Dasar Radiologi Kedokteran Gigi
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Intraoral Exposure
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Periapical
detailed examination of the entire tooth and surrounding structures
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Biseksi
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Paralel → pake film holder
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Bitewing (Interproximal)
Used to examine crowns of teeth, alveolar crests and proximal surfaces
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Occlusal
buccal/ lingual view
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RA=
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Topografi/ Standart oklusal
- Menghasilkan gambaran radiografik bagian anterior / gigi-gigi anterior rahang atas sampai dengan daerah apikalnya.
- Sinar-X diarahkan ke bawah, kearah batang hidung, dengan sudut 65° – 70° terhadap film.
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Crossection Rahang Atas/ Vertex
- Memperlihatkan gambaran radiografik potongan melintang rahang atas.
- Untuk memperoleh potongan melintang rahang atas dapat dilakukan dengan memodifikasi teknik Topografi Rahang Alas, yaitu dengan memperbesar sudut sinar-X terhadap film, menjadi + 80° dan di arahkan ke dahi pasien.
- Tube pada atap tengkorak bagian depan
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Oklusal Oblik Rahang Atas
Memperlihatkan gambaran radiografik satu sisi rahang atas / gigi gigi daerah • posterior. • Sinar-X diarahkan ke bawah, kearah pipi dengan sudut 65° – 70° terhadap
• film, di pertengahan regio yang diperiksa.
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RB=
- Standar/ topografi Oklusal RB
- Memperlihatkan rahang bawah/gigi anterior rahang bawah Gambaran radiografiknya mirip teknik biseksi, tapi mencakup daerah yang lebih luas.
- Sinar-X diarahkan ke atas di pertengahan rahang bawah, mengarah ke dagu penderita dengan sudut 45° terhadap film.
- Crossection RB/ True 90
- Memperlihatkan potongan melintang rahang bawah / gigi gigi dan dasar mulut.
- Sinar-X diarahkan ke atas di pertengahan rahang bawah, mengarah ke daerah Molar, dengan sudut 90° terhadap film.
- Oklusal Oblik Rahang Bawah
- Menghasilkan gambaran radiografik satu sisi rahang bawah, terutama daerah kelenjar submandibula. Akan tetapi karena sinar-X arahnya oblik, maka gambaran anatomis RB yang terproyeksi mengalami distorsi.
- Sinar-X diarahkan ke atas dan ke depan, dari arah belakang, di bawah angulus mandibula
- Standar/ topografi Oklusal RB
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Titik Penetrasi
Titik penetrasi ditentukan berdasarkan patokan : Gigi I1: ala nasi Gigi I2: 0,5cm dari ala nasi Gigi C: cuping hidung Gigi P1: proyeksi dari pupil mata tegak lurus ke garis khayal Ra/Rb Gigi P2: 1cm dari titik penetrasi gigi P1 Gigi M1: proyeksi dari canthus mata tegak lurus ke garis khayal Ra/Rb Gigi M2: 1 cm dari titik penetrasi gigi M1 Gigi M3: 1 cm dari titik penetrasi gigi M2 (McCall & Wald, 1957)
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Sudut horizontal dan vertikal (Whaites, 2002)
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Sudut horizontal
I=0
C=45
P=75
M=90
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Sudut Vertikal
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RA
I=+45
C=+50
P=+40
M=+45
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RB
I=-25
C=-20
P=-15
M=-5
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Prinsip ALARA (as low as reasonably achieveable)
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Falsafah:
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Justifikasi
Manfaatnya harus lebih besar dari risiko radiasi yang diterima
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Limitasi
Jumlah dosis yang diterima harus tidak melebihi NBD yang ditetapkan dan dilakukan pada daerah kerja tertentu
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Optimasi
Penggunaan dosis yg optimal
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Penerapan:
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- Time:
“Time” simply refers to the amount of time you spend near a radioactive source. Minimize your time near a radioactive source to only what it takes to get the job done. If you are in an area where radiation levels are elevated, complete your work as quickly as possible, and then leave the area. There is no reason to spend more time around it than necessary.
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- Distance:
“Distance” refers to how close you are to a radioactive source. Maximize your distance from a radioactive source as much as you can. This is an easy way to protect yourself because distance and dose are inversely related. If you increase your distance, you decrease your dose.
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- Shielding:
To shield yourself from a radiation source, you need to put something between you and the radiation source. The most effective shielding will depend on what kind of radiation the source is emitting. Some radionuclides emit more than one kind of radiation.
For an example of using shielding, click here
Alpha particles can be shielded with something as thin as a sheet of paper, or our outer layer of dead skin cells
Beta particles can be shielded effectively with a few inches of plastic, or a layer of clothing.
Gamma rays can be shielded effectively by adding a few inches of lead or other dense substance between you and the source of radiation.
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4. Dosimetry
Radiation monitor at the operator's console monitor radiation dose
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Efek
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Rasio Penyinaran pada Fetus
2 minggu awal kehamilan→ minimal
3-8→ malform
8-15→ retardasi mental
16-25 → parah
kehamilan→ keganasan
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Jaringan paling rentan
most: colon, stomach, lungs, bone marrow
moderate: breast, oesophagus
low: bladder, liver, tyroid, skin, bone surface, brain, kel saliva
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Jenis Efek
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Deterministik → langsung terlihat → muncul jika diatas ambang batas
Efek deterministik timbul bila dosis yang diterima di atas dosis ambang (threshold dose) dan umumnya timbul beberapa saat setelah terpapar radiasi. Tingkat keparahan efek deterministik akan meningkat bila dosis yang diterima lebih besar dari dosis ambang yang bervariasi bergantung pada jenis efek. Pada dosis lebih rendah dan mendekati dosis ambang, kemungkinan terjadinya efek deterministik dengan demikian adalah nol. Sedangkan di atas dosis ambang, peluang terjadinya efek ini menjadi 100%.
Adapun ciri-ciri efek non-stokastik a.l :
- Mempunyai dosis ambang
- Umumnya timbul beberapa saat setelah radiasi
- Adanya penyembuhan spontan (tergantung keparahan)
- Tingkat keparahan tergantung terhadap dosis radiasi
- Efek ini meliputi : luka bakar, sterilitas / kemandulan, katarak (efek somatik)
Darai penjelasan di atas dapat disimpulkan :
- Efek Genetik merupakan efek stokastik, sedangkan
- Efek Somatik dapat berupa stokastik maupun deterministik (non-stokastik)
Efek radiasi secara biologis terhadap manusia dapat dilihat dari bagan berikut :
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Stokastik →tidak langsung terlihat → tidak dapat dipastikan kapan
Bila sel yang mengalami perubahan adalah sel genetik, maka sifat-sifat sel yang baru tersebut akan diwariskan kepada turunannya sehingga timbul efek genetik atau pewarisan. Apabila sel ini adalah sel somatik maka sel-sel tersebut dalam jangka waktu yang relatif lama, ditambah dengan pengaruh dari bahan-bahan yang bersifat toksik lainnya, akan tumbuh dan berkembang menjadi jaringan ganas atau kanker.
- Maka dari itu dapat disimpulkan ciri-ciri efek stokastik a.l :
- Tidak mengenal dosis ambang
- Timbul setelah melalui masa tenang yang lama
- Keparahannya tidak bergantung pada dosis radiasi
- Tidak ada penyembuhan spontan
- Efek ini meliputi : kanker, leukemia (efek somatik), dan penyakit keturunan (efek genetik)
- Fisiologis radiasi: temporary
- Genetik radiasi: bentuk mutasi pada keturunan organisme dengan sifat yang berbeda dari induknya
- Somatik radiasi: menghasilkan bentuk sel somatik abnormal sebagai hasil pembelahan secara mitosis (cancer, luka bakar, kemandulan)
- letal radiasi: mematikan
- Maka dari itu dapat disimpulkan ciri-ciri efek stokastik a.l :
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Kesalahan
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Technique and Projection errors
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Patient preparation error:
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Radiopaque artifact
Dental appliances, body piercings, jewelry & eye glasses left in the mouth during exposure will appear as radiopaque artifact superimposed over the dental image. Correction: all this items should be removed before placing of the film.
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Blurred image
Movement of the film, patient or X-ray tube head during exposure will result in a blurred image. Correction: the operator should explain for the patient & remind him to remain motionless during exposure.
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Pressure mark
Pressure from the incisal edge & cusps of the teeth (mostly in the pediatric occlusal radiograph). May appear black or white. Correction: ask the patient to bite gently.
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Film placement artifact:
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Double image
When an exposed film is re-exposed the resulting film will have 2 superimposed images
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Reversed film
Low density with herring bone, tire-track or dotted pattern, as a result of directing the X-ray through the lead foil side of the film back.
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Dot artifact
The identification (embossed) dot produce a circular radiolucent artifact on the final radiograph. This may interfere with interpretation of the apical areas of the teeth.
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Apices cut off
Occur when the film is not positioned apically enough to record the entire tooth.
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Crown not shown
There is no enough film extending occlusally.
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Dropped film corner
The film edge is not placed parallel to the occlusal surface of the teeth
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Area of interest not shown
This is the result of not placing the film to cover all the teeth in the area of interest and not centralizing the film over the area of interest.
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Black line
Due to excessive bending of the film prior to its placement inside the patient’s mouth (pressure causes ionization of silver halide upon processing will be darker).
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Distortion
Due to bending of the film to eliminate the patient’s discomfort specially in lower premolar area and upper central incisors
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Projection errors:
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Incorrect vertical angulation.
It will lead to: •Elongated image due to insufficient v angulation ( too flat), or •Shortened image due to excessive v.angulation ( too steep)
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Incorrect horizontal angulation
Is the appearance of the interproximal urfaces of the adjacent teeth over each ther. This is due to improper H.A. due toimproper alignment of the C.R. throughthe contact points i.e. not // to interproximal surfaces.
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PID alignment artifact (Positioning Indicator Device)
If the PID is misaligned and the x-ray isnot centered over the film, a partial image is seen on the resultant radiograph, thispartial image is called cone-cut. It appear as a clear area with curvedoutline.
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Exposure Errors
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Blank image
A film that didn’t receive radiation will have no image and will appear clear.
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Low Density image
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High density image.
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Chemical errors:
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Light image.
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Dark image.
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Blank image.
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Reticulation.
When the film subjected to a sudden temperature changes between the developer and water. Appear as cracked film.
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Black spot or patch.
Developer contamination before immersion into the developer solution.
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Black line.
Developer contamination processing hanger clips Dirty roller in automatic processor
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White spot or patch.
Contamination with fixer before processing
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Yellowish brown discoloration.
Exhausted solution or insufficient rinsing
Film Handling errors:
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Writing lines Appear on the radiograph due to writing on the film packet with ballpoint pen or lead pencil. It may appear black or white.
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Developer cut off A straight blank white border due tounderdeveloped portion. The film maynot be completely immersed in thedeveloper solution.
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Fixer cut off A straight black border. The film may not becompletely immersed in the developer solution.
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Overlapped film Film that overlap in developer arewhite, while that overlap in fixer areblack
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Finger nail artifact Black or whit crescent shape mark due torough handling of the film.
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Smudge. When the film touched by fingerscontaminated with developer or fixer
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Scratched film White lines appear onthe film due to carelesshandling of the film.
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Static electricity
Thin black branching lines Occurs whentwo surfaces are rubbed together againsteach other vigorously, this creates anelectric charges with visible light emittedwhich is capable of exposing the x-rayfilm, thus leading to ionization of AgBrcrystals at this area. Occur most frequently during periods oflow humidity
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Processing
- Persiapan
- asepsis
- save lamp menyala
- developer, fixer fresh
- lepaskan wadah film dan led foil
- Developing
- 15-20 detik
- Terionisasi AgBr → Ag^+ + Br^-
- Menghasilkan endapan Ag hitam - memberi warna hitam/ radiolusen
- Rinsing
- 10-30 detik
- Membersihkan film dari larutan developer agar tidak terbawa ke proses selanjutnya
- Fixation
- 3-10 menit
- pengerasan gelatin dalam emulsi film
- melarutkan AgBr yang undeveloped atau unexposed
- Washing
- 20-30 detik
- menghilangkan ion thiosulfate dan senyawa perak thiosulfate dalam air
- Drying
- mengeringkan film dengan dryer atau diangin-anginkan
- menghilangkan air pada emulsi. Hasil akhir film adalah emulsi yang tidak rusak, bebeas dari partikel debu, endapan kristal, noda, dan artefak
- Mounting
- Persiapan
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