Development of an Anthropomorphic Shoulder Phantom Model That Simulates Bony Anatomy for Sonographic Measurement of the Acromiohumeral Distance

The purpose of this project was to create a sonographic phantom model of the shoulder that was accurate in bone configuration. Its main purpose was for operator training to measure the acromiohumeral distance. A computerized 3‐dimensional model of the superior half of the humerus and scapula was rendered and 3‐dimensionally printed. The bone model was embedded in a gelatin compound and set in a shoulder‐shaped mold. The materials used had speeds of sound that were well matched to soft tissue and epiphyseal bone. The model was specifically effective in simulating the acromiohumeral distance because of its accurate bone geometry.     

Evaluation of the Accuracy of 3‐Dimensional Ultrasonography of the Kidney Using an In Vitro Renal Model

Objective. Three‐dimensional ultrasonography (3DUS) has recently become a reality because of advances in ultrasound probes and machine processing ability. We have developed an anthropomorphic phantom of the human loin to assess both the accuracy of 3DUS of the kidney and its potential usefulness for training in ultrasonographically guided percutaneous renal intervention. Methods. The model was built with easily available and inexpensive materials such as agar and latex with known ultrasonographic properties. The accuracy of 2‐dimensional ultrasonography (2DUS) and 3DUS was assessed by measuring the dimensions of the pelvicalyceal system (PCS) ultrasonographically (pelvis width and calyx diameters) and then comparing these with measurements obtained at the time of construction. Radiology interventional trainees then punctured the PCS with 2DUS and 4‐dimensional ultrasonographic (real‐time/time‐resolved 3DUS) guidance and reported the phantom's performance. Results. The 3‐dimensional nature of the model's PCS could be clearly visualized on 2DUS and 3DUS, and the scan characteristics were very similar to those in real life. Measurements using 3DUS proved to be closer to the true dimensions of the model's PCS than those using 2DUS. The mean error percentage for 2DUS measurements was ?10.2%, and that for 3DUS was ?2.2% (P < 0.0001). Interventional trainees were satisfied with the “tissue feel” and level of difficulty posed on puncturing the phantom. Conclusions. Three‐dimensional ultrasonography proved to be more accurate than 2DUS for intrarenal measurements using this in vitro renal model. Three‐dimensional ultrasonography has the potential to ease diagnostic renal scanning with the ability to further scrutinize and postprocess the scanned volumes. The model was realistic in its anthropomorphic properties and simulated human tissue during puncture.     

Elements of commissioning step-and-shoot IMRT: Delivery equipment and planning system issues posed by small segment dimensions and small monitor units

The implementation of intensity-modulated radiation therapy (IMRT) in the clinic necessitates commissioning for all systems involved. This paper describes work carried out for the treatment planning system (Helax-TMS version 6.1) and the treatment delivery equipment (Siemens Primus) available at our center. Particular regard was paid to small monitor units (MUs) and small field segments typical of step-and-shoot IMRT plans. The beam profile stability of the Siemens Primus accelerators when delivering small MU was examined with a linear detector array. Dose monitor linearity and intersegment variations were measured with a 0.6-cm³ ionization chamber. Treatment planning system calculated total scatter factors (S_cp) and beam profiles for symmetric and asymmetric small fields for 6- and 15MV beams were compared against measurements in water using a 0.125-cm³ ionization chamber and a diamond detector. The 6- and 15MV beams from the Primus accelerators were found to be stable at MUs less than 10. Dose monitor linearity for small exposures under 10 MU was within ± 2% for 6 MV, but found to be not so initially for 15 MV. This could be remedied by an adjustment of a soft spot on the Siemens Primus. The delivery of small MU segments as part of an IMRT sequence was found to be consistent down to segment sizes of 1 MU. The treatment planning system pencil-beam convolution model agreed with measurement within ± 5% for fields collimated down to 3 × 3 cm. The collapsed cone point-kernel model better predicted the output for the smallest field, but displayed some unpredictable shifts in the position of the penumbra. The startup characteristics of Siemens Primus accelerators were found suitable for step-and-shoot IMRT. The diminution in accuracy of Helax-TMS dose calculation models for multileaf collimated fields of less than 2 × 2 cm has led us to avoid these in IMRT treatments at our center.     

AN INVESTIGATION OF INTERFACE PRESSURES IN LOW AIR LOSS BEDS

Prospective randomised trials indicate that the low air loss bed is a successful method of treatment for pressure sores. To study the properties of these beds interface pressures were measured in two different low air loss beds. Ten healthy volunteers had eight readings at six different body sites taken supine and sitting. Occipital and heel pressures for both products exceeded 4.7 kPa, the accepted capillary closing pressure, while pressures at other sites were below this. These findings suggest that pressure relief alone is not the sole reason for the clinical acceptance of low air loss beds in the treatment of pressure sores.     

Elements of commissioning step-and-shoot IMRT: Delivery equipment and planning system issues posed by small segment dimensions and small monitor units

The implementation of intensity-modulated radiation therapy (IMRT) in the clinic necessitates commissioning for all systems involved. This paper describes work carried out for the treatment planning system (Helax-TMS version 6.1) and the treatment delivery equipment (Siemens Primus) available at our center. Particular regard was paid to small monitor units (MUs) and small field segments typical of step-and-shoot IMRT plans. The beam profile stability of the Siemens Primus accelerators when delivering small MU was examined with a linear detector array. Dose monitor linearity and intersegment variations were measured with a 0.6-cm³ ionization chamber. Treatment planning system calculated total scatter factors (S_cp) and beam profiles for symmetric and asymmetric small fields for 6- and 15MV beams were compared against measurements in water using a 0.125-cm³ ionization chamber and a diamond detector. The 6- and 15MV beams from the Primus accelerators were found to be stable at MUs less than 10. Dose monitor linearity for small exposures under 10 MU was within ± 2% for 6 MV, but found to be not so initially for 15 MV. This could be remedied by an adjustment of a soft spot on the Siemens Primus. The delivery of small MU segments as part of an IMRT sequence was found to be consistent down to segment sizes of 1 MU. The treatment planning system pencil-beam convolution model agreed with measurement within ± 5% for fields collimated down to 3 × 3 cm. The collapsed cone point-kernel model better predicted the output for the smallest field, but displayed some unpredictable shifts in the position of the penumbra. The startup characteristics of Siemens Primus accelerators were found suitable for step-and-shoot IMRT. The diminution in accuracy of Helax-TMS dose calculation models for multileaf collimated fields of less than 2 × 2 cm has led us to avoid these in IMRT treatments at our center.