Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Computers, Handheld”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,063 records · Page 59Linked to original sources
PubMed2006

Subjective somatosensory vertical during dynamic tilt is dependent on task, inertial condition, and multisensory concordance.

To investigate how visual and vestibular cues are integrated for the perception of gravity during passive self-motion, we measured the ability to maintain a handheld object vertical relative to gravity without visual feedback during sinusoidal roll-tilt stimulation. Visual input, either concordant or discordant with actual dynamic roll-tilt, was delivered by a head-mounted display showing the laboratory. The four visual conditions were darkness, visual-vestibular concordance, stationary visual scene, and a visual scene 180 degrees phase-shifted relative to actual tilt. Tilt-indication performance using a solid, cylindrical joystick was better in the presence of concordant visual input relative to the other visual conditions. In addition, we compared performance when indicating the vertical by the joystick or a full glass of water. Subjects indicated the direction of gravity significantly better when holding the full glass of water than the joystick. Matching the inertial characteristics, including fluid properties, of the handheld object to the glass of water did not improve performance. There was no effect of visual input on tilt performance when using the glass of water to indicate gravitational vertical. The gain of object tilt motion did not change with roll-tilt amplitude and frequency (+/-7.5 degrees at 0.25 Hz, +/-10 degrees at 0.16 Hz, and +/-20 degrees at 0.08 Hz), however, the phase of object tilt relative to subject tilt showed significant phase-leads at the highest frequency tested (0.25 Hz). Comparison of the object and visual effects observed suggest that the task-dependent behavior change may be due to an attentional shift and/or shift in strategy.

Attention↗
PubMed2005

Analysis of the contact interactions between fingertips and objects with different surface curvatures.

Previous experimental observations indicated that the contact interactions between finger and tool handle interfere with the grasp stability, affecting the comfort and manipulations of handheld tools. From a biomechanical point of view, the curvature of the contact surface should affect the contact pressure and contact area, and thereby the comfort and manipulations of hand tools. The current authors analysed, via a finite element model, the contact interactions between fingertips and objects with different curvatures. The effects of the curvature on the contact stiffness, fingertip deformations, contact pressure distributions, and stress/strain distributions within the soft tissues were analysed. The simulation results indicated that the curvature of the contact interface influences the contact characteristics significantly. For a given contact force, the contact area and the contact stiffness increase but the contact pressure and the fingertip deformation decrease with the decrease of the contact surface curvature. The present simulation results will be useful for ergonomic designers in their aim to improve the design of tool handles.

Animals↗
PubMed2001

Real-time optical coherence tomography of the anterior segment at 1310 nm.

BACKGROUND: Recent advances in high-speed scanning technology have enabled a new generation of optical coherence tomographic (OCT) systems to perform imaging at video rate. Here, a handheld OCT probe capable of imaging the anterior segment of the eye at high frame rates is demonstrated for the first time. OBJECTIVE: To demonstrate real-time OCT imaging of anterior segment structures. DESIGN: Survey of anterior segment structures in normal human subjects. SETTING: Laboratory. MAIN OUTCOME MEASURES: Achieving real-time imaging of the anterior segment, satisfactory image quality, and convenience of a handheld probe. RESULTS: Optical coherence tomographic imaging of the anterior segment of the eyes of human subjects was performed using 1310-nm wavelength light with an image rate of 8 frames per second. Imaging trials demonstrated clear resolution of corneal epithelium and stroma, sclerocorneal junction, sclera, iris pigment epithelium and stroma, and anterior lens capsule. The anterior chamber angle was clearly visualized. Limited imaging of the ciliary body was performed. Real-time imaging of pupillary constriction in response to light stimulus was also performed. CONCLUSION: High-speed OCT at 1310-nm wavelength is a potentially useful technique for noninvasive assessment of anterior segment structures. CLINICAL RELEVANCE: Our results suggest that real-time OCT has potential applications in glaucoma evaluation and refractive surgery.

Anterior Chamber↗
PubMed2002

Handheld, portable ultrasound in the neonatal intensive care nursery: a new, inexpensive tool for the rapid diagnosis of common neonatal problems.

The use of ultrasound imaging in the neonatal intensive care unit (NICU) has become an essential part of the evaluation and delivery of care for most neonates. Until recently, ultrasound machines were large, expensive, and often not immediately available, particularly at night and during weekends. Additionally, serial studies to define the evolution of an acute clinical situation were often not practical because of the dedicated time required and the expense involved. The recent introduction into our NICU of a high-quality, reasonably priced, and completely portable neonatal ultrasound unit (Sonosite, Bothell, WA) has now made it possible for neonatologists to rapidly obtain the hour-by-hour information that can be extremely helpful in the evaluation of a critically ill neonate. This paper illustrates some of the capabilities of this simplified device, and the value of having continuous on-site ultrasound availability in the NICU.

Cost-Benefit Analysis↗
PubMed2006

Molecular imaging and radioimmunoguided surgery.

Molecular imaging comprises a series of diagnostic modalities that provide information on the physiology and molecular composition of cells and tissues. One of these modalities, radioimmunodetection, uses radiolabeled monoclonal antibodies (mAbs) to image tissues. Two radioimmunodetection modalities are described in this article: immunoscintigraphy and radioimmunoguided surgery (RIGS). In immunoscintigraphy, the radioactivity is measured with the use of an external gamma camera and used to create images. In RIGS, the radioactivity is detected intraoperatively with the use of a handheld gamma probe to help the surgeon detect foci of otherwise occult disease. Both techniques have the potential to improve the preoperative and intraoperative localization of cancer. Multiple studies have been performed on the efficacy of RIGS on different malignancies, especially colorectal cancer. Despite the good sensitivity of the technique, some concerns revolve around the high rate of false positives and the real significance of leaving RIGS-positive tissue behind in terms of long-term outcomes and survival. More studies are warranted to further develop the technique and determine the specific role it will play on the diagnosis and management of surgical disease. Surgeons should actively participate in these studies and in expanding the applications of this promising technology.

Child↗
PubMed2003

Estimation of the SAR in the human head and body due to radiofrequency radiation exposure from handheld mobile phones with hands-free accessories.

It was reported by others that hands-free accessories increase the absorption of RF energy in a human head compared to a handset alone. The results of this study show that the opposite is observed when proper dosimetric methods are employed. It is pointed out that for correct estimation of the exposure level it is necessary to use appropriate physical and experimental models and measurement instrumentation, following internationally recommended standards. The human phantoms used for measurements involving the hands-free accessories should include the torso; i.e., measurements should not be performed on the head phantom alone. This has a significant impact on the results because the RF energy coupled into the leads of hands-free accessories is strongly attenuated by the body. Numerical simulations using the Finite-Difference Time-Domain (FDTD) method and experimental measurements with a miniature electric-field probe are in good agreement and show a decrease, not an increase, in RF energy exposure in the human head from hands-free accessories.

Cell Phone↗
PubMed2003

Intraoperative ultrasonographically guided excisional biopsy or vacuum-assisted core needle biopsy for nonpalpable breast lesions.

OBJECTIVE: To compare duration and rates of underestimation and complete excision for nonpalpable breast lesions using either intraoperative ultrasonographically guided excisioned biopsy (IUGE) or directional vacuum-assisted biopsy (DVAB). SUMMARY BACKGROUND DATA: Percutaneous ultrasonography-guided core needle biopsy is preferable to stereotactic biopsy for treatment of nonpalpable breast lesions; however, underestimation and false-negative results can occur, and rebiopsy may be required. To date, however, there has been no comparison of these two procedures in terms of diagnostic accuracy and duration. METHODS: For 4 consecutive years, IUGE was performed for 104 nonpalpable breast lesions and DVAB for 128 lesions at Chang Gung Memorial Hospital. Of the DVAB cases, the handheld mammotome was used for 53 procedures, with all lesions removed as completely as possible. The duration of the two procedures was calculated from initial skin incision until completion of wound closure. Most of the patients with benign pathology underwent ultrasonographic examination at 3 months after surgery, with a follow-up examination at 1 year. Surgery was performed subsequently for all of the malignancy cases. RESULTS: The average ages and mean tumor sizes for patients undergoing IUGE or DVAB were 46 and 47 years and 1.1 and 1.0 cm, respectively. The average IUGE and DVAB surgery durations for 88 benign tumors and 117 benign lesions were 44.3 and 21.5 minutes, respectively (P < 0.001), and 43.5 and 20.6 minutes for the malignant tumors (n = 16 and n = 11), respectively (P = 0.036). The IUGE and DVAB surgery durations for tumors <1 cm in diameter were 43.5 and 20.6 minutes, respectively, and 44.2 and 23.6 minutes for tumors over that size (P < 0.001). An older-model mammotome was used for 75 patients, with an average duration of 24 minutes in comparison to 18 minutes for the handheld variant (P < 0.001). No false-negative results were noted and, except in the case of the malignant tumors, there was no need for reexcisional biopsy. Further, there were no underestimates of the disease for the 4 cases of atypical ductal hyperplasia and the 12 of noninvasive carcinoma. No further ultrasonographic evidence of tumors was noted for 95% of the benign pathologies, with no residual abnormality detected for 13 of the 27 malignant tumors after IUGE or DVAB. CONCLUSIONS: For treatment of nonpalpable breast lesions, both IUGE and DVAB eliminate false-negative results, underestimates, and the requirement for reexcisional biopsies. In comparison to IUGE, DVAB is more convenient and time efficient for excisional biopsy of nonpalpable breast lesions.

Biopsy, Needle↗
PubMedDate not supplied

Intraoperative gamma probe detection of head and neck paragangliomas with 111In-pentetreotide: a pilot study.

AIMS AND BACKGROUND: The aim of this study was to assess whether intraoperative radiolocalization of head and neck paragangliomas with 111In-pentetreotide may increase surgical effectiveness, reducing the risk of recurrence. METHODS: Our study included eight patients with untreated, recently diagnosed paragangliomas (four unilateral and four bilateral tumors of the carotid body). After i.v. injection of approximation 150 MBq 111In-pentetreotide, preoperative somatostatin receptor scintigraphy (SRS) was performed. SPECT of the neck was performed at four hours and planar images of the head and neck were also obtained at four and 24 hours post injection. Scintigraphy was always compared with the results of conventional imaging methods (MRI, angiography and sonography). Intraoperative detection was performed on 11 lesions 24 hours after radiopharmaceutical administration using a handheld gamma probe. RESULTS: Preoperative SRS showed high radiotracer uptake in all patients. All the intraoperatively detected lesions were radically resected and histologically confirmed to be involved by tumor. No false positive results were recorded. Gamma probe detection revealed a small intracranial extension not detected by other imaging methods in a patient with a paraganglioma of the right carotid, and partial involvement of the carotid artery in another patient. During follow-up (median 3.5 years; range, 4 months-7 years) all patients remained disease free according to all parameters. CONCLUSIONS: To our knowledge, this is the first experience of radioguided surgery in paraganglioma. Although our study included a relatively small number of patients, we suggest that intraoperative gamma probe detection may be a powerful tool to improve surgical effectiveness.

Adult↗
PubMedDate not supplied

In vivo absorption, scattering, and physiologic properties of 58 malignant breast tumors determined by broadband diffuse optical spectroscopy.

Diffuse optical imaging (DOI) may be a beneficial diagnostic method for women with mammographically dense breast tissue. In order to evaluate the utility of DOI, we are developing broadband diffuse optical spectroscopy (DOS) to characterize the functional origins of optical signals in breast cancer patients. Broadband DOS combines multifrequency intensity-modulated and continuous-wave near-infrared light to quantify tissue absorption and scattering spectra from 650 to 1000 nm. Values of intrinsic physiological properties (oxy- and deoxy-hemoglobin, water, lipid, and scatter power) derived from absorption and scattering spectra provide detailed information on breast physiology. We present the results of clinical studies of 58 stage II/III malignant breast tumors using a noninvasive, handheld, broadband DOS probe. On average, eight positions were scanned over tumor and contralateral normal breast for each subject. Intrinsic physiological properties were statistically significantly different for malignant vs. normal tissues for all subjects, without patient age or tumor size/type stratification. Breast tissues containing malignant tumors displayed reduced lipid content ( approximately 20%) and increased water, deoxy-, and oxy-hemoglobin (>50% each) compared to normal breast tissues. Functional perturbations by the tumor were significantly larger than functional variations in normal tissues. A tissue optical index (TOI) derived from intrinsic physiological properties yielded an average two-fold contrast difference between malignant tumors and intrinsic tissue properties. Our results demonstrate that intrinsic optical signals can be influenced by functional perturbations characteristic of malignant transformation; cellular metabolism, extracellular matrix composition, and angiogenesis. Our findings further underscore the importance of broadband measurements and patient age stratification in breast cancer DOI.

Adolescent↗
PubMed2001

The palm as a real-time wide-area data-access device.

Handheld wireless technologies offer great promise in helping to improve healthcare. However, it is not clear whether off-the-shelf wireless networking will work as well within medical centers as this technology works outside of the medical center. Therefore, we evaluated the coverage of wide-area wireless technology within two representative academic medical centers. The study determined the rate of connectivity by testing both the Palm VII and the Minstrel V modem in a set of locations typically frequented by house staff in their daily activities. Within one hospital, connectivity was 59% for OmniSky service, and 78% for Palm.net. The second hospital's connectivity was over 93% with both devices. Differences in connectivity were likely due to the number of rooms visited with externally exposed walls, the suburban versus urban location of the academic medical center, and the relative location of service transponders. When examined by the Johns Hopkins Clinical Devices Laboratory, both devices were found to operate without interfering with other hospital equipment.

Academic Medical Centers↗
PubMed2005

High-resolution optical coherence tomographic imaging of osteoarthritic cartilage during open knee surgery.

This study demonstrates the first real-time imaging in vivo of human cartilage in normal and osteoarthritic knee joints at a resolution of micrometers, using optical coherence tomography (OCT). This recently developed high-resolution imaging technology is analogous to B-mode ultrasound except that it uses infrared light rather than sound. Real-time imaging with 11-microm resolution at four frames per second was performed on six patients using a portable OCT system with a handheld imaging probe during open knee surgery. Tissue registration was achieved by marking sites before imaging, and then histologic processing was performed. Structural changes including cartilage thinning, fissures, and fibrillations were observed at a resolution substantially higher than is achieved with any current clinical imaging technology. The structural features detected with OCT were evident in the corresponding histology. In addition to changes in architectural morphology, changes in the birefringent or the polarization properties of the articular cartilage were observed with OCT, suggesting collagen disorganization, an early indicator of osteoarthritis. Furthermore, this study supports the hypothesis that polarization-sensitive OCT may allow osteoarthritis to be diagnosed before cartilage thinning. This study illustrates that OCT, which can eventually be developed for use in offices or through an arthroscope, has considerable potential for assessing early osteoarthritic cartilage and monitoring therapeutic effects for cartilage repair with resolution in real time on a scale of micrometers.

Aged↗
PubMed1998

Optical coherence tomography for neurosurgical imaging of human intracortical melanoma.

OBJECTIVE: Intraoperative identification of brain tumors and tumor margins has been limited by either the resolution of the in vivo imaging technique or the time required to obtain histological specimens. Our objective was to evaluate the feasibility of using optical coherence tomography (OCT) as a high-resolution, real-time intraoperative imaging technique to identify an intracortical melanoma. INSTRUMENTATION: OCT is a new, noncontact, high-speed imaging technology capable of resolutions on the micrometer scale. OCT is analogous to ultrasound B-mode imaging, except that reflections of infrared light, rather than sound, are detected. OCT uses inherent tissue contrast, rather than enhancement with dyes, to differentiate tissue types. The compact, fiberoptic-based design is readily integrated with surgical instruments. METHODS: A portable handheld OCT surgical imaging probe has been constructed for imaging within the surgical field. Cadaveric human cortex with metastatic melanoma was harvested and imaged in two and three dimensions. Changes in optical backscatter intensity were used to identify regions of tumor and to locate tumor margins. Structures within the optical coherence tomographic images were compared with the histological slides. RESULTS: Two-dimensional images showed increased optical backscatter from regions of tumor, which was quantitatively used to determine the tumor margin. The images correlated well with the histological findings. Three-dimensional reconstructions revealed regions of tumor penetrating normal cortex and could be resectioned at arbitrary planes. Subsurface cerebral vascular structures could be identified and were therefore avoided. CONCLUSION: OCT can effectively differentiate normal cortex from intracortical melanoma based on variations in optical backscatter. The high-resolution, high-speed imaging capabilities of OCT may permit the intraoperative identification of tumor and the more precise localization of tumor margins.

Brain Neoplasms↗
PubMed2005

Breast cancer detection based on incremental biochemical and physiological properties of breast cancers: a six-year, two-site study.

RATIONALE AND OBJECTIVES: To demonstrate that near-infrared spectroscopy would achieve sufficient sensitivity and specificity in human breast cancer to reach ROC/AUC values in the 90s and yet to warn of the potential liabilities of introduction of a novel technology in this field. MATERIALS AND METHODS: 116 subjects from two nations (44 were cancer-verified by biopsy and histopathology) were reviewed. NIR spectroscopy of total hemoglobin and its relative oxygenation were monitored in breast cancers and compared to their contralateral breast in a 2D nomogram for diagnostic evaluation. A novel handheld NIR breast cancer detector pad with a 3-wavelength LED and 8 detectors with 4 cm separation between source and detectors was placed on the subject's breast. The method is convenient, rapid, and safe and has achieved high patient compliance with minimal patient apprehension of compression, confinement, or radioactivity. RESULTS: The absorbance increments of the cancerous region are referred to the mirror image location on the contralateral breast. The two metrics are increased hemoglobin concentration due to angiogenesis and decreased hemoglobin saturation due to hypermetabolism of the cancer. The 2D nomogram display of these two metrics shows Zone 1 contains verified cancers and Zone 2 contains noncancers. ROC evaluation of the nomogram gives 95% AUC for the two sites, Philadelphia and Leipzig. CONCLUSION: A simple, economical breast cancer detector has achieved high patient compliance and a high ROC/AUC score for a population which involved a range of tumors down to and including those of 0.8-1 cm in diameter.

Area Under Curve↗
PubMed2001

18F-labeled fluorodeoxyglucose positron emission tomography-guided surgery for recurrent colorectal cancer: a feasibility study.

OBJECTIVE: Positron emission tomography (PET) scanning is an accepted diagnostic tool for the detection of colorectal cancer (CRC). The purpose of this study was to determine whether diagnostic information offered by preoperative PET scan could be used to detect disease intraoperatively using beta and gamma handheld probes. METHODS: Two studies were carried out. First, tumor "phantoms" were created using 62 microCi fluorodeoxyglucose (FDG) in a saline-filled basin. Gamma and beta handheld probes were used to determine detection characteristics with respect to probe type, distance from source, and isotope half-life. In a second study, probes were used intraoperatively to detect tumor in 10 patients with recurrent colorectal cancer as determined by preoperative PET scan. Counts relative to background were determined for each probe as was histopathologic correlation with probe-positive tissue. RESULTS: Phantom studies documented that FDG detection by each probe was nonlinearly related to source proximity and half-life. In human subjects, abnormal findings on preoperative PET studies were detected by both probes with tumor:normal ratios of 1.6 (beta) and 1.5 (gamma). All probe-positive tissue was histologically confirmed to be recurrent colorectal cancer. CONCLUSIONS: Intraoperative detection of CRC using an FDG source and beta and gamma probes correlates with preoperative PET. With further improvements in probe technology, successful differentiation of normal and tumor tissue as shown here may allow for more precise localization and directed resection.

Beta Particles↗
PubMed2003

Improved results using ultrasound guidance for central venous access.

Central venous cannulation is an essential part of patient management in a variety of clinical settings. The complications of cannulation may be as high as 10 per cent and include arterial puncture, pneumothorax, hemothorax, cardiac tamponade, hematoma, malposition of catheter, nerve injury, and death. Standard technique for placement of central venous catheters is by use of a blinded, external landmark-guided technique. Success rates and complication rates vary according to the technique employed. Ultrasound use in general surgery has gained popularity and is now readily available in most operating suites. A prospective study was conducted to evaluate the feasibility of ultrasound-guided placement of central venous access devices. Ultrasound guidance was used to place central venous ports for chemotherapy in 29 patients. Catheters were placed using a handheld ultrasound (7.5 MHz, linear probe, Aloka, Wallingford, CT) with the Seldinger technique. The internal jugular vein was used as the primary site. Accurate placement within the superior vena cava was confirmed with fluoroscopy. All procedures were performed under local anesthesia with intravenous sedation. The data analyzed included length of procedure, complications, and success rates. The right internal jugular vein was used in all but 4 of our patients. In 2 of those patients, the left internal jugular was chosen initially. In the other 2, anatomical variants were discovered requiring a modification of technique to cannulate the right internal jugular vein. Overall, ultrasound led to a change in management in 14 per cent of patients. The average time for placement was 30 minutes (range, 22-42 minutes). There were no failures in placement or misplacement of the catheters. Detection of anatomy prior to venipuncture and direct real-time visualization are the keys to success with ultrasound guidance. This study shows that placement of central venous catheters, using ultrasound guidance, may be done in a timely manner while minimizing risks and maximizing success.

Adult↗
PubMed2006

[Clinical application of sentinel lymph node detection to early stage cervical cancer].

BACKGROUND & OBJECTIVE: Sentinel lymph node (SLN) identification has been increasingly used in the treatment design of a variety of solid tumors, particularly breast cancer and melanoma. A negative SLN predicts the absence of tumor metastases in the regional lymph nodes with high accuracy. This study was to investigate the clinical value of combined isotope-dye technique for detecting SLN, and to evaluate the accuracy of SLN in predicting the pelvic lymph nodes status in patients with early stage cervical cancer. METHODS: A total of 27 patients with early stage cervical cancer,scheduled for radical hysterectomy and total pelvic lymphadenectomy, were eligible for the study. Lymphoscintigraphy was performed with injection of radioactivity isotope (99m)Tc-labeled dextran ((99m)Tc-DX) into the uterine cervix 16 h before surgery. Methylthioninium (4 ml) was injected into the same points as (99m)Tc-DX during surgery, and the patients underwent lymphatic mapping with a handheld gamma-detecting probe. After resection of SLNs, standard radical hysterectomy with pelvic lymph node dissection was performed. All removed lymph nodes, including the SLNs, were examined by routine histopathology. The histopathologic results of SLNs and non-SLNs were compared. RESULTS: The detection rates of SLN were 96.3% by blue dye method, and 100% by radiolabeled tracer or combined isotope-dye. Blue dye method identified 61 SLNs, radiolabeled tracer identified 69 SLNs, and combined isotope-dye identified 70 SLNs. Preoperative SPECT/CT fusion images detected 4 SLNs in the parametrium. Seven (25.9%) patients had lymph node metastasis. The sensitivity, accuracy, negative predictive value, and false negative rate of SLN detection were 85.7% (6/7), 96.3% (26/27), 95.2% (20/21), and 14.3% (1/7), respectively. CONCLUSIONS: SPECT/CT imaging not only is superior to planar imaging in detecting SLN but also enables precise localization of SLNs. The combined isotope-dye method can improve the accuracy of SLN detection. SLN detection can accurately predict the pelvic lymph nodes status in early stage cervical cancer.

Adult↗
PubMed2000

Automated rejection of contaminated surface measurements for improved surface registration in image guided neurosurgery.

Most image guided Neurosurgery employs adhesively mounted external fiducials for registration of medical images to the surgical workspace. Due to high logistical costs associated with these artificial landmarks, we strive to eliminate the need for these markers. At our institution, we developed a handheld laser stripe triangulation device to capture the surface contours of the patient's head while oriented for surgery. Anatomical surface registration algorithms rely on the assumption that the patient's anatomy bears the same geometry as the 3D model of the patient constructed from the imaging modality employed. During the time interval from which the patient is imaged and placed in the Mayfield head clamp in the operating room, the skin of the head bulges at the pinsite and the skull fixation equipment itself optically interferes with the image capture laser. We have developed software to reject points belonging to objects of known geometry while calculating the registration. During the course of development of the laser scanning unit, we have acquired surface contours of 13 patients and 2 cadavers. Initial analysis revealed that this automated rejection of points improved the registrations in all cases, but the accuracy of the fiducial method was not surpassed. Only points belonging to the offending instrument are removed. Skin bulges caused by the clamps and instruments remain in the data. We anticipate that careful removal of the points in these skin bulges will yield registrations that at least match the accuracy of the fiducial method.

Artifacts↗
PubMed1997

A calculator based program to optimize the simulation of breast irradiation.

The simulation of breast fields using an isocentric set-up technique can be a lengthy process involving the placement of the isocentre, the determination of the gantry angles, and the selection of the lung shields, which in our center is one of six standard blocks. We show that with a body contour taken through central axis, five measurements and a calculator program, it is possible to significantly decrease the amount of time required to simulate a breast patient. We have developed a program for an HP48GX handheld calculator to determine the gantry angles, the isocentre, the field width, the standard angled block, and the couch and collimator rotation. The calculations are based on measurements of the field length, the horizontal distance between midline and mid axillary line, and the vertical distances from the mid axillary line to the inferior and superior beam border and central axis at midline. We use spherical geometry to perform the calculations to reflect the true environment and do not make any assumptions about the average patient's shape. For the simulation process a jig was developed that is inserted into the tray holder of the simulator to show the optical and radiological shadow of the calculated shielding along the patient's midline for clinical assessment during simulation and on the simulation film. The jig also has a holder for an aluminum wedge to improve the image quality of the simulation film. We admit that the lung shield increases the dose to the contralateral breast because of increased scatter and transmission through the shield; however, the block decreases the volume of irradiated lung while keeping the beam edge along the midline of the patient. The technique has been in use for two years and has resulted in time savings of up to 30% per patient. It has proven to be an easy and accurate way of setting up isocentric treatments to the breast.

Breast↗