Diagnostic reference levels in spinal CT: Jordanian assessments and global benchmarks

Abstract

BACKGROUND:

To reduce radiation dose and subsequent risks, several legislative documents in different countries describe the need for Diagnostic Reference Levels (DRLs). Spinal radiography is a common and high-dose examination. Therefore, the aim of this work was to establish the DRL for Computed Tomography (CT) examinations of the spine in healthcare institutions across Jordan.

METHODS:

Data was retrieved from the picture archiving and communications system (PACS), which included the CT Dose Index (CTDI_(vol)) and Dose Length Product (DLP). The median radiation dose values of the dosimetric indices were calculated for each site. DRL values were defined as the 75th percentile distribution of the median CTDI_(vol) and DLP values.

RESULTS:

Data was collected from 659 CT examinations (316 cervical spine and 343 lumbar-sacral spine). Of the participants, 68% were males, and the patients’ mean weight was 69.7 kg (minimum = 60; maximum = 80, SD = 8.9). The 75th percentile for the DLP of cervical and LS-spine CT scans in Jordan were 565.2 and 967.7 mGy.cm, respectively.

CONCLUSIONS:

This research demonstrates a wide range of variability in CTDI_(vol) and DLP values for spinal CT examinations; these variations were associated with the acquisition protocol and highlight the need to optimize radiation dose in spinal CT examinations.

Keywords

Diagnostic reference level DRL computed tomography radiation dose dose optimization

1 Introduction

Spinal pain is the most common reason patients attend physicians in the USA, with healthcare expenditures for spine problems totalling approximately $86 billion annually [1]. Many patients receive medical imaging, including X-rays, Magnetic Resonance Imaging (MRI), or Computed tomography (CT). CT examinations represent 50% of all man-made radiation delivered to humans [2, 3], with radiation doses per examination and frequency of examinations increasing rapidly. Increases are due to technological advances in technology and increased complexity of examinations [4]. However, cancer risks have long been identified with CT examinations, with reports suggesting up to 27,000 neoplasms being induced by CT exposure in a year [5]. There is limited evidence in Jordan or elsewhere that radiation dose reduction coupled with optimal image quality can be achieved.

Physicians may request a CT scan of the lumbar spine before or after x-rays. With submillimetre information obtained by CT scanners and the increase in the number of CT scans requested, the risk of inducing cancer with a CT examination of the entire lumbar spine is reported to be approximately 1 in 3,200, and in the thoracic spine (approximately 1 in 1,800). The increased risk with the thoracic spine is due to the additional coverage required and the anatomic implications of the cervical-dorsal junction CT scan range [6]. To reduce the potential risks associated with high radiation doses from CT, it is recommended that the “As Low As Reasonably Achievable”(ALARA) principle established by the International Commission on Radiological Protection (ICRP) [7] be applied.

DRLs are radiation dose values set, that should not be exceeded for average-sized patients when good practice is applied. They are usually protocol-specific for examinations and provide a reference level for that examination. DRLs are not dose limits but rather guidelines. However, if regularly exceeded, corrective action should be sought. DRLs were first introduced in the United Kingdom two decades ago [8]. They have been cited as effective tools for reducing radiation doses, with reports indicating a reduction of up to 50% since their adoption [9]. Also, in the absence of DRLs, dose variations for the same examination up to 23 times have been reported between centres for non-CT X-ray examinations [10] and CT examinations [11]. The dominant method of establishing a DRL is to determine radiation dose levels delivered for specific studies in several tertiary institutions in an individual country (or state) and then use these data to determine the 75th percentile of the dose distribution. Due to the varying procedures and equipment across different countries, most countries prefer to produce their own DRL rather than adopt levels established in other jurisdictions. The requirement for DRLs has been described in legislative documents in Jordan and throughout Europe, and their implementation has been observed in Europe and the United States [8 , 12–16]. Still, there is no national DRL value for spine CT exams in Jordan. This research project aims to establish DRL for spinal CT and, in doing so, investigate the causes of variation and identify the lowest radiation dose required to facilitate the accurate detection of spine pathology by multi-detector CT.

2 Methods

2.1 Ethical approval

Institutional Review Board (IRB) approval (43/140/2021) was obtained, and the ethics committee exempted informed consent. Approval from the study institution’s medical director and IRB office was obtained before collecting data.

2.2 Study design and population

In line with a methodology previously described (NRPB, 1992), the DRL part of the study consisted of two primary data collections: 1) protocol data and 2) actual scan sequence data. Both parts involved sending out questionnaires to 30 centres across Jordan. Nine centres agreed to participate in the current work, and a clinical coordinator with CT experience was assigned to each centre to receive and administer the questionnaires. The data questionnaires and forms have been previously designed and validated [8]. In the first part of the questionnaire, information was provided on standard protocols used for specific examinations, including exposure factors, procedures, and radiation doses. The second part recorded the same data, but this time for protocols employed for each of the last 30 average-sized patients (60–80) kg [8] (Table 1). The number of centres chosen (n = 9) represents approximately 30 % of CT units in Jordan, exceeding sample sizes previously used to establish DRLs [8 –10]. The study excluded patients younger than 18 years old. Documents were reviewed for each institution to determine if they had a quality assurance program in place.

Table 1
For each scanning sequence, parameters were collected from each clinical centre

Exposure factors Procedural data Dose data

Tube voltage (kVp) Anatomical range CTDI_(vol)

Tube rotation time (s) Standard sequence always used? DLP

Tube current (mA) Beam collimation

Displayed mAs: Intravenous contrast used?

mAs/slice Axial or helical scanning?

effective mAs Table increment &pitch

Auto dose reduction used? Imaged slice thickness

Field of view (FOV) Scan length

Exposure factors	Procedural data	Dose data
Tube voltage (kVp)	Anatomical range	CTDI_(vol)
Tube rotation time (s)	Standard sequence always used?	DLP
Tube current (mA)	Beam collimation
Displayed mAs:	Intravenous contrast used?
mAs/slice	Axial or helical scanning?
effective mAs	Table increment &pitch
Auto dose reduction used?	Imaged slice thickness
Field of view (FOV)	Scan length

2.3 Dose data

CT scanners provide dosimetric indices for each sequence and examination, including Computed Tomography Dose Index (CTDI_(vol)) and Dose Length Product (DLP).

2.4 Examinations chosen

Currently, the research will focus on the most common adult spine investigations, cervical spine (C-spine) (n = 316) and lumbar-sacral spine (LS-spine) (n = 343). Thoracic spine studies were excluded due to a lack of sufficient cases.

2.5 Data analysis

The first, second, and third quartiles for CTDI (vol) and DLP were calculated using SPSS 22.0 (IBM Corp., Armonk, NY, USA). Each institution’s median radiation dose values were calculated, and the 75th percentile distribution of the median value of CTDI_(vol) and DLP was used to define DRL. In addition to the above calculations, a stepwise regression was performed to identify exposure or procedural parameters associated with higher doses and to quantify each factor’s contribution to observed variations. An anonymised histogram, with the 75th percentile marked, will be circulated to each cipating centre. The provided information will enable each centre to identify the histogram bar(s) corresponding to their data, along with the specification of factors potentially responsible for higher doses. Additionally, international DRL levels were compared with the current national DRL levels. No other identifying features were presented.

3 Results

The patients demographic age range was from 18 to 92 years. In line with a methodology previously published, 659 protocol and scan sequence details were collected (Table 2).

Table 2
Detailed information about each hospital’s scanners

Hospital Manufacturer Year of CT model Installation Gantry Capacity

manufacture type rotation (Slice No.)

1 Philips 2017 Brilliance CT 128 slice 2018 360 128

2 Siemens 2015 SOMATOM Force 2016 360 64

3 Philips 2010 Philips Brilliance 16-Slice CT Scanner 2016 360 16

4 Philips 2010 Philips Brilliance 16-Slice CT Scanner 2013 360 16

5 GE 2011 RT CT 16 Refurbished GE Light Speed Scanner 2015 360 64

6 Philips 2010 IQon Elite Spectral CT 2013 360 16

7 Toshiba 2015 Refurbished Toshiba Dual slice CT Scan Machine 2015 360 64

8 Philips 2008 Brilliance CT 16 slice 2011 360 16

9 Philips 2010 Philips Brilliance 16-Slice CT Scanner 2010 360 16

Hospital	Manufacturer	Year of	CT model	Installation	Gantry	Capacity
1	Philips	2017	Brilliance CT 128 slice	2018	360	128
2	Siemens	2015	SOMATOM Force	2016	360	64
3	Philips	2010	Philips Brilliance 16-Slice CT Scanner	2016	360	16
4	Philips	2010	Philips Brilliance 16-Slice CT Scanner	2013	360	16
5	GE	2011	RT CT 16 Refurbished GE Light Speed Scanner	2015	360	64
6	Philips	2010	IQon Elite Spectral CT	2013	360	16
7	Toshiba	2015	Refurbished Toshiba Dual slice CT Scan Machine	2015	360	64
8	Philips	2008	Brilliance CT 16 slice	2011	360	16
9	Philips	2010	Philips Brilliance 16-Slice CT Scanner	2010	360	16

The survey focused on the cervical and lumbar spine CT examinations, and CT scans included one single scan per examination, and repeated scans were excluded. To prevent variability in radiation dose recording, patients who weighed between 60 and 80 kg were included in the study [8].

Nine hospitals (four militaries, two private, and three governmental) participated in the study. Recordings from 659 (316 c-spine and 343 LS-spine s) CT examinations were collected. Of the participants, 68% were males and 31.6% were females, and the mean weight for both genders was 69.8 kg (min = 60; max = 80, SD = 8.9). Data was collected from nine scanners, of which three and five centres acquired image data in 64 and 16 slices. Only one centre used 128 slices. A sample size calculation indicated that a difference in dose of 5% at 0.8 power would be detectable. Table 3 shows patient and equipment characteristics as well as spine CT protocols.

Table 3

Patients and equipment’s characteristics

Characteristics	No. of patients or mean
(% or interquartile range)
Gender
Male	451 (68.4%)
Female	208 (31.6%)
Procedure
C-spine	316 (48.0 %)
LS-spine	343 (52.0 %)
FOV
C-spine	17.6 cm (7.6–34.3)
LS-spine	18.4 (7.1–42.3)
Number of slices
C-spine	132 (62–601)
LS-spine	132 (43–832)
Slice thickness
C-spine	1.25 mm (0.625–5)
LS-spine	1.25 mm(0.625–5)
kVp
C-spine	120 (120–140)
LS-spine	120 (120–140)
mAs
C-spine	200 (83–764)
LS-spine	190 (76–568)
Patient age (years)	41.8 (IQR 18–92)
Patient weight (kg)	69.8 (IQR 61–80)
Body mass index (kg/m2)	32.6 (IQR 24.1–38.6)
CT model (slice)
Philips (16)	359 (54.4%)
Philips (128)	60 (9.1%)
Siemens (64)	99 (15%)
Toshiba dual (64)	39 (6%)
Ge healthcare (64)	102 (15.5%)

IQR: Interquartile range.

The median CTDI_(vol) and DLP per CT examination were collected for each site and used to compare doses across CT centres. Hospitals surveyed found wide variations in median CTDI (vol) between c-spine and l-spine examinations, with differences of 4.2 and 5.6 folds, respectively. DLP reported a similar pattern for the examinations surveyed, with differences of 3.2 and 5.4 for c-spine and LS-spine scans retrospectively (Table 4). Figure 1 illustrates the median CTDI_(vol) and DLP distribution for the nine surveyed hospitals, with the horizontal line representing the DRL for both the cervical and LS-spine. The median CTDI_(vol) values for the c-spine and LS-spine s were 5.63–23.8 and 6.43 –36.1 mGy, while the median DLP values for the c-spine and LS-spine were in the range of 184.6–679.9 and 266.9 and 1025.0 mGy.cm. Except in cases where some dosimetric values were doubled, there was no statistical significance between the centres. For example, the median CTDI_(vol) value for the LS-spine for the hospital (5) was 6.4 milli-gray (mGy) compared with 36.1 mGy for the hospital (7). For the same centre, similar radiation dose values were observed for DLP values. Two hospitals have higher local median CDTI values (vol) than DRL; a third hospital has a slightly higher local median DLP value than DRL.

Table 4

DRLs for the C-spine and LS-spine are stratified by centre

		Centre	1 (n = 30)	2 (n = 41)	3 (n = 31)	4 (n = 39)	5 (n = 46)	6 (n = 35)	7 (n = 30)	8 (n = 30)	9 (n = 36)
C-spine	CTDI_(vol)	Minimum	7.4	8.2	4.7	6.74	3.1	16.1	4.7	5.77	10.1
		25th	14.5	9.8	5.8	12.19	5.24	18.3	7.7	11.15	14.13
		Median	16.12	11.9	9.8	17.14	5.63	22.6	10.7	16.95	23.75
		75th	16.25	19.39	17.2	22.14	9.465	29.2	40.15	21.35	27.22
		Maximum	18.9	27.69	52	31.92	24.78	39.72	52.1	29.2	30.1
	DLP	Minimum	235.3	38	112.3	59.14	71.2	350	139	121.2	420.1
		25th	384.6	333.5	210.1	270.7	143.6	509	247.7	260.1	558.6
		Median	470	416	321	322.7	184.6	679	337.8	424.7	660.3
		75th	520.2	614.5	720.3	550.4	292.8	760	937.1	596.4	740.1
		Maximum	580.2	908.3	1276	720.9	1181	1200	1795	1302	1103
		Centre	1 (n = 30)	2 (n = 55)	3 (n = 71)	4 (n = 30)	5 (n = 30)	6 (n = 30)	7 (n = 35)	8 (n = 31)	9 (n = 30)
LS- spine	CTDI_(vol)	Minimum	5.7	8.4	6.6	6.6	5.3	16.2	10.5	3.2	11.9
		25th	16.15	13.31	11.5	14.40	6.17	18.81	19.4	8.1	14.9
		Median	22	15.7	15.9	18.44	6.43	20.42	36.1	22.47	19.3
		75th	23.9	17.5	23.9	21	7.05	39.51	36.2	37.1	23.9
		Maximum	31.5	29.1	54.9	54.9	24.78	42.4	41.7	61.3	31.5
	DLP	Minimum	185.9	6.4	44.8	191	184.6	320.6	200.8	142	35.8
		25th	654.2	43.8	350.5	404.8	219.9	457.8	881.7	261.4	681.8
		Median	1003	332	485.7	624.3	266.9	614	1025	512.3	950.5
		75th	1557	598.6	739.3	727.9	295.8	1586	1277	1043	1113
		Maximum	2440	1070	2001	2001	1699	2600	2126	2482	2404

Fig. 1

(A) Distributions of median CTDI_(vol) values for c-spine CT examination. (B) Distributions of median DLP values for c-spine CT examinations. (c) Distributions of median CTDI_(vol) values for LS-spine CT examinations. (D) Distributions of median DLP values for LS-spine CT examinations.

A summary of DRLs per scan (C-spine and LS-spine CT scanning examinations) and per centre is shown in Table 5. The DRL for the CTDI_(vol) for the C-spine was 19.2 mGy and 565.2 mGy.cm for the DLP. Similarly, the CTDI_(vol) for the LS-spine was 22.2 mGy and 976.8 mGy.cm for the DRL. Table 6 compares the findings with DRLs published in other countries [8 , 12–16].

Table 5

DRLs for C-spine and LS-spine CT scans in Jordan

	Scan type	C-spine (n = 316)	LS-spine (n = 343)
CTDI_(vol)	Minimum	5.63	6.43
	25th	10.25	15.8
	Median	16.12	19.3
	75th	19.87	22.23
	Maximum	19.87	36.1
	Standard deviation	10.28	10.14
	Minimum	184.6	266.9
DLP	25th	321.85	408.85
	Median	414.0	614
	75th	565.15	976.75
	Maximum	679.0	1025
	Standard deviation	284.41	537.81

Table 6

C-spine and LS-spine CT DRLs in Jordan compared with other international: C-spine and LS-spine CT DRLs

		Switzerland	Australian	France	American	Ireland	EU	Jordan
		(Treier et al.,	(Lee et al.,	(Roch et al.,	(Kalpana et al.,	(Foley et al.,	(Shrimpton	(current
		2010)¹²	2020)¹³	2018)¹⁴	2017)¹⁵	2012)¹⁶	et al., 2006)⁸	study)
CTDI_(vol)	C-spine	30	23	–––	28	19.4	70	19.87
	LS-spine	–––	26	30	–––	–––	–––	22.23
DLP	C-spine	600	470	770	562	418	460	565.15
	LS-spine	–––	670	–––	–––		–––	976.75

Multiple regression analysis suggested that combining of kVp, mAs, and several slices accurately predicted CTDI_(vol) more than any individual variable alone. The multiple linear regression results showed that mAs, kVp, and the number of slices were significant predictors of DLP. Table 7 shows that all factors were significant positive predictors.

Table 7

The prediction of CTDI_(vol) and DLP by using stepwise regression factors

			R2	P-value
C-spine	CTDI_(vol)	mAs	0.414	≤0.001
		kVp	0.496	≤0.001
		Number of slices	0.530	≤0.001
	DLP	mAs	0.243	≤0.001
		kVp	0.335	≤0.001
		Number of slices	0.364	≤0.001
LS-spine	CTDI_(vol) .	mAs	0.600	≤0.001
		kVp	0.342	≤0.001
		Number of slices	0.625	≤0.001
	DLP	mAs	0.167	≤0.001
		kVp	0.232	≤0.001
		Number of slices	0.268	≤0.001

4 Discussion

We conducted a nationwide survey of delivered radiation for adult cervical and lumbosacral spine CT examinations to establish DRL in Jordan. For the first time, our survey revealed information on the radiation doses of adult patients from spinal CT (median and 75th percentile for the DLP of each anatomical area). These values represent the current CT radiation dose levels and activities in Jordan. We collected data about the radiation doses according to different parameters, the type of institution, the type of CT scan manufacturer, and the number of CT detectors. Then, we benchmarked our doses with internationally reported DRLs. When compared with six international countries, Jordan demonstrated high CT radiation levels. These doses should raise concern and attention from health professional organisations to investigate their causes and establish methods for optimisation to achieve radiation reduction. This research demonstrates a wide range of radiation dose variations for spinal CT scans across the hospitals. With a range of 184.6–679 mGy cm, the highest median DLP was 3.7 times higher than the median value. Multiple regression analysis predicted that low DLP depended on mAs, kVp, and the number of slices.

We recommend that radiology centres, government agencies, and radiographers develop patient dose management systems and quality improvement programs. Radiology departments should provide radiographers with continuous training to enhance their knowledge of radiation protection, protocol justification, and optimization methods to answer clinical questions with minimal radiation dose while maintaining an acceptable level of image quality for accurate radiological diagnosis. Medical imaging personnel must also audit and monitor their radiation dose levels regularly, comparing them with Jordan’s established DRL. A new CT technology and iterative image reconstruction algorithms are also valuable. All radiation emitting units in government institutions should be subject to mandatory audits [17, 18]. Furthermore, they should follow up on regional and DRL in Jordan annually, considering all medical imaging procedures. Moreover, physicians should always consider the risk-benefit ratio when referring patients for imaging, which can only occur through radiologists’ intervention, and radiographers should follow ALARA principles, study justification, protocol optimisation, and radiation protection.

Ultimately, size-specific dose estimates (SSDE), including patient diameter measurements to correct CTDI_(vol) for patient size, are the most accurate form of radiation dose received and how it affects the organs specifically. This was introduced by the AAPM and implemented in the United States of America national DRL [19 –23]; however, SSDE is not part of the current Jordanian DRL procedures. Further work is recommended to address achievement for radiation optimisation. There are shortcomings in our study. Firstly, effective doses were not calculated, which are good measurements to establish DRL. Secondly, we didn’t record different established protocols for each anatomical area, which may vary from institution to institution. Thirdly, no control for the patient’s height was established, which may influence the DLP values. Fourthly, we did not consider the different reconstruction algorithms employed in other institutions that potentially affect radiation levels. Finally, we did not assess image quality, which was beyond the scope of our survey. However, further work should investigate image quality to achieve optimisation of CT examination.

In conclusion, the radiation doses resulting from CT examinations result in radiation doses with proven risks of inducing cancers. This work addressed the requirement to reduce CT doses stated by legislative, regulatory, scientific, and professional bodies. It will benefit the millions of individuals who undergo this procedure in Jordan and elsewhere each year. This study marks the establishment of the first National Diagnostic Reference Level (NDRL) for adult spine CT scans in Jordan. The established Jordanian DRLs for CT scans of cervical and lumber were higher than most international doses. The differences were associated with variations in the mAs, kVp, and slice number. This demonstrates the importance of DRLs in Jordan to assist in the optimization of CT scanning procedures and protocols.

References

Martin

B.I.

, Deyo

R.A.

, Mirza

S.K.

, Turner

J.A.

, Comstock

B.A.

, Hollingworth

, et al. Expenditures and health status among adults with back and neck problems, JAMA-J 299(6) (2008), 656–664.

Hart

, Wall

B.F.

Radiation exposure of the UK population from medical and dental X-ray examinations (p. W4), Chilton UK: NRPB; 2002.

Mettler

F.A.

Jr , Bhargavan

, Faulkner

, Gilley

D.B.

, Gray

J.E.

, Ibbott

, et al. Radiologic and nuclear medicine studies in theUnited States and worldwide: frequency, radiation dose, and comparison with other radiation sources—1950–2007, Radiology 253(2) (2009), 520–531.

Rosiak

, Lusakowska

, Milczarek

, Konecki

, Fraczek

, Rowinski

, et al. Ultra-low radiation dose protocol for CT-guided intrathecal nusinersen injections for patients with spinal muscular atrophy and severe scoliosis, NeuroRadiology 63(4) (2021), 539–545.

Trott

K.R.

The Carcinogenic Risk in Radiation Medicine, In Sustainable Risk Management (pp. 159–164), Springer, Cham; 2018.

Richards

P.J.

, George

, Metelko

, Brown

, computed tomography doses and cancer induction, Spine 35(4) (2010), 430–433.

The Recommendations of the International Commission on Radiological Protection, ICRP publication 103, Ann ICRP 37(2-4) (2007), 1–332 doi: 10.1016/j.icrp.2007.10.003. PMID: 18082557.

Shrimpton

P.C.

, Hillier

M.C.

, Lewis

M.A.

, Dunn

, A national survey of doses from CT in the UK: 2003, Br J of Radiol 79(948) (2006), 968–980.

Suliman

I.I.

, Estimates of patient radiation doses in digitalradiography using DICOM information at a large teaching hospital inOman, J Digit Imaging 33(1) (2020), 64–70.

10.

Johnston

D.A.

, Brennan

P.C.

, Reference dose levels for patientsundergoing common diagnostic X-ray examinations in Irish hospitals, Br J Radiol 73(868) (2000), 396–402.

11.

Smith-Bindman

, Lipson

, Marcus

, Kim

K.P.

, Mahesh

, Gould

, et al. Radiation dose associated with common computedtomography examinations and the associated lifetime attributablerisk of cancer, Arch Intern Med 169(22) (2009), 2078–2086.

12.

Treier

, Aroua

, Verdun

F.R.

, Samara

, Stuessi

, Trueb

P.R.

, Patient doses in CT examinations in Switzerland: implementation of national diagnostic reference levels, Radiat Prot Dosimetry 142(2-4) (2010), 244–254.

13.

Lee

K.L.

, Beveridge

, Sanagou

, Thomas

, Updated Australian diagnostic reference levels for adult CT, J Med Radiat Sci 67(1) (2020), 5–15.

14.

Roch

, Celier

, Dessaud

, Etard

, Usingdiagnostic reference levels to evaluate the improvement of patientdose optimisation and the influence of recent technologies inradiography and computed tomography, , Eur J Radiol 98 (2018), 68–74.

15.

Kanal

K.M.

, Butler

P.F.

, Sengupta

, Bhargavan-Chatfield

, Coombs

L.P.

, Morin

R.L.

, US diagnostic reference levels and achievable doses for 10 adult CT examinations, Radiology 284(1) (2017), 120–133.

16.

Foley

S.J.

, McEntee

M.F.

, Rainford

L.A.

, Establishment of CTdiagnostic reference levels in Ireland,, Br J Radiol 85(1018) (2012), 1390–1397.

17.

Al Ewaidat

, Zheng

, Khader

, Abdelrahman

, Mustafa Alhasan

M.K.

, et al. Assessment of Radiation Dose and Image Quality of Multidetector Computed Tomography, Br J Radiol 15(3) (2018), e59554.

18.

Rawashdeh

, McEntee

M.F.

, Zaitoun

, Abdelrahman

, Brennan

, Alewaidat

, Lewis

, Saade

, Knowledge and practice of computed tomography exposure parameters amongst radiographers in Jordan, Comput Biol Med 102 (2018), 132–137.

19.

Karout

, Khalife

, Awad

M.F.

, Arnous

, Roumie

Rawashdeh , et al. Poor practice and governance in Lebanese national diagnostic reference levels of adult head and body computed tomography: A nationwide study, , Radiat Phys Chem 192 (2022), 109888.

20.

Rawashdeh

, Saade

Establishment of diagnostic reference levels in low-dose renal computed tomography, Acta Radiol (2022), 02841851221095238.

21.

Rawashdeh

, Abdelrahman

, Zaitoun

, Saade

, Alewaidat

, McEntee

M.F.

, Diagnostic reference levels for paediatric CT in Jordan, J Radiol Prot 39(4) (2019), 1060–1073.

22.

Yaseen

, Radzi

, Almohiy

, Kohli

, Rawashdeh

, Strategies to Improve CT Dose Optimization for Hybrid PET/CT Imaging, , OJMI 11 (2021), 48–57.

23.

Rawashdeh

, Saade

, Al Mousa

D.S.

, Abdelrahman

, Kumar

, McEntee

, A new approach to dose reference levels in pediatric CT: Age and size-specific dose estimation, Radiation Physics and Chemistry 205 (2023), 110698.