Undoubtedly, the use of radiographic imaging has entirely revolutionized the diagnosis and treatment planning in medical sciences. The role of imaging in oral malignancies can be broadly grouped in those used to evaluate primary disease and those to evaluate metastatic disease.

1. radiographic techniques of oral tumors
By
Romissaa Aly
Assistant lecturer of Oral Medicine,
Periodontology, Diagnosis and Dental
Radiology (Al-Azhar Univerisity)

2. Undoubtedly, the use of radiographic imaging has entirely
revolutionized the diagnosis and treatment planning in medical
sciences. The role of imaging in oral malignancies can be broadly
grouped in those used to evaluate primary disease and those to
evaluate metastatic disease.
It is a useful tool for staging and management planning in oral
cancers. Awareness of the presence of cervical node metastasis is
important in treatment planning and in prognostic prediction for
patients with head and neck cancer (HNC).

3. EVALUATION OF PRIMARY DISEASE

4. 1.Intraoral radiographic examination is of very limited use
though occlusal radiographs (maxillary and mandibular
projections) have been occasionally used to determine the
medial or lateral extent of the disease and to detect their
presence in palate or floor of the mouth. It may aid in
evaluating patients with trismus

5. 2. Extraoral radiographic examination includes lateral skull
projections and Water projections (occipitomental
projections). The former is more useful for pre- and post-
treatment records for prosthesis and oral surgery, while the
later is useful for evaluating maxillary sinus.
Mandibular lateral oblique body/ramus projections are
largely replaced by panoramic radiography

6. 3. Panoromic radiography (also called pantomography or
rotational radiography) is a radiographic technique for producing
a single image of the facial structures that includes both
maxillary and mandibular arches and their supporting structures.
 Its principal advantages include broad anatomic coverage, low
radiation dosage for patient, convenience of examination, and
the fact that it can be used in patients unable to open their
mouth. The usual procedure lasts 3-4 minutes.

7. The main disadvantage is that the resultant image does not
resolve the fine anatomic detail that may be seen on intraoral
and periapical radiograph.
Commonly used panoromic machines include the
orthopantomograph and the panorex. Recent panoramic
radiographic machines are capable of producing digital
images.

8. CT scan is useful for evaluating bony invasion. A sophisticated
software program called Dentascan provides more accurate
details of the mandible.[16,17]
CT can identify tumors based upon either anatomic distortion
or specific tumor enhancement.
 Imaging of lymph nodes by CT or MRI is complementary to
the clinical examination for the staging of the neck. CT is also
highly sensitive for detection of extracapsular spread of
tumor.[18

9. Compared with MRI, CT provides equal or greater
spatial resolution, it can be performed with fast
acquisition times thereby virtually eliminating the
problem of motion artifact and it is better for the
evaluation of bone destruction.
CT also has the subjective advantage of being relatively
straightforward to interpret.[19,20

10. Size criteria for pathologic nodes - using clinical criteria of a
palpable node greater than 1.5 cm or fixed or matted nodes, error
rates have been shown to range from 20% to 28%.
 Size criteria for pathologic lymph nodes vary although most
agree that homogeneous cervical lymph nodes up to 10 mm in
maximum diameter may be considered normal, and in some areas
(e.g., jugulodigastric and anterior submandibular nodes), lymph
nodes up to 15 mm may be considered normal.[19

11. Magnetic resonance imaging (MRI) and computed tomography (CT)
are commonly used to assess the primary tumor and the neck
status.[1-5] Doppler ultrasound with fine-needle aspiration is also
used these days.[6]
Positron emission tomography (PET) is a functional imaging that can
detect cancer lesions by pinpointing regions of high metabolism. It is
also used in cases demanding assessment of metastases to lymph
nodes that appear morphologically normal.[7,8]

12. PHYSICS OF MRI
MRI is based on the magnetization properties of atomic nuclei. A
powerful, uniform, external magnetic field is employed to align the
protons that are normally randomly oriented within the water nuclei
of the tissue being examined.
 This alignment (or magnetization) is next perturbed or disrupted
by introduction of an external Radio Frequency (RF) energy. The
nuclei return to their resting alignment through various relaxation
processes and in so doing emit RF energy..

13. Repetition Time (TR) is the amount of time between successive
pulse sequences applied to the same slice. Time to Echo (TE) is
the time between the delivery of the RF pulse and the receipt
of the echo signal.
Tissue can be characterized by two different relaxation times –
T1 and T2..

14. T1 (longitudinal relaxation time) is the time constant which
determines the rate at which excited protons return to equilibrium.
It is a measure of the time taken for spinning protons to realign
with the external magnetic field.
 T2 (transverse relaxation time) is the time constant which
determines the rate at which excited protons reach equilibrium or
go out of phase with each other. It is a measure of the time taken
for spinning protons to lose phase coherence among the nuclei
spinning perpendicular to the main field

15. Magnetic resonance imaging (MRI) is an excellent clinical imaging technique for the
noninvasive detection of tumor. To improve the imaging contrast between normal and
diseased tissues, contrast agents are employed to change proton relaxation rates 17, 18.
Nowadays, the MRI contrast agents are generally in the form of T1-
positive and T2-negative contrast agents. T1 contrast agents, such as
gadolinium (Gd)-based chelates (e.g., Gd-DTPA) 19, 20, can facilitate the spin-lattice
relaxation of protons and provide a brighter MR image.
 T2 contrast agents, such as superparamagnetic iron oxide (SPIO) NPs
(e.g., Feridex) 21, can cause protons in the vicinity to undergo spin-spin
relaxation and produce a darker MR image.


16. However, such single mode contrast agents still have
disadvantages. The Gd-based T1-positive contrast agents
have suffered from their short body circulation time due
to their low molecular weights, making it hard to acquire
high-resolution images, which requires a long scan
time 22. Besides, the clinical use of T2 contrast agents is
quite limited due to their inherent darkening contrast
effect and magnetic susceptibility artifacts 23.
T1-weighted MRI enhances the signal of the fatty tissue and suppresses the
signal of the water. T2-weighted MRI enhances the signal of the water.

19. parapharyngeal space (PPS)

23. CECT is contrast-enhanced computed tomography

27. CT imaging protocols —
 CT imaging depends upon the site and stage of the tumor and
also depends on the type of scanner used.
We typically obtain thin (2.5 to 3 mm in thickness, depending
on scanner technology) axial contiguous sections.
Intravenous contrast is administered by a pressure injector in
all cases. After a 40 to 60 sec delay, contrast is injected at 2
mL/sec for a total of 100 to120 mL

28. With ultrafast multidetector scanner technology, scanning
after a shorter delay can result in essentially a CT
arteriogram, with failure to opacify veins, and inadequate
tissue contrast opacifi cation. Soft tissue windows are
routinely evaluated.[17,21]
Both soft tissue and bone should be evaluated, but it may
not be necessary to routinely reconstruct bone “algorithm”
images.

29. CT bone “windows”, even if reviewed on a picture archiving
and communication system (PACS) with a soft tissue algorithm,
are particularly useful to evaluate for erosion of thyroid, cricoid
or tracheal cartilage, or erosion of the mandible, vertebra or
skull base.
 When in fact there is none. In these cases, MRI may be
helpful, as it may identify tumor invasion of bone marrow[22]

31. RADIOISOTOPE IMAGING

32. A radionuclide scan (also known as a radioisotope scan)
is an imaging technique used to visualise parts of the
body by injecting a small dose of a radioactive chemical
into the body.
These chemicals localise to specific organs and tissues
depending on the type of substance used and then emit
small beams of radiation (called gamma rays) that can be
detected by the gamma camera.

33. Radionuclide scans are used in various fields of medicine such as
identifying areas of infection or excess bone turnover.
Bone scans and thyroid scans are common examples of
radionuclide scans. In the gastrointestinal tract they can be used
to identify sites of bleeding, measure the extent of inflammation
and assess the movement of food substances through the
stomach.

34. Radionucleide bone scans are often positive prior to
radiographic appearance of bone destruction but they may
seldom provide accurate information regarding the extent of
bone invasion.[8]
Bone scans may also be positive in non-neoplastic
conditions like inflammations.

41. Single-photon emission tomography/computed tomography
(SPECT/CT) is another radionuclide imaging study and is used to
visualize three-dimensional multiplanar tracer distribution in the
region of interest with CT using an integrated CT scanner [33].
With the aid of SPECT/CT, the exact anatomical location and
pathological metabolism can be assessed.

46. PET SCAN

47. F-Fluorodeoxyglucose positron emission tomography (F-FDG PET) is
a functional imaging technique that provides information about
tissue metabolism and has been successfully applied to the
evaluation of HNCs.[18,9,27]
PET is based on identifying increased glycolytic activity in malignant
cells, in which radiolabeled FDG is preferentially concentrated due to
increases in membrane glucose transporters as well as in
hexokinase, an enzyme which phosphorylates glucose

48. After phosphorylation, radiolabeled FDG continues to
accumulate in cancer cells instead of glycolysis, allowing imaging
by PET.[18,27] F-FDG PET is more sensitive than CT or MRI in
detecting cervical node metastases.
It can help identify metastatic nodes which are morphologically
normal.
Currently available data from various studies[28-33]
demonstrate large variations in the sensitivity and specifi city of F-
FDG PET in the detection of cervical lymph node metastases in
HNCs

49. False positives of F-FDG PET are mainly due to its
inherent inability to discriminate inflammatory processes
and reactive hyperplasia from tumor infiltration, because
high metabolic changes occur in both instances.[34]
The main drawback of PET remains its relatively poor
anatomic resolution.

50. CT/MRI merely depicts anatomic details but PET provides
information about tissue perfusion and metabolism.[29]
• FDG is taken up by tissue cells similarly as natural
glucose.[29,30]
• Neoplastic cells have been shown to incorporate more radio
intense images than surrounding tissues: Thus, PET scan is
usually indicated for the identification of metastatic nodal
disease post-radiation or recurrent/ residual tumor.

51. However, it lacks in anatomic detail reproduction
and the thickness of resolution size may prevent
micro deposits from being visualized.[31,32] That is
why PET scan is considered as research tool rather
than frequently used clinical diagnostic entity

54. The fundamental characteristic of human malignancies is the
overexpression of the glucose transporter, especially in HNSCC

55. Figure 4.
Schematic of the metabolic trapping of F18-FDG in a tumor cell showing the
trapping mechanism in FDG imaging.
 The glucose transporter 1 (GLUT1) serves as a channel for its uptake. It
accumulates in tumor cells, where the metabolism by hexokinase and
glucose-6-phosphatase takes place.
FDG will be phosphorylated by hexokinase.
Glucose-6-phosphotase (G6Pase) counteracts hexokinase phosphorylation
by converting glucose-6-phosphate (G6P) to glucose.
Therefore, high G6Pase activity leads the accelerated conversion of FDG-6-
phosphate (FDG6P) to its FDG form, as a result, the uptake reduces, and it
will be released from the cell.

56. PET–CT

65. They described the sentinel lymph node as the first node, which
is the first portal in the diseased cell migration from the lesion.
They proposed the importance of the first node on the localization
of the lesion.
In their paper they emphasized that a “sentinel node” is the
initial lymph node upon which the primary tumor drains. Today we
know that the sentinel lymph node is the first node on the
lymphatic pathway that drains directly from the tumor [41].

66. In the field of nuclear medicine, the sentinel lymph node is
the first node that is visible after the administration of the
tracer. Flow imaging or “dynamic phase” is the first phase,
immediately after injection, which shows the lymphatic
pathway and clearance.
In the late stage also known as the “static phase”, can the
very first node or sometimes more than one node be
visualized and anatomically pinpointed.

67. Recently, to overcome the limitations of the conventional colloid
tracers, a new tracer has been developed to fulfill the aforementioned
shortcomings.
Technetium 99m-diethylenetriaminepentaacetic acid (DTPA)-
mannosyl-dextran (also known as 99mTc-tilmanocept) is a novel
radiopharmaceutical agent that selectively binds to CD206 receptors,
which presents in high concentration in lymph nodes on the
membrane of macrophages and dendritic cells

68. Tilmanocept structure consists of a dextran main domain and
the DTPA as well as mannose units which are attached to the
central part.
The average diameter of this macromolecule is 7nm.
The mannose binds to the CD206 receptor, whereas the DTPA
serves as the binding part for technetium 99m.
Due to its small size, it has a rapid uptake in lymph nodes, and its
targeted binding prevents its migration to distal nodes [43, 44].

69. CONCLUSION
In clinical practice, CT and MRI are commonly because they can
delineate the extent of the primary head and neck tumors in the
same session.
PET is a functional imaging technique that is more sensitive than
CT and MRI. However, it lacks anatomical detail and is seldom used
alone.
Side-by-side visual correlation of PET and CT/MRI is a simple
technique that can increase the diagnostic accuracy of PET. The
combined PET/CT device is an advance in PET technology that can
simultaneously provide precise integrated functional and
anatomical information.

70. Conclusion
Nuclear medicine by using radionuclide substances can detect
the dynamic aspect of a disease process, and when this
dynamic study is mingled by a morphological study, CT or MRI,
the management team can see a clearer picture of the disease
process and plan treatment protocols accordingly.
 Sentinel lymph node biopsy is gaining momentum in cancer
treatment protocols as a MUST-DO procedure before the
definitive treatment plan is implemented.

71. The main drawback of PET is its poor anatomical resolution.
 Side-by-side visual correlation of PET and CT/MRI can help
determine the anatomical location of abnormal PET uptake and
eliminate some false-positive PET findings caused by spatial errors.[9-
11]
Fused PET/CT is considered to be the most accurate imaging
modality, because it simultaneously provides prompt and accurate
coregistration of functional and anatomical images. However, it is
expensive, less-often available, and still constrained by technical
resolution limits.[12-15]

77. D mandibular reconstruction. (a) In case 4, an extensive defect across the
mandibular midline is completed and demonstrated in different views. (b) The
function of CTGAN in reconstructing different defects with diverse positions
and features [157]
CTGAN is a collection of Deep Learning based synthetic data generators for single table
data, which are able to learn from real data and generate synthetic data with high
fidelity.

78. A simple GAN Model