New Technic Imaging Radiology

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Lebanese Medical Journal 2009 • Volume 57 (1) 55

R DIOLOGY FOR PR CTITIONERS

ORIGINALITY OF NEW IMAGING TECHNIQUES IN PEDIATRIC RADIOLOGYhttp://www.lebanesemedicaljournal.org/articles/57-1/doc5.pdf

Soha HADDAD-ZEBOUNI1, Samer ABI KHALIL

1, Hubert DUCOU-LEPOINTE

2

INTRODUCTION

Maturation and growth observed during childhoodaccount for the originality of pediatric radiology, a sub-specialty that combines performances of imaging andradioprotection of the child. One of the major concernsof radiopediatricians is the good choice of the imagingprocedure that one should perform in a given situation,and to avoid repetitive and not adapted exam. From thispoint of view, pediatric radiology has reached a promi-nent place.

Conventional radiology gives us very good informa-tion with minimal risks because of very selective indica-tions and optimization of techniques (adjustment of para-meters and diaphragms, digitalization, and limitation of views). Ultrasound, a non irradiating technique, is the firstchoice exam whenever it can be contributive. MRI shouldhave a predominant place for the same reasons. Technical

easiness offered by the multichannel scanner constitutes aconsiderable progress.

New indications appear thus continuously in pediatricradiology that we must pursue to be able to give the bestmanagement for the child.

DISCUSSION

HistoryAt the time of discovery of X-rays by Roentgen in 1896,applications to child pathology were very limited becauseof the length of the exposition time. Years after, technolo-gy made it possible to lessen the exposition time render-ing indications wider. The first organ that benefited fromthis kind of exam was the bone, followed by the lungs.

But the main handicap for pediatric radiologists was thatthey were dealing with children, very often uncooperative,that resulted in bad quality images, blurred and very diffi-cult to interpret [1].

In the 40’s, a new breakthrough happened. Advancesin surgery pushed surgeons to be more innovative andasking for more sensitive exams that were possible withthe new technologies, thus increasing the applications [1].

By the end of the 60’s, the advent of ultrasound took place. Its continuous technical improvement made pedi-atric radiologists more and more interested in its use [1].

From the 70’s began the scanner era, and that of MRIby the 80’s. Here too technology was rapidly progressingin both spatial resolution and reduction in the length of acquisition time [1].

Radioprotection / SedationDuring this chronological evolution, and precisely from the60’s, pediatric radiology became a sub-specialty gatheringnumerous practitioners. Pediatric radiology societies beganto grow. Irradiation was their main topic [2]. Recommen-dations started to be applied by selecting the indications,reducing the acquisition doses and limiting control exams:an irradiating exam should not be performed unless it is of absolute necessity; whenever we have to chose betweentwo exams giving the same information, the one that is lessinvasive and less irradiating should be chosen; between an

image of high resolution and another of lesser resolutionand irradiation but giving the information needed, oneshould choose the second alternative [3]. In 1997, in Eu-rope, a new directive relative to the population protectionagainst medical irradiation (Euratom 97-43) was elaboratedand imposed to all EU states. It claims for exams justifica-tion and techniques optimization [4].

Immobilization plays a key role in the radioprotectionof the child. It reduces the number of repetitive radio-graphs. One must always be looking for patient coopera-tion, whenever the age permits. For newborns undersix months of age, nursing the child before or duringthe exam remains a good solution for putting the childto sleep. Another way is to give medication for babies

Haddad-Zebouni S, Abi Khalil S, Ducou-Lepointe H. Originalityof new imaging techniques in pediatric radiology. J Med Liban2009 ; 57 (1) : 55-61.

1Service d’Imagerie médicale, CHU Hôtel-Dieu de France,Beirut, Lebanon; 2Service de Radiologie, Hôpital Trousseau,Paris, France.

Correspondence: Soha Haddad-Zebouni, MD. Serviced’Imagerie médicale. CHU Hôtel-Dieu de France. Alfred Naccache Street. POBox 16-6830 Achrafieh - Beirut. Lebanon.

e-mail : [email protected]

ABSTRACT : Pediatric radiology is a specialty thatcombines the performances of imaging and radio-protection. It also has to deal with absence of coopera-tion and motion of the child which have limited for along time many radiological applications. Technical

advances with shorter acquisition time in CT andMRI, higherfrequencies in ultrasound, and digitaliza-tion in conventional radiology have widened the indi-cations especially with the new modalities. We presentin this article the originalities and the benefits of cur-rent pediatric radiology and perform a historic reviewoutlining its evolution.



56 Lebanese Medical Journal 2009 • Volume 57 (1) S. HADDAD-ZEBOUNIet al. – New Imaging Techniques in Pediatric Radiology

between six months and four years of age. If unsuccessful,general anesthesia should be the last resort [3].

PRACTICALAPPLICATIONS

Conventional RadiologyConventional radiology is essential. It is often performedat first, especially in all malformations to study the mor-phology of the skeleton. In metabolic diseases, it high-lights the abnormal bone densities and the associatedfindings. Its contribution is fundamental in traumatology.Conventional radiology has benefited from digitalizationthat made exams easier and less irradiating [3]. The intro-duction of flat panels has increased digital performance.

UltrasoundWith ultrasound (US) progress, and development of high

frequency probes together with improvement of imageresolution, indications of sonography are increasing taking

into account its easy use and the child morphology [5]. Itsrole, first recognized in the investigation of solid organsof the abdomen, became essential in investigating thedigestive tract.

Ultrasound has become the most important examinationmethod for the diagnosis of intestinal intussusception(Fig. 1) and the detection of edema at the ileocecal valveafter reduction of the intussusception [6]. Opacificationwith water-soluble contrast is only used for therapeutic rea-sons (Fig. 1). Its usefulness is recognized in appendicitis[7] and other bowel diseases (Fig. 2 & 3) [8]. Ultrasoundhelps in the diagnosis and the follow-up of neonatal portalthrombosis and its ischemic effects in the liver.

Transfontanellar ultrasound has replaced, during theneonatal period, the irradiating scanner used for ventric-ular dilatation, for subventricular hemorrhage and themalformations of the medial line [9]. A new ultrasound

window in neonates, the mastoid window, has beenrecently described [10]. It offers a panoramic view of the

FIGURE 1Intussusceptionin a 4-month-old boy.

a. Transverse ultrasoundshows the layered bowelwalls of the outer andinner loop (arrow),the intussuscipiens, and

the intussusceptum.b. Note the convex-shaped

filling defect of the intussusceptum (double

arrows), which is reducedto the level of the cecumon a contrast enema.

FIGURE 2Pyloric stenosisin a newborn

a. The pylorus is viewed inlongitudinal plane (arrow).The sonographic hallmark is the thickened pyloricmuscle.

b.On the upper gastro-intestinal series note thecollection of bariumin the dilated prepyloricantrum and the presenceof two thin tracks of barium compressedbetween thickenedpyloric mucosa andmuscle.



anatomical structures that can be identified in each USslice. However, MRI is the reference for neurologicalexplorations.

Its indications in osteoarticular imaging are increas-ing; it includes congenital dysplasia of the hip (Fig. 4),detection of articular effusion, and traumatic lesions of

FIGURE 4Developmentaldysplasia of the hip

a (neutral position) .The hip is viewedin a coronal planeshowing themaximum depth of the acetabulum.Note the lack of the amount of the bony (arrow) and cartilaginous (double arrows) cover of the femoral head by the acetabulum.

b (dynamic examination). Gentle but firm pressure placed on the hip in a posterior and/or lateral direction reveals to a betteradvantage the dysplasia of the hip.

c (normal hip

). Note good acetabular coverage of at least one half of the femoral head.

S. HADDAD-ZEBOUNIet al. – New Imaging Techniques in Pediatric Radiology Lebanese Medical Journal 2009 • Volume 57 (1) 57

FI G U R E 3

Intestinal malrotationin a 2-year-old girl

a. Note that the superiormesenteric vein (a rr o w) liesto the left side of the arteryin contrary to the normalposition on this transverseUS image.

b, c . Note the “whirl sign”representing the superiormesenteric vein twistingtoward the artery.

d . In this upper gastrointestinalseries, the duodenum (double arrows)does not crossthe midline to the left side,and the small bowel ispresent only in the rightside of the abdomen.




the non ossified skeleton. Some pediatric radiologistsadvocate the use of color Doppler to characterize inflam-matory diseases (Fig. 5). One must not forget its rolein differed emergencies; it can detect occult fracturesunrevealed by conventional radiography, either by show-ing cortical irregularities (Fig. 6), or by revealing a

juxtaphysial hematoma (Fig. 7) [11], but this requiresmuch expertise that only few radiologists have nowadays.

CT ScanThe tremendous technical advances in scanner and MRIwith the introduction of multichannel CT scanners andfaster MRI sequences have multiplied the indications of these two techniques.

CT scan allows rapid and detailed evaluation of lesions. Its increasing resolution and its multiplanarcapacity allows an excellent 3D evaluation of the bone intraumatology [12], congenital and developmental lesions(Fig. 8). In infectious and tumoral pathologies, eventhough MRI is superior for the evaluation of medullar

FIGURE 5Tenosynovitis of the long head of the biceps in an 8-year-old child.

Longitudinal (a) and transverse (b)US images of the anterior aspect of the shoulder demonstrate thickeningof synovial tissue (arrows) aroundthe tendon related to synovialhypertrophy. Color Doppler bloodflow imaging (b) showshypervascularity of the synovialsheath as a sign of activesynovial inflammation.

FIGURE 6. Occult fracture in a 12-year-old boy.Cortical irregularity of the diaphyseal radius (arrows)seen on ultrasound (b) and not revealed on the radiograph (a).

FIGURE 8. Craniostenosis in a 6-month-old boy.Premature closure of the sagittal suture.

FIGURE 7. Physeal fracture of the proximal fifth metatarsalphysis in an 11-year-old girlJuxtaphyseal hematoma (star) visualized on ultrasoundindicating a physeal fracture not seen on the conventionalradiograph.




bone, scanner still has the superiority in the detection of cortical lesions, periosteal reactions, calcifications andsequestrations [13].

Cardiovascular exploration by the scanner constitutesthe ultimate achievement in this field [6]. These examsrequire on one hand to master technical control of se-quences, acquisition modes and data processing, and on

the other hand diagnostic skills. Cardiac gating has brokenthe obstacle to this application caused by cardiac beat arti-facts. Coronary arteries can thus be explored as in theadult. Scanner is also being helpful to study pulmonaryarteries and congenital lesions where it is superior toangiography [14]. Abnormalities like pulmonary seques-tration (Fig. 9) can be easily revealed. Its sensitivity to

FIGURE 9. Intralobar pulmonary sequestration in a 13-year-old boy.The feeding artery is originating from the descending thoracic aorta. The venous drainage is via pulmonary vein.

Note that the hemiazygos vein is not enlarged.




make the diagnosis of aortic coarctation has been alreadydemonstrated (Fig. 10). The evaluation of collateral circu-lation in relation with the stenosis is readily achievable.

MRIMRI is considered now as the exploration modality ofreference in neuroradiology (Fig. 11). The apparitionof new sequences has increased indications of this tech-nique. Sequences of diffusion and tractography are welldeveloped and used in the diagnosis of certain pathologies(e.g. ischemic diseases), as well as in their therapeutic

follow-up [15-16].Functional MRI is feasible in the fetus, and contributes

to localize the origin of the convulsive seizures in the caseof cortical heterotopy [6].

The application of spectroscopic imaging is represent-ed by the exploration of cerebral tumors and their pre-operative workup [6]. The most discriminative elementsin favor of a high grade lesion for example, are the eleva-tion of choline and lactate.

However, taking into account the constraints related tothe use of MRI, the usage of this kind of exploration couldnot be regular and transfontanellar ultrasound remains thefirst explorative technique for the diagnosis of neonatalintracranial hemorrhages and for ischemia [17].

In osteoarticular pathology, it permits recognition of articular lesions that were ignored by other techniques[18]. As with the scanner, it can screen traumatic spinallesions that used to be ignored on simple X-rays, orinversely redress over-diagnosis of fracture. It is superiorto scanner in the evaluation of tumoral or infectiouspathologies of the medullary bone.

MR study of the digestive tract is promising. This tech-nique is evaluated as a futurist alternative to conventionalradiology, with a good correlation compared to the colo-noscopic data. It is also presented as a reliable tool in the

therapeutic follow-up of Crohn’s disease [6].The whole body MRI realized in coronal STIR

sequence is of interest in cancerology for detection of metastases. This technique can also be applied for evalu-ation of other diseases such as histiocytosis. In theseinstances, one can skip radiography and thus avoid irra-diation for the child [19-20].

CONCLUSION

Technical progress will always continue and the actualconcerns that we have just exposed will always be pre-sent. Conventional radiology will not disappear soon andit is at the present time facilitated by digitalization that

FI G U R E 1 0 . Aortic coarctation in a 2-year-old girl.Note the narrowing of the aorta just distal to the origin of the left subclavian artery.




reduces the irradiating doses. The performances of theultrasound will continue to grow. The multislice scanner,which already has very short acquisition time and greatquality images, will certainly continue to advance medicalapplications. This is also true for MRI with shorter time of acquisition. Functional MRI will have surely a promisingfuture. Concomitantly, one must evolve by adapting thenew techniques to the needs of the child.

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FI G U R E 11. Medullary tumor in a 2-year-old girl.

Note the gadolinium enhancement of the tumor tissue.

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