**Abstract**

Retinoblastoma is the most common primary ocular malignancy in children. Diagnosing retinoblastoma relies mainly on the clinical appearance of the lesion and not on histological description. Although histology still remains the gold standard in evaluation of tumor extension and progression risk factor, a tumor biopsy carries high risk of dissemination and is difficult to obtain. Retinoblastoma has characteristic clinical features of creamy-white mass associated with subretinal fluids and may be accompanied by retinal detachment and vitreous seeding. There are many factors contributing to metastatic risk factors like postlaminar optic nerve infiltration, scleral and choroidal invasion, and peribulbar fat invasion. Ancillary testing is necessary for any patient with a suspected retinoblastoma to assess the dimensions of the tumor as well as the tumor extension. An ultrasonography (B scan) will show the mass dimensions as well as the hyperechoic calcifications, which are commonly present with retinoblastoma. CT scan is not the modality of choice for diagnosis of retinoblastoma in children because of the radiation exposure. Magnetic resonance imaging is considered the examination of choice to assess the tumor extension as it has high soft tissue contrast. The use of MRI changed the accuracy of assessing metastatic risk factors as the results yielded before and after the use of MRI differed. This chapter will address the use of radiological imaging in retinoblastoma defining diagnostic characteristics and identifying parameters of metastatic risk factor assessment. This chapter will also include evidence-based review on the efficacy of radiological imaging of retinoblastoma and its impact on the choice of treatment and disease prognosis.

**Keywords:** magnetic resonance imaging, retinoblastoma, metastasis, optic nerve invasion, vitreous seeding, retinal detachment, calcification, prognosis

## **1. Introduction**

Retinoblastoma is the most common primary ocular malignancy in children. It is usually unilateral but may be bilateral in one-third of cases. It presents in childhood as leukocoria or acute onset strabismus. Diagnosing retinoblastoma relies mainly on the clinical appearance of the lesion and not on histological description. Although histology still remains the gold standard in evaluation of tumors extension and progression risk factor, a tumor biopsy carries high risk of dissemination and is difficult to obtain. Retinoblastoma has characteristic

clinical features of creamy-white mass associated with sub retinal fluids and may be accompanied by retinal detachment. Endophytic tumors grow inwards towards the vitreous cavity which may result in vitreous seeding of the tumor cells. Exophytic tumors grow into the sub retinal space causing progressive retinal detachment and subretinal seeing. There are many factors contributing to metastatic risk factors like post laminar optic nerve infiltration, scleral and choroidal invasion, and peribulbar fat invasion. Ancillary testing is necessary for any patient with a suspected retinoblastoma to assess the dimensions of the tumor as well as the tumor extension.

The main ancillary tests that can be used with retinoblastoma are ultrasound imaging (US), computerized tomography (CT), and magnetic resonance imaging (MRI).

Ultrasonography (B scan) will show the mass dimensions as well the hyperechoic calcifications which is commonly present with retinoblastoma. These imaging modalities and their uses in retinoblastoma detection will be discussed in this chapter with the main focus on MR imaging.

## **2. Ultrasonography imaging in retinoblastoma**

Ultrasound imaging is a cost-effective widely available modality that is noninvasive and easy to perform. This modality is especially useful in patient when the ocular light-conducting media is opaque. It can detect tumor dimensions and characteristics as well as vitreous seeding. It is usually conducted at a 10 MHz high frequency probe. B scans can also visual the optic nerve which can be seen within the retrobulbar fat. The optic nerve is usually seen as a hypoechoic structure within the echogenic surrounding fat.

In case of retinoblastoma, the tumor is visualized as a hyperechoic tumor with irregular borders. It may present a diffuse lesion or a localized well-defined lesion (**Figure 1**). The calcium deposits are clearly visualized by ultrasonography as highly hyper-echoic and they are a pathognomonic feature [1]. Ultrasound imaging can also identify any associated retinal detachment or choroidal thickening (**Figure 2**). The vitreous surrounding the lesion may show hyper-reflective particles representing the calcified tumor seeding into the vitreous cavity.

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**Figure 3.**

*Uses of Radiological Imaging in Retinoblastoma DOI: http://dx.doi.org/10.5772/intechopen.86828*

tubular hypo-echoic nature of it is altered.

**Figure 2.**

*detachment.*

Extraocular invasion of the optic nerve can also be detected once the normal

*B scan of an eye with retinoblastoma showing an exophytic growth pattern with an associated retinal* 

Computerized tomography (CT) is a combination of multiple X-ray images from different angles producing cross sectional images. Like standard X-ray, CT depends on relative the radio-density of different tissue structures. CT delivers ionization radiation reaching to 1–10 mSv per brain CT. Retinoblastoma appears as a hyperdense lesion on CT in relation to the surrounding hypodense ocular vitreous (**Figure 3**). CT scan is also another beneficial tool in detecting calcification which may be seen in a non-homogenous pattern in most large tumors (**Figure 4**) or in a homogenous pattern in smaller tumors. In certain studies, CT scan has failed to show calcification in small retinoblastoma tumors [2–4] CT images can also be useful to

CT scan is not the modality of choice for diagnosis and follow-up of children with retinoblastoma due to radiation exposure (ionizing radiation) and the high sensitivity of MRI for soft tissue. This reduces the implantation of CT in retinoblas-

*CT (soft tissue window image) showing right globe hyperdense vitreous, retrolental intraocular solid mass with* 

**3. Computerized tomography imaging in retinoblastoma**

detect any associated metastatic brain lesions (**Figure 5**).

*dystrophic calcification and proximal calcified optic nerve local invasion.*

toma cases especially in areas where MR studies are accessible [3].

**Figure 1.** *B scan of an eye with diffuse pattern retinoblastoma showing areas of calcification.*

*Uses of Radiological Imaging in Retinoblastoma DOI: http://dx.doi.org/10.5772/intechopen.86828*

**Figure 2.**

*Retinoblastoma - Past, Present and Future*

well as the tumor extension.

the echogenic surrounding fat.

this chapter with the main focus on MR imaging.

**2. Ultrasonography imaging in retinoblastoma**

(MRI).

clinical features of creamy-white mass associated with sub retinal fluids and may be accompanied by retinal detachment. Endophytic tumors grow inwards towards the vitreous cavity which may result in vitreous seeding of the tumor cells. Exophytic tumors grow into the sub retinal space causing progressive retinal detachment and subretinal seeing. There are many factors contributing to metastatic risk factors like post laminar optic nerve infiltration, scleral and choroidal invasion, and peribulbar fat invasion. Ancillary testing is necessary for any patient with a suspected retinoblastoma to assess the dimensions of the tumor as

The main ancillary tests that can be used with retinoblastoma are ultrasound imaging (US), computerized tomography (CT), and magnetic resonance imaging

Ultrasonography (B scan) will show the mass dimensions as well the hyperechoic calcifications which is commonly present with retinoblastoma. These imaging modalities and their uses in retinoblastoma detection will be discussed in

Ultrasound imaging is a cost-effective widely available modality that is noninvasive and easy to perform. This modality is especially useful in patient when the ocular light-conducting media is opaque. It can detect tumor dimensions and characteristics as well as vitreous seeding. It is usually conducted at a 10 MHz high frequency probe. B scans can also visual the optic nerve which can be seen within the retrobulbar fat. The optic nerve is usually seen as a hypoechoic structure within

In case of retinoblastoma, the tumor is visualized as a hyperechoic tumor with irregular borders. It may present a diffuse lesion or a localized well-defined lesion (**Figure 1**). The calcium deposits are clearly visualized by ultrasonography as highly hyper-echoic and they are a pathognomonic feature [1]. Ultrasound imaging can also identify any associated retinal detachment or choroidal thickening (**Figure 2**). The vitreous surrounding the lesion may show hyper-reflective particles representing the calcified tumor seeding into the vitreous cavity.

*B scan of an eye with diffuse pattern retinoblastoma showing areas of calcification.*

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**Figure 1.**

*B scan of an eye with retinoblastoma showing an exophytic growth pattern with an associated retinal detachment.*

Extraocular invasion of the optic nerve can also be detected once the normal tubular hypo-echoic nature of it is altered.
