Gridless adult cervical spine radiography and its' effect on image quality and radiation dose: A phantom study

INTRODUCTION

Imaging of the cervical spine in general radiography is most frequently performed using an anti-scatter grid. The purpose of this study was to investigate the effects of a gridless setting on image quality and radiation dose during digital radiography of the anteroposterior (AP) and lateral (LAT) cervical spine.

METHODS

A phantom study was performed with a variety of tube voltages (63-75 kV) with and without an anti-scatter grid. The tube current time product (mAs) and dose area product (DAP) were recorded and used to calculate effective dose (ED) and individual organ dose using PCXMC 2.0 software, as well as entrance surface dose (ESD) and objective image quality: signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Subjective visual image quality grading characteristics (VGC) was performed by five qualified radiographers.

RESULTS

In a gridless setting, the AP and LAT positions showed significantly lower DAP (1.6 μGym2; 61.3 % and 1.6 μGym2; 51.2%), ESD (27.6 μGy; 57.3% and 77.2 μGy; 47.2%) and ED (4.2 μSv; 61.3% and 2.3 μSv; 48.9%). In a gridless setting in the AP position, there is a slight significant deterioration in image quality. In the lateral projection, on the other hand, the image quality without the use of grid was only significantly reduced in three of six criteria and there was no difference in the objective image quality between the two settings examined.

CONCLUSION

The results of this study show that gridless setting significantly decreases radiation dose and image quality, but the quality in the lateral projection is still acceptable for diagnostic purpose.

IMPLICATIONS FOR PRACTICE

The protocol without the use of the anti-scatter grid in cervical spine radiography leads to a reduction in the radiation dose in both projections, but the image quality in the AP is significantly reduced for all criteria examined, with a slight deterioration in image quality in the lateral projection.

Immobilization of Notch ligand, Delta-1, is required for induction of notch signaling

Cell-cell interactions mediated by Notch and its ligands are known to effect many cell fate decisions in both invertebrates and vertebrates. However, the mechanisms involved in ligand induced Notch activation are unknown. Recently it was shown that, in at least some cases, endocytosis of the extracellular domain of Notch and ligand by the signaling cell is required for signal induction in the receptive cell. These results imply that soluble ligands (ligand extracellular domains) although capable of binding Notch would be unlikely to activate it. To test the potential activity of soluble Notch ligands, we generated monomeric and dimeric forms of the Notch ligand Delta-1 by fusing the extracellular domain to either a series of myc epitopes (Delta-1(ext-myc)) or to the Fc portion of human IgG-1 (Delta-1(ext-IgG)), respectively. Notch activation, assayed by inhibition of differentiation in C2 myoblasts and by HES1 transactivation in U20S cells, occurred when either Delta-1(ext-myc) or Delta-1(ext-IgG) were first immobilized on the plastic surface. However, Notch was not activated by either monomeric or dimeric ligand in solution (non-immobilized). Furthermore, both non-immobilized Delta-1(ext-myc) and Delta-1(ext-IgG) blocked the effect of immobilized Delta. These results indicate that Delta-1 extracellular domain must be immobilized to induce Notch activation in C2 or U20S cells and that non-immobilized Delta-1 extracellular domain is inhibitory to Notch function. These results imply that ligand stabilization may be essential for Notch activation.

The Notch ligand, Jagged-1, influences the development of primitive hematopoietic precursor cells

We examined the expression of two members of the Notch family, Notch-1 and Notch-2, and one Notch ligand, Jagged-1, in hematopoietic cells. Both Notch-1 and Notch-2 were detected in murine marrow precursors (Lin-Sca-1+c-kit+). The Notch ligand, Jagged-1, was not detected in whole marrow or in precursors. However, Jagged-1 was seen in cultured primary murine fetal liver stroma, cultured primary murine bone marrow stroma, and in stromal cell lines. These results indicate a potential role for Notch-Notch ligand interactions in hematopoiesis. To further test this possibility, the effect of Jagged-1 on murine marrow precursor cells was assessed by coculturing sorted precursor cells (Lin-Sca-1+c-kit+) with a 3T3 cell layer that expressed human Jagged-1 or by incubating sorted precursors with beads coated with the purified extracellular domain of human Jagged-1 (Jagged-1(ext)). We found that Jagged-1, presented both on the cell surface and on beads, promoted a twofold to threefold increase in the formation of primitive precursor cell populations. These results suggest a potential use for Notch ligands in expanding precursor cell populations in vitro.

Youthful and older biases as special cases of a self-age optimization bias

Two concepts of subjective age are measured for two cohorts (college students and older persons with an age range of 50 to 91 years). Functional age (Kastenbaum et al., 1972 Ages-of-Me Scale) shows the typical youthful bias for the older cohort. An older bias is shown for the Best/Ideal Age by the older cohort in comparison to the younger cohort. Taken together, the youthful bias, being like someone of younger chronological age, and the bias of selecting a relatively older age as best represents a "Self Age Optimization Bias." A sub-set of Best Age items dealing with work and career are identified for gender and cohort comparisons.

Subjective age and health perceptions of older persons: maintaining the youthful bias in sickness and in health

Self-reports of 250 persons fifty years of age and older confirm the increasing bias toward reporting a more youthful age as one increases in years. Optimistic perceptions of health care also maintained in older persons. Results from two subsets of this sample (N = 48) further indicate that the youthful and optimistic bias occurs in older persons with poorer and failing health (N = 23) as well as for persons in stable and good health (N = 25). Given the importance of self-perceptions in quality of life and in determining survivability, and given the indication that such measures are modifiable, it is suggested that future research be aimed at identifying those self-perceptions of health and age that are most susceptible to intervention.

Future time perspective, response rates, and older persons: another chapter in the story

Data quality is compromised when response rates to items vary with age group. Shmotkin (1992) found a 29% nonresponse rate to future-oriented items in persons older than 60 years and suggested future apprehension as a cause. The authors administered similar items to 251 older persons and found fewer instances of nonresponding to future-oriented items. On the basis of the high response rate to an enlarged Cantril ladder measuring future quality of life, presented in interview, the authors question the generality of future apprehension as a determinant of nonresponding. The authors suggest that mode of administration, size of items, and scale complexity, as well as future apprehension, are determinants of nonresponding to future-oriented items and scales.

Internal versus external locus of control for three age groups

Rotter's I-E Scale was administered to a non-college population of males and females in 3 age groups: 5–15, 16–25, and 46–60. Internal locus of control expectations increased with age. A trend for males to be more internal in their beliefs was suggested.