Denoising techniques combined to Monte Carlo simulations for the prediction of high-resolution portal images in radiotherapy treatment verification.

This work investigates the possibility of combining Monte Carlo (MC) simulations to a denoising algorithm for the accurate prediction of images acquired using amorphous silicon (a-Si) electronic portal imaging devices (EPIDs). An accurate MC model of the Siemens OptiVue1000 EPID was first developed using the penelope code, integrating a non-uniform backscatter modelling. Two already existing denoising algorithms were then applied on simulated portal images, namely the iterative reduction of noise (IRON) method and the locally adaptive Savitzky-Golay (LASG) method. A third denoising method, based on a nonparametric Bayesian framework and called DPGLM (for Dirichlet process generalized linear model) was also developed. Performances of the IRON, LASG and DPGLM methods, in terms of smoothing capabilities and computation time, were compared for portal images computed for different values of the RMS pixel noise (up to 10%) in three different configurations, a heterogeneous phantom irradiated by a non-conformal 15 × 15 cm(2) field, a conformal beam from a pelvis treatment plan, and an IMRT beam from a prostate treatment plan. For all configurations, DPGLM outperforms both IRON and LASG by providing better smoothing performances and demonstrating a better robustness with respect to noise. Additionally, no parameter tuning is required by DPGLM, which makes the denoising step very generic and easy to handle for any portal image. Concerning the computation time, the denoising of 1024 × 1024 images takes about 1 h 30 min, 2 h and 5 min using DPGLM, IRON, and LASG, respectively. This paper shows the feasibility to predict within a few hours and with the same resolution as real images accurate portal images, combining MC simulations with the DPGLM denoising algorithm.

Malignant tumors of the female pelvic floor: self-assessment module.

The educational objectives for this self-assessment module are for the participant to exercise, self-assess, and improve his or her understanding of malignant tumors of the female pelvic floor and the imaging features that determine therapy.

Morphological assessment of the interface between tumor and neighboring tissues, by magnetic resonance imaging, before and after radiotherapy in patients with locally advanced rectal cancer.

BACKGROUND: Magnetic resonance imaging (MRI) in rectal cancer is sometimes performed after radiotherapy (MRI 2) to evaluate tumor response and to choose alternative forms of surgery. The accuracy of MRI 2 in distinguishing tumor delineation might be difficult due to fibrosis. PURPOSE: To evaluate the morphological changes in the interface between the tumor and neighboring organs on MRI 2 performed after radiotherapy, and to assess the accuracies of MRI before and after radiotherapy compared to histopathology after surgery. MATERIAL AND METHODS: Sixteen patients with locally advanced primary rectal cancer, with MRI before and after radiotherapy, were retrospectively studied, concerning the interface between the tumor and neighboring structures. The accuracies of MRI before and after radiotherapy were compared based on histopathology as a reference. RESULTS: The accuracies of both MRI before and after radiotherapy were moderate, with no additional value of MRI after radiotherapy compared to MRI before radiotherapy. The most predictive form of interface for involvement of a neighboring organ after radiotherapy was nodular growth of the tumor into a neighboring structure. CONCLUSION: The morphological assessment of pelvic MRI after preoperative radiotherapy does not provide any significant new information about tumor extent in patients with locally advanced rectal cancer.

Pre-operative MR assessment of recurrent rectal cancer.

The potential for curative resection of recurrent rectal cancer and the recognized benefits of palliative resection have led to increased numbers of patients being referred for MRI assessment. This study assesses the use of MRI to provide a roadmap of tumour recurrence to allow for appropriate surgical planning. Differentiation of recurrent rectal cancer from post-surgical and post-radiotherapy changes on MR proved particularly problematic when assessing the pelvic sidewalls. Areas of uncertainty on imaging, therefore, need to be discussed on a case by case basis regarding the decision to proceed to curative or explorative surgery.

Does the molecular staging in pelvic lymph nodes improve the detection of relevant prostate cancer metastases? An assessment after 6 years.

OBJECTIVE: To assess the course of cancer-free survival and thus determine how reliably reverse transcriptase-polymerase chain reaction (RT-PCR) can detect prostate-specific antigen (PSA)-expressing cells, as patients with untreated lymph node-positive prostate cancer tend to have a poor prognosis, whereas those treated with radical prostatectomy (RP) and immediate adjuvant hormonal therapy show excellent local disease control and a disease-free survival comparable with that of patients with negative lymph nodes, but the detection of micrometastatic disease in pelvic lymph nodes remains a major challenge. PATIENTS AND METHODS: Quantitative RT-PCR was used to detect PSA mRNA expression in total RNA of 457 pelvic lymph nodes from 70 patients who had RP (53 patients) or laparoscopic lymphadenectomy (17) at our clinic in 1999/2000. For this purpose, alternate sections of lymph node tissue were either snap-frozen for later RNA isolation or examined by standard histopathological methods. Clinicopathological data, adjuvant treatments and follow-up data were recorded for all patients. RESULTS: After January 2006 (6-year observation period), 13 patients had no follow-up data, while 27 had biochemical (PSA) recurrence or other evidence of clinical progression (two died from prostate cancer), and 30 had no signs of recurrence. Compared to the 'reference' standard (histopathology), the PCR method had a sensitivity of 83% and a specificity of 66%. The method had a positive predictive value of 52% and a negative predictive value of 57%. CONCLUSION: Considered alone, pelvic lymph node PSA RT-PCR does not predict the clinical course better than a histopathological assessment of lymph nodes. However, it also identifies some patients with negative histology who later show progression. When added to the pathological classification, PSA RT-PCR improves the detection rate of primary lymphatic dissemination.

Ultrasonography, computed tomography and magnetic resonance imaging in the assessment of pelvic pathology.

OBJECTIVE: Ultrasound (US) is the primary imaging modality in the investigation of pelvic pathology in women however it can be very inaccurate. MRI and CT provide a more detailed pelvic examination and hence we compared their accuracies with that of ultrasound to find out if these two modalities should be used more often. PATIENTS AND METHODS: 136 women who had MRI examination of the pelvis for investigation of probable pelvic pathology were studied. Hundred and twenty-five of these women had an initial ultrasound scan and 23 had an initial CT. Diagnostic accuracy was assessed against histopathology or clinical follow-up. RESULTS: Histopathology was available in 127/136 women. Overall 36% of the lesions were malignant. The overall accuracy of MRI, US and CT were 97%, 77% and 87%, respectively. MRI confidently identified the tissue of origin in 94% compared to only 66% for US. There was a significant difference in accuracy between MRI and US in diagnosing adnexal and uterine pathology. MRI was better than CT and US in diagnosing peritoneal metastases whereas CT was superior in diagnosing omental infiltration. CONCLUSION: We suggest that all women with a pelvic abnormality identified on US or in whom there is a strong clinical suspicion of disease should undergo MR pelvic imaging in preference to CT because of its better soft tissue resolution and multi-planar capability.

Assessment of availability of magnetic resonance angiography (MRA) in renal arteriovenous fistula.

We report two cases of cirsoid-type renal arteriovenous fistula (RAVF) which were difficult to differentiate from renal pelvic tumor by intravenous pyelogram (IVP) and computed tomography (CT) scan. Two women visited our department complaining of sudden asymptomatic macroscopic hematuria. CT scans showed an irregular mass in the right kidney. Magnetic resonance angiography (MRA) revealed a cirsoid-type RAVF. These patients were treated with transarterial embolization (TAE) using ethanol, geratin sponge, and a coil. It is suggested that MRA is useful for the diagnosis of renal arteriovenous fistula.

Endorectal ultrasonography for the assessment of rectal wall invasion in intrapelvic tumor: a preliminary report.

BACKGROUND: The purpose of the present study was to determine the usefulness of endorectal ultrasonography (ERUS) in assessing rectal wall involvement in intrapelvic tumors. METHODS: Rectal wall invasion was assessed in 16 patients; 14 with deeply invasive bladder tumors, one with prostatic leiomyosarcoma, and one with prostatic leiomyoma. Computed tomography (CT), magnetic resonance (MR) imaging and ERUS with a flexible-type radial scanner (7.5 MHz) were used and the results were compared with the histopathologic findings in surgical specimens. RESULTS: The normal rectum was shown by ERUS to be a five- or seven-layer structure. Characteristic abnormal ERUS findings included disappearance of the perirectal fat tissue layer with or without disruption of the propria muscle layer. Endorectal ultrasonography accurately assessed rectal wall involvement in all four patients who had two bladder tumors, plus the one patient with prostatic leiomyoma and the one with prostatic leiomyosarcoma. However, ERUS overstaged one of 12 bladder tumors with no rectal wall involvement, which was strongly adhesive to the rectum because of an inflammatory change but had no tumor invasion. There were no cases of understaging by ERUS. In comparison, CT accurately assessed rectal wall involvement in two patients, but overstaged in three and understaged in two. Magnetic resonance imaging, which was performed in 14 patients, accurately assessed rectal wall involvement in two patients, but overstaged in three and understaged in one. CONCLUSION: This preliminary study suggests that ERUS more accurately assesses rectal wall involvement in intrapelvic tumor than CT or MRI.

[Magnetic resonance tomography of the lesser pelvis. Clinical application in disparity with technology]. / Magnettresonanstomografi av lilla bäckenet. Klinisk förankring i otakt med tekniken.

Technological innovations which change diagnostic routines are continually being introduced in medical care, as exemplified by magnetic resonance imaging (MRI) with its advanced diagnostic capacity, now considered indispensible for the investigation of many disorders of the central nervous system. The article consists in an outline of applications of MRI in the investigation of the lower abdomen, a field characterised by substantial technical improvements in recent years, and a brief review of subject literature. Based on their experience of pelvic MRI, the authors advocate its more frequent use in investigating disorders of the lesser pelvis.

Magnetic resonance imaging of lower abdominal and pelvic lesions: assessment of oral magnetic particles as an intestinal contrast agent.

To determine the value of oral magnetic particles (OMP) as a superparamagnetic MR contrast agent for the gastrointestinal tract in lower abdominal and pelvic lesions, 30 patients underwent spin-echo imaging before and after ingestion of OMP at a dose of approximately 80 mg of iron in 800 ml water. The preparation was divided into four portions and taken by the patient over a 2-h period. Two readers independently reviewed the MR images. The contrast material was well tolerated and the distribution of the contrast material was good to excellent in the proximal and pelvic small bowel, but was not sufficient in the colon with the dose and timing used in the study. Postcontrast images showed a significantly better delineation of the lesions, the small bowel, and the paraaortic region, but no significant improvement in the delineation of the colon, the iliac vessels area, the bladder or genital tract. Compared with precontrast images, confidence in defining or excluding disease on postcontrast images was better, equal or worse in 40, 60 and 0% of cases, respectively (P less than 0.001) with a substantial agreement between readers (kappa = 0.71). OMP produced susceptibility artefacts of significant intensity in only one case. These results indicate that OMP may be useful in the delineation of lower abdominal and pelvic lesions at MR imaging. Marking of the colon by a contrast agent might improve the results.

[A prospective evaluation of transvaginal ultrasonic scanning in the initial assessment of suspected pelvic masses]. / Prospektiv evaluering af transvaginal ultralydskanning ved den initiale vurdering af mistaenkt gynaekologisk udfyldning.

Eighty-six patients with suspected pelvic masses were evaluated with transvaginal sonography in connection with pelvic examination. The scans were performed by gynecologists with a limited experience in sonography. Sixty-nine cases could be verified by operation, laparoscopy, autopsy or by clinical follow-up. The predictive value of positive and negative findings were 97.6 and 87.5%, respectively. In 73% of the positive cases, a correct pathoanatomical diagnosis was made. The procedure was readily accepted by the patients. It is concluded that transvaginal sonography may easily be introduced in a gynecological department as a rapid and accurate aid in the evaluation of patients with suspected pelvic masses.

Magnetic resonance imaging of the abdomen and pelvis. Council on Scientific Affairs.

Magnetic resonance imaging (MRI) of the abdomen presents greater inherent difficulties than other anatomic regions. However, new techniques now allow imaging comparable in quality to computed tomography (CT). Magnetic resonance imaging offers the advantages of greater tissue contrast, multiplanar imaging, and lack of ionizing radiation or risk of toxic reactions from iodinated contrast media. Its use remains limited by high cost, limited availability, lack of a bowel contrast agent, and long imaging time, which some patients cannot tolerate. In many areas of abdominal imaging, MRI is now comparable to CT, but because of the greater availability and lesser cost, CT remains the procedure of choice. Magnetic resonance imaging is more accurate for staging neoplasms of the liver, adrenal glands, kidneys, bladder, prostate, uterus, and cervix and may aid in diagnosis of hepatic, adrenal, and uterine masses. In selected patients, especially those in whom CT is inconclusive or those who cannot tolerate iodinated contrast material, MRI can provide valuable information. Development of faster scanning techniques and MRI contrast agents and wider availability will probably increase the usefulness of abdominal MRI. At this time, MRI complements other abdominal imaging procedures. In a small number of patients, however, it can provide unique information in a virtually risk-free manner.

The value of computed tomography and ultrasound in assessment of pelvic lymph node metastases in patients with clinically locally confined carcinoma of the prostate.

With the aim of detecting any metastases in pelvic lymph nodes, computed tomography (CT) was performed in 42 patients with clinically localized prostatic carcinoma, and ultrasound (US) examination in 35 of them, prior to pelvic lymphadenectomy. CT was positive in only one patient, and US was negative in all examined patients. At lymph node dissection macrometastases were found in four patients and histopathologic examination revealed micrometastases in a further ten patients. It is concluded that in clinically locally confined prostatic carcinoma CT and US are insensitive in diagnosing pelvic lymph node metastases, and that lymph node dissection remains the only method for staging of the regional lymph nodes.

Pelvic abnormalities in children: assessment with MR imaging.

Multiplanar images of 62 pelvic lesions in 58 children and adolescents (aged 7 months to 19 years; mean, 10.6 years) were obtained with 0.3-T magnetic resonance (MR) imaging. Lesions were divided into three categories: congenital anomalies, cystic lesions and fluid collections, and neoplasms. MR demonstrated lesions well in all categories. Midline lesions were best imaged sagittally, and lesions of paired structures, axially. The coronal plane was useful in evaluating the superoinferior extent of lesions and in defining the extent of lymphadenopathy. T1-weighted sequences were sufficient to depict most congenital and cystic lesions. T2-weighted sequences were useful in demonstrating the extent of neoplasms and the position of ectopic gonads. Ultrasonography (US) was also performed in 45 cases. MR and US delineated lesions equally well in 25 cases (55.5%), MR was superior in 19 (42.4%), and US was superior in one (2.2%). Computed tomography (CT) was performed in 13 cases. MR and CT delineated lesions equally well in eight cases (61.5%), MR was superior in four (30.8%), and CT was superior in one (7.7%).