Pelvic Bone Structures Research Articles

Pelvic exenteration for locally advanced and recurrent prostate cancer

Locally advanced or recurrent prostate cancer which invades adjacent pelvic organs, bone or other soft tissue structures is a rare situation. This study aimed to report the outcomes of ten consecutive patients who underwent total pelvic exenteration for prostate cancer at a high-volume specialist centre. Two patients had locally advanced primary tumours, while eight had locally recurrent prostate cancer. Median operating time, blood loss, ICU stay, and hospital stay was 12.2 h (range 9.6–13.8), 2500 ml (500–3000), 4.5 days (2–7) and 36 days (21–78), respectively. There was no inpatient, 30-day, or 90-day mortality. Six patients developed a Clavien-Dindo III complication. R0 resection was achieved in eight patients. Median follow up was 16 months (range 2–77). At last follow up, five patients were alive without disease. These findings suggest that pelvic exenteration for locally advanced and recurrent prostate cancer is safe and represents a potentially curative treatment option for highly selected patients.

Machine learning based gray-level co-occurrence matrix early warning system enables accurate detection of colorectal cancer pelvic bone metastases on MRI.

The mortality of colorectal cancer patients with pelvic bone metastasis is imminent, and timely diagnosis and intervention to improve the prognosis is particularly important. Therefore, this study aimed to build a bone metastasis prediction model based on Gray level Co-occurrence Matrix (GLCM) - based Score to guide clinical diagnosis and treatment. We retrospectively included 614 patients with colorectal cancer who underwent pelvic multiparameter magnetic resonance image(MRI) from January 2015 to January 2022 in the gastrointestinal surgery department of Gezhouba Central Hospital of Sinopharm. GLCM-based Score and Machine learning algorithm, that is,artificial neural net7work model(ANNM), random forest model(RFM), decision tree model(DTM) and support vector machine model(SVMM) were used to build prediction model of bone metastasis in colorectal cancer patients. The effectiveness evaluation of each model mainly included decision curve analysis(DCA), area under the receiver operating characteristic (AUROC) curve and clinical influence curve(CIC). We captured fourteen categories of radiomics data based on GLCM for variable screening of bone metastasis prediction models. Among them, Haralick_90, IV_0, IG_90, Haralick_30, CSV, Entropy and Haralick_45 were significantly related to the risk of bone metastasis, and were listed as candidate variables of machine learning prediction models. Among them, the prediction efficiency of RFM in combination with Haralick_90, Haralick_all, IV_0, IG_90, IG_0, Haralick_30, CSV, Entropy and Haralick_45 in training set and internal verification set was [AUC: 0.926,95% CI: 0.873-0.979] and [AUC: 0.919,95% CI: 0.868-0.970] respectively. The prediction efficiency of the other four types of prediction models was between [AUC: 0.716,95% CI: 0.663-0.769] and [AUC: 0.912,95% CI: 0.859-0.965]. The automatic segmentation model based on diffusion-weighted imaging(DWI) using depth learning method can accurately segment the pelvic bone structure, and the subsequently established radiomics model can effectively detect bone metastases within the pelvic scope, especially the RFM algorithm, which can provide a new method for automatically evaluating the pelvic bone turnover of colorectal cancer patients.

Evaluation of prostate multi parameter bone structures for martial arts practitioners based on magnetic resonance imaging

ObjectiveIn this paper, we studied the feasibility of automatic segmentation of bone structures for rehabilitation and disease prevention from diffusion-weighted and apparent diffusion coefficient images obtained from prostate multi-parameter magnetic resonance imaging (mpMRI) in the healthy promotion of Chinese Taijiquan martial arts. MethodsThe mpMRI images of 15 patients practicing Taijiquan martial arts were analyzed retrospectively. We manually annotate bone structures on DWI (b = 800 s/mm2), DWI (b = 0S/mm2), and ADC images. Then, we use different sequence combinations as input data to test the segmentation model, and evaluate the impact of six different sequence combinations on the region-based segmentation performance, such as the watershed model. The model evaluation indicators include quantitative indicators (DICE coefficient, label capacity) and qualitative indicators (subjective score). The model evaluation standard calculates the coincidence rate of all sequences in the test set, and more than 80% are considered to meet the clinical application requirements. ResultsThe DICE value of the watershed segmentation model was 0.75 (0.70–0.81) −0.81 (0.73–0.85) on DWI images, and the ADC value was 0.79 (0.78–0.81) −0.83 (0.80–0.85). However, there was no significant difference in DICE value between different models (HDWI = 2.978, PDWI>0.05; HADC = 1.140, PADC>0.05). There was no significant difference in the volume difference between model prediction and manual labeling among different models (HDWI = 2.900, PDWI>0.05; HADC = 2.236, PADC>0.05). Qualitative scoring models 1 and 3 achieved the highest standard rate in DWI and ADC image segmentation, both above 80%. ConclusionAfter Taijiquan martial arts exercise, it is found that the DWI segmentation model based on watershed region combined with ADC sequence can achieve high-performance segmentation of pelvic bone structure in prostate mpMRI, meet the needs of clinical application, and is conducive to healthy sports for all.

Pelvic Insufficiency Fractures and Bone Pain after Radiation Therapy for Anal Cancer: Relation to Pelvic Bone Dose-Volume Parameters

PurposeChemoradiation therapy is the primary treatment for anal cancer. Radiation therapy (RT) can weaken the pelvic bone structure, but the risk of pelvic insufficiency fractures (PIFs) and derived pain in anal cancer is not yet established. We determined the frequency of symptomatic PIFs after RT for anal cancer and related this to radiation dose to specific pelvic bone substructures. Methods and MaterialsIn a prospective setting, patients treated with RT for anal cancer had magnetic resonance imaging 1 year after RT. PIFs were mapped to 17 different bone sites, and we constructed a guideline for detailed delineation of pelvic bone substructures. Patients were interviewed regarding pain and scored according to Common Terminology Criteria for Adverse Effects. Dose-volume relationships for specific pelvic bone substructures and PIFs were determined for V20 to V40 Gy mean and maximum doses. ResultsTwenty-seven patients were included, and 51.9% had PIFs primarily located in the alae of the sacral bone. Patients with PIFs had significantly more pelvic pain (86% vs 23%, P = .001) and 43% had grade 2 bone pain. Dose-volume parameters for sacral bone and sacral alae were significantly higher in patients with PIFs (P < .05). V30 Gy (%) for sacral bone and alae implied an area under the curve of 0.764 and 0.758, respectively, in receiver operating characteristic analyses. ConclusionsWe observed a high risk of PIFs in patients treated with RT for anal cancer 1 year after treatment. A significant proportion had pain in the sites where PIFs were most frequently found. Radiation dose to pelvic bone substructures revealed relation to risk of PIFs and can be used for plan optimization in future clinical trials.

Development of a total hip replacement phantom for the assessment of CT-image quality.

The quality of computed tomography (CT) imaging is important when used to judge the success of joint replacement surgery. Metal artefacts are a known source of error, typically compensated by noise reduction software. To develop a transportable and stable system for the assessment of image quality of bone lesions around orthopedic implants. The design and manufacture of a bone-implant-phantom is described, which is based on a calf acetabulum with surrounding pelvic bone structures. Bone lesions of several sizes were created in the acetabulum before implanting the cup of an uncemented hip prosthesis, which was fixed with a stainless-steel bone screw. Plastic strips were placed on a cobalt-chromium stemmed femoral component, simulating typical bone lesions around loosening or infected prostheses, before embedding the stem in material similar to bone and shaped like a femur. The head of the femoral component was then placed in the acetabular cup and CT scans were produced. It was possible to construct a durable CT hip phantom for quality assurance work. The usability of different materials and the choices made for the phantom are discussed. It is possible to construct a durable joint implant phantom for quality assurance and scanner hardware and software assessment with limited resources. The phantom was successfully used in the assessment of the hardware and software performance of different CT scanners.

114. Pelvic bone marrow dosimetric parameters analysis relating to hematologic toxicity in gynecological tumors patients treated with volumetric modulated arc therapy

Purpose To test the hypothesis that the volume of pelvic bone marrow (PBM) receiving 10–20-30–40 Gy (V10-V20-V30-V40) and median dose is associated with hematologic toxicity (HT) in gynecological cancer patients treated with concurrent chemoradiotherapy. Methods and materials We analyzed 29 consecutive gynecological cancer patients (21 only RT and 8 with concurrent chemotherapy) and volumetric-modulated-arc radiation therapy at the Varese Hospital between 2013 and 2015. The median radiation dose prescribed was 50.4 Gy (1,8 Gy daily fractions). The external contour of the PBM was delineated on the planning CT using bone windows was defined as the region extending from the iliac crests to the ischial tuberosities, including the os coxae, lumbosacral spine and proximal femora, and the relative dose volume histogram (DVHs) were calculated. HT was graded according to CTCAE and endpoints included the white blood cell count, absolute neutrophil count, hemoglobin, and platelet count nadirs. Results Non-parametric test for independent samples (Mann–Whitney test) show that the difference between the two groups was not significant for any Vx (p = 0.49). The Table 1 shows the mean values referred all patients in relation to the dose constraints used in the treatment planning. We identified only one patient associated with acute HT G3 (Table 1). Conclusion Techniques to limit PBM irradiation may reduce HT in cervical cancer patients. Only one patient developed acute HT G3, however, the values of DVH(Vx) related to pelvic bone structures are within the dose constraints. V40 results the most critical volume, this value is above the limit in 58.6% of patients, but none of them has developed acute HT. The Vx proposed by the scientific community are valid and safe for HT. We’re working on calculating cumulative DVH area-equivalent using the Lymann algorithm in order to evaluate if this parameter is capable of describing toxicity better than usual indexes like V10-V40.

Bone development of the skull, pectoral and pelvic fins in Seriola rivoliana (Valenciennes, 1833) larvae.

Skull, pectoral and pelvic fin bone structures in longfin yellowtail Seriola rivoliana were studied from 3.43±0.15 to 16.20±0.73mm standard length (SL) specimens. The S. rivoliana skull started to mineralize with the appearance of the parasphenoid and maxillary by 3.43±0.15mm SL at the neurocranium and jaw regions, respectively. The first pectoral structure to mineralize was the cleithrum at 3.75±0.14mm SL shortly followed by the supracleithrum and posttemporal. The pelvic fin started by 6.16±0.32mm SL with the spine and continued with the soft rays and basipterygium. The present study determined the onset of the skull, pectoral and pelvic fin mineralization. These results might be used as a reference for future studies in S. rivoliana or related species.

Does hemipelvis structure and position influence acetabulum orientation?

BackgroundAlthough acetabulum orientation is well established anatomically and radiographically, its relation to the innominate bone has rarely been addressed. If explored, it could open the discussion on patomechanisms of such complex disorders as femoroacetabular impingement (FAI). We therefore evaluated the influence of pelvic bone position and structure on acetabular spatial orientation. We describe this relation and its clinical implications.MethodsThis retrospective study was based on computed tomography scanning of three-dimensional models of 31 consecutive male pelvises (62 acetabulums). All measurements were based on CT spatial reconstruction with the use of highly specialized software (Rhinoceros). Relations between acetabular orientation (inclination, tilt, anteversion angles) and pelvic structure were evaluated. The following parameters were evaluated to assess the pelvic structure: iliac opening angle, iliac tilt angle, interspinous distance (ISD), intertuberous distance (ITD), height of the pelvis (HP), and the ISD/ITD/HP ratio. The linear and nonlinear dependence of the acetabular angles and hemipelvic measurements were examined with Pearson’s product − moment correlation and Spearman’s rank correlation coefficient. Correlations different from 0 with p < 0.05 were considered statistically significant.ResultsComparison of the axis position with pelvis structure with orientation in the horizontal plane revealed a significant positive correlation between the acetabular anteversion angle and the iliac opening angle (p = 0.041 and 0.008, respectively). In the frontal plane, there was a positive correlation between the acetabular inclination angle and the iliac tilt angle (p = 0.025 and 0.014, respectively) and the acetabular inclination angle and the ISD/ITD/HP ratio (both p = 0.048).ConclusionsThere is a significant correlation of the hemipelvic structure and acetabular orientation under anatomic conditions, especially in the frontal and horizontal planes. In the anteroposterior view, the more tilted-down innominate bone causes a more caudally oriented acetabulum axis, whereas in the horizontal view this relation is reversed. This study may serve as a basis for the discussion on the role of the pelvis in common disorders of the hip.

Automated Localization of Multiple Pelvic Bone Structures on MRI

In this paper, we present a fully automated localization method for multiple pelvic bone structures on magnetic resonance images (MRI). Pelvic bone structures are at present identified manually on MRI to locate reference points for measurement and evaluation of pelvic organ prolapse (POP). Given that this is a time-consuming and subjective procedure, there is a need to localize pelvic bone structures automatically. However, bone structures are not easily differentiable from soft tissue on MRI as their pixel intensities tend to be very similar. In this paper, we present a model that combines support vector machines and nonlinear regression capturing global and local information to automatically identify the bounding boxes of bone structures on MRI. The model identifies the location of the pelvic bone structures by establishing the association between their relative locations and using local information such as texture features. Results show that the proposed method is able to locate the bone structures of interest accurately (dice similarity index >0.75) in 87-91% of the images. This research aims to enable accurate, consistent, and fully automated localization of bone structures on MRI to facilitate and improve the diagnosis of health conditions such as female POP.

Fully automated localization of multiple pelvic bone structures on MRI.

In this paper, we present a fully automated localization method for multiple pelvic bone structures on magnetic resonance images (MRI). Pelvic bone structures are currently identified manually on MRI to identify reference points for measurement and evaluation of pelvic organ prolapse (POP). Given that this is a time-consuming and subjective procedure, there is a need to localize pelvic bone structures without any user interaction. However, bone structures are not easily differentiable from soft tissue on MRI as their pixel intensities tend to be very similar. In this research, we present a model that automatically identifies the bounding boxes of the bone structures on MRI using support vector machines (SVM) based classification and non-linear regression model that captures global and local information. Based on the relative locations of pelvic bones and organs, and local information such as texture features, the model identifies the location of the pelvic bone structures by establishing the association between their locations. Results show that the proposed method is able to locate the bone structures of interest accurately. The pubic bone, sacral promontory, and coccyx were correctly detected (DSI > 0.75) in 92%, 90%, and 88% of the testing images. This research aims to enable accurate, consistent and fully automated identification of pelvic bone structures on MRI to facilitate and improve the diagnosis of female pelvic organ prolapse.

MRI-based segmentation of pubic bone for evaluation of pelvic organ prolapse.

Pelvic organ prolapse (POP) is a major women's health problem. Its diagnosis through magnetic resonance imaging (MRI) has become popular due to current inaccuracies of clinical examination. The diagnosis of POP on MRI consists of identifying reference points on pelvic bone structures for measurement and evaluation. However, it is currently performed manually, making it a time-consuming and subjective procedure. We present a new segmentation approach for automating pelvic bone point identification on MRI. It consists of a multistage mechanism based on texture-based block classification, leak detection, and prior shape information. Texture-based block classification and clustering analysis using K-means algorithm are integrated to generate the initial bone segmentation and to identify leak areas. Prior shape information is incorporated to obtain the final bone segmentation. Then, the reference points are identified using morphological skeleton operation. Results demonstrate that the proposed method achieves higher bone segmentation accuracy compared to other segmentation methods. The proposed method can also automatically identify reference points faster and with more consistency compared with the manually identified point process by experts. This research aims to enable faster and consistent pelvic measurements on MRI to facilitate and improve the diagnosis of female POP.

TU‐G‐134‐03: MR‐Only‐Based Generation of Electron Density Maps and Digitally Reconstructed Radiographs of the Pelvis

Purpose: To generate electron density (ED) maps and digitally reconstructed radiographs (DRRs) of the pelvis based only on magnetic resonance imaging (MRI). Methods: A conventional 3D fast‐field dual‐echo sequence was used to acquire image data of 8 healthy subjects with a Philips 3.0T Ingenia TX system in approximately 1:50 min scan time per volunteer. Dixon reconstruction of the nearly out‐of‐phase (echo 1) and in‐phase images (echo 2) allowed for water and fat classification. A bone‐enhanced image was generated by automatically thresholding the noise level of the in‐phase image with subsequent background removal. ED maps were then produced by assigning known bulk electron densities to the classified bone and tissue fractions. A bone probability atlas derived from CT data was registered to the ED map in order to filter out misclassified voxels. Finally, DRRs were reconstructed from bone‐enhanced images as well as from ED maps. Results: The proposed MRI sequence with subsequent Dixon reconstruction and probabilistic filtering makes it possible to classify cortical bone, soft tissue and adipose tissue in the pelvis and yields ED maps and corresponding DRRs. Bowel content was misclassified as cortical bone or air and compromised the segmentation in some slices as well as in the DRRs. Automatic probabilistic atlas filtering can significantly reduce artifacts induced by bowel content without affecting pelvic bone structures markedly. In total, the artifact/bone fraction dropped from 1.7 before filtering to 0.2 after filtering. The average reduction of artifact volume is 87%, and the average bone preservation is 99%. Remaining artifacts are spatially close to the true bone in areas of positive bone probability. Conclusion: This study demonstrated the feasibility of generating realistic ED maps of the pelvis by using MRI only. The method has the potential to become an essential component of emerging applications such as MR‐only‐based radiation therapy planning. All authors have the following relevant financial interest or relationship to disclose with regard to the subject matter of this presentation: Company name: Philips Research; Type of relationship: Employee

A standardized classification of hypospadias

ObjectiveSystems for categorizing hypospadias are based on the location of the external meatus. The presented proposal draws on the organogenesis of the urethra and its position against the bone structure of the pelvis. The aim of the study was to examine the position of the corpus spongiosum division relative to pelvic bone structures as an indicator of the true level of hypospadias. Patients and methodsThe study involved 150 patients aged 6 months to 22.8 years admitted for primary repair. The division of the corpus spongiosum was examined relative to the shaft of the penis and the upper pubis. Hypospadias above the pubis was categorized as penile, while below was proximal, with further subcategorization. The quality of the distal urethral canal was assessed. ResultsThe external meatus was above the pubis in 94.1% while the division of corpus spongiosum was located above the pubis in 90% (distal penile 38%, mid shaft 25.3%). There was a considerable difference in hypospadias level relative to the indicator used. The distal meatus/urethra was stenotic in 84%, hypoplastic in 86.8% with true chordee in 10.4%. ConclusionsA classification of hypospadias based on organogenesis and in respect to bony structures of the pelvis seems reliable, consistent, and more surgically oriented. The distal urethral canal should be regarded as a fistula.

Automated Preoperative Planning Procedure for Acetabular Cup Based on 3D Pelvic Bone Structure in Total Hip Replacement

Automated Preoperative Planning Procedure for Acetabular Cup Based on 3D Pelvic Bone Structure in Total Hip Replacement

Biomechanical response of the pubic symphysis in lateral pelvic impacts: A finite element study

Automotive side impacts are a leading cause of injuries to the pubic symphysis, yet the mechanisms of those injuries have not been clearly established. Previous mechanical testing of isolated symphyses revealed increased joint laxity following drop tower lateral impacts to isolated pelvic bone structures, which suggested that the joints were damaged by excessive stresses and/or deformations during the impact tests. In the present study, a finite element (FE) model of a female pelvis including a previously validated symphysis sub-model was developed from computed tomography data. The full pelvis model was validated against measured force–time impact responses from drop tower experiments and then used to study the biomechanical response of the symphysis during the experimental impacts. The FE models predicted that the joint underwent a combination of lateral compression, posterior bending, anterior/posterior and superior/inferior shear that exceeded normal physiological levels prior to the onset of bony fractures. Large strains occurred concurrently within the pubic ligaments. Removal of the contralateral constraints to better approximate the boundary conditions of a seated motor vehicle occupant reduced cortical stresses and deformations of the pubic symphysis; however, ligament strains, compressive and shear stresses in the interpubic disc, as well as posterior bending of the joint structure remained as potential sources of joint damage during automotive side impacts.

Fatigue failure in the cement mantle of a simplified acetabular replacement model

Although the role of fatigue failure in aseptic loosening of cemented total hip replacements has been extensively studied in femoral components, studies of fatigue failure in cement mantle of acetabular replacements have yet to be reported, despite that the long-term failure rate in the latter is about three times that of femoral components. Part of the reason may be that a complex pelvic bone structure does not land itself readily for a 2D representation as that of a femur.In this work, a simple multilayer model has been developed to reproduce the stress distributions in the cement mantle of an acetabular replacement from a plane strain finite element pelvic bone model. The experimental multilayer model was subjected to cyclic loading up to peak hip contact force during normal walking. Radial fatigue cracks were observed in the vicinity of the maximum tangential and compressive stresses, as predicted by the FE models. Typical fatigue striations were also observed on the fracture surfaces post cyclic testing. The results were examined in the context of retrieval studies, 3D FE analysis and in vitro experimental results using full-sized hemi-pelvic bone models.

Use and uncertainties of mutual information for computed tomography/magnetic resonance (CT/MR) registration post permanent implant of the prostate

Post-implant dosimetric analysis for permanent implant of the prostate benefits from the use of a computed tomography (CT) dataset for optimal identification of the radioactive source (seed) positions and a magnetic resonance (MR) dataset for optimal description of the target and normal tissue volumes. The CT/MR registration process should be fast and sufficiently accurate to yield a reliable dosimetric analysis. Since critical normal tissues typically reside in dose gradient regions, small shifts in the dose distribution could impact the prediction of complication or complication severity. Standard procedures include the use of the seed distribution as fiducial markers (seed match), a time consuming process that relies on the proper identification of signals due to the same seed on both datasets. Mutual information (MI) is more efficient because it uses image data requiring minimal preparation effort. A comparison of MI registration and seed-match registration was performed for twelve patients. MI was applied to a volume limited to the prostate and surrounding structures, excluding most of the pelvic bone structures (margins around the prostate gland were approximately 2 cm right-left, approximately 1 cm anterior-posterior, and approximately 2 cm superior-inferior). Seeds were identified on a 2 mm slice CT dataset using an automatic seed identification procedure on reconstructed three-dimensional data. Seed positions on the 3 mm slice thickness T2 MR data set were identified using a point-and-click method on each image. Seed images were identified on more than one MR slice, and the results used to determine average seed coordinates for MR images and matched seed pairs between CT and MR images. On average, 42% (19%-64%) of the seeds (19-54 seeds) were identified and matched to their CT counterparts. A least-squares method applied to the CT and MR seed coordinates was used to produce the optimum seed-match registration. MI registration and seed match registration angle differences averaged 0.5 degrees, which was not significantly different from zero. Translation differences averaged 0.6 (1.2 standard deviation) mm right-left, -0.5(1.5) mm posterior-anterior, and -1.2(2.0) mm inferior-superior. Registration error estimates were approximately 2 mm for both the MI and seed-match methods. The observed standard deviations in the offset values were consistent with propagation of error. Registration methods as applied here using mutual information and seed matching are consistent, except for a small systematic difference in the inferior-superior axis for a minority of cases (approximately 15%). Cases registered with mutual information and with bony anatomy misregistration of greater than approximately 5 mm should be evaluated for rescan or seed-match registration. The improvement in efficiency of use for the MI registration method is substantial, approximately 30 min compared to several hours using seed match registration.

Posterior approach to the sciatic nerve in adults: is euclidean geometry still necessary?

Every approach to the sciatic nerve in the buttocks currently requires the identification of pelvic bone structures. The large size of the nerve and its constant trajectory suggest that a simplified approach is possible. During the first stage, 24 sciatic nerves in adult cadavers were dissected. The most significant findings were, (1) caudal to the piriformis muscle the sciatic nerve runs parallel to the midline (intergluteal sulcus); (2) the distance between the nerve and the intergluteal sulcus during this course is approximately 10 cm in adults, regardless of their gender, size, or body habits. In the clinical stage 20 blocks were performed at 10 cm from the midline of the buttocks using a nerve stimulator and insulated needles. All blocks were accomplished in less than 8.5 min. The technique proved easy to teach. Residents performed most of the blocks. Incision time, measured from the time of the injection, was less than 29 min in all cases. There were 18 successful blocks and 2 failures. Because of the intimate relationship of the sciatic nerve to the bony pelvis, the position of this nerve in the buttocks is constant. Caudal to the piriformis muscle the nerve runs vertically between the ischium and the greater trochanter. The location of this narrow passage, not the buttocks' size, determines the position of the nerve. While the size of the buttocks is variable among different individuals and in the same individual at different stages of adult life, the relationship of the sciatic nerve to the pelvis is constant throughout life. Using this relationship to our advantage, a sciatic block in adults can be accomplished at 10 cm lateral to the intergluteal sulcus without a need for identification of buried structures or line tracings.

Electronic portal imaging device detection of radioopaque markers for the evaluation of prostate position during megavoltage irradiation: A clinical study

Purpose : This study was designed to assess daily prostatic apex motion relative to pelvic bone structures during megavoltage irradiation. Methods and Materials : Radioopaque markers were implanted under ultrasound guidance near the prostatic apex of 11 patients with localized prostatic carcinoma. Patients were subsequently treated with a four field-box technique at a beam energy of 23 MV. During treatment, on-line images were obtained with an electronic portal imaging device (EPID). The marker was easily identified, even on unprocessed images, and the distance between the marker and a bony landmark was measured. Timelapse movies were also reviewed. After the completion of treatment, a transrectal ultrasound examination was performed in 8 of 11 patients, to verify the position of the marker. Results : We acquired over 900 digital portal images and analyzed posterioanterior and right lateral views. The quality of protal images obtained with megavoltage irradiation was good. It was possible to evaluate pelvic bone structures even without image histogram equalization. Moreover, the radioopaque marker was easily visible on every online portal image. The review of timelapse movies showed important interfraction motion of the marker while bone structures remained stable. We measured the position of the marker for each fraction. marker displacements up to 1.6 cm were measured between 2 consecutive days of treatment. Important marker motions were predominantly in the posteroanterior and cephalocaudal directions. In eight patients, we verified the position of the marker relative to the prostatic apex with ultrasound at the end of the treatments. The marker remained in the trapezoid zone. Intratreatment images reviewed in two cases showed no change in marker position. Our results, obtained during the treatment courses, indicate similar or larger prostate motions than previously observed in studies that used intertreatment x-ray films and CT images. Marker implantation under transrectal ultrasound was well tolerated. Conclusion : Radioopaque marker and the use of electronic portal imaging give a direct evaluation of prostatic motion during radiation treatment. As suggested in previous studies the motions observed are predominantly in the posteroanterior and cephalocaudal directions. Therefore, prostate motion during treatment is important and must be considered especially when using conformal therapy.

Superimposition of computed tomography and single photon emission tomography immunoscintigraphic images in the pelvis: validation in patients with colorectal or ovarian carcinoma recurrence.

A method of superimposing computed tomography (CT) and immunoscintigraphic (IS) single photon emission tomography (SPET) slices is presented and has been applied to 10 patients with suspected cancer recurrence. IS was performed with carcinoembryonic antigen (CEA)-specific indium-111 monoclonal antibodies (MoAbs) in 5 patients with colorectal cancer, and with OC125 111In-MoAbs in 5 patients with ovarian cancer. All patients had an abnormal CT image result in the pelvis, which was interpreted 5 times as recurrence, once as doubtful and four times as scar fibrosis. Recurrence was subsequently proven in all patients. Bone scintigraphy (BS) SPET was recorded at the same time as IS. No special technique was used during BS, IS or CT acquisition. CT images were fed into a computer using a CCD camera. Using the internal anatomical landmarks provided by the pelvic bone structures seen on CT and BS, an operator had to select corresponding fiducial points, which were used by the software to register the images. The final results were CT-BS and CT-IS superimposed images. CT-BS images were used for quality control. In all patients, the inspection of CT-BS and CT-IS showed that the registration process is accurate and assists in the co-interpretation of CT and IS images.