Biomedical subjects

Dwight Heron

Publications and source records attributed to Dwight Heron.

3 recordsLinked to original sources

PubMed2006

Abdominal organ motion measured using 4D CT.

PURPOSE: To measure respiration-induced abdominal organ motion using four-dimensional computed tomography (4D CT) scanning and to examine the organ paths. METHODS AND MATERIALS: During 4D CT scanning, consecutive CT images are acquired of the patient at each couch position. Simultaneously, the patient's respiratory pattern is recorded using an external marker block taped to the patient's abdomen. This pattern is used to retrospectively organize the CT images into multiple three-dimensional images, each representing one breathing phase. These images are analyzed to measure organ motion between each phase. The displacement from end expiration is compared to a displacement limit that represents acceptable dosimetric results (5 mm). RESULTS: The organs measured in 13 patients were the liver, spleen, and left and right kidneys. Their average superior to inferior absolute displacements were 1.3 cm for the liver, 1.3 cm for the spleen, 1.1 cm for the left kidney, and 1.3 cm for the right kidney. Although the organ paths varied among patients, 5 mm of superior to inferior displacement from end expiration resulted in less than 5 mm of displacement in the other directions for 41 of 43 organs measured. CONCLUSIONS: Four-dimensional CT scanning can accurately measure abdominal organ motion throughout respiration. This information may result in greater organ sparing and planning target volume coverage.

Abdomen↗

PubMed2006

Localizing moving targets and organs using motion-managed CTs.

Respiration-induced target and organ motion impacts the radiotherapy strategies of some cancers. Various methods and techniques have been used to investigate motion-related radiotherapy issues, including retrospective 4-dimensional (4D) computed tomography (CT), prospective gated CT, and breath-hold CT scans. This paper reviews these methods and, particularly, the method using retrospective 4D CT scans, which has been developed at our institution. Some motion studies based on retrospective 4D CT images of patients are also examined. These studies have led to reduced planning target volume (PTV) margins for a number of patients, because the respiratory motion was observed to be minimal or gated radiotherapy was used. Respiratory motion managed CTs and, particularly, retrospective 4D CTs are proving to be useful for measuring soft tissue motion, identifying patients who could benefit from gated radiotherapy, and evaluating the effects of respiratory motion during radiotherapy.

Humans↗

PubMedDate not supplied

Twice-daily high-dose-rate brachytherapy for medically inoperable uterine cancer.

PURPOSE: Medically inoperable patients with uterine cancer pose a therapeutic challenge. We developed a twice-daily schedule of high-dose-rate brachytherapy (HDRB) after a single insertion procedure that required a hospitalization of 3 days. METHODS AND MATERIALS: Favorable patients were offered brachytherapy alone, and all other patients received HDRB after pelvic external beam radiation therapy (EBRT). The prescribed dose was 7Gyx5 fractions and 4-5Gyx4-5 fractions for those treated after EBRT. HDRB was delivered with a b.i.d. schedule (4-6-h interval). RESULTS: Twenty-two patients (21 Stage I, 1 Stage IIB) were deemed medically inoperable. Sixteen patients received EBRT followed by HDRB, and six received HDRB alone. There were no procedural complications or significant acute toxicity. No thromboembolic events occurred within 30 days of the implant. CONCLUSIONS: This technique allows patients to be treated using a single procedure for insertion, with brief hospitalization for twice-daily HDRB.

Adult↗