technique. There was unanimous agreement that patients should receive coaching and explanation of commands used during MR defecography, the rectum should be distended with contrast agent, and that sagittal T2-weighted images should include the entire pelvis within the field of view. The panel also agreed unanimously that IV contrast should not be used for MR defecography. Additional areas of consensus ranged in agreement from 75 to 92%.

CONCLUSION

We provide a set of consensus recommendations for MR defecography technique based on a survey of expert radiologists in the SAR pelvic floor dysfunction disease-focused panel. These recommendations can be used to develop a standardized imaging protocol.

Development of Upright Computed Tomography With Area Detector for Whole-Body Scans: Phantom Study, Efficacy on Workflow, Effect of Gravity on Human Body, and Potential Clinical Impact

OBJECTIVES

Multiple human systems are greatly affected by gravity, and many disease symptoms are altered by posture. However, the overall anatomical structure and pathophysiology of the human body while standing has not been thoroughly analyzed due to the limitations of various upright imaging modalities, such as low spatial resolution, low contrast resolution, limited scan range, or long examination time. Recently, we developed an upright computed tomography (CT), which enables whole-torso cross-sectional scanning with 3-dimensional acquisition within 15 seconds. The purpose of this study was to evaluate the performance, workflow efficacy, effects of gravity on a large circulation system and the pelvic floor, and potential clinical impact of upright CT.

MATERIALS AND METHODS

We compared noise characteristics, spatial resolution, and CT numbers in a phantom between supine and upright CT. Thirty-two asymptomatic volunteers (48.4 ± 11.5 years) prospectively underwent both CT examinations with the same scanning protocols on the same day. We conducted a questionnaire survey among these volunteers who underwent the upright CT examination to determine their opinions regarding the stability of using the pole throughout the acquisition (closed question), as well as safety and comfortability throughout each examination (both used 5-point scales). The total access time (sum of entry time and exit time) and gravity effects on a large circulation system and the pelvic floor were evaluated using the Wilcoxon signed-rank test and the Mann-Whitney U test. For a large circulation system, the areas of the vena cava and aorta were evaluated at 3 points (superior vena cava or ascending aorta, at the level of the diaphragm, and inferior vena cava or abdominal aorta). For the pelvic floor, distances were evaluated from the bladder neck to the pubococcygeal line and the anorectal junction to the pubococcygeal line. We also examined the usefulness of the upright CT in patients with functional diseases of spondylolisthesis, pelvic floor prolapse, and inguinal hernia.

RESULTS

Noise characteristics, spatial resolution, and CT numbers on upright CT were comparable to those of supine CT. In the volunteer study, all volunteers answered yes regarding the stability of using the pole, and most reported feeling safe (average rating of 4.2) and comfortable (average rating of 3.8) throughout the upright CT examination. The total access time for the upright CT was significantly reduced by 56% in comparison with that of supine CT (upright: 41 ± 9 seconds vs supine: 91 ± 15 seconds, P < 0.001). In the upright position, the area of superior vena cava was 80% smaller than that of the supine position (upright: 39.9 ± 17.4 mm vs supine: 195.4 ± 52.2 mm, P < 0.001), the area at the level of the diaphragm was similar (upright: 428.3 ± 87.9 mm vs supine: 426.1 ± 82.0 mm, P = 0.866), and the area of inferior vena cava was 37% larger (upright: 346.6 ± 96.9 mm vs supine: 252.5 ± 93.1 mm, P < 0.001), whereas the areas of aortas did not significantly differ among the 3 levels. The bladder neck and anorectal junction significantly descended (9.4 ± 6.0 mm and 8.0 ± 5.6 mm, respectively, both P < 0.001) in the standing position, relative to their levels in the supine position. This tendency of the bladder neck to descend was more prominent in women than in men (12.2 ± 5.2 mm in women vs 6.7 ± 5.6 mm in men, P = 0.006). In 3 patients, upright CT revealed lumbar foraminal stenosis, bladder prolapse, and inguinal hernia; moreover, it clarified the grade or clinical significance of the disease in a manner that was not apparent on conventional CT.

CONCLUSIONS

Upright CT was comparable to supine CT in physical characteristics, and it significantly reduced the access time for examination. Upright CT was useful in clarifying the effect of gravity on the human body: gravity differentially affected the volume and shape of the vena cava, depending on body position. The pelvic floor descended significantly in the standing position, compared with its location in the supine position, and the descent of the bladder neck was more prominent in women than in men. Upright CT could potentially aid in objective diagnosis and determination of the grade or clinical significance of common functional diseases.

Underestimation of pelvic organ prolapse in the supine straining position, based on magnetic resonance imaging findings

Objective

Pelvic organ prolapse (POP) is clinically diagnosed in the supine position, where the effect of gravity is simulated by having the patients put strain on their pelvic floor. The objective of this study was to determine the degree of POP underestimation in the supine position based on magnetic resonance imaging (MRI) findings.

Methods

This prospective study was conducted with symptomatic POP grade ≥ 2 patients. Fifteen female patients were examined with an MRI system that allows supine and upright imaging. The differences between supine and upright in distances of the bladder neck, cervix, and pouch of Douglas from the pubococcygeal line (PCL) were estimated, together with changes in the genital hiatal area. Patients were scanned at rest and during straining. All distances were compared using the Wilcoxon ranking test.

Results

All mean distances from the PCL increased from the supine–strain to the upright–rest and from the supine–strain to the upright–strain position. These distances were found in the supine and upright positions: the bladder descended 1.3 cm to 1.4 cm, the cervix 1.1 cm to 2.2 cm, and the pouch of Douglas 0.8 cm to 1.5 cm respectively (all p values <0.05). The hiatal area was larger in the upright–strain position (mean 42.0 cm²; SD ±14.8) than during the supine–strain position (mean 33.5 cm²; SD ±14.5), with a p value of 0.02.

Conclusion

Upright MRI scanning of patients with POP grade ≥ 2 both at rest and during straining shows a significantly larger extent of the prolapse than that observed during supine straining.