An exploratory study of pelvis anatomy to revise the bony canal used for LC2 screw insertion.

BACKGROUND: Percutaneous screw placement, especially the insertion of LC2 screws, is technically demanding. Although the traditional LC2 bony canal spans the anterior inferior iliac spine (AIIS) to the posterior superior iliac spines (PSIS), a high perforation rate has been reported. OBJECTION: The aim of this research was to design a revised bony canal, measure the canal width and length and guide the insertion of LC2 screws for pelvic fractures. MATERIALS AND METHODS: The plane tool in the Mimics analysis menu was used to draw a midplane connecting the midpoint between the anterior inferior spine and the PSIS upper flat region with pelvic CT data. The minimum widths of the upper, middle, lower surfaces of the tunnel and perforation rate were measured and compared. The ideal screw length was also measured along the longitudinal axis running through the midpoint of the midplane. RESULTS: The minimum widths of the upper, middle and lower surfaces of the revised canal were 3.63 mm, 7.7 mm, and 11.93 mm, respectively, in males and 5.97 mm, 9.93 mm, and 12.45 mm, respectively, in females. Significant differences were observed among the upper, middle and lower surfaces of the revised canal in male patients (P < 0.001). In female subjects, the upper canal surface was significantly different from the middle and lower canal surfaces (P < 0.001). The perforation rate was significantly decreased especially in females pelvic. The channel length passing through the midpoint of the narrowest position of the pelvis was 130.85 ± 8.02 mm in males and 124.30 ± 7.71 mm in females and was significantly different for male and female pelvises (P = 0.004). CONCLUSION: The LC2 screw should be inserted along the intersection line of the AIIS lateral wall and the iliac body. The screw should be inserted under the line between the midpoint of the AIIS and the PSIS upper flat region to ensure accuracy of placement. LC2 screws can be more easily inserted in males than in females, and the rate of cortical perforation can be significantly decreased under the guidance of the newly proposed canal.

Dosimetric evaluation of an atlas-based synthetic CT generation approach for MR-only radiotherapy of pelvis anatomy.

PURPOSE: To investigate the potential of an atlas-based approach in generation of synthetic CT for pelvis anatomy. METHODS: Twenty-three matched pairs of computed tomography (CT) and magnetic resonance imaging (MRI) scans were selected from a pool of prostate cancer patients. All MR scans were preprocessed to reduce scanner- and patient-induced intensity inhomogeneities and to standardize their intensity histograms. Ten (training dataset) of 23 pairs were then utilized to construct the coregistered CT-MR atlas. The synthetic CT for a new patient is generated by appropriately weighting the deformed atlas of CT-MR onto the new patient MRI. The training dataset was used as an atlas to generate the synthetic CT for the rest of the patients (test dataset). The mean absolute error (MAE) between the deformed planning CT and synthetic CT was computed over the entire CT image, bone, fat, and muscle tissues. The original treatment plans were also recomputed on the new synthetic CTs and dose-volume histogram metrics were compared. The results were compared with a commercially available synthetic CT Software (MRCAT) that is routinely used in our clinic. RESULTS: MAE errors (±SD) between the deformed planning CT and our proposed synthetic CTs in the test dataset were 47 ± 5, 116 ± 12, 36 ± 6, and 47 ± 5 HU for the entire image, bone, fat, and muscle tissues respectively. The MAEs were 65 ± 5, 172 ± 9, 43 ± 7, and 42 ± 4 HU for the corresponding tissues in MRCAT CT. The dosimetric comparison showed consistent results for all plans using our synthetic CT, deformed planning CT and MRCAT CT. CONCLUSION: We investigated the potential of a multiatlas approach to generate synthetic CT images for the pelvis. Our results demonstrate excellent results in terms of HU value assignment compared to the original CT and dosimetric consistency.

3D Models of Female Pelvis Structures Reconstructed and Represented in Combination with Anatomical and Radiological Sections.

We present a computer program designed to visualize and interact with three-dimensional models of the main anatomical structures of the female pelvis. They are reconstructed from serial sections of corpse, from the Visible Human project of the Medical Library of the United States and from serial sections of high-resolution magnetic resonance. It is possible to represent these three-dimensional structures in any spatial orientation, together with sectional images of corpse and magnetic resonance imaging, in the three planes of space (axial, coronal and sagittal) that facilitates the anatomical understanding and the identification of the set of visceral structures of this body region. Actually, there are few studies that analysze in detail the radiological anatomy of the female pelvis using three-dimensional models together with sectional images, making use of open applications for the representation of virtual scenes on low cost Windows® platforms. Our technological development allows the observation of the main female pelvis viscera in three dimensions with a very intuitive graphic interface. This computer application represents an important training tool for both medical students and specialists in gynecology and as a preliminary step in the planning of pelvic floor surgery.

Renal pelvic anatomy is associated with incidence, grade, and need for intervention for urine leak following partial nephrectomy.

BACKGROUND: Although the effect of tumor complexity on perioperative outcome measures is well established, the impact of renal pelvic anatomy on perioperative outcomes remains poorly defined. OBJECTIVE: To evaluate renal pelvic anatomy as an independent predictor of urine leak in moderate- and high-complexity tumors undergoing nephron-sparing surgery. DESIGN, SETTING, AND PARTICIPANTS: Patients undergoing open partial nephrectomy (PN) for localized RCC were stratified into intermediate- and high-complexity groups using a nephrometry score (7-9 and 10-12, respectively). A renal pelvic score (RPS) was defined by the percentage of renal pelvis contained inside the volume of the renal parenchyma. On this basis, patients were categorized as having an intraparenchymal (>50%) or extraparenchymal (<50%) renal pelvis. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Characteristics of patients with and without an intraparenchymal renal pelvic anatomy were compared. RESULTS AND LIMITATIONS: Inclusion criteria were met by 255 patients undergoing PN for intermediate (73.6%) and complex (26.4%) localized renal tumors (mean size: 4.6±2.9cm). Twenty-four (9.6%) renal pelves were classified as completely intraparenchymal. Following stratification by RPS, groups differed with respect to Charlson comorbidity index, body mass index, and largest tumor size, while no differences were observed between hospital length of stay, nephrometry score, estimated blood loss, operative time, and age. Intrarenal pelvic anatomy was associated with a markedly increased risk of urine leak (75% vs 6.5%; p=0.001), secondary intervention (37.5% vs 3.9%; p<0.001), and prolonged duration of urine leak (93±62 d vs 56±29 d; p=0.025). CONCLUSIONS: Intraparenchymal renal pelvic anatomy is an uncommon anatomic variant associated with an increased rate of urine leak following PN. Elevated pressures within a small intraparenchymal renal pelvis might explain the increased risk. Preoperative imaging characteristics suggestive of increased risk for urine leak should be considered in perioperative management algorithms.