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Biomedical subjects

Mark Ritter

Publications and source records attributed to Mark Ritter.

10 recordsLinked to original sources
PubMed2007

Impact of hybrid fluorodeoxyglucose positron-emission tomography/computed tomography on radiotherapy planning in esophageal and non-small-cell lung cancer.

PURPOSE: The aim of this study was to investigate the impact of a hybrid fluorodeoxyglucose positron-emission tomography/computed tomography (FDG-PET/CT) scanner in radiotherapy planning for esophageal and non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: A total of 30 patients (16 with esophageal cancer, 14 with NSCLC) underwent an FDG-PET/CT for radiotherapy planning purposes. Noncontrast total-body spiral CT scans were obtained first, followed immediately by FDG-PET imaging which was automatically co-registered to the CT scan. A physician not involved in the patients' original treatment planning designed a gross tumor volume (GTV) based first on the CT dataset alone, while blinded to the FDG-PET dataset. Afterward, the physician designed a GTV based on the fused PET/CT dataset. To standardize PET GTV margin definition, background liver PET activity was standardized in all images. The CT-based and PET/CT-based GTVs were then quantitatively compared by way of an index of conformality, which is the ratio of the intersection of the two GTVs to their union. RESULTS: The mean index of conformality was 0.44 (range, 0.00-0.70) for patients with NSCLC and 0.46 (range, 0.13-0.80) for patients with esophageal cancer. In 10 of the 16 (62.5%) esophageal cancer patients, and in 12 of the 14 (85.7%) NSCLC patients, the addition of the FDG-PET data led to the definition of a smaller GTV. CONCLUSION: The incorporation of a hybrid FDG-PET/CT scanner had an impact on the radiotherapy planning of esophageal cancer and NSCLC. In future studies, we recommend adoption of a conformality index for a more comprehensive comparison of newer treatment planning imaging modalities to conventional options.

Carcinoma, Non-Small-Cell Lung↗
PubMed2006

Clinical implementation of adaptive helical tomotherapy: a unique approach to image-guided intensity modulated radiotherapy.

Image-guided IMRT is a revolutionary concept whose clinical implementation is rapidly evolving. Methods of executing beam intensity modulation have included individually designed compensators, static multi-leaf collimators (MLC), dynamic MLC, and sequential (serial) tomotherapy. We have developed helical tomotherapy as an innovative solution to overcome some of the limitations of other IMRT systems. The unique physical design of helical tomotherapy allows the realization of the concepts of adaptive radiotherapy and conformal avoidance. In principle, these advances should improve normal tissue sparing and permit dose reconstruction and verification, thereby allowing significant biologically effective dose escalation. Recent radiobiological findings can be translated into altered fractionation schemes that aim to improve the local control and long-term survival. This strategy is being tested at the University of Wisconsin using helical tomotherapy with its highly precise delivery and verification system along with meticulous and practical forms of immobilization. Innovative techniques such optical guidance, respiratory gating, and ultrasound assessments are being designed and tailored for helical tomotherapy use. The intrinsic capability of helical tomotherapy for megavoltage CT (MVCT) imaging for IMRT image-guidance is being optimized. The unique features of helical tomotherapy might allow implementation of image-guided IMRT that was previously impossible or impractical. Here we review the technological, physical, and radiobiological rationale for the ongoing and upcoming clinical trials that will use image-guided IMRT in the form of helical tomotherapy; and we describe our plans for testing our hypotheses in a rigorous prospective fashion.

Humans↗
PubMed2006

Microbial colonization of tourniquets used in orthopedic surgery.

This study analyzed tourniquets used for orthopedic surgery in our hospital to determine the frequency and type of microbial contamination. Group A tourniquets were from our main operating room, Group B tourniquets were from our ambulatory surgicenter, Group C tourniquets were unused, prepackaged, sterile tourniquets from our main operating room, and Group D tourniquets were sterilely packed tourniquets from our ambulatory surgicenter. Tourniquets from Groups A, B, C, and D had 100%, 40%, 0%, and 0% microbial growth, respectively. For Group A tourniquets, coagulase-negative staphylococci, Bacillus, and Staphylococcus aureus were present in 100%, 60%, and 20% of tourniquets, respectively. Twenty percent were contaminated either with Streptococcus sanguis, Aerococcus viridans, or Cornyebacterium species. Coagulase-negative staphylococci and Bacillus were present in 40% and 30% of Group B tourniquets, respectively. Tourniquet contamination may be a risk factor for the development of surgical site infection in orthopedic surgery.

Equipment Contamination↗
PubMed2004

Access and use of the internet in a hand surgery population.

Internet use is increasing and its applications to medicine and patient information are widening daily. Previous studies have focused on the quality and quantity of medical information on the Internet. The current study focuses on a population of 120 new patients presenting to a hand surgery practice. A questionnaire was used to analyse patterns of Internet access, use of the Internet to look up personal symptoms, and patients' opinions on the use of electronic mail by office staff. Results showed that approximately 90% of the group had some form of Internet access, with a significant age-related decrease in Internet access. Only 17% used the Internet to look up their symptoms, but this group was more likely to correctly match their self-diagnosis to the surgeon's diagnosis. On average, 65% of the study group favoured the use of electronic mail for office staff's communications with patients.

Adolescent↗
PubMed2003

Image guidance for precise conformal radiotherapy.

PURPOSE: To review the state of the art in image-guided precision conformal radiotherapy and to describe how helical tomotherapy compares with the image-guided practices being developed for conventional radiotherapy. MATERIALS AND METHODS: Image guidance is beginning to be the fundamental basis for radiotherapy planning, delivery, and verification. Radiotherapy planning requires more precision in the extension and localization of disease. When greater precision is not possible, conformal avoidance methodology may be indicated whereby the margin of disease extension is generous, except where sensitive normal tissues exist. Radiotherapy delivery requires better precision in the definition of treatment volume, on a daily basis if necessary. Helical tomotherapy has been designed to use CT imaging technology to plan, deliver, and verify that the delivery has been carried out as planned. The image-guided processes of helical tomotherapy that enable this goal are described. RESULTS: Examples of the results of helical tomotherapy processes for image-guided intensity-modulated radiotherapy are presented. These processes include megavoltage CT acquisition, automated segmentation of CT images, dose reconstruction using the CT image set, deformable registration of CT images, and reoptimization. CONCLUSIONS: Image-guided precision conformal radiotherapy can be used as a tool to treat the tumor yet spare critical structures. Helical tomotherapy has been designed from the ground up as an integrated image-guided intensity-modulated radiotherapy system and allows new verification processes based on megavoltage CT images to be implemented.

Animals↗
PubMed2003

3D-ultrasound guided radiation therapy in the post-prostatectomy setting.

Daily transabdominal ultrasound-directed localization has proven valuable in correcting for setup error and organ motion in the treatment of prostate cancer with three-dimensional conformal radiation therapy (3DCRT). The present study sought to determine whether this transabdominal ultrasound technology could also be reliably applied in the post-operative adjuvant or salvage setting to improve the reproducibility of coverage of the intended volumes and to enhance conformal avoidance of adjacent normal structures. Sixteen consecutive patients who received external beam radiotherapy underwent daily localization using an optically guided 3D-ultrasound target localization system (SonArray, Zmed, Inc., Ashland, MA). Six of the above patients were treated in a post-prostatectomy setting, either adjuvantly or for salvage, while the remaining 10 with intact prostates were treated definitively. Because the bladder neck generally approximates the postoperative prostatic fossa, it was used during ultrasound localization as the primary reference structure for the post-prostatectomy patients. For patients treated definitively, the prostate was the primary reference structure. Daily shifts were recorded and port films were taken weekly immediately after ultrasound-based repositioning. By comparing port films taken after ultrasound localization, which evaluates for both set-up error and internal shift, with the original digitally reconstructed radiographs (DRRs), which represents a zero clinical set-up error situation, the degree of variability in organ position was determined. The average absolute, ultrasound-based shifts from the clinical set-up position in the anterior/posterior, lateral, and cranial/caudal directions for the post-prostatectomy patients were 5 +/- 4 mm SD, 3 +/- 3 mm SD, and 3 +/- 4 mm SD over the entire course of treatment, respectively. The average vector length shift was 8 +/- 4 mm SD. For patients treated with an intact prostate, the analogous average absolute shifts in the anterior/posterior, lateral, and cranial/caudal directions were 4 +/- 3 mm SD, 4 +/- 3 mm SD, and 4 +/- 3 mm SD over the entire course of treatment. The average vector length shift was 7 +/- 4 mm SD. Vector length shifts representing interfraction internal motion were estimated by comparing post-ultrasound port films with DRRs. These were 5 +/- 3 mm SD and 4 +/- 4mm SD for post-prostatectomy and intact prostate patients, respectively. These ultrasound-based displacements were not statistically different in patients with an intact prostate versus patients post-prostatectomy (p > 0.1). In conclusion, daily transabdominal 3D-ultrasound localization proved to be a clinically feasible method of correcting for set-up and internal motion displacements. The bladder neck, which serves as an adequate localization reference structure for the prostatic fossa, could be readily ultrasound imaged and repositioned as necessary. Daily internal motion errors that would have occurred if only pre-treatment port films were used were similar in magnitude to those observed for the patients with intact prostates and were of sufficient magnitude to support the use of daily pre-treatment ultrasound localization in the post-prostatectomy setting.

Humans↗
PubMedDate not supplied

Functional outcomes and general health status after ulnohumeral arthroplasty for primary degenerative arthritis of the elbow.

Ulnohumeral arthroplasty (UHA) is considered a satisfactory surgical treatment option for patients with primary degenerative arthritis of the elbow. Most series have used categoric elbow scoring systems to evaluate the outcome of this procedure. The purpose of our study was to evaluate the outcome of UHA with patient-derived functional and general health status outcome instruments. We evaluated 17 patients (18 elbows) with primary degenerative arthritis of the elbow at a mean of 85 months after UHA. The mean age at the time of surgery was 42 years (range, 26 to 58 years). At the follow-up evaluation, the patients were assessed with a physical examination, outcome assessment tools, and plain radiographs. The mean elbow flexion arc improved by 16 degrees (range, -15 degrees to 60 degrees ; P = .012), and the mean forearm rotation arc (supination/pronation) improved by 35 degrees (range, -20 degrees to 90 degrees ; P < .001). Of the elbows, 11 were painless, 4 were painful with motion, and 3 were painful at rest and with motion. The mean Hospital for Special Surgery elbow score was 70 (range, 40 to 99), and the mean Mayo Elbow Performance Score was 83 (range, 50 to 100). The mean Disabilities of the Arm, Shoulder and Hand score was 9.75 (range, 0 to 43.48). The Short Form-36 scores were better than the mean age- and sex-adjusted normal values. Patient self-assessed outcomes and general health status after UHA for primary degenerative elbow arthritis appear to be better than those determined by some categoric scoring systems. Consequently, the clinical utility of UHA may be underrepresented if physician-derived categoric scoring systems are the only measures of outcome assessment.

Adult↗