A computerized remote table control for fast on-line patient repositioning: implementation and clinical feasibility

A computerized remote control for a Siemens ZXT treatment couch was implemented and its characteristics were investigated to establish its feasibility for on-line setup corrections, using portal imaging. Communication with the table was obtained by connecting it via a serial line to a work station. The treatment couch enables "goto" commands in the three main directions and around the isocenter. The accuracy of the movements after giving such a command was checked and the time for each movement was recorded. First, the movements into a single direction were studied (range of -4 to +4 cm and -4 degrees to +4 degrees). Each command was repeated four times. Second, the table was moved into the three main directions simultaneously. For this experiment a clinically relevant three-dimensional (3-D) normal distribution of shifts was used [N = 200, standard deviation (SD) 5 mm in the three main directions]. This latter experiment was done twice: without and with rotations (a distribution with SD 1 degrees). During the first experiment, with shifts into one direction, no systematic deviations were found. The overall accuracy of the shifts was 0.6 mm (1 SD) in each direction and 0.04 degrees (1 SD) for the rotations. The time required for a translation ranged between 4 and 13 s and for the rotation between 8 and 20 s. The second experiment with the 3-D distribution of setup errors yielded an error in the 3-D vector length equal to 0.96 mm (1 SD), independent of rotations. Shifts were performed in less than 11 s for 95% of the cases without rotations. When rotations were also performed, 95% of the movements finished in less than 16 s. In conclusion, the table movements are accurate and enable on-line setup corrections in daily clinical practice.     

Assessment of secondary patient motion induced by automated couch movement during on-line 6 dimensional repositioning in prostate cancer treatment.

BACKGROUND AND PURPOSE: The purpose of this study is to assess retrospectively secondary patient motion induced by 6D patient setup correction. MATERIALS AND METHODS: For 104 patients, treated with Novalis, 6D setup correction prior to treatment was performed by ExacTrac5.0/NovalisBody in combination with the Robotic Tilt Module mounted underneath the Exact Couch top. This 6D correction might induce additional setup errors due to patient reaction against the rotations. To evaluate induced secondary motion, the 6D setup correction is verified and evaluated with respect to the tolerance limits. RESULTS: The majority of measured secondary motions are found within the tolerance limits. Detected secondary motions are mostly found in longitudinal shifts and lateral rotations, and mainly found in only 1 dimension during the same verification. The verifications indicate that the patient population can be divided into a group that hardly moves and a group that moves throughout all 6D setup corrections. The patient's behavior can be predicted by the evaluation of the first five fractions as none of the patients demonstrate a learning curve during the treatment. CONCLUSIONS: 6D setup correction does not induce secondary motion for the majority of the patients and can therefore be applied for all treatment indications.     

An assessment of the use of skin flashes in helical tomotherapy using phantom and in-vivo dosimetry.

BACKGROUND AND PURPOSE: In helical tomotherapy the nature of the optimizing and planning systems allows the delivery of dose on the skin using a build-up compensating technique (skin flash). However, positioning errors or changes in the patient's contour can influence the correct dosage in these regions. This work studies the behavior of skin-flash regions using phantom and in-vivo dosimetry. MATERIALS AND METHODS: The dosimetric accuracy of the tomotherapy planning system in skin-flash regions is checked using film and TLD on phantom. Positioning errors are induced and the effect on the skin dose is investigated. Further a volume decrease is simulated using bolus material and the results are compared. RESULTS: Results show that the tomotherapy planning system calculates dose on skin regions within 2 SD using TLD measurements. Film measurements show drops of dose of 2.8% and 26% for, respectively, a 5mm and 10mm mispositioning of the phantom towards air and a dose increase of 9% for a 5mm shift towards tissue. These measurements are confirmed by TLD measurements. A simulated volume reduction shows a similar behavior with a 2.6% and 19.4% drop in dose, measured with TLDs. CONCLUSION: The tomotherapy system allows adequate planning and delivery of dose using skin flashes. However, exact positioning is crucial to deliver the dose at the exact location.     

A feasibility study of image-guided hypofractionated conformal arc therapy for inoperable patients with localized non-small cell lung cancer.

We treated 36 cases of stage I/II non-small cell lung cancer in inoperable patients. Treatments were planned to a total isocenter dose of 60Gy (8x7.5Gy) based on a dynamic field shaping arc, employing one arc to span as much area as possible and if needed additional weighted segments. The 2 year infield progression free probability is 65%. Disease-specific survival is 75% at 2 years. No patients experienced grade 3-4 toxicity.     

Importing measured field fluences into the treatment planning system to validate a breathing synchronized DMLC-IMRT irradiation technique.

BACKGROUND AND PURPOSE: Recalculating dose distributions using measured IMRT fluence fields imported into the treatment planning system (TPS) to evaluate the technical feasibility of a prototype developed for breathing synchronized irradiation. PATIENTS AND METHODS: DMLC-IMRT fluence patterns acquired on radiographic film, generated by the linac in non-gated and gated mode, have been imported into the TPS. The effect of dose blurring and possible interplay between organ motion and leaf motion, and the efficacy of a breathing synchronized irradiation technique (an adapted version of a commercially available image-guidance system: NOVALIS BODY/ExacTrac4.0, BrainLAB AG) have been evaluated using radiographic film mounted to a simple phantom simulating a breathing pattern of 16 cycles per minute and covering a distance of 4 cm to obtain the resulting fluence maps. Two situations have been investigated to illustrate this principle: (a) a tumor located close to the diaphragm to assess the influence of organ motion on the dose to the target volume as well as to the gastro-intestinal tract that presents a high risk at intersecting with the beam during the breathing cycle. (b) A mediastinal lesion requiring complicated fluence patterns. RESULTS: Importing measured fluence maps yielded highly disturbed reconstructed dose distributions in case of the non-gated delivery with the phantom in motion (both orthogonal and parallel to the leaf direction), whereas the measurements from the static (film fixed in space) and the gated delivery showed good agreement with the original theoretical dose distribution. These findings have been confirmed by the dose-volume histograms, corresponding tumor control probabilities, conformity index and dose heterogeneity values. The normal tissue complication probabilities investigated in this study seem to be affected to a lesser degree, which concurs with the observation that the motion effects result in a dose spread in the direction of motion. The applied breathing synchronization technique introduced an increased treatment time with a factor 3-4. CONCLUSIONS: The use of measured fluence fields, delivered by the linac in non-gated and gated mode, as imported fluence maps for the treatment planning system is an interesting quality assurance tool and revealed the dramatic impact of dose blurring and interplay between DMLC-IMRT dose delivery and organ motion, as well as the potential of breathing synchronization to resolve this issue. The possible advantage of breathing synchronized irradiation is compromised with an increased treatment time.     

Choanal atresia: a retrospective study of 39 cases]

The purpose of this study was to investigate the clinical characteristics and the surgical management in patients with choanal atresia. We performed a retrospective study at the Saint-Luc University hospital, Brussels, between January 1988 and June 2000. Surgical corrections were performed using different approach (transnasal endoscopic, transpalatal) and different instrumentations (urethral sounds, laser nd-YAG, laser CO2, microdebrider). Portex endotracheal tubes were inserted as nasal stents in the vast majority of the patients with bilateral choanal atresia. Thirty-nine children with choanal atresia (22 unilateral and 17 bilateral) (9: M, 30: F) were studied. 38 of them were surgically managed. Based on clinical inspection and On CT-Scan, choanal atresia was defined as membranous for 4 patients, osseous for 6 and mixte for 29. Associated congenital anomalies were found in 22.7% of unilateral and in 70.5% of bilateral choanal atresia (Total: 43.5%). Of those children with bilateral choanal atresia, 75% were asymptomatic after four surgical procedures. In children with unilateral choanal atresia, 45% were asymptomatic after one surgical correction and 100% after three surgical corrections. Four patients were managed using an endoscopic endonasal approach with the microdebrider and showed no evidence of recurrence. Outcome analyses of factors that may influence the results of surgery are difficult to establish since many different surgical options were taken during this period. However, it seems that bilateral choanal atresia is associated with more surgical corrections before achieving a normal nasal breathing than unilateral choanal atresia. After this review, our current strategy regarding the choanal atresia will be to begin with the endoscopic endonasal approach using the microdebrider (stents if bilateral) and to propose the transpalatal approach in case of recurrence.     

Contact between patients with suicidal ideation and nurses in mental health wards: Development and psychometric evaluation of a questionnaire

Suicide prevention and treatment opportunities often depend on interpersonal contact between patients and professionals. Presently, there is a lack of valid and reliable instruments to obtain the perspective of patients with suicidal ideation regarding their contact with professionals in mental health wards. This was a three‐stage study to develop and psychometrically evaluate a questionnaire: the Contact with Nurses from the perspective of Patients with Suicidal ideation (CoNuPaS). First, the construct was defined by a systematic review, qualitative study, and face validity among experts. Second, the content was validated through a Delphi procedure with professional experts (n = 14) and cognitive interviews with hospitalized patients (n = 12). Third, using a sample of adult patients with suicidal ideation in the past year (n = 405), the psychometric properties were assessed by an exploratory factor analysis, a test‐retest procedure, and the internal consistency. The CoNuPaS comprises 23 items and two subsections, to examine patients’ perceptions of contact experiences with nurses (CoNuPaS‐experience) and what they find important in that contact (CoNuPaS‐importance). The subsections comprise four components: encountering a space to express suicidal thoughts and explore needs, being recognized as a unique and self‐determining individual, encountering nurses’ availability/information‐sharing/transparency on expectations, and trusting nurses in communication about suicidality. Content validity scores were excellent (0.78–1.00); test‐retest intraclass correlation coefficient and internal consistency were >0.90. Thus, the CoNuPaS demonstrated good psychometric properties. The availability of a valid questionnaire to examine patient‐nurse contact in mental health wards is central to improving understanding of nurses’ contributions to suicide prevention and suicidal ideation treatment.     

Spontaneous ruptures of the flexor carpi radialis tendon secondary to STT osteoarthritis.

Two cases of closed ruptures of the flexor carpi radialis which resulted from attrition of the tendon caused by bony spurs secondary to Scapho Trapezo Trapezoidal (STT) osteoarthritis are described. Treatment is conservative.