Radiation protection standards: their evolution from science to philosophy.

The concept of applying constraints on individual sources to a small fraction of the public dose limit has been deemed inappropriate when shielding the medical X-ray sources. This represents a broad-based consensus of medical physics and radiological societies in the United States, and the report series on the shielding design for medical X-ray sources (including dental, X-ray imaging and therapeutic X ray) from the National Council on Radiation Protection and Measurements (NCRP) utilises 1 mSv y(-1) as a source control limit. In the present study, the rationale for such a conclusion is discussed, and a somewhat critical look at the current model of radiation protection of the public is made.

Management of patient skin dose in fluoroscopically guided interventional procedures.

PURPOSE: To simulate dose to the skin of a large patient for various operational fluoroscopic conditions and to delineate how to adjust operational conditions to maintain skin dose at acceptable levels. MATERIALS AND METHODS: Patient entrance skin dose was estimated from measurement of entrance air kerma (dose to air) to a 280-mm water phantom for two angiographic fluoroscopes. Effects on dose for changes in machine floor kVp, source-to-skin distance, air gap, electronic magnification, fluoroscopic dose rate control settings, and fluorographic dose control settings were examined. RESULTS: Incremental changes in operational parameters are multiplicative and markedly affect total dose delivered to a patient's skin. For long procedures, differences in doses of 8 Gy or more are possible for some combinations of operational techniques. CONCLUSIONS: Effects on skin dose from changes in operational parameters are multiplicative, not additive. Doses in excess of known thresholds for injury can be exceeded under some operating conditions. Adjusting operational parameters appropriately will markedly reduce dose to a patient's skin. Above all other operational factors, variable pulsed fluoroscopy has the greatest potential for maintaining radiation exposure at low levels.

Protecting patients by training physicians in fluoroscopic radiation management.

During the past 15 years, developments in x-ray technologies have substantially enhanced the ability of practitioners to treat patients using fluoroscopically guided interventional techniques. However, many of these procedures require a greater use of fluoroscopy and serial imaging (cine). This has increased the potential for radiation-induced dermatitis, epilation, and severe radiation-induced burns to patients. It has also increased the potential for radiation injury and radiation-induced cancer in personnel. This work will describe a number of the cases that have appeared in the literature and current recommendations and credentialing requirements of various organizations whose members use fluoroscopy. Finally, a program for implementing training of physicians in radiation management as a means of reducing the risk of injury to patients and personnel is recommended.

The AAPM/RSNA physics tutorial for residents. Typical patient radiation doses in diagnostic radiology.

Factors affecting patient dose in all x-ray imaging modalities include beam energy, filtration, collimation, patient size, and image processing. In conventional radiography, the most important determinant of acceptable patient dose is use of the highest peak kilovoltage that results in diagnostic images. Digital radiography allows a much wider range of exposures than conventional radiography for producing diagnostic images. However, operators must be aware of the subtle differences in techniques used with digital systems to avoid unnecessary increases in patient dose. Low-dose mammography requires lower ranges of peak kilovoltage; different target materials, filters, and screen-film combinations; special attention to breast thickness, composition, and compression during the study; and different standards for grids, magnification, and optical density. Although peak kilovoltage and tube current are important for controlling patient dose in fluoroscopy, collimation, source-to-skin and patient-to-image intensifier distances, and control of beam-on time have perhaps greater importance. Computed tomography (CT) involves greater patient dose than conventional radiography, and, although the primary radiation dose is delivered to smaller volumes, dose calculations must account for dose received by adjacent tissue sections. Many variables are involved in fetal exposure and fetal dose effects, but a solid understanding of them can help in developing responsible patient management practices.

Depot medroxyprogesterone. Management of side-effects commonly associated with its contraceptive use.

Depot medroxyprogesterone acetate is one of the most popular, effective methods of contraception used in the United States. Many women experience unpleasant side effects from this method, including episodic vaginal bleeding, hair loss, depression, and weight gain. This Clinical Practice Exchange describes the treatment strategies for these side-effects used by nurse-midwives from a variety of settings and locales. Contraceptive use can be more acceptable for many women if they are better able to cope with unpleasant side effects of the method. This Clinical Practice Exchange provides knowledge to enhance client coping.

PIP: In this clinical practice exchange, nurse-midwives in a variety of settings and US regions describe their treatment strategies for addressing the side effects associated with depot medroxyprogesterone acetate (DMPA). Although DMPA is a safe, effective, long-acting method of hormonal contraception, this injectable has been linked with side effects such as weight gain, menstrual changes, headache, dizziness, acne, abdominal bloating, breast swelling, depression, reduced libido, and alopecia. Approximately one-third of DMPA acceptors discontinue use by the end of the first year and half discontinue by the end of the second year, primarily because of these side effects. Nurse-midwives report that adolescents who are unable to take the pill consistently and breast-feeding women are ideal candidates for DMPA use. Constant vaginal bleeding, the most troublesome side effect, can be treated through use of ibuprofen, oral estrogen, or oral DMPA. Potential or actual weight gain can be averted through life-style changes such as reduced dietary fats and increased exercise. Unanticipated pregnancies can be avoided by administering the initial DMPA injection within 5 days after the onset of menses. Pre-acceptance anticipatory counseling, along with regular support and encouragement, increase user satisfaction with DMPA.

Island flaps including the Bezier type in the treatment of malignant melanoma.

Despite the trend in current surgical practice in the treatment on melanoma to produce smaller excisional defects, any technique which can introduce a surgical closure that does not require split skin grafting must be of benefit. This paper introduces and illustrates a range of island flap techniques that employ no skin grafting for the treatment of malignant melanoma defects. The new cutaneous island flap described, termed the Bezier or the French Curve, employs a double V-Y appositional closure method, thus giving a more refined reconstructive result that fits into the line of the body curves aesthetically. The design of the Bezier flap is almost identical in size and shape to the excisional defect, with a facial or muscular base for vascular support. Appropriate guidelines that determine the design and application of this island flap technique are listed. They are illustrated both diagrammatically and clinically. Other flaps illustrated include fasciocutaneous island flaps and myocutaneous island flaps that use a single V-Y flap appositional closure technique. All these flaps were designed with special reference to the dermatomes, which act as an aid memoire upon which the flaps are marked.

Treatment of Aeromonas hydrophila infection in a deep tissue wound.

We report the case of a young woman who sustained a knee laceration in an automobile accident and was subsequently exposed to water. Although properly cleansed and closed, her wound became infected and she was initially treated with a single-dose parenteral cephalosporin. The infection progressed and cultures indicated a polymicrobial infection which included Aeromonas hydrophila. Significant tissue damage ensued and a lengthy hospitalization was required. Aeromonas, although rarely a cause of infection in otherwise healthy individuals, should be suspected in wounds exposed to fresh water.

History of the shielding of diagnostic x-ray facilities.

The results of inadequate protection of radiation workers against the harmful effects of diagnostic x-rays became appallingly apparent shortly after the turn of this century. After these effects (which included erythema, malignancy, and even death) became widely known, efforts were begun to implement recommendations to reduce the hazards to radiologic workers and members of the general public. This work will trace the development of diagnostic radiation shielding standards from the earliest days to the present time.

Attenuation properties of diagnostic x-ray shielding materials.

Single- and three-phase broad-beam x-ray attenuation data have been obtained using lead, steel, plate glass, gypsum wallboard, lead acrylic, and wood. Tube voltages of 50, 70, 100, 125, and 150 kVp were employed and the resulting curves were compared to transmission data found in the literature. To simplify computation of barrier requirements, all data sets were parametrized by nonlinear least-squares fit to a previously described mathematical model. High attenuation half value layers and the lead equivalence of the alternate materials were also determined.

Exposure rates during special procedures with C-arm type fluoroscopic systems.

PURPOSE: To test for regulatory compliance of free-in-air entrance air kerma rates (EAKR) in C-arm type fluoroscopic equipment, measurements are frequently made under minimum source-to-image receptor distance (SID) and at 300 mm from the image intensifier. However, this is not representative of normal patient geometry, and the automatic brightness controls on these units frequently increase tube output as SID increases. This study investigated effects of these circumstances on actual EAKRs. MATERIALS AND METHODS: Typical patient geometries were observed and recorded for 23 consecutive body vascular procedures. EAKRs were measured under compliance and normal patient geometries with use of five modern C-arm type systems for special procedures. RESULTS: SIDs of 1 m were typical when rapid film changers were employed and the patient's entrance skin surface was typically 500 mm from the image receptor. Actual EAKRs were found to be up to 2.5 times those measured under compliance geometry. CONCLUSION: Actual patient geometries should be used to ensure correct estimates of EAKRs.

Aqueous beclomethasone dipropionate in the treatment of ragweed pollen-induced rhinitis: further exploration of "as needed" use.

BACKGROUND: The objective of this study was to compare regular and "as required" (prn) use of aqueous beclomethasone dipropionate nasal spray (Beconase AQ nasal spray) in the treatment of ragweed pollen-induced rhinitis and to examine possible predictors of unsatisfactory symptom control in the group of patients who used it on a prn basis. METHODS: Sixty adults with ragweed pollen-induced rhinitis, who had participated in previous hay fever studies or who responded to media notices, were enrolled in the study. The study design was a randomized, unblinded, parallel group comparison between regular use (400 micrograms daily) and prn use of Beconase AQ spray during the 6 weeks of the ragweed pollen season. Patients recorded daily symptoms and medication use in diaries. The Rhinoconjunctivitis Quality of Life Questionnaire was administered, and patient satisfaction with symptom control was assessed at clinic visits. RESULTS: Symptoms and quality of life tended to be better in the regular group, but differences were not statistically significant. Twenty-seven percent of patients in the prn group reported unsatisfactory control of symptoms; they experienced significantly worse symptoms and quality of life than the remainder of the prn group and used significantly more Beconase. No obvious predictors of unsatisfactory control were identified. Patients who achieved satisfactory control in the prn group had symptom and quality of life scores that were very similar to those of the regular group. CONCLUSIONS: Most patients can use Beconase AQ as needed successfully for the treatment of hay fever, but there may be an apparently unpredictable minority who do not achieve satisfactory symptom control or quality of life with this approach and who require regular treatment.

Computed tomography before lumbar puncture in acute meningitis: a review of the risks and benefits.

OBJECTIVE: To determine the indications, if any, for routine computed tomography (CT) of the brain before lumbar puncture in the management of acute meningitis. DATA SOURCES: Original research papers, reviews and editorials published in English from 1965 to 1991 were retrieved from MEDLINE. The bibliographies of these articles and of numerous standard texts were examined for pertinent references. A survey of local neurologists was conducted, and legal opinion was sought from the Canadian Medical Protective Association. DATA EXTRACTION: There were no studies directly assessing the risks of lumbar puncture in meningitis; however, all sources were culled for other pertinent information. RESULTS: No cases could be found of patients with acute meningitis deteriorating as a result of lumbar puncture. The neurologic consensus refuted the need for CT in typical acute meningitis. All sources stressed speedy lumbar puncture and the early institution of appropriate antibiotic therapy to minimize the severity of the illness and the risk of death. CONCLUSIONS: (a) There is no evidence to recommend CT of the brain before lumbar puncture in acute meningitis unless the patient shows atypical features, (b) for patients with papilledema the risks associated with lumbar puncture are 10 to 20 times lower than the risks associated with acute bacterial meningitis alone, (c) CT may be necessary if there is no prompt response to therapy for meningitis or if complications are suspected, (d) the inability to visualize the optic fundi because of cataracts or senile miosis is not an indication for CT and (e) there are no Canadian legal precedents suggesting liability if physicians fail to perform CT in cases of meningitis.

Low resolution spin echo: a simple timesaving technique for MRI liver exams.

MR evaluation of the liver at mid-field strength requires relatively lengthy T2-weighted sequences (T2W) for differentiation of benign cavernous hemangiomas from malignant lesions. A short duration T2W, which maintains standard signal-to-noise ratio and also contrast relationships, can be easily implemented by increasing the pixel size in the phase-encoding direction (thus reducing spatial resolution) and proportionally decreasing the number of phase-encoding steps in the matrix (thus reducing acquisition time). Blinded interpretations of a quick (4 min), low resolution (3.4 mm x 1.7 mm pixel) T2W sequence (matrix 64 x 256, FOV 21.7 cm phase x 43.5 cm frequency) were compared to the 17 min standard resolution (1.7 mm x 1.7 mm) T2W sequence (256 x 256 matrix, FOV 43 x 43 cm) in 25 patients suspected of having liver metastasis. Lesions felt to be cavernous hemangiomas showed a 100% (24/24) agreement for interpreter "A" and 96% (22/23) agreement for interpreter "B" when 4 min low resolution T2W was compared to the standard 17 min sequence. Sensitivity (for all types of lesions) of the low resolution T2W sequence ranged from 100% (31/31) for interpreter "A" to 80% (28/35) for interpreter "B." Missed lesions (interpreter "B") were either partially obscured by excessive fat (wrap around) (N = 4), less than 1 cm in size (N = 2), or degraded by motion artifact (N = 1). Thus in many situations low resolution T2 may provide a substantial timesaving alternative to standard T2W particularly where T2W is used primarily for lesion classification in normal sized patients.

A MRI gradient waveform model for automated sequence calibration.

In order to set up magnetic resonance imaging (MRI) procedures of arbitrary voxel dimensions, slice orientation, and sequence timing in a reasonable time, some form of automatic gradient pulse calibration is required. One such method, involving simulation of gradient waveforms, is presented. Waveforms are modeled based on measurements of the step response. The model used divides each transition into three time regions: a "start" region in the first 0.3 ms, a "slew" region, and a "tail" region representing decay of the eddy current compensation error. In the "slew" region, the time derivative of the gradient, G' (t), is expressed as a function of G(t). The first two regions are nonlinear with respect to demand. The mean error in the simulated gradient is generally less than 0.04 mT m-1 in spin echo sequences. Image signal/noise ratios resulting from sequences calibrated using the model are within 5% of those of empirically calibrated sequences.