Prone Magnetic Resonance Imaging Research Articles

Target Volumes Comparison between Postoperative Simulation MRI and Preoperative Diagnostic MRI for Prone Breast Radiotherapy after Breast-Conserving Surgery

To investigate the correlation and difference between target volumes determined by postoperative prone positioning magnetic resonance imaging (MRI) and preoperative prone diagnostic MRI for breast radiotherapy after breast-conserving surgery (BCS) based on deformable image registration (DIR). A total of 17 patients undergoing prone whole breast-irradiation after BCS were enrolled, all these patients were undergoing preoperative and postoperative prone MRI scans. The gross tumor volume (GTV) was delineated on the preoperative MRI images, then expanding 10 mm to simulate the preoperative lumpectomy cavity (LC). The LC were expended to clinical target volume (CTV), and planning target volume (PTV) on preoperative and postoperative MRI sequences, respectively. Preoperative and postoperative MRI was registered based on DIR by a commercially available software system. The target volume, the distance between the centers of mass (dCOM), conformity index (CI), degree of inclusion (DI) were compared to explore the target volume variation for pre- and post-surgery delineation. And evaluated the relationship between CILC/CIPTV and clinical factors. The volume of GTVpre was 3.05cm3(range, 1-23.63cm3). The median volume of LCpre were 26.84 cm3 (range, 11.75-102.28 cm3). 0.85cm3 smaller than the LCpre, the LCpost were 25.99 cm3 (range, 5.98-41.95) (P = 0.04). The dCOM, CI, and DI between LCpre and LCpost were 1.371cm (range, 0.533-5.447), 0.221 (range, 0.041-0.516), and 0.472 (range, 0.108-0.804). There was no significant statistically difference between PTVpre and PTVpost (120.73cm3 vs 131.67cm3, p = 0.723). Compared with LC, the CI and DI between PTVpre and PTVpost were increased to 0.446 (range, 0.233-0.700), 0.636 (range, 0.362-0.834), respectively. Meanwhile, the dCOM was reduced to 1.239cm (range, 0.413-3.642). There was no obvious linear correlation between the CI with the GTV volume, the ratio of the primary tumor volume to the breast volume, the distance from the primary tumor to the nipple and chest wall, and the Body Mass Index (BMI), respectively. For prone breast irradiation, even based on DIR, the spatial correspondence of the target volumes between preoperative and postoperative MRI images were still poor. Therefore, it is not reasonable to delineate postoperative LC refer to preoperative diagnostic MRI based on DIR. Preoperative MRI also cannot provide individualized guidance for LC delineation according to tailored patient.

Improvement of semantic segmentation through transfer learning of multi-class regions with convolutional neural networks on supine and prone breast MRI images

Semantic segmentation of breast and surrounding tissues in supine and prone breast magnetic resonance imaging (MRI) is required for various kinds of computer-assisted diagnoses for surgical applications. Variability of breast shape in supine and prone poses along with various MRI artifacts makes it difficult to determine robust breast and surrounding tissue segmentation. Therefore, we evaluated semantic segmentation with transfer learning of convolutional neural networks to create robust breast segmentation in supine breast MRI without considering supine or prone positions. Total 29 patients with T1-weighted contrast-enhanced images were collected at Asan Medical Center and two types of breast MRI were performed in the prone position and the supine position. The four classes, including lungs and heart, muscles and bones, parenchyma with cancer, and skin and fat, were manually drawn by an expert. Semantic segmentation on breast MRI scans with supine, prone, transferred from prone to supine, and pooled supine and prone MRI were trained and compared using 2D U-Net, 3D U-Net, 2D nnU-Net and 3D nnU-Net. The best performance was 2D models with transfer learning. Our results showed excellent performance and could be used for clinical purposes such as breast registration and computer-aided diagnosis.

Can Supine Breast Magnetic Resonance Imaging After a Dynamic Contrast-Enhanced Breast Magnetic Resonance Imaging Provide Information for Supine Procedures?

A retrospective analysis was conducted on 75 lesions in 50 patients with pathologically proven breast cancer who underwent MRI in prone and supine positions between December 2019 and December 2020. The transverse, anteroposterior, and craniocaudal dimensions (in millimeters) of the tumor in the x -, y -, and z -axes were measured. Distances from the center of the tumor to the chest wall and the adjacent skin were measured on transverse and reformatted sagittal images. In cases where multifocal lesions were present, the transverse, anteroposterior, and craniocaudal distances between the tumor centers in the x -, y -, and z -axes were measured. Differences between measurements in supine and prone MRI were evaluated with the Mann-Whitney U and the Wilcoxon tests. P values of less than 0.05 were considered to indicate a statistically significant difference. The analysis revealed 31 MRIs with 1 and 20 with multifocal lesions. The x -axis dimension of the lesions in prone and supine positions did not significantly differ ( P = 0.198) between the 2 positions. A significant difference in the y - and z -axes dimensions was observed between the prone and supine position ( P = 0.00 for both). The distance from the tumor to the chest wall and the adjacent skin showed significant difference ( P = 0.00 for both). For multifocal lesions, the distance between the lesions showed a significant difference on the y -axis ( P = 0.00). This study showed a significant difference in the tumor size, location, and tumor-to-tumor distances due to change of patient position, from the standard prone MRI to the supine position in the operating room, resulting in distortion, spatial repositioning, and convergence of the lesions. Supine MRI may be considered in providing a less extensive surgery.

Prospective Evaluation of Ultrasound in a Novel Position with MRI Virtual Navigation for MRI-Detected Only Breast Lesions: A Pilot Study of a More Efficient and Economical Method

The aim of this study was to evaluate the clinical utility of ultrasound (US) with magnetic resonance imaging (MRI) virtual navigation in a novel prone position for MRI-detected incidental breast lesions. Between June 2016 and June 2020, 30 consecutive patients with 33 additional Breast Imaging Reporting and Data System (BI-RADS) category 4 or 5 lesions that were detected on MRI but occult on second-look US were enrolled in the study. All suspicious lesions were located in real-time US using MRI virtual navigation in the prone position and then followed by US-guided biopsy or surgical excision. Pathological results were taken as the standard of reference. The detection rate of US with MRI virtual navigation was calculated. The MRI features and pathological types of these lesions were analyzed. A total of 31 lesions were successfully located with real-time US with MRI virtual navigation and then US-guided biopsy or localization, and the detection rate was 93.9% (31/33). Twenty-seven (87.1%, 27/31) proved to be benign lesions and four (12.9%, 4/31) were malignant lesions at pathology. Of the 33 MRI-detected lesions, 31 (93.9%, 31/33) were non-mass enhancements and two (6.1%, 2/33) were masses. This study showed that real-time US with prone MRI virtual navigation is a novel efficient and economical method to improve the detection and US-guided biopsy rate of breast lesions that are detected solely on MRI.

How Prone Position Affects the Anatomy of Lumbar Nerve Roots and Psoas Morphology for Prone Transpsoas Lumbar Interbody Fusion

Lumbar nerve root injury is a serious complication of transpsoas lumbar interbody fusion. Researchers have reported lumbar nerve roots and psoas muscle anatomy in the supine position, but no previous studies have used prone position magnetic resonance imaging to evaluate these structures. The purpose of this study was to show the changes in the lumbar nerve roots and psoas muscle related to the lumbar intervertebral disc using supine and prone magnetic resonance imaging. Thirty volunteers without spinal or hip abnormalities were included in this observational study. Each volunteer underwent supine and prone lumbosacral magnetic resonance imaging without abdominal compression. The lumbar nerve roots, psoas muscle, aorta, superior vena cava, common iliac artery, and vein were identified at each lumbar disc level. The lumbar plexus position relative to the transpsoas working channel, psoas muscle morphology, and great vessels relative to the anterior and posterior aspects of the annulus fibrosus in the axial plane were measured by 1 observer, and intraobserver reliability was calculated. Fifteen men and 15 women were included in this study. There were no significant differences in the axial image distance of the lumbar nerve roots, psoas/disc ratio, and location of other related anatomy between the supine and prone positions. More lordosis (both upper and lower arc lordosis) was noted in the prone position (51.98° ± 10.54°) than in the supine position (42.12°± 10.13°). Lumbar nerve roots, psoas morphology, and great vessel position were not affected by the prone position compared with the supine position.

Can supine breast magnetic resonance imaging help hit the target in extreme oncoplastic surgery?

ObjectivesTo evaluate the clinical value of supine magnetic resonance imaging (MRI) for tumor localization in breast cancer patients with large or multifocal tumors detected by prone MRI, scheduled for oncoplastic breast conserving surgery (OBCS). Outcomes were compared with those of patients who underwent wide local excision (WLE) or OBCS without MRI guidance. MethodsOver a 2-year period, consecutive patients with large or multifocal disease scheduled for OBCS with MRI-only findings were invited to participate (Group-1). Supplementary supine MRI was performed, and tumor margins were marked in the surgical position. Consecutive patients with early, non-palpable breast cancer who underwent WLE (Group-2) or OBCS (Group-3) were included for comparisons. The primary outcome was reoperation due to an insufficient margin. Secondary outcomes included surgical complications and delayed adjuvant treatment. ResultsAltogether, 102 breasts (98 patients) were analyzed. All preoperative demographic data were comparable among the three groups. Multifocality, tumor-to-breast volume ratio, and the volume of excised breast tissue were significantly greater in Group-1 than in Groups-2 and 3. Operation time was longer and the need for axillary clearance or surgery for both breasts was more common in Groups-1 and 3 than in Group-2. Adequate margins were achieved in all patients in Groups-1 and 2, and one patient underwent re-excision in Group-3. ConclusionsSupine MRI in the surgical position is a new, promising method to localize multifocal, large tumors visible on MRI. Its short-term outcomes were comparable with those of conventional WLE and OBCS.

Determining the axillary nodal status with four current imaging modalities including 18F-FDG PET/MRI in newly diagnosed breast cancer: A comparative study using histopathology as reference standard.

Purpose: To compare breast magnetic resonance imaging (MRI), thoracal MRI, thoracal 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET)/MRI and axillary sonography for the detection of axillary lymph node metastases in women with newly diagnosed breast cancer. Materials and Methods: This prospective double-center study included patients with newly diagnosed breast cancer between March 2018 and December 2019. Patients underwent thoracal (18F-FDG PET/)MRI, axillary sonography, and dedicated prone breast MRI. Datasets were evaluated separately regarding nodal status (nodal+ vs. nodal-). Histopathology served as reference standard in all patients. The diagnostic performance of breast MRI, thoracal MRI, thoracal PET/MRI and axillary sonography in detecting nodal positive patients was tested by creating receiver-operating-characteristic curves (ROC) with a calculated area under the curve (AUC). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated for all four modalities. A McNemar test was used to assess differences. Results: 112 female patients (mean age 53.04 ± 12.6 years) were evaluated. Thoracal PET/MRI showed the highest ROC-AUC with a value of 0.892. The AUC for breast MRI, thoracal MRI and sonography were 0.782, 0.814 and 0.834, respectively. Differences between thoracal PET/MRI and axillary sonography, thoracal MRI and breast MRI were statistically significant (PET/MRI vs. axillary sonography, P = 0.01; PET/MRI vs. thoracal MRI, P = 0.02; PET/MRI vs. breast MRI, P = 0.03). PET/MRI showed the highest sensitivity (81.8%, 36/44) (95%-CI: 67.29-91.81%) while axillary sonography had the highest specificity (98.5%, 65/66), 95%-CI: 91.84-99.96%). Conclusion: 18F-FDG PET/MRI outperforms axillary sonography, breast MRI and thoracal MRI in determining the axillary lymph node status. In a clinical setting, the combination of 18F-FDG PET/MRI and axillary sonography might be considered to provide even more accuracy in diagnosis.

Breast tumor movements analysis using MRI scans in prone and supine positions

We quantitatively evaluated breast tumor movement and volume changes between magnetic resonance imaging (MRI) scans in prone and supine positions. Twenty-seven breast tumor patients who received neoadjuvant systemic therapy (NST) for breast-conserving surgery were studied. Before and after NST, MRI scans in prone and supine positions were performed immediately. Tumor segmentation, volume, and position of tumors were evaluated in both positions. Average tumor volumes in prone and supine positions did not significantly differ (p = 0.877). Tumor movement from prone to supine positions from the origin of the bottom center of the sternum was strongly correlated with the distance from the tumor center to the chest wall (r = 0.669; p < 0.05). Tumor changes from prone to supine positions measured from the origin of the nipple depended on the location of the tumor in the breast. The prone-to-supine movement of all tumors from the origin of the bottom center of the sternum tended to move outward from the sagittal centerline of the body on the coronal plane, to the inside of the body on the sagittal plane, and outward and downward close to the body on the axial plane, which might help in planning operations using prone MRI in supine-position breast cancer surgery.

Feasibility of supine MRI (Magnetic Resonance Imaging)-navigated ultrasound in breast cancer patients

The purpose of this study was to evaluate the feasibility of image fusion between US and supine MRI in breast cancer patients, and to evaluate differences in tumor location between prone and supine positions. This prospective study included 88 patients who underwent an additional supine MRI (MRsup) sequence following routine prone MRI (MRpro) for breast cancer between May 2016 and December 2017. The location of the tumor and discrepancies in the distances from nipple to lesion (NLD), skin to lesion (SLD), and chest wall to lesion (CLD) were evaluated between MRpro and MRsup (MRpro-sup), MRpro and MRsup-navigated US (MRpro-USnav), and MRsup and USnav (MRsup-USnav). Associations between breast thickness and measurement discrepancies were analyzed. Total 91 index lesions were evaluated. The intraclass correlation coefficients (ICCs) for the location of MRpro and MRsup compared with USnav were 0.994 (range: 0.990-0.996) and 0.998 (range: 0.996-0.999), respectively. The mean MRpro-sup and MRpro-USnav measurement discrepancies were greater than those of MRsup-USnav, significantly. Most outer locations showed greater mean measurement discrepancies than inner locations, and each NLD, SLD, and CLD mean measurement discrepancy showed different tendencies according to location (upper or lower) and lesion depth (superficial, middle, or deep). High breast thickness showed significantly greater mean measurement discrepancies than low breast thickness. Image fusion between US and supine MRI is feasible in breast cancer patients, although there is a considerable difference in tumor location measurements between prone and supine positions, especially with thicker breasts.

Evaluation of breast stiffness measured by ultrasound and breast density measured by MRI using a prone-supine deformation model

BackgroundThis study evaluated breast tissue stiffness measured by ultrasound elastography and the percent breast density measured by magnetic resonance imaging to understand their relationship.MethodsMagnetic resonance imaging and whole breast ultrasound were performed in 20 patients with suspicious lesions. Only the contralateral normal breasts were analyzed. Breast tissue stiffness was measured from the echogenic homogeneous fibroglandular tissues in the central breast area underneath the nipple. An automatic, computer algorithm-based, segmentation method was used to segment the whole breast and fibroglandular tissues on three dimensional magnetic resonanceimaging. A finite element model was applied to deform the prone magnetic resonance imaging to match the supine ultrasound images, by using the inversed gravity loaded transformation. After deformation, the tissue level used in ultrasound elastography measurement could be estimated on the deformed supine magnetic resonance imaging to measure the breast density in the corresponding tissue region.ResultsThe mean breast tissue stiffness was 2.3 ± 0.8 m/s. The stiffness was not correlated with age (r = 0.29). Overall, there was no positive correlation between breast stiffness and breast volume (r = − 0.14), or the whole breast percent density (r = − 0.09). There was also no correlation between breast stiffness and the local percent density measured from the corresponding region (r = − 0.12).ConclusionsThe lack of correlation between breast stiffness measured by ultrasound and the whole breast or local percent density measured by magnetic resonance imaging suggests that breast stiffness is not solely related to the amount of fibroglandular tissue. Further studies are needed to investigate whether they are dependent or independent cancer risk factors.

Surgery of nonpalpable breast cancer: First step to a virtual per-operative localization? First step to virtual breast cancer localization.

Preoperative localization procedures of occult breast cancer (radioisotopic and wire localization) are invasive and uncomfortable. We have evaluated a novel technique which allows a virtual localization. Our retrospective study focused on patients treated for occult and unifocal breast cancer from September 2016 to June 2017. All patients had radioisotopic preoperative localization. We included patients who had a preoperative prone Magnetic Resonance Imaging (MRI) and an intraoperative 3D optical scan. During surgery, the surgeon localized the tumor thanks to a gamma detection probe and marked the localization on the skin with a black marker. The breast was then optically scanned. MRI was adjusted to the optical surface to match the exact breast position in the Operating Room. The virtual localization provided by the 3D breast modeling tool was retrospectively compared with the radioisotopic localization, defined as the pen mark visible in the optical scan. Nine patients were included in this feasibility study. Tumors were successfully localized in the respective breast quadrant. The mean cutaneous distance between virtual and radioisotopic localization was 1.4cm in patients with low breast volume (5/9) and 2.8cm in those with large breast volume (4/9). We developed a research prototype which enables virtual preoperative localization of nonpalpable breast lesions using MRI images and intraoperative optical scanning. Parameter optimization is required and will lead to a precise and noninvasive tool. By adding augmented reality, it will be possible to initiate a prospective study to compare this tool with the traditional localizations.

A comparative study based on deformable image registration of the target volumes for external-beam partial breast irradiation defined using preoperative prone magnetic resonance imaging and postoperative prone computed tomography imaging

BackgroundTo explore the differences and correlations between the target volumes defined using preoperative prone diagnostic magnetic resonance imaging (MRI) and postoperative prone computed tomography (CT) simulation imaging based on deformable image registration (DIR) for external-beam partial breast irradiation (EB-PBI) after breast-conserving surgery (BCS).MethodsEighteen breast cancer patients suitable for EB-PBI were enrolled. Preoperative prone diagnostic MRI and postoperative prone CT scan sets for all the patients were acquired during free breathing. Target volumes and ipsilateral breast were all contoured by the same radiation oncologist. The gross tumor volume (GTV) delineated on the preoperative MRI images was denoted as the GTVpreMR and the tumor bed (TB) delineated on the postoperative prone CT images was denoted as the GTVpostCT. The MIM software system was used to deformably register the MRI and CT images.ResultsWhen based on the coincidence of the compared target centers, there were statistically significant increases in the conformity index (CI) and degree of inclusion (DI) values for GTVpostCT-GTVpreMR, GTVpostCT-CTVpreMR + 10, CTVpostCT + 10-GTVpreMR, and CTVpostCT + 10-CTVpreMR + 10 when compared with those based on the DIR of the thorax (Z = − 3.724, − 3.724, − 2.591, − 3.593, all P < 0.05; Z = -3.724, − 3.724, − 3.201, − 3.724, all P < 0.05, respectively).ConclusionsAlthough based on DIR, there was relatively poor spatial overlap between the preoperative prone diagnostic MRI images and the postoperative prone CT simulation images for either the whole breast or the target volumes. Therefore, it is unreasonable to use preoperative prone diagnostic MRI images to guide postoperative target delineation for EB-PBI.

Deformation of breast masses between supine ultrasound and prone magnetic resonance imaging.

BackgroundBreast masses will deform between different postures and modalities in the background mammary gland. However, this difference in deformation between benign and malignant masses has not be...

Second-look US Using Real-time Virtual Sonography, a Coordinated Breast US and MRI System with Electromagnetic Tracking Technology: A Pilot Study

Our aim was to retrospectively evaluate the utility of second-look ultrasound (US) using real-time virtual sonography (RVS) for detection of conventional B-mode (cB-mode) occult magnetic resonance imaging (MRI)-detected breast lesions. Between July 2011 and May 2015, 53 consecutive patients who underwent second-look US to identify lesions detected by prone MRI were enrolled in this study. Second-look US using RVS was performed for cB-mode occult MRI-detected breast lesions after an additional supine MRI. In the 53 patients, 59 lesions were initially detected by prone MRI, followed by second-look US. Of the 59 lesions, 20 (34%) were identified by second-look US using cB-mode. Of the 39 (66%) cB-mode occult lesions, 38 (97%) were detected in supine MRI and 33 (85%) were detected by second-look US using RVS. MRI morphology types of the 33 lesions were as follows: mass, 16; non-mass enhancement, 5; and focus, 12. US-guided biopsy under RVS or excisional biopsy demonstrated that of the 33 lesions, 8 (24%) were malignant and the remaining 25 (76%) were benign. A total of 53 (90%) MRI-detected lesions were sonographically identified using both cB-mode and RVS (p < 0.001). All five remaining US-occult lesions could be followed up under RVS after the enhancing area was marked on the breast surface using RVS. Although further prospective studies are required, the findings of our pilot study suggest that second-look US using RVS with additional supine MRI may improve the sonographic and histopathologic detection rate of cB-mode occult MRI-detected breast lesions.

Supine Breast MRI Using Respiratory Triggering

This study aims to evaluate if navigator-echo respiratory-triggered magnetic resonance acquisition can acquire supine high-quality breast magnetic resonance imaging (MRI). Supine respiratory-triggered magnetic resonance imaging (Trig-MRI) was compared to supine non-Trig-MRI to evaluate breathing-induced motion artifacts (group 1), and to conventional prone non-Trig-MRI (group 2, 16-channel breast coil), all at 3T. A 32-channel thorax coil was placed on top of a cover to prevent breast deformation. Ten volunteers were scanned in each group, including one patient. The acquisition time was recorded. Image quality was compared by visual examination and by calculation of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and image sharpness (IS). Scan time increased from 56.5 seconds (non-Trig-MRI) to an average of 306 seconds with supine Trig-MRI (range: 120-540 seconds). In group 1, the median values (interquartile range) of SNR, CNR, and IS improved from 11.5 (6.0), 7.3 (3.1), and 0.23 (0.2) cm on supine non-Trig-MRI to 38.1 (29.1), 32.8 (29.7), and 0.12 (0) cm (all P < 0.01) on supine Trig-MRI. All qualitative image parameters in group 1 improved on supine Trig-MRI (all P < 0.01). In group 2, SNR and CNR improved from 14.7 (6.8) and 12.6 (5.6) on prone non-Trig-MRI to 36.2 (12.2) and 32.7 (12.1) (both P < 0.01) on supine Trig-MRI. IS was similar: 0.10 (0) cm vs 0.11 (0) cm (P = 0.88). Acquisition of high-quality supine breast MRI is possible when respiratory triggering is applied, in a similar setup as during subsequent treatment. Image quality improved when compared to supine non-triggered breast MRI and prone breast MRI, but at the cost of increased acquisition time.

Clinical Utility of Real-Time MR-Navigated Ultrasound with Supine Breast MRI for Suspicious Enhancing Lesions Not Identified on Second-Look Ultrasound

This study evaluated the usefulness of magnetic resonance (MR)-navigated ultrasound (US) for evaluation of magnetic resonance imaging (MRI)-detected lesions not visible on second-look US and analyzed differences in lesion-to-nipple distance between supine and prone positions. Of the 831 consecutive patients who were diagnosed with breast cancer and examined with breast MRI from June 2013 to September 2015, 40 lesions in 37 patients who underwent MR-navigated US for MRI-detected lesions that were not visible on second-look US were included. First, MRI was performed in a prone position using a 1.5-T imager, and second, MRI was performed in a supine position for MR-navigated US. Of 40 lesions, 31 (78%) were identified with MR-navigated US, whereas 5 (13%) lesions disappeared on supine MRI and 4 (10%) exhibited no correlation on MR-navigated US. Of 31 lesions with pathologic confirmation, 7 (23%) were malignant, 2 (6%) were high-risk lesions and 22 (71%) were benign lesions. Comparison of the US findings of benign and malignant lesions revealed that orientation of the lesion differed significantly (p = 0.045), whereas lesion shape, margin and echo pattern did not significantly differ between the two groups (p = 0.088, p = 0.094 and p = 0.412, respectively). Median difference in lesion-to-nipple distance on supine and prone MRI was 8 mm (0–34 mm) in the horizontal direction and 5 mm (0–39.5 mm) in the vertical direction. Thirteen lesions exhibited a >1-cm difference in both horizontal and vertical directions. In conclusion, MR-navigated US was useful for the evaluation of MRI-detected lesions that were not visible on second-look US in breast cancer patients.

Lumbar spinal canal dimensions measured intraoperatively after decompression are not properly rendered on early postoperative MRI.

BackgroundIn cases of lumbar spinal stenosis (LSS) treated with surgical decompression, a postoperative magnetic resonance imaging (MRI) is sometimes required. In the experience of the investigators of this study, the obtained decompression observed on early postoperative MRI tends to be disappointing compared to the decompression achieved intraoperatively. This raises the question of whether the early postoperative MRI, performed after lumbar decompression, is a fair representation of the ‘real’ decompression. This study investigated the correlation between intraoperative and postoperative measurements of the lumbar spinal canal.MethodTwenty patients with LSS underwent surgical decompression on a single level. The orthopaedic surgeon performed direct intraoperative measurements of width, length and height of the spinal canal. Preoperative supine MR images and postoperative prone and supine MR images were acquired. Two radiologists (R.B. and M.G.) measured width, length and height of the spinal canal on the preoperative and postoperative MRIs. Intraoperative measurements were compared to measurements on postoperative MRI in prone position (thus reproducing the intraoperative situation) to avoid positioning bias. Preoperative and postoperative measurements on MR images were also compared. In addition to this, postoperative measurements on supine and prone MR images were also compared.ResultsInterobserver reliability for MRI measurements by both radiologists was generally excellent (intraclass correlation coefficients ≥0.71). The postoperative spinal canal dimensions improved on both prone and supine MRI compared to the preoperative imaging (P < 0.05). Intraoperatively measured dimensions demonstrated a significantly greater height (difference 2.8 ± 3.3 [R.B.] and 1.9 ± 3.7 [M.G.]) and greater width (difference 2.1 ± 3.2 [R.B.] and 2.5 ± 2.7 [M.G.]) compared to postoperative MRI in the prone position (P < 0.05). Postoperative dural sac height was greater on the supine MRI compared to the prone MRI (P < 0.05).ConclusionsSurgical decompression of the spinal canal effectively decreases the compression of the dural sac. However, early postoperative MRI after lumbar decompression does not adequately represent the decompression achieved intraoperatively.

Assessment of MRI image quality for various setup positions used in breast radiotherapy planning

This study investigates breast magnetic resonance imaging (MRI) image quality for 3 different breast radiotherapy positions (prone, supine flat and supine inclined) and associated choice of breast coils. Supine breast MRI has comparable image quality to prone breast MRI for the purposes of radiotherapy delineation for T2-weighted sequences.

Prediction of prone-to-supine tumor displacement in the breast using patient position change: investigation with prone MRI and supine CT.

One of the challenges for clinical use of preoperative breast magnetic resonance imaging (MRI) is how to transfer prone MRI information to the operating theater with a supine surgical position. The aim of this study was to retrospectively evaluate tumor displacement in the breast by changing the patient position from prone to supine (prone-to-supine tumor displacement), using preoperative prone MRI and supine computed tomography (CT). Preoperatively, 55 Japanese women with 57 breast cancer lesions underwent breast MRI in the prone position and breast CT in the supine position. Tumor positions in both the prone and supine positions were measured on X-, Y-, and Z-coordinates by fixing the nipple to the origin (0, 0, 0). As an indicator of the mobility of the breast, the ratio of the breast projection between the prone MRI and supine CT (prone-to-supine projection ratio) was calculated. The direction and distance of prone-to-supine tumor displacement was analyzed by dividing the breast into four quadrants according to the tumor position. When changing the patient position from prone to supine, tumors located in the inner-upper and inner-lower quadrants tended to move radially toward the center of the nipple. The movement distance of the tumors in the inner-lower and outer-lower quadrants was very strongly correlated with the prone-to-supine breast projection ratio (r ≥ 0.8, p < 0.05). Conversely, in the outer-upper quadrant, the direction of tumor displacement was variable, and the distance of tumor displacement did not correlate with the prone-to-supine projection ratio. The present study showed that prone-to-supine tumor displacement in the breast differs depending on tumor location. The inner-lower quadrant of the breast may be the most predictable area for prone-to-supine tumor displacement.

Supine Breast MRI and 3D Optical Scanning: A Novel Approach to Improve Tumor Localization for Breast Conserving Surgery

Wire localization for excision of nonpalpable breast cancer is an inefficient and inexact technique. A total of 18 women with palpable invasive breast cancers underwent preoperative prone and supine magnetic resonance imaging (MRI). Intraoperatively, the edges of the tumor were palpated and marked on the skin surface. The breast was optically scanned, and the supine MRI was adjusted to match the actual breast position at the time of surgery. Image-defined tumor edges were marked on the surface of the breast. The main outcome measure was the distance between the image-defined and palpation-defined edges of the tumor. No significant difference was found between the mean maximal tumor diameter as measured by histopathology (29.6 ± 14.3 mm), supine MRI (25.3 ± 9.7 mm), prone MRI (27.6 ± 13 mm), or palpation (30.5 ± 9.3 mm). The distance from the tumor to the chest wall was markedly different in prone versus supine MRI (56.4 ± 38 vs 19.5 ± 20 mm, p = .002). The average distance between the palpated and supine MRI image-defined tumor edge locations was 7.2 mm (range, 0-19 mm). Accuracy improved over time; the average difference in edge locations in the last 7 patients was 4.0 mm. All 4 image-defined edge locations in the last 5 patients were ≤ 1 cm away from the palpated locations. We have developed a method of breast tumor localization using preoperative supine MRI and intraoperative optical scanning that defines tumor size and position as accurately as palpation.